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who-is-shades · 2 years

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Ok!

In the majority of species individual flowers have both pistils and stamens. These flowers are described by botanists as being perfect, bisexual, or hermaphrodite. However, in some species of plants the flowers are imperfect or unisexual: having only either male (stamens) or female (pistil) parts. In the latter case, if an individual plant is either female or male the species is regarded as dioecious. However, where unisexual male and female flowers appear on the same plant, the species is called monoecious.[20] Many flowers have nectaries, which are glands that produce a sugary fluid used to attract pollinators. They are not considered as an organ on their own.[21]

Inflorescence

Main article: Inflorescence

The calla lily is not a single flower. It is actually an inflorescence of tiny flowers pressed together on a central stalk that is surrounded by a large petal-like bract.[22]

In those species that have more than one flower on an axis, the collective cluster of flowers is called an inflorescence. Some inflorescences are composed of many small flowers arranged in a formation that resembles a single flower. The common example of this is most members of the very large composite (Asteraceae) group. A single daisy or sunflower, for example, is not a flower but a flower head—an inflorescence composed of numerous flowers (or florets).[23] An inflorescence may include specialized stems and modified leaves known as bracts.[24]

Floral diagrams and formulae

Main articles: Floral formula and Floral diagram

A floral formula is a way to represent the structure of a flower using specific letters, numbers and symbols, presenting substantial information about the flower in a compact form. It can represent a taxon, usually giving ranges of the numbers of different organs, or particular species. Floral formulae have been developed in the early 19th century and their use has declined since. Prenner et al. (2010) devised an extension of the existing model to broaden the descriptive capability of the formula.[25] The format of floral formulae differs in different parts of the world, yet they convey the same information.[26][27][28][29]

The structure of a flower can also be expressed by the means of floral diagrams. The use of schematic diagrams can replace long descriptions or complicated drawings as a tool for understanding both floral structure and evolution. Such diagrams may show important features of flowers, including the relative positions of the various organs, including the presence of fusion and symmetry, as well as structural details.[30]

Development

A flower develops on a modified shoot or axis from a determinate apical meristem (determinate meaning the axis grows to a set size). It has compressed internodes, bearing structures that in classical plant morphology are interpreted as highly modified leaves.[31] Detailed developmental studies, however, have shown that stamens are often initiated more or less like modified stems (caulomes) that in some cases may even resemble branchlets.[32][13] Taking into account the whole diversity in the development of the androecium of flowering plants, we find a continuum between modified leaves (phyllomes), modified stems (caulomes), and modified branchlets (shoots).[33][34]

Transition

The transition to flowering is one of the major phase changes that a plant makes during its life cycle. The transition must take place at a time that is favorable for fertilization and the formation of seeds, hence ensuring maximal reproductive success. To meet these needs a plant is able to interpret important endogenous and environmental cues such as changes in levels of plant hormones and seasonable temperature and photoperiod changes.[35] Many perennial and most biennial plants require vernalization to flower. The molecular interpretation of these signals is through the transmission of a complex signal known as florigen, which involves a variety of genes, including Constans, Flowering Locus C and Flowering Locus T. Florigen is produced in the leaves in reproductively favorable conditions and acts in buds and growing tips to induce a number of different physiological and morphological changes.[36]

The ABC model of flower development

The first step of the transition is the transformation of the vegetative stem primordia into floral primordia. This occurs as biochemical changes take place to change cellular differentiation of leaf, bud and stem tissues into tissue that will grow into the reproductive organs. Growth of the central part of the stem tip stops or flattens out and the sides develop protuberances in a whorled or spiral fashion around the outside of the stem end. These protuberances develop into the sepals, petals, stamens, and carpels. Once this process begins, in most plants, it cannot be reversed and the stems develop flowers, even if the initial start of the flower formation event was dependent of some environmental cue.[37]

Organ development

Main article: ABC model of flower development

The ABC model is a simple model that describes the genes responsible for the development of flowers. Three gene activities interact in a combinatorial manner to determine the developmental identities of the primordia organ within the floral apical meristem. These gene functions are called A, B, and C. A genes are expressed in only outer and lower most section of the apical meristem, which becomes a whorl of sepals. In the second whorl both A and B genes are expressed, leading to the formation of petals. In the third whorl, B and C genes interact to form stamens and in the center of the flower C genes alone give rise to carpels. The model is based upon studies of aberrant flowers and mutations in Arabidopsis thaliana and the snapdragon, Antirrhinum majus. For example, when there is a loss of B gene function, mutant flowers are produced with sepals in the first whorl as usual, but also in the second whorl instead of the normal petal formation. In the third whorl the lack of B function but presence of C function mimics the fourth whorl, leading to the formation of carpels also in the third whorl.[38]

