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cedar-glade · 4 years

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Taxanomists: “What exactly am I looking at?”

Sure this is Spiranthes cernua, and we might be able to agree on that concept; or can we?

Spiranthes cernua is a species that perhaps fits the concept of intermediate abrupt speciation more than most species fitting into the contemporary and distant past time slot so much so that it may be the next new model speices.

Here is an R. A. style blurb that I plan on highly modifiying before the end of september as I collect more photos and take more photos of specimens. I also want to add article statements on each microspecies and add several method sections. I hope y’all enjoy this.

Abstract:

Spiranthes cernua has been problematic for taxonomists for more than 100 years and is constantly having species being added or removed to its aggregate taxon. Spiranthes cernua complex is a consistent topic for debate: to resolve taxonomic issues, discuss hybridization and abrupt speciation, and view apomictic strategies for colonialization and genetic persistence. The focus of this paper is on apomictic persistence and the mechanism as a potential point of discussion for the persistence of hybrid populations, autopolyploid populations that are used as hypothetical taxonomic units , and for the idea of discussing it as potential model species for apomixis studies.

Indroduction:

Orchidaceae, Spiranthes spp. and Spiranthes cernua:

Orchidaceae is a nested taxon, specifically ‘the orchid family’ and it’s derivatives; Orchidaceae is a vastly complex group located within’ the Lilianae super order (Monocots, characterized monocotyledon), taxon, and is perhaps one of the most discussed families for a number of reasons: discussed for it’s number of species, it’s families distribution, it’s morphological adaptations, symbiotic ‘strategies’, phenology and life stages, associated pollinator syndromes, and the reproductive abilities known(Catling, 1982)(Dressler, 2005). All of which may be considered concepts that are driving factors for evolutionary success or failures according to Dr. David Briggs and Dr. Stuart M. Walters (Briggs and Walters, 1969-2016). North America is considered the center for Spiranthes spp. diversity, with potential to expand this specific genera’s diversity and thus expand Orchidaceae too (Sheviak and Catling, 1980) (Dueck et. al. ,2005). Orchidaceae can be further broken down from subfamilies to tribes and tribes to genera with specific species and their subspecies, botanical varieties, isolated forms, mutation forms, and cytotypes; scrutinized complex resolution and the discovery of new species may disrupt the historic validity of sources, an approximate number may be 24,500 Orchidaceae members, unique enough to be species, currently inhabiting the globe(Dressler ,2005) )(Taylor et. al. ,2007-2009) (Dueck et. al., 2015). In the United States, Spiranthes spp. is one such genera in the Orchidaceae that is known for it’s apomictic behavior to some extent, and is distributed across the United States, found in every state except for Hawaii, and distinguished to have ~ 45 species present standing (Catling and Richard, 1980)(Catling, 1981/1982)(Catling and Brown, 1983)(Argue, 2011). Spiranthes spp., in general, is “The most diverse species in Eastern North American flora” and Spiranthes cernua seems to be at the center of this issue (Sheviak and Catling, 1980) (Sheviak, 1982/ 1991). Spiranthes cernua, colloquially ‘the nodding ladies’ tresses’, has been a major subject of taxonomic study, evolutionary origins, and molecular and genetic study as a species noted in North America’s flora (Dueck et. al., 2005) (Dueck et. al., 2015) (Pace and Cameron, 2017). Though difficult to grow from seed, tissue cultures are a process widely used in the cloning of orchid species and can be done on a massive scale; “Spiranthes cernua is a facultatively agamospermic polyploid compilospecies in which unidirectional gene flow from related diploids generates a wide range of novel forms and races” and could be potential model species for apomixis research based on model species criteria (Briggs and Walters, 1969-2016) ( Griesbach, 1986) ( Gonzalez and Concha et. al., 2002) (Dueck et. al., 2014). What is known from Spiranthes cernua’s apomixis habit is critical to understand to make conclusions on potential driving factors for Spiranthes spp. speciation events as a whole is definitely key to understanding species diversity.

Morphological Representation in Spiranthes cernua:

Spiranthes cernua is as morphologically diverse as it is distributed, and ecotypes from specific ecoregions are still not enough to truly represent a limit to the morphology present (Dueck et. al., 2014). One perceived problem with specific statewide flora’s can have different mechanisms for how they describe this species with overlap and in some cases federally threatened designation is ‘potentially’ not placed due to the var. or form maintaining it’s status as Spiranthes cernua, making studying Spiranthes cernua critical to conservation in the genus (Dueck et. al., 2014). Morphological characteristics that are critical to arriving at an ~ identification is somewhat associated with the minimum need that a basal rosette is present with no cauline patterning present, a single rachis like spike as an inflorescence is present and grows directly from the basal rosette, rachis is pubescent to canescent( densely pubescent to some degree), but not hirsute( densely pubescent with large hairs); hairs along the inflorescence are mixed in form: “trichomes capitate, glands obviously stalked” (Sheviak and Brown, 2002). The nod and flower color, leaf morphology, floral tube morphology, all display differences in populations, though they are usually completely white, creamy, or silverfish in sheen, instead of having yellow or green tints (Sheviak and Brown, 2002). The nod that occurs is caused by the reflexing at the base of the perianth; however, the exaggeration of the nod is variable (Sheviak and Brown, 2002).

Apomixis and it’s Potential:

Apomixis is a complicated asexual regenerative behavior that certain plant species undergo and is widely accepted as one of many successful reproductive mechanisms that has developed many times over history(Walters and Briggs, 1969-2016). Apomixis, through agospermic seed setting, is considered a pseudo-selfing mechanism that appears to parallel with cleistogamous mechanisms; however, mechanically it is different as gametogenesis and reduced tissue structures under scrutiny are less associated ,or not at all, with the ladder, and even delineated, to cell type generation from previously developed tissue types without reduction; in this way, it isn’t necessarily a ‘self-fertilizing’ event that creates offspring, but cellular propagation from a vegetative part of the original organism to produce seed(Walters and Briggs, 1969-2016) (Sharma and Thorpe, 1995). Another way to term apomictic mechanism for “Pathenogenetic seed setting” is “adventitious embryony”, “gametophytic apomixis”, and “asexual embryogenesis” (Sharma and Thorpe, 1995). Asexual propagation from non-reproductive vegetative organs as an inclusion in the concepts behind the definition of apomixis is notable, clarification of this type of apomixis, or vivipary, needs to be separated out in the definition for discernible definitions(Walters and Briggs, 1969-2016)(Sharma and Thorpe, 1995)(Carneiro et. al., 2006). The exception for the term ‘apomixis’ including asexual propagules, vegetative apomixis, comes from the idea that a species may not be able to set seed and only survives from this form of clonal propagation from a non-seed vegetative organ (Walters and Briggs, 1969-2016). Both forms are considerably advantageous to some degree, theoretical examples are areas where introduction events may occur and founders’ effects may be avoided (Walters and Briggs, 1969-2016) (Sharma and Thorpe, 1995). If we factor in allopolyploidy, which is considered a potential driving mechanism for speciation, or aiding to back up hypotheses delineating species (Walters and Briggs, 1969-2016). In North America we do see Spiranthes spp. exhibit polyploidy mechanism as the genus; a bimodal distribution of chromosome numbers becomes apparent from statistical analysis done from North American operational taxonomic units as a cohort: “two groups having either a base number of n = 15 or 22 (except for one with 12), or are amphiploid products of hybridization between members of the two groups (i.e., n = 15 + 22) and thus also allopolyploids”(Dueck et. al., 2014). Many known examples of allopolyploidy have already been noted in Spiranthes cernua complex and evolutionary developments may occur in temporal span from a potentially speciating specimen that persists by these apomictic mechanisms in new environments until other evolutionary driving events occur like polyploidy events; and if these events have already happened, they can be persist in a population due to this mechanism (Walters and Briggs, 1969-2016) (Dueck et. al., 2014).