Function

See also: Plant reproductive morphology

The principal purpose of a flower is the reproduction of the individual and the species. All flowering plants are heterosporous, that is, every individual plant produces two types of spores. Microspores are produced by meiosis inside anthers and megaspores are produced inside ovules that are within an ovary. Anthers typically consist of four microsporangia and an ovule is an integumented megasporangium. Both types of spores develop into gametophytes inside sporangia. As with all heterosporous plants, the gametophytes also develop inside the spores, i. e., they are endosporic.

In the majority of plant species, individual flowers have both functional carpels and stamens. Botanists describe these flowers as perfect or bisexual, and the species as hermaphroditic. In a minority of plant species, their flowers lack one or the other reproductive organ and are described as imperfect or unisexual. If the individual plants of a species each have unisexual flowers of both sexes then the species is monoecious. Alternatively, if each individual plant has only unisexual flowers of the same sex then the species is dioecious.

Pollination

Main article: Pollination

A Tūī, Prosthemadera novaeseelandiae, feeding on flax flower nectar, with yellow pollen on its forehead

Grains of pollen sticking to this bee will be transferred to the next flower it visits.

The primary purpose of the flower is reproduction.[39] Since the flowers are the reproductive organs of the plant, they mediate the joining of the sperm, contained within pollen, to the ovules — contained in the ovary.[8] Pollination is the movement of pollen from the anthers to the stigma.[40] Normally pollen is moved from one plant to another, known as cross-pollination, but many plants are able to self-pollinate. Cross-pollination is preferred because it allows for genetic variation, which contributes to the survival of the species.[41] Many flowers are dependent, then, upon external factors for pollination, such as: the wind, water, animals, and especially insects. Larger animals such as birds, bats, and even some pygmy possums,[42] however, can also be employed.[43][44] To accomplish this, flowers have specific designs which encourage the transfer of pollen from one plant to another of the same species. The period of time during which this process can take place (when the flower is fully expanded and functional) is called anthesis,[45] hence the study of pollination biology is called anthecology.[46]

Flowering plants usually face evolutionary pressure to optimize the transfer of their pollen, and this is typically reflected in the morphology of the flowers and the behaviour of the plants.[47] Pollen may be transferred between plants via a number of 'vectors,' or methods. Around 80% of flowering plants make use of biotic, or living vectors. Others use abiotic, or non-living, vectors and some plants make use of multiple vectors, but most are highly specialised.[48]

Though some fit between or outside of these groups,[49] most flowers can be divided between the following two broad groups of pollination methods:

*Fascinating!*

Yes, thank you very much!

#mystery person #shades?#utdr rp

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survivingcollegeonefanficatatime · 3 months

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biology 2

star wars, just as eddited as the last one (it's not) although I spelt Ahsoka's name rigt more often than before

After the first impromptu lecture, Ahsoka made plans for the event to be a regular thing. She’d passed her first exam, not exactly with flying colors, but with a wide enough margen she was sitting happily above class average. The entire 501st was ecstatic at the news and practically demanded to be a part of Ahsoka’s next ‘I forgot there was a test coming up and I need to study RIGHT NOW’ binge. The little Togruta had flushed in embarrassment, and tried to explain that she’d definitely host more of these events after each lecture rather than waiting until the last minute to go over everything at once…. Except…. She forgot. In her defense there was at least one battle and a minor mision she’d participated in after clases but that didn’t really change the fact that it was, yet again, the day before the exam, and Ahsoka was in a panic. So she took over one of the less used rooms on the Resolute and set up shop.

Rex was busy this time, having been claimed by Anakin to go over mission reports (read: write them for Anakin) and Pebble, Jesse, Shadow, and Pattern had been called away to do something or another but that still left Echo, Fives, Kix, Dogma, Hardcase, Suture, Leif, and Wraith behind. Ahsoka took a deep, steady breath, as she looked over the room.

“Unit two is about plants.” she explained “they originally came from protists if you remember them and can be divided into groups just like animals could be. Plants are multicellular, they’re eukaryotic, and are generally photosynthetic, so, in other words they typically eat light in order to get energy.” the clones' attention flicked into place, zeroing in on Ahsoka all at once.