Reproductive output and phenology in Spiranthes cernua:

In populations, environmental factors and life cycles may need to be analyzed in this complex to isolate how much apomixis is associated with a populations success and this can be done to some extent by juxtaposing resource availability and allocation and its contribution to normal reproduction and apomictic reproduction; reproductive output, resource allocation costs in reproduction, in many species is considered to be a factor in measuring fitness (Walters and Briggs, 1969-2016) (Antlfinger and Wendel, 1997). In most taxon, and at least historically speaking, the view of reproductive output is viewed as a compromise in usable energy for species survival; however, “Positive rates of net photosynthesis by reproductive structures have been measured in many species ,including orchids” (Antlfinger and Wendel, 1997). Long term phenology studies of a specific population adds a certain level of approximation to reproductive output or at the very least the methods used may be used as a guide to further studies on the Spiranthes cernua complex; methods included were: fire studies, morphological assays, gas exchange surface area assays, plant growth assays, and chlorophyll assays (Antlfinger and Wendel, 1997).

Spiranthes cernua complex, hybridization, and apomictic events:

Hybridization, polyploidy events, cleistogamous crossing, apomictic progression, and cryptic origins are all present in Spiranthes cernua (Pace and Cameron, 2017). These sets of irregular population hereditary persistence phenomena, peloria, can occur in different rates at the same time in any specific population (Pace and Cameron, 2017). “Complicated set of issues is further obfuscated by the lack of a universally accepted species concept” (Pace and Cameron, 2017). Legitimate species diagnosis specifically seems to have troubles with overlapping species or those closely related; Spiranthes cernua is known to hybridize and are related to S. magnicamporum, S. caesi, S. odorata, S. parksii, and S. ochroleuca with the level of hybridization varying and the level of polyploidy outcomes varying to the extent isolating a hybrid becomes difficult and complex ( Pace and Cameron, 2017). Combinations of methods are used, being critical to OTU sequences (from plastids, mitochondria, and nuclear DNA) ,specific to a standing/~delineate species, and using morphology from records of these OTU done by taxonomic analysis and utilizing matrix comparisons of a hybrids’ amplified fragment length polymorphism, present, and juxtaposing them to theorized parent species (Dueck and Fowler et. al., 2005) (Pace and Cameron, 2017). Synonymous taxonomical groupings have been made and removed due to hybrid history, and contemporary hybridization, with discernable amounts of claims on polyphyletic and paraphyletic linking being focused on; although clade crossing, reticulation, occurs enough to disrupt delineation(Pace and Cameron, 2017). This concept becomes an issue when planning out state resources and monitoring of federally threatened taxa; S. parksii is an example of federally threatened taxa that is now under scrutiny of placement under S. cernua, “as a localized sub-peloric form promulgated through apomixis” (Pace and Cameron, 2017). Spiranthes cernua complex apomixis events does not stop being present in operable resolution of hybrid origin’s and species housed under this complex (Pace and Cameron, 2017). Several other species in this complex are known to have levels of apomixis effecting their population occurrences and evolutionary history: S. casei, S. incurve (a polyploid hybrid originated species between S. cernua and S. magnicamporum), and S. ochroleuca (Dueck and Fowler et. al., 2005) (Pace and Cameron, 2017). These are noted as “micro species” of S. cernua in the complexes case; S. casei and S. incurve are specific micro species components that show a trend of majority apomictic population growth in comparison to those that have more mixed stratification of crossing habit seed setting and apomictic persistence (Pace and Cameron, 2017). S. xkapnosperia, which has distinct components from accepted S. ochroleuca, is another current hybrid that has questionable taxonomic stratification and phylogenetic presence that seems to follow trends of apomictic growth; but, population persistence is questionable as it stands( Pace and Cameron, 2017).

Conclusions:

Apomixis in Spiranthes cernua species complex does not successfully delineate one species, micro species, from the other as a solitary mechanism of evolution; instead evolution within this complex can be viewed as incorporating apomixis in high levels as a means to justify a hypothesis and describe evolutionary trends in species. The evolutionary developements in Spiranthes cernua complex usually are a factor of both facultative apomixis and some level of polyploidy event or hybridization event. Since apomictic linages are persistent in preserving genetic trends and occur in a common frequency in certain members of Spiranthes cernua complex, these members are good examples to study the driving mechanisms of apomixis. Some species in Spiranthes cernua complex may be cloned from tissue culture in mass utilizing well known orchid tissue culture methods. A combination of tissue culture and the frequency of apomixis as a strategy for maintaining characteristics in a population make this species concepts’ members potential model organisms to study apomixis as a mechanism for evolution.

Work cited:

Web references, Journal articles, R.A., and Taxon Sources:

Antlfinger, A. and Wendel, L.“Reproductive Effort and Floral Photosynthesis in Spiranthes Cernua (Orchidaceae)”. 1, June. 1997. American Journal of Botany Vol. 84, No. 6, pp. 769–780. https://doi.org/10.2307/2445813

Argue, C. L. “Subtribe Spiranthinae”. 18, August. 2011. Springer. The Pollination Biology of North American Orchids. Vol. 2, pp 19-52. https://link.springer.com/chapter/10.1007/978-1-4614-0622-8_2

Carneiro, V. T. C.; Dusi, D. M. A.; and Ortiz, J. P. A. “Apomixis: Occurrence, Applications and Improvements”. 2006. GSB. Floriculture, Ornamental and Plant Biotechnology. Vol 1, pp. 555-571. http://www.globalsciencebooks.info/Books/images/FOPBVolume1sample.pdf

Catling, P. M. “Breeding Systems of Northeastern North American Spiranthes (Orchidaceae)”. 1982. Canadian Journal of Botany. Vol. 60, No. 12, pp. 3017-3039. https://doi.org/10.1139/b82-358

Corrias, S. D. and Villa, R. “Embryology and Embryogenesis of Spiranthes L.C.M. Richard (Orchidaceae): S. spiralis (L.) Cheval and S. aestivalis (Poiret) L.C.M. Richard”. 1983. GBI. Vol. 117, No. 5-6 pp. 193-200. https://doi.org/10.1080/11263508309427969

Dressler, R. L. “How Many Orchids”. 2005. Selbyana. Vol. 26, No. 1, pp. 155-158. https://www.jstor.org/stable/41760186

Dueck, L. A. ; Aygoren, D.; and Cameron, K. M. “A Molecular Framework for Understanding the Phylogeny of Spiranthes (Orchidaceae), A Cosmopolitan Genus with a North American Center of Diversity”. 1, September. 2014. Wiley. American Journal of Botany. Vol. 101, No 9, pp. 1551-1571. https://doi.org/10.3732/ajb.1400225

Dueck, L. A.; Fowler, J. A.; et. al. “Genetic Discrimination of Spiranthes Cernua Species Complex in South Carolina”. 2005. Selbyana Vol. 26, No. 1, pp. 145-154. https://www.jstor.org/stable/41760185

Griesbach, R.J. “Orchid Tissue Culture”. 1986. Springer, Dordrecht. Current Plant Science and Biotechnology in Agriculture. Vol. 2, pp. 343-345. https://doi.org/10.1007/978-94-009-4444-2_29

Loyet, C. D. “Breeding Systems in Spiranthes magnicamporum (Sheviak)”. 1993. Masters Theses 2179. EIU. The Keep. https://thekeep.eiu.edu/theses/2179/

Nygren, A. “Apomixis in the Angiosperms II” December. 1954. Vol 20. No 10, pp. 577-649. https://www.jstor.org/stable/4353528

Pace, M. C. and Cameron, K. M. “The Systematics of the Spiranthes cernua Species Complex (Orchidaceae): Untangling the Gordian Knot”. 27, December. 2017. ASOPT. Systematic Botany. Vol 42, No. 4, pp. 640-669. https://doi.org/10.1600/036364417X696537

Schmidt, J. M. and Antlfinger, A. E. “The Level of Agospermy in a Nebraska Population of Spiranthes cernua (Orchidaceae)” 1, May. 1992. Wiley. American Journal of Botany. Vol. 79, No. 5, pp. 501-507 https://doi.org/10.1002/j.1537-2197.1992.tb14585.x

Sharma, K. K. and Thorpe, T. A. “Asexual Embryogenesis in Vascular Plants in Nature”. 1995. SSBMD. Current Plant Science and Biotechnology in Agriculture: In Vitro Embryogenesis in Plants, Vol 20, pp 17-72. https://link.springer.com/chapter/10.1007/978-94-011-0485-2_2

Sheviak, C. J. and Brown, P. M. “Orchidaceae: Spiranthes cernua”.1, June. 2002-2003. MOBOT, New York and Oxford. FNA: Vol. 26, pp. 498-499, 530-537, 541-542. http://www.efloras.org/florataxon.aspx?flora_id=1&taxon_id=242101948 and http://beta.floranorthamerica.org/Spiranthes_cernua

Sheviak, C. J. and Catling, P. M. “The Identity and Status of Spiranthes Orchroleuca”. October. 1980. JONEBC. Rhodora No. Vol. 82, No. 832 , pp. 525-562. https://www.jstor.org/stable/23314094

Sheviak, C. J. “ Biosystematic study of the Spiranthes cernua complex”. 1982. Bull. New York State Mus. Sci. Serv. pg 448. https://doi.org/10.5962/bhl.title.135544

Sheviak, C. J. “Morphological variation in the compilospecies Spiranthes cernua: Ecologically-limited Effects of Gene Flow”.1991. Lindleyana. Vol. 6, pp 228–234.

Sun, M. “Genetic Diversity in Three Colonizing Orchids with Contrasting Mating Systems”. 1, February. 1997. Wiley. American Journal of Botany. Vol. 84, No. 2, pp. 224–232. https://doi.org/10.2307/2446084

Taylor, T. N.; Taylor, E. L.; Krings, M. “Flowering Plants”.2007-2009. Paleobotany (Second Edition): The Biology and Evolution of Fossil Plants. Pp. 873-997. https://doi.org/10.1016/B978-0-12-373972-8.00022-X

Yeung, E. C. and Law, S. K. “Ovule and Megagametophyte Development in Orchids”.1997. SSBM, KAP. Orchid Biology: Reviews and Perspectives. Vol. 7, pp. 31-73. https://link.springer.com/chapter/10.1007/978-94-017-2498-2_2

Book references:

Briggs, D. and Walters, S. M. ““Polyploidy: In Chromosome Changes, Allopatric Speciation and Hybridization, and Abrupt speciation; Apomixis: In Breeding Systems, Abrupt Speciation,”. 1969-2016. CUP. Plant Variation and Evolution: 4E, pp. (57-59)(251-274)(287-329)(106-134, 144, 296.) Http://lccn.loc.gov/2015038104

#RA styled Blurb #ecology #spiranthes #orchidaceae #evolution #spiranthes cernua #apomixis #plantblr #botany #ohio

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ricmlm · 2 years

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🛸As promised... tell her and/or him... [Dandelion is the common name of several species belonging to the botanical genus Taraxacum, of which the most widespread is Taraxacum officinale. Class: Magnoliopsid Division: Magnoliophyta Family: Asteraceae Genre: Taraxacum Order: Asterales Kingdom: Plantae - but I do think that one is a... Taraxacum erythrospermum, known by the common name red-seeded dandelion, is a species of dandelion introduced to much of North America, but most commonly in the north. It is often considered as a variety of Taraxacum laevigatum (i.e., Taraxacum laevigatum var. erythrospermum) Dandelions have a trick up their sleeve. They can reproduce by apomixis – they don't need pollination to set seed, and each seed, with its little parachute, will form a clone of its “parent”. From generation to generation they remain the same genetically. There are usually 150-200 seeds per flower and up to 10 flowers per plant. Dispersal Mechanisms: Seeds can be dispersed long distances by wind because they move in updrafts. Longevity: Dandelion seeds are not long lived in the soil.] Dandelions do not do Ghosting! Alien Dandelions anyway! They just... fly away! To the Isle!! Well, tell that green👽alien lifeform, that... I'll do my best!👾alienpedia - WHAT HAS TO BE DONE. {👌🏻👐🏻👏🏻} HAVE A CONCERT GRAND Hope you've already done the rerun of the show! WIN THE CROWD... AS ALWAYS!🤘🏻 https://www.instagram.com/p/CeG8ABTjIaD/?igshid=NGJjMDIxMWI=

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megabadbunny · 7 years

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Rose x Ten, post GitF-au/fixit; angst, fluff, romance, more angst, and possibly some smut later, but this part (and all parts on ff.net) is sfw (minor exception for brief language). And a huge thank you to everyone who left a comment encouraging me to continue, as well as everyone who didn’t completely lose patience with me--this chapter is dedicated to you lovely peaches!!! <3 <3 <3

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Minuet, Part IV

The next day, the Doctor’s behavior can only be described as jumpy.

“And here we have the great lakes of Therran Vox!” he announces, throwing open the TARDIS doors to reveal a bleach-bright vision of sparkling water and dazzling white sky. “Not to be confused with Academy-Award-winning actress Charlize Theron, mind, nor the lakes of TheronnEx, though much of the plant life is certainly related, evolutionarily speaking.”

The Doctor plucks three umbrellas from their resting-place against the TARDIS wall, tossing one to Rose and Mickey each in turn before stepping out of the TARDIS with an umbrella of his own. “Something like third cousins, maybe third cousins once removed, maybe twice,” he continues. “Bit hard to know for certain, sort of tricky trying to gauge that sort of thing when your generations span centuries and solar systems. Speaking of reproduction, did you know that the Therranian water lily is one of the few angiosperms in the known universe that can reproduce via spores? Well, they don’t technically reproduce via spores, per se, but their pollen has been known to hitch a ride on them a time or two. Sort of like a botanical hitchhiker, only on a semi-mesoscopic scale. And when you’re talking spores and pollen able to withstand the vaccums of space, well, that sort of explains the galaxy-hopping, doesn’t it? Though the waterlilies on TheronnEx have a sort of unfortunate expired meat smell about them…”

Rose stretches and yawns, ignoring the Doctor’s prattling in favor of taking in the sights all around her. She’s surrounded on all sides by an intricate network of perfectly round lakes, connected only by slim strips of grassy land. Reflecting the world above—everything from willowy trees to the pearl-white sky to the metallic towerlike structures reaching high up, up, up into the swollen candyfloss clouds—the lakes glimmer and sparkle like a collection of mirrors, glasslike and silver and still. Stepping closer to one of the lakes, Rose inspects a tree by its banks, whose slender roots creep gently into the water. Her eyes travel over the trunk, which stretches high into the morning air, lifting its canopy of paper-thin roots far above the water surface. It doesn’t take an architect to observe the similarity between the trees and the tower structures, whose engineers clearly looked to the willows for inspiration in constructing both the complex, interwoven-strut foundations of the towers as well as their observation decks spreading up above. Rose jumps as a handful of water droplets fall across her upturned face, just before a light drizzle descends all around, tiny water droplets singing through the air before they land with a series of dainty plops and splashes. Their touch on the grass releases a mild fragrance into the air, something delightfully fruitlike and soft.