“Phyte means plant, so you’ll probably see that affix show up a lot, and Sterpto means twisted, so the clade sterptophyes means twisted plants. After that is the kingdom Plantae, or land plants, so that means the stretophyes include some ocean plants, that said most ocean plants are not ‘true’ plants. Seagrass is, but uhhh anyways under plantae which are also embryophytes are the vascular plants, tracheophytes, and then the seed plants, spermatophytes, we can divide plants into green algae, bryophytes are nonvascular plants seedless vascular plants, gymnosperms and angiosperms.” Ahsoka took another breath, there was a lot to explain.

“Land plants came from green algae, they started their transition to land a long time ago, over 475 million years ago, like most things on the scale of planetary and biological time, it’s such a long time ago it’s almost impossible to imgen, does anyone know what some common features of land plants are?”

Echo spoke up. “You mentioned photosynthesis? So I assume that’s something they can do” Ahsoka nodded. She waited a few moments and was just about to continue when Kix spoke up.

“Cell walls?”

“Yeah, cellulose cell walls, chlorophyll which is the pigment that is involved with photosynthesis, and common enzymes, they have a common sperm structure and use starch to store carbon. well photosynthesis too but we already mentioned that.” nodes passed around the room “there’s a big difference between water and air, so plants had to compensate, one of the ways they did that was through tissues that came from something called the Apical Meristems which are growing tips. Plants are very diverse, and are often sessile, which means they don’t move a whole lot.”

The padawan szed, she was hardly a few slides in and she already had to get into her least favorite part of the plant section. She wrinkled her nose, why couldn’t plants be easy or at least easy to understand, why did they have to delight in being so strange. She steadied herself and jumped in.

“Plants are, annoyingly weird. They have a life cycle which honestly gives me a headache, but unfortunately, it’s real, and it's going to be on my exam so…. Plant life cycles. Plants can reproduce sexually, and they alternate between haploid and diploid phases, however both phases are multicellular, so basically an entire portion of their life, and this is called the ‘alternation of generations’ which is a headache and a half to deal with.” The men smiled, a few huffed breathless laughs. Ahsoka wished it was as amusing to her as it was to her men. She used the force to flick on a holo projector, a different kind than the one she used last time, and pulled her stylus out. With a gesture the projector forms lines around where she draws. A circle appears in the air.

“Alright, the alternation of generations is going to get a lot more complicated but let’s start with something simple.” Ahsoka writes ‘gametophyte’ at the top of the circle, and ‘sporophyte’ at the bottom. She takes a breath and starts filling in steps, mitosis after gametophyte, then fertilization, mitosis again, the sporophyte and a longer gap to meiosis before mitosis hits and the circle completes with gametophyte. To finish the circle off Ahsoka draws a horizontal line though the middle, between fertilization on one side, and meiosis on the other, on the top, towards gametophyte she writes ‘haploid’ and on the bottom ‘diploid’

“We’re going to start with this mitosis' ' she points towards the word that directly follows ‘gametophyte’ and it lights up as she tapps the stylus to it. “O wait, uh first, Gametophyte is the word for the haploid multicellular part and sporophyte is the diploid multicellular part. A good way to remember that is that the Sporophyte is the Diploid generation, there’s this holo-vid franchise Master Obi-Wan likes, and his favorite sub-series in the franchise is called Digital Space nine or DS9, so DS--diploid sporophyte.” Ahsoka huffed out a breathless laugh, it was a stupid way to remember but it worked well, Anakin had never been all that much of a fan of ‘digital voyage’ he was much more interested in the more action focused ‘distant conflict’ but Ahsoka liked both, and if using Obi-Wan’s interest in media with a heavy dose of political drama helped her pass her exam then she’d use it.

The togruta blinked and continued “Anyways, uh mitosis, the gametophyte made a haploid gametes via mitosis oh and haploid cells cannot undergo meiosis because meiosis is the process of a diploid cell splitting into haploid cells and you can’t do that without a diploid cell. Anyways, after the gametophyte makes haploid gametes the gametes fuse to make a zygote” Ahsoka moves her pen to highlight ‘fertilization’ then slowly moves her pen to the next ‘mitosis’ as she speaks “this zygote develops into a diploid Sporophyte” she traces the circle, passing over the sporophyte as it’s more the product of something than a step in and of itself. The next word highlighted is meiosis “the sporophyte which has made haploid spores can undergo meiosis which transitions the plant from diploid to haploid, or at least leads to it, because the final step has spores germinating and dividing to make the haploid gametophyte”

“That seems complicated” Leif huffs Ahsoka and can't help but nodd, and it will only get worse as they pass through the lecture. She’s already dreading angiosperms.

“Despite its seeming complexity we can compare this to the reproductive cycle of naboo's native sapients. which do technically have a haploid stage, but the main difference here is that the plant generation is multicellular and also more confusing.” the little jedi paused for a moment, she basked in the amusement that flickered through the small crowd.

“Sperm and eggs are unicellular, so despite being haploid they’re not like plants. It’s also worth pointing out that where gametophytes--the haploid generation--reproduce sexually, sporophyes--which are diploid--repoduce axesually. That may also be confusing considering they're both sorta involved in sexual reproduction but…. That’s just how plants are.” Ahsoka waved her stylus dismissing her little doodle, she tapped it against the datapad that rested on her arm, and flicked upwards, transferring the diagram from her notes to the air in front of her.

“Over time, or rather, with evolution the gametophyte--haploid--generation has become more prominent, conversely the diploid, or sporophyte generation has gotten less prominent. This means that bryophytes have a large gametophyte generation and a much smaller sporophyte generation. Vascular seedless plants have a larger sporophyte generation, and smaller gametophyte generation, and angiosperms have even smaller gametophyte generations.” she gestured to her diagram, highlighting the generations in different colors, it demonstrated the way the gametophyte generation got smaller over time.

“Plants, as I mentioned had to overcome some challenges when coming to land. Start thinking about what those challenges might be, we’ll go over an official list later but for now I just want you to come up with a few on your own.” She paused for a few beats “one of the ways plants had to adapt was the creation of sporopollenin, which is a resistant polymer that protects spores and pollen, this helps them prevent drying and decay. On land plants need to survive in a way that means they won’t dry out. Creating spores is one way they do that. There are special structures, called sporangia, that help plants make, protect and send spores out. This is important for land plants. Te gametangia do the same but for gametes. This makes it fairly easy to remember, spores come from sporangia, gametes come from gametangia. The gametangia are one of the key adaptations of land plants, as I mentioned they help prevent the plant from drying out. There are also the antheridia which are haploid and produce sperm, and the archegonia which are also haploid and produce eggs. Young plants also come in embryos, that are inside a protective structure, if you remember the land plants were also called embryophytes, this is why, green algae don’t have embroeos but alnd plants do. Individuals that are larger diploids produce more spores, this is why a lot of plants have chosen to grow up.”

“There are nine phyla of land plants. The first three are bryophytes which are nonvascular plants, these are liverworts, mosses and hornworts. Seedless vascular plants have lycophytes, and pteridophytes, then the gymnosperms have cycads, ginkgos and conifers, finally the angiosperms just have angiosperms. I’m going to go over all these phylums so we can learn a little more about them. The bryophytes could be a clade, anyone remember what clade means?”

“It’s a group that includes a common ancestor and all its descendants right?” Wraith asked, Ahsoka nodded.

“So bryophytes might be a clade, they’ve got mosses, liverworts, and hornworts which are all monophyletic phylums, which means?”

“A group with only one phylum, which is similar to a clade but not quite” Dogma added.

“That’s right! All three bryophytes grow in damp environments and are nonvascular, they don’t have roots and they don’t produce seeds. They’re very early on the timeline of plants, and they’re gametophyte or haploid dominant, if you remember simple plants are more often gametophyte dominant. And they also introduce us to our second plant life cycle chart!” Ahsoka cimed with mock enthuseasum, her men groaned, already starting to see the pattern. “Don’t worry, this one’s more complicated!” The smile on her lips did nothing to prevent the glare that Gives leveled her with.

Once again Ahsoka took her stylus and held it to the air. After a second she decided to fill this one in as she went. First she drew a tallish structure, and labeled it as the gametophyte, the top of which was the gametangia ``this will split into two paths, one of the archegonia, and one to the antheridia, what were those again?”

Leif perked up “the archegonia is where eggs are produced, it's the female part of the plant, and the antheridium is where sperm is produced, it’s the male part of the plant!”