It’s absolutely wonderful, a proper exotic alien planet, and Rose lifts her face completely toward the sky, eyes closed as the rain peppers kisses on her cheeks. God, she’s missed this.

Without even thinking about it, Rose reaches for the Doctor’s hand, but he sets off at a brisk pace before her hand can do anything more than brush against his, blathering on about para-symbiotic relationships and rhizomes and apomixis and god knows what else.

(Scratch that earlier thought—he’s ridiculously jumpy.)

“Is this normal?” Mickey asks under his breath.

Rose watches the Doctor as he wanders off, chattering loudly to no one in particular, and she tries to ignore the sick feeling bubbling up in her chest, the hurt aching in her gut. It’s just because she didn’t sleep well last night, she reasons. For all that she had dreamed of being back aboard the TARDIS, snuggling into her bed replete with plush foam and soft blankets and squishy pillows, she slept absolutely dreadfully. Probably she’d just got used to the hard and unforgiving beds back at the palace; certainly the lack of sleep can’t be blamed on anything else. Or anyone, for that matter.

Great fat rain droplets smack against her head like a dozen tiny missiles and Rose wipes water out of her face, deploying her umbrella with a sigh. “No,” she replies. “This is new.”

“Did something happen last night?”

“No. Nothing happened.”

Rose knows Mickey doesn’t believe her, would be able to tell by his suspicious silence even if she couldn’t see the eyebrow arching off his forehead, but mercifully, he doesn’t press for more. Instead, he proffers his arm to Rose, standing ramrod-straight like he’s posing for a school formal photo. He would look a little silly even if his umbrella wasn’t covered in bright yellow smiley faces.

“C’mon, babe,” he says in response to her questioning look. “Let’s go for a stroll and you can tell me all about your adventures back in fancypants France.”

Rose smiles despite herself. “Are you sure you’d rather hear about that than whatever thrilling greenhouse trivia the Doctor’s throwing our way?”

“Nah, we’ll just make sure to toss a few uh-huh’s and oh how fascinating’s his way every once in a while.”

Threading her arm through his, Rose laughs.

“…and here it is!” announces the Doctor, several thousand steps and two grumpy and wet-shoed humans later. The trail stops at an impressive, five-meter tall wall, rainbow-bismuth-colored and extending as far as the eye can see in either direction; the Doctor presents it all with a flourish of his umbrella. “The main attraction, the big to-do, the pièce de résistance—the grand Temple of the High Chauncery, perfect for viewing Therran Vox’s universe-renowned celebration of transient luminous events!”

He turns to Rose and Mickey with a wide grin, only to be met by a pair of identical blank stares. “Oh, come on,” says the Doctor, undeterred. “Mickey, you must have heard me mention the High Chauncery’s luminous wassail at least once!”

“Pretty sure I’ve never heard any of those words in my life,” Mickey replies flatly.

“So what’s a transient luminous event?” asks Rose. “I mean, luminous—that means light, right?”

“Right you are,” the Doctor replies, and is Rose just imagining it, or does he meet her gaze even less than usual? “The term refers to electrical phenomena produced during a thunderstorm.”

“So, lightning,” says Mickey, unimpressed.

“Well, yes, if you want to be reductive,” the Doctor responds, rolling his eyes. “But it’s not just lightning, it’s spectacular lightning. Like I said, phenomenal. Lots of worlds experience it, Earth included, but on most planets the events flash by so quickly, so high in the atmosphere, that you can’t observe them with the naked eye. That’s what makes the storms on Therran Vox so special; the chemical composition of the atmosphere here makes for an event that’s far more visible. You can catch the light show in all its glory, from front-row seats! Nothing quite like it in the universe, but why would I tell you when I can just show you?”

He raps his knuckles against the gate wall and a small round window opens in the metallic surface, a liquid movement like oil springing away from soap. A humanoid face appears on the other side, her eyes a fascinating multicolor, her forehead bedecked in rows of ornamental dots.

“Invitation?” the owner of the face inquires.

The Doctor produces the psychic paper from his jacket-pocket. “Sir Doctor and his traveling companions, Dame Tyler and Majordomo Smith of the Powell Estate,” he says rather grandly, “here to view some of the universe’s finest luminescent theatre!”

“Of course, your Grace,” replies the gatekeeper, peering at the psychic paper through the rain. She turns around and issues a curt nod to her comrade (another humanoid, another set of ornamental dots), and the window in the wall slowly opens up, widening by inches into a round doorway.

“Your timing is most fortuitous, sir—all of the other guests have already arrived, and we’re closing the outer shield any moment now,” the gatekeeper continues. “Per your itinerary, the first ritual doesn’t take place until the morning, but that gives you the evening to settle in and enjoy the first stirrings of the storm. In the meantime, Votary Uruud here will give you a quick tour through the Temple before showing you to your quarters, and we’re happy to take your luggage for you as well—”

“Sorry, sorry,” says the Doctor, his eyebrow arching in confusion. “Our quarters?”

“Our luggage?” asks Mickey under his breath.

“Yes, Sir Doctor, your quarters. For the duration of the event.”

The Doctor blinks. “The duration of the event,” he repeats, his eyebrow arching further.

“For the month, sir.”

The Doctor’s eyebrow has now arched so high it’s in danger of disappearing into his hairline. “Right,” he says. “The month-long ritual. The month-long ritual storm celebration. The month-long ritual storm celebration for which we are totally, completely, and utterly prepared. With luggage and toiletries and things. For a month.” He tugs on one ear. “Except—”

“Oh, silly us!” Rose interrupts, throwing her hands up in mock-surprise. “We left all of our things back at our ship!”

“Yes, quite!” the Doctor agrees. “So we’ll just run back and grab it all, shall we?”

Rose and Mickey nod vigorously.

Glancing at each of them, the gatekeeper’s face wrinkles in concern. “Forgive my impudence, your Graces, but it’s too late to turn back now. You won’t reach your ship before the Allstorm arrives.”

“The Allstorm?” Mickey asks, incredulous even as rain dodges his umbrella to splatter against his cheek. Rose elbows him in the ribs and he clears his throat. “I mean, of course, the Allstorm!” he laughs nervously. “I know what that is. Sure, why not?”

“Thanks for the warning, but we’ll take our chances,” says the Doctor. “Bit of rain will do us more good than harm.”

“Please, your Graces, I must protest—the blessed High Chauncery is a generous man and will supply you with all that you could need. You mustn’t remain outdoors any longer, it’s not safe—”

No sooner has the Doctor turned to leave than a great bolt of lightning splits open the sky, followed by a blast of thunder so violent it shakes the ground beneath everyone’s feet, their ears ringing after. Looking skyward, Rose can’t help but notice that the formerly friendly-looking clouds appear significantly more ominous now, less fluffy-pink and more threatening-red and heavy with rain. They cluster overhead, slowly blocking out the sun, and Rose watches as the world is painted crimson around them. She suddenly thinks of Sunday school, of pharaohs and plagues and endless night, of storms that send blood pouring from the skies and swelling in the rivers. She shudders.