“Perfect!” Ahsoka doodled with little structures, then drew them slightly larger and indicated that the two plant parts were in water. “In bryophytes water is necessary for sexual reproduction, this is because the water helps the sperm flow from the antheridium to the archegonium so federalization can take place.” she drew an arrow from the doodle and labeled it ‘ferelization’ she then drew the archegonium again, only this time, instead of drawing a little ball for the egg, she drew it with the opening closed, and a bundle of cells that were slightly larger than the egg had been in its place. “This is where the diploid or sporophyte generation starts. And in mosses theory grow a sporangium, to house spores right from the archegonium, it rises up in stalks” she drew the sporophyte form of the moss, then an arrow from it, and wrote meiosis, before drawing the sporangium opens with little dots escaping it, she labeled these ungerminated spores. Then she drew a few sketches in quick succession, between each arrows were drawn. From the ungerminated spores to a germinating spore to a bid placed on a protonema and a rhizoid, to that bud growing larger and then the circle completed back at the gametangia. “As you can see the haploid or gametophyte generation is larger, with the diploid stage only taking up a single step. You can also see that the steps are quite similar to the previous example, only there’s a bit more going on.” several men were squinting at her doodle, a small line of frustration or confusion clear on their faces.

“Clear as mud, Sir.” Hardcase huffed, causing Ahsoka to snort.

“That’s about how I felt about it” the togruta admitted, unfortunately my exam is coming up and I need to at least attempt to understand this mess, so moving on to vascular plants, horsetails and ferns, or lycophytes and pteridophytes” Echo held his hand up.

“Yes?”

“Does Not pterid just mean fern?”

“Huh yeah I guess it does, so that makes it easy enough to keep track of this one . These were the earliest plants to process stems, roots , leaves and a vascular system. They had to use lignified cells to gather straight to fight against gravity. The vascular tissue system has xylem which carries water. These cells are dead at maturity and will form sort of… empty tube like structures, then there’s the phloem which is alive at maturity and transports carbohydrates and other such neuterants. To be honest it’s not so much that the phloem is alive that the companion cells are but it’s still alive enough to count. There are consequences to having a more structured and strengthened vascular system, anyone got any ideas as to what they may be?”

“They can get bigger? If they've got more strength then they’ll probably grow larger, and you said that larger plants can send their spores farther.” Dogma phrased his words like a question.

“Yeah, they can get bigger, in some dryer environments especially, in peat bogs you may not need to have such massive plants because the water is closer to the ground, this will leave them mostly as grasses but in some larger forests you can maintain stable water content and get very big. Vascular plants also maintain stable internal water content because they have a waxy cuticle and stomata, the cuticle is a coating outside the cell that limits water loss, and the stomata is a closable opening that regulates water loss and gas exchange. Lycophytes and prediophyes are diploid or sporphyte dominent” Ahsoka took a deep breath, how she was still in the first lecture was beyond her, but she still had so much to cover. She swore it didn't take quite so long to cover everything the first time around, but then again, she understood the first unit more than she understood the second one. Growing a little frustrated she let emotions over her, and jumped back into her lecture.

“After vascular systems seeds showed up, these appeared in gymnosperms, which just means naked seed, because the seeds are uncovered. In this case the seeds protect the embryos and have chemicals that help plants grow and develop. In this case gymnosperms include cycads, ginkgos and gnetophytes and conifers, which lack flowers, fruits, and endosperms. In these plants the eggs and sperm are usually contained in cones, with te male cones being much smaller than the female cones. After that we have angiosperms which are covered seeds or seeds within vessels, they’re flowering plants. They’ve replaced gymnosperms as thedomente plants on Naboo. They make flowers fruits and endosperm they also have wood ovules seeds and pollen. As well as xylem and phloem. If we go back to gymnosperms there are a few of them, cycads which are the oldest phylum and are endangered, like a lot of species on Naboo. The planet as a whole is facing a mass extinction event, and current top scientists are working to help them prevent it from worsening. Regardless, the second group is the Ginkgo which only really remains as the ginkgo biloba, it's almost extinct in the wild and is often used for decoration. They can live for over a thousand years but every modern one was grown in captivity. Conifers are easy to remember because they’re named for their seed cones, and modern conifer families have more than 50 genera, they often appear in cold and dry climates, and are commonly referred to as pine trees, they’ve got needle leaves and are often evergreen. These are going to be our next life cycle!”

“Let me guess?” Fives called “it’s even more complicated than the last one?”

“So you’ve noticed the trend huh?” Ahsoka asked

“Unfortunately It was fairly clear from the start that this was only going to get more confusing.” Kix admonished. The padawan nodded and groaned, she quickly realized she hadn’t waved away her last chart and tapped it away. Then she looked down at the datapad in her arm, she had no idea who she was supposed to transfer the mess of a chart in her notes to something she could explain. If she was being honest it was so busy she struggled to read it in places. Still that didn’t change the fact that, fundamentally, it held the same steps as the others, so she took a deep breath and held her stylus to the air. “Sporophyes produce ovule cones and pollen cones” Asoka explained as she doodled a conofer, she wrote mature spophye next to it, then drew two arrows one to the ovule cone and one to the pollen cone, “this is where the paths split, in ovule cones emaspores are made by meiosis within the megasprangia, in pollen cones microspres are produced by meiosis within the microsprangia” she drew the larger cone and labled it, then followed the ovole cone, following the path by drawing a megaspora dn megasoprangim with scales, she proceed to draw an egg, and spoke “in ovoule cones megaspore onder go mitosis and produce female gamaphotes these have eggs and are in the achregnonia, the entire structure includes the oter integers and each of the cones has two ovoles” she labled the drawing with the intergument the female gametophye, the megasporangium and the archegnonium, then she drew a diagram of the polen grain entering the ovule “pollen grains are dispersed into the wild and will encounter ovules” from there the last drawing on the ovole path was a male gretophtye, she then returned to the pollen cone, and traced it’s path, staring with mitosis “in pollen comes micorpsores undergomitosis develop into pollen grains which are young male gemotphyes” she then drew the pollen grains that would fly away form the microsprangium, te two arrows met back up under the label of ferterlization, “the pollen tube delivers sperm to eggs where fertalization occures, only one egg per ocule is fertalized” she wrote mitosis next, and continue d”the zygote produces and embryo in a seed, amtrue seeds are then dispersed” the embryo was abled 2n, and finally Ahoka drew a scale, withcontained seeds “seeds germinate and embroidery sporophytes grow into seedlings” the last thing she drew was a seedling. The togruta huffed and moved on.

“Conifers also include gentiles, a gentum, and ephedra, they also include welwitschia which only has one living species and angiosperms have flowers.” she grinned as she waved away the image on the projector, and shifted it to images of flowers she gestured to a ball-looking plant that was made up of a collection of flowers

“An inflorescence is a group of flowers! And umble is one pod of a group of flowers, there are also flowers that look like they’re only one flower but in reality they have ray flowers at the edges and disk flowers inside” she waved towards the image of a red flower with the center surrounded by little yellow blooms'' her smile was genuine she loved the way those flowers looks

“Flowers have a bunch of parts” she explained and gestured to the flower diagram “the stamen contains the male parts of the flower and contains the anther and filament, the pistil contains the female part and has the stigma style and ovary, then there’s the perianth, which ahs the petal and sepal” Ahsoka waved away her diagram and continued “carpels are also what bear the female megasporangia, although Pistil is also sometimes used but I think the pistil is more spsuficalc. And carpels is just the general term. Statements don’t have a more general term, a perfect flower has both megasporangia and microsporangia, so male parts and female parts.”

“Like--” someone called and was instantly cut off by noise

“We’re talking about plants right now” Ahsoka emphasized with a roll of her eyes. “Plants which are monoecious have both male and female flowers on the same plant, mono-one so one plant, whereas diecious have male and female flowers that are on different plants, a monoecious plant can be perfect or imperfect but a dioecious plant cannot be perfect. Plants also go through something called double fertilization, this basically means that a male gametophyte will end up fusing with two cells both the egg and gametophyte nuclei” Ahsoka huffed she could have made another plant life cycle chart but this one was fairly simple and she was tired.

“There are two main types of angiosperms, monocots and dicots which will be referred to as dicots, I’m not sure why they have two names but they do. Anyways here’s some difference, the monocots have onle ctyledon and includes grassees cattails lilies orcheds and palms, whereas the dicots have two cotyledons and are most species of seed plants, or at least the familiar ones.'' The padawan took a breath, and wrapped up the first lesson.

“Flowers have a lot of variation, monocots and dicots are included in this, dicots often have organs in sets of 4 or fives, whereas monocots often have flower organs in mutables of fress. There are variations of shape because of this and flowers can have radial or bilateral symmetry, like like animals could plants also have their own life cycle diagram we have to cover