Another barrage of thunder strikes, so loud Rose can feel it in her bones, rattling her teeth. The Doctor heaves an impatient sigh. “Our quarters it is, then,” he says reluctantly.

The gatekeeper beams at him. “Oh, very good, sir. Thank you, sir. Welcome to the High Chauncery’s Temple of the Allstorm!”

While the storm rages overhead, its searing white lightning and murderous clouds all-too-visible through a ceiling that, to all appearances, seems to be made of a thick stained glass, Votary Uruud leads the Doctor, Rose, and Mickey on a tour of the opulent beauty that is the Temple. They show the party through a marble-lined courtyard into a veranda replete with columns and overflowing in ornamental greenery and other Votaries carrying a generous surplus of niblets on trays. Mickey and Rose inspect the food eagerly, sampling things spicy and salty, sugary and sweet; Rose tries not to notice how the Doctor, strangely, avoids all of the niblets altogether. The veranda opens to a garden lush with flora of every color imaginable, vibrant vermillion and stunning cobalt and brilliant fuschia and everything in-between. Some of the flowers bloom as large as dinner plates, others as small as thimbles, and Rose watches in fascination as each of them slowly turn their faces toward the sky, almost as if they’re looking for the storm, like they can sense it.

“They’re lumosynthetic,” the Doctor murmurs to Rose. “They’ve evolved to feed off light from any source, even lightning in a storm. You should see them when the real storm starts.”

She nods in response, and wonders at how he doesn’t lean in nearly as close as usual, how he draws away so much quicker.

The garden leads to a chamber of swimming pools nearly identical to the perfectly round lakes outside, save that their water glows with the otherworldy light of bioluminescent algae. At Uruud’s gentle urging, Rose and Mickey each dip a hand into the water and delight at the glow that dances across their skin, lingering in a smattering of ghostly footprints several moments after leaving the pool.

In addition to the wonders that call the Temple home, Rose, Mickey, and the Doctor also encounter other guests as they dutifully follow Uruud, people of all shapes and shades and sizes, everyone from other Therrans to bird-people with special goggles to fish-people with special suits to upright rhinoceri and even a group of New Earth’s cat folk, though thankfully, Rose notes, none of them appear to be nuns. Almost all of the Therrans bear the same dots on their faces as Uruud and the gatekeeper, all in different numbers and configurations. One such woman, a gorgeous figure clad in a semisheer gold and scarlet gown with facial markings to match, watches them from the safety of her richly-clad party, her eyes lingering on the Doctor long after he walks by.

(Half a year ago, Rose would have threaded her arm through the Doctor’s and shot the woman a dagger-filled glance until she drew back in surprise, would have done it without even thinking. Now she just bites her lip and silently wishes for the woman to slip on a banana-peel.)

As they pass through the menagerie afterward, peering through latticework enclosures at a host of incredible creatures (winged lizards and scaled mammoths and jewel-skinned snakes, oh my), Rose starts to notice the walls around them—wide as they are, and as full as the space is between them, it’s sort of difficult to tell, but she could almost swear they were curved. In fact, she thinks, stepping closer so she can fit her palm to one wall’s smooth surface, she would be willing to bet that all the rooms in the Temple are built this way, round-walled and circular like the lakes outside.

“It’s like a ripple,” she realizes aloud when the party reaches the entertainment library, whose walls are lined with curving shelves that are not packed with books or movies so much as hundreds upon hundreds of glowing white orbs.

“Beg pardon?” asks Votary Uruud with a polite small.

“The Temple. It’s built like a ripple, isn’t it?”

Uruud’s smile brightens into something genuine then. “It is indeed, your Grace!”

“You’re not wrong,” says the Doctor thoughtfully. “The Temple is made up of a series of concentric rings, each split into different chambers for different purposes. The deeper into the Temple you go, the smaller and more important the chambers become—entertainment and feasting and grand ritual gives way to spaces of study, sleep, work, and personal worship.”

He pauses for a moment, musing. “And with the glass ceiling exposing everything to the gods above, I’d imagine you’re right—from a bird’s-eye view, the structure would look just like a ripple. Well-spotted, Rose.”

“Your Graces are most observant,” says Uruud, beaming at each of them in turn. “Although few are as resplendent as the High Chauncery’s Temple, each of the Allstorm Temples is inspired by the form of water in honor of They Who Provide.”

“Who’s that? Like a bunch of gods?” Mickey asks, interest piqued.

“They are one god,” Uruud replies, and then, continuing in much the same fashion as someone reciting an oft-spoken Bible verse, “for just as our gods cannot be tamed by earthly will, neither can man nor woman tame the form of water.”

Confused, Rose and Mickey both turn to the Doctor. “They Who Provide is the genderless water god,” he explains. “Our hosts don’t really adhere to a binary the same way you lot tend to. Gender isn’t assigned at birth, but rather chosen at the coming-of-age. You choose one or the other, or both, or neither, and you can change it at any time.”

“So which one did you choose?” Mickey asks Uruud. “If that’s not a rude question or anything,” he adds hurriedly.

“I follow in the footsteps of They Who Provide,” replies Uruud, bowing their head in deference.

“So, like, do you have a special party for it, or something? Like a bar mitzvah?”

Uruud laughs, quickly sobering after. “Forgive me, your Graces! I’m merely surprised—even though the Temple receives a great many honored guests for each Allstorm, most of them seem to prefer the delights of our leisure chambers and pleasure rituals rather than inquire after our ways. Storm bless them, but…”

“Let me guess,” Rose cuts in with a grin. “They’re all either snooty prigs, entitled prats, or insufferable know-it-alls who love telling you how to do your job?”

“Oh, I would never dare besmirch the name of our honored guests,” replies Uruud, the very picture of politeness even as a spark of mirth twinkles in their eyes. “But I also wouldn’t dare argue with the wise words of such an honored guest, either.”

“Of course not,” Rose replies, tapping the side of her nose.

A chirping sound fills the air then, and Uruud lifts their wrist to check their watch (or at least Rose assumes it’s a watch, though she imagines they probably call it a timekeeper or something fancy like that). “And now, your Graces, I must assume my other duties for the evening,” says Uruud. “However, I would be happy to show you to your quarters first!”

They rap their knuckles on a blank patch of wall, just like the Doctor did earlier, and just like before, a round doorway opens up, widening like a mouth. Uruud steps through, Mickey following after; the Doctor pauses, however, so Rose does as well. She watches him as he stares up through the ceiling, his hands tucked in his pockets, his brow wrinkled in deep consideration.

Rose draws a deep breath. All right. They’re alone, now. Just the two of them. No big deal. They can still be normal. Right?

“Penny for your thoughts?” Rose prompts.

The Doctor’s eyes narrow at a particularly bright arc of lightning dancing overhead. “I’m still mulling over what the gatekeeper said. For the duration of the event, for the month. But I checked and double-checked the TARDIS chronometer before we stepped out, and this is the wrong time of year for the Allstorm, I’m sure of it. I wanted to show you two the sights, to be sure, but this isn’t quite what I had in mind. It’s like trying to buy a dog and receiving a coyote instead. I wouldn’t have brought us here if I’d known…”

Sighing, he shakes his head. “At any rate, why would so many people willingly lock themselves up in one building for an entire month? Spectacular lightning-show or no, that’s a dreadfully long time to be cooped up in the same building.”

“Well, Uruud mentioned other stuff too, pleasure rituals and whatnot,” Rose points out. An unfortunate thought pops into her head and her eyes widen in alarm. “Oh god, that’s not like a fertility ritual or forced-mating thing, is it?”

“What? No!” laughs the Doctor. “It’s just regular ol’ fun, sanctioned by the god of your choice. Feasts and plays and weddings and galas and drinking a little too much of the holy libations, that sort of thing. An Allstorm is always an excuse for celebration.”

“Even if it’s taking place at the wrong time?”

“Even if.” The Doctor quiets then, suddenly thoughtful. “Still, though. An entire month? Granted, it’s been a few decades since my last visit. Not to mention, they don’t call it the Allstorm for nothing—it covers the whole planet, wrapping all of Therran Vox in a brilliant display of water and light. But you’re talking about something that lasts a few days, a week, tops. Certainly not a whole month!”

“Well, I’m sure Uruud would be happy to tell us more about it, if we asked,” Rose suggests. “Maybe it’s a one-off thing, or—I don’t know, maybe things are just different now.”

The Doctor’s gaze shifts to her, and Rose could swear a shadow flickered across his face for just the briefest second. If she didn’t know any better, she would say it looked a little like sadness. Or worse, resignation.

“Yep,” he says, his voice clipped even as he smiles. “You’re probably right.”

Rose frowns. It feels like something just happened, like she just said the wrong word and the Doctor shuttered the gates after, but she can’t put her finger on it, and the Doctor hardly seems in the mood to help. He brushes past her without another word, following after Mickey and Uruud through the round doorway, hands firmly tucked in his pockets.

Worrying her lower lip between her teeth, Rose lingers for a moment after, wondering. Guilt and frustration bubble up in her gut, churning in equal measure. Is this just how it’s going to be between them, now? Awkward and distant and stiff, and forever?

(How the hell is she supposed to fix this?)

“My sincerest apologies,” says Uruud, frowning as they peruse the screen of their wristwatch. The light from the screen bathes their face in a gentle blue, highlighting their dots in stark relief. “I’m so sorry, but I cannot seem to find your names in the database. I can only think the electrical interference from the Allstorm is affecting our information network…”

“Oh, it’s no worries,” replies the Doctor with a breezy wave of the hand. “Just chuck a few rooms our way, any rooms will do.”

“Of course, sir. I have two rooms available; will that suit the needs of your party?”

“If you need additional space,” calls a soft voice behind them, smooth and silken, “I would be delighted to share.”

Rose and the Doctor turn to see the red-and-gold woman from before, her immaculately-painted crimson mouth spread in a beatific smile, and god, she’s even more beautiful up close. Voluminous black hair, eyes as blue as lapis, features that couldn’t be more perfect if they’d been chiseled by a master sculptor; Rose can’t blame the woman for being so beautiful, or showcasing it so well (how can she, when even she can’t tear her eyes away?), but the self-assurance she projects, the confidence in her gait as she strolls up to their party, looking the Doctor up and down, makes something burn in Rose’s chest, twisting and growling like a tiny little green-eyed beast. This, Rose thinks, is a woman who has received everything she has ever wanted, and has no doubts now that anything else she wants will soon be hers as well.

And then there’s the fact that the Doctor hasn’t said anything to rebuff her, and Rose fumes, and worries, and wonders if—

"He’s taken,” she blurts out.

In her periphery, Rose sees the Doctor glance her way, his expression unreadable. The woman, however, offers her an imperious look that she knows all too well. Her gaze travels over Rose, appraising. Rose is suddenly very aware of what she must look like right now, all damp jeans and dripping umbrella and shoes squelching with mud. But she didn’t spend half a year in the French court for nothing; she draws herself up to her full height, chin up, and looks the woman square in the eye, offering a sly smile.

“Thank you for your kind offer, but I’m afraid we can’t accept,” Rose says, the words falling into place like the dials on a slot machine. “See, he’s married—”

“To Mickey!” the Doctor interrupts with a mad grin.

Now it’s Rose’s turn to stare.

What?

The Doctor just beams at the noblewoman, his smile gigawatt-bright. Rose turns to Mickey for help, for a dose of sanity, for anything, but he can’t offer anything useful; he’s too busy looking surprised.

“Ah, it feels like it was just yesterday,” the Doctor says wistfully, looping an arm around Mickey’s shoulders. “Quite possibly because it was just yesterday. It’s all still very new, you see. Bit of a whirlwind affair. Almost completely unexpected. But the heart wants what the heart wants. Isn’t that right, Peaches?”

“Erm,” says Mickey.

“And we thought, what better place to honeymoon than Therran Vox during the Allstorm?” continues the Doctor. “I wanted a trip to Barcelona, personally, but I just can’t say no to this face.” He tenderly pinches Mickey’s chin and Mickey looks very much like he wouldn’t mind being swallowed up by the floor right about now. “He’s a dreadful romantic, my Mickey.”

“Peaches?” Mickey asks, voice faint.

“We’re still figuring out the pet names,” the Doctor whispers conspiratorially to the noblewoman, and Rose fights the urge to roll her eyes, or stomp her foot, or maybe to scream. “Like I said, it’s all very new. But we’re very much in love, isn’t that right?”

Mickey shoots Rose an uncertain look, and the Doctor tightens his arm around Mickey’s shoulders until he yelps in surprise. “So in love, right, darling?”

“So in love it’s almost unbelievable,” Mickey replies through a teeth-gritted smile.

“So in conclusion, my dove and I would be more than happy to share a room,” the Doctor finishes.

“Very good, sir,” replies Uruud, relief washing over their face. “Now, if you’ll just follow me, we’ll get you settled in!”

“Anyway, thanks again for the generous offer!” the Doctor calls back to the red-and-gold woman as he follows Uruud down the corridor. Mickey trails after the two of them in something of a daze, as if he still can’t quite believe what’s going on. Rose can’t say she blames him. She’s having a little trouble processing it all herself.

(So is she just supposed to pretend that everything is normal, then, except when the Doctor starts to feel flighty? Five and a half months she waits for him, she waits, and at the end of it he’ll shout and then fall silent and then act all remorseful, he’ll insult Rose and then apologize and then, out of nowhere, apropos of nothing, grab her and kiss her, not six hours after he was ready to jump through that window and leave her and Mickey stranded, not six hours after he was kissing another woman? And then after all that, the mood swings and the almost-confessions and the bullshit refusal to discuss anything that truly matters, and now he’s the one pushing her away? And what, is Rose just supposed to accept it, roll with the punches, fall in line like a good little tin soldier? She’s just supposed to stand there and take it?)

The guilt from earlier subsides, a tide drawing back to reveal a shore littered in broken shells and bits of glass and something black and sticky, an oil spill slowly staining the sand.

“Rose?” Mickey calls from down the corridor, stopping to wait for her.

Hands balled into fists, Rose follows after them, wondering how her day could possibly get any worse.

***

Next Part (forthcoming)

***

#ficandchips #tenrose #ten/rose #tenxrose #gitf fixit #post-gitf #angst #angst with a happy ending #(ultimately - though it might take them a minute to get there ;)#also sweet baby jesus has it seriously been six months since my last update for this story???#my godddddd #i'm so sorry i hope all my readers are still alive and well and flourishing #<3 <3 <3 <3 <3 <3 <3 <3 <3 <3 #but for reals it feels so good to get this posted #ahhh #relief

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breyesbioblog · 4 years

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Plants and their Soilmates

In the previous blog I talked about reproduction in microorganisms in this blog I'll talk about how plants reproduce with their “soilmates”. Plants are one of the most important parts of our ecosystem, we rely on plants for food and oxygen we breathe. Since plants are so essential to us why not learn about how they reproduce and maintain their population despite the growing population of the organisms that need them to survive.

Like those I mentioned in the previous blog, plants can also reproduce using asexual and sexual modes of reproduction. Asexual reproduction can be categorized into artificial sexual reproduction and natural asexual reproduction. In artificial sexual reproduction, humans will have to involved to mediate the processes which in turn allows to further increase the rates of propagation as well as create new varieties, examples of artificial sexual reproductions are grafting, cutting, laying, and micropropagation. On the other hand natural asexual reproduction, the plants have specialized stems to grow into new individuals, it's like budding but they don’t get separated unless an external force makes them so. Examples of these specialized stems are tubers for potatoes, rhizomes for ginger, bulbs for onions, corms for gabi, stolons for grass, and apomixis which means a plant can produce seeds even without fertilization.

Moving on to sexual reproduction, just like what I said in the last blog sexual reproduction allows the diversity of genes among the species that can help them survive or adapt to the environment it is living in. when you see a flower you wouldn’t think it was tool plants use to reproduce will you? Flowers produce seeds, and seeds are very essential for the survival of plants that reproduce using sexual means, they are also used as nourishment of young plants. Some plants have evolved to have their seeds be covered by the mature ovaries of flowers called fruit, which is eaten by some animals and helps disperse the seed. Through pollination, plants are able to reproduce over distances with the assistance of insects and other animals, and for the wind-pollinated counterpart. As pollen reaches another plant, their egg cells are fertilized and grow into seeds.

#science #blog #plants

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pantherwriterblogger · 4 years

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Find out the answer for What is apomixis and what is its importance? at #AskSawal Ask Sawal is a question answer discussion forum. You can find answers for more than 2 billion questions targetting more than 50000 topics.

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margdarsanme · 4 years

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NCERT Class 12 Biology Chapter 2 Sexual Reproduction in Flowering Plants

NCERT Class 12 Solutions for Biology Chapter 2 Sexual Reproduction in Flowering Plants

QUESTIONS FROM TEXTBOOK SOLVED

1. Name the parts of anangiosperm flower in which development of male and female gametophytes take place.Ans. Development of male gametophyte (micro- gametogenesis) occurs in pollen sac of anther up to 2 – celled stage. The female gametophyte develops (megagametogenesis) in the nucellus of ovule.

2. Differentiate between microsporogenesis and megasporogenesis. Which type of cell division occurs during these events? Name the structures formed at the end of these two events?Ans.Differences between microsporogenesis and megasporogenesis are as follows –

Each microspore mother cell and megaspore mother cell contain two sets of chromosomes and are therefore diploid. The diploid megaspore mother cell and microspore mother cell enlarges and undergo meiosis to produce, four haploid cells called megaspores and microspores respectively.The chromosome number is reduced by half and therefore megaspores and microspores are haploid.Microsporogenesis and megasporogenesis give rise to pollen grains and embryo sac respectively. Pollen grain is the male gametophyte and embryo sac represents the female gametophyte.

3. Arrange the following terms in- the correct developmental sequence : Pollen grain, sporogenous tissue, microspore tetrad, pollen mother cell, male gametes.Ans. Sporogenous tissue – pollen mother cell – microspore tetrad – pollen grains – male gametes.

4. With a neat, labelled diagram, describe the parts of a typical angiosperm ovule.Ans.A typical angiospermic ovule is a small structure which is formed in the ovary. Ovule first develops as a projection on the placenta and composed of multilayered cellular tissue called the nucellus. The hypodermal cell of die nucellus enlarges and transformed into megaspore mother cell. This cell undergoes meiosis to produce four haploid cells only one of which develops & forms embryo sac (female gametophyte). An ovule may be surrounded by one or two protective layers called integuments, leaving a small opening at one end termed as micropyle which acts as passage for the entry of the pollen tube into the ovule. Thus, a typical ovule consists of a fully developed embryo sac with the nucellus and integuments.

5. What is meant by monosporic development of female gametophyte?Ans. In many flowering plants, only one out of the four megaspores enlarges and develops into female gametophyte or embryo sac. The other three megaspores degenerate. This type of embryo sac formation is called as monosporic type of development.

6. With a neat diagram explain the 7-celled, 8- nucleate nature of the female gametophyte.Ans.Embryo sac (or female gametophyte) is formed by three successive mitotic divisions that take place in the nucleus of megaspore.The nucleus of the functional megaspore divides meiotically to form two nuclei which move to the opposite poles, forming the 2-nucleate embryo sac. Two more sequential mitotic nuclear divisions result in the formation of the 4-nucleate and later the 8-nucleate stages of the embryo sac. After the 8-nucleate stage, cell walls are laid down leading to the organisation of the typical female gametophyte or embryo sac. Six of the eight nuclei are grouped together at micropylar and chalazal end and form the egg apparatus and antipodals respectively. The large central cell left over with two polar nuclei. Thus, a typical female gametophyte consists of 7 cells with 8 nucleus.

7. What are chasmogamous flowers? Can cross-pollination occur in cleistogamous flowers? Give reasons for your answer.Ans. Chasmogamous flowers or open flowers in which anther and stigma are exposed for pollination. Cross-pollination cannot occur in cleistogamous flowers. These flowers remain closed thus causing only self-pollination. In cleistogamous flowers, anthers dehisce inside the closed flowers. So the pollen grains come in contact with stigma. Thus there is no chance of cross¬pollination, e.g., Oxalis, Viola.

8. Mention two strategies evolved to prevent self-pollination in flowers.Ans. Continued self-pollination decreases the vigour and vitality of a particular race. Thus, flowering plants have developed many devices to discourage self-pollination and to encourage cross-pollination.Dichogamy and self-sterility are.two most common devices that ensure cross-pollination. Dichogamy – Maturation of anther and stigma at different times in a bisexual flower prevent self-pollination.Self-sterility (or self-incompatibility) – Due to the presence of self-sterile gene in some flowers, pollen grains do not germinate on the stigma of that flowers. e.g.,- tobacco, potato.

9. What is self-incompatibility? Why does self-pollination not lead to seed formation in self-incompatible species?Ans. When the pollen grains of an anther do not germinate on the stigma of the same flower, then such a flower is called self-sterile or incompatible and such condition is known as self¬incompatibility or self-sterility.The transference of pollen grains shed from the anther to the stigma of the pistil is called pollination. This transference initiate the process of seed formation. Self-pollination is the transfer of pollen grain shed from the anther to stigma of pistil in the same flower. But in some flower self¬pollination does not lead to the formation of seed formation because of the presence of same sterile gene on pistil and pollen grain.

10. What is bagging technique? How is it useful in a plant breeding programme?Ans. It is the covering of emasculated flowers (removal of anthers in bud condition from a bisexual flower by a bag of butter paper or polythene in their bud condition i.e., before anthesis) to prevent contamination of its stigmas with unwanted pollens. When the stigmas of emasculated flowers mature the bags are removed, stigmas are dusted with pollen grains of desired male . plants by means of a presterilized brush and flowers are rebagged till fruit develop. This technique is mainly used in artificial hybridization. Plant breeders often use this technique to prevent the contamination of stigma of the flowers from unwanted pollen grains.

11. What b triple fusion? Where and how does it take place? Name the nuclei involved in triple fusion.Ans. Fusion of second male gamete with die two polar nuclei located in the central cell to form the triploid primary endosperm nucleus (PEN) is called triple fusion or vegetative fertilization. This process takes place in the embryo sac. After reaching the ovary, pollen tube enters into the embryo sac from the micropylar end. After penetration, the tip of the pollen tube ruptures releasing the two male gametes. The one male gamete fuses with the egg to form the diploid zygote. This process is called syngamy and the other male gamete fuses with the two polar nuclei to form the triploid primary endosperm & this process is known as triple fusion. These two events of fertilization constitute the process of double fertilization.

12. Why do you think the zygote is dormant for sometime in a fertiUsed ovule?Ans. The zygote after a period of rest develops into embryo. Most zygotes remain dormant till certain amount of endosperm forms. They do so, to provide assured nutrition to the developing embryo.

13. Differentiate between:(a)hy pocotyl and epicotyl;(b)coleoptile and coleorrhiza;(c)integument and testa;(d)perisperm and pericarp.Ans:

14. Why is apple called a false fruit? Which Part(s) of the flower forms the fruit?Ans. Botanically ripened ovary is called a true fruit. The fruits in which thalamus and other floral parts develop along with the ovary are called false fruits. For example – apple, strawberry, cashew etc. In apple the main edible portion of the fruit is the fleshy thalamus. Ovary forms the fruit after fertilization or without fertilization in parthenocarpic fruits.

15. What is meant by emasculation? When and why does a plant breeder employ this technique?Ans. Emasculation is the removal of stamens mainly the anthers from the flower buds before their dehiscence. This is mainly done to avoid self-pollination. Emasculation is one of the measures in the artificial hybridization. Plant breeders employed this technique to prevent the pollination within same flower or to pollinate stigmas with pollens of desired variety.

16. If one can induce parthenocarpy through the application of growth substances, which fruits would you select to induce parthenocarpy and why?Ans. Parthenocarpic fruits are seedless. They develop from ovary without fertilization. Banana, grapes, oranges, Pineapple, Guava, Watermelon, lemon are selected because these seedless of units are of high economic importance. The fruits in which seeds or seed part form edible portion (e.g.,Pomegranate) are not selected to induce parthenocarpy.

17. Explain the role of tapetum in the formation of pollen-grain wall.Ans. Tapetum is the innermost layer of the microsporangium. The tapetal cells are multinucleated and polyploid. They nourish the developing pollen grains. These cells contain ubisch bodies that help in the ornamentation of the microspores or pollen grains walls. The outer layer of the pollen grain is called exine and is made up of the sporopollenin secreted by the ubisch bodies of the tapetal cells. This compound provides spiny appearance to the exine of the pollen grains.

18. What is apomixis and what is its importance?Ans. Apomixis is a mode of asexual reproduction that produces seeds without fertilization, e.g.- some species of Asteraceae and Grasses. This method is important in hybrid seed industry. Hybrids are extensively cultivated for increasing productivity. But the main drawback is that the hybrid seeds are to be produce every year because the seeds of the hybrid plants da not maintain hybrid characters for longer period due to segregation of characters. This can be avoided if apomixis can be introduced in hybrid seeds. For this reason scientists are trying hard to identify genes for apomixis.

from Blogger http://www.margdarsan.com/2020/09/ncert-solutions-for-class-12-biology_17.html

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evoldir · 5 years

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Conference: Portland_Oregon.SexAsex.Jun2-4

June is soon! Make sure to register for Sex & Asex: The Genetics of Complex Life Cycles the American Genetic Association President's Symposium 2-4 June 2019, Portland, Oregon Join AGA President Maria Orive at beautiful McMenamins Edgefield. AGA symposia are small, friendly gatherings and provide wonderful opportunities for researchers and students to engage with one another and share their science. Details on the AGA website: http://www.theaga.org Key Distinguished Lecturer: Sally Otto, University of British Columbia, Canada Selective interference and the evolution of sex Invited Speakers: Matthew Hartfield, University of Edinburgh, Scotland Determinants of genetic diversity in facultative sexuals Laura Katz, Smith College Germline/soma distinction across the (eukaryotic) tree of life Stacy Krueger-Hadfield, University of Alabama, Birmingham What┬ ploidy got to do with it? Mating system variation in haplodiplontic algae Curt Lively, Indiana University Through the looking glass: host/parasite coevolution and sex Tanja Schwander, Universite de Lausanne, Switzerland Genomic consequences of asexual reproduction in animals Rebecca Zufall, University of Houston Amitosis and the Evolution of Asexuality in Tetrahymena ciliates Catherine Rushworth, UC Davis Disentangling the fitness effects of hybridization and asexuality in natural plant populations Jennifer Anderson, Uppsala University, Sweden Life history lessons from Neurospora crassa and other filamentous fungi Solenn Stoeckel, INRA Rennes, France The dynamics of genetic diversity in partially clonal populations Nadia Singh, University of Oregon Variation in Recombination Rate: Causes and Consequences Mercedes Burns, University of Maryland Baltimore County Maintenance of sex via geographic heterogeneity and facultative parthenogenesis in a Japanese harvestman Jeannette Whitton, University of British Columbia, Canada How important is male function in the maintenance of sex? Data from plant systems Oral Presenters (Short talks): Elora Lopez, Stanford University Patterns and frequency of variation among asexual clones in a long-lived coral species Karen Barnard-Kubow, University of Virginia Mechanisms and consequences of balancing selection in a model cyclic parthenogen Trung Huynh, University of Texas Arlington Differentially expressed genes between reproductive modes: a primer to identifying the genetic basis of facultative apomixis in Daphnia Sissi Donna Lozada Gobilard, Institute of Biochemistry and Biology, Potsdam, Germany Patterns of genetic diversity of plant species occurring in a metapopulation wetland system is explained by clonality rather than dispersal mechanisms Linnea Sandell, University of British Columbia Sex, drugs, and mating competition: effects of frequent outcrossing in Saccharomyces cerevisiae Jamie Schwock, Portland State University Somatic mutation and cell lineage selection during vegetative growth promotes rapid adaptation in plants Mark Smithson, Washington State University Epigenetic variation in asexual adaptation: explaining shell shape variation Karel Janko, Institute of Animal Physiology and Genetics, Czech Republic Why do animals abandon sex? On the interconnection between asexuality hybridization and speciation Anjanette Baker Anjanette Baker

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pantherwriterblogger · 4 years

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Find out the answer for What is apomixis? at #AskSawal Ask Sawal is a question answer discussion forum. You can find answers for more than 2 billion questions targetting more than 50000 topics.

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pantherwriterblogger · 4 years

Link

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pantherwriterblogger · 4 years

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Find out the answer for What is apomixis? at #AskSawal Ask Sawal is a question answer discussion forum. You can find answers for more than 2 billion questions targetting more than 50000 topics.

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margdarsanme · 4 years

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NCERT Class 12 Biology Chapter 2 Sexual Reproduction in Flowering Plants

NCERT Class 12 Solutions for Biology Chapter 2 Sexual Reproduction in Flowering Plants

QUESTIONS FROM TEXTBOOK SOLVED

13. Differentiate between:(a)hy pocotyl and epicotyl;(b)coleoptile and coleorrhiza;(c)integument and testa;(d)perisperm and pericarp.Ans:

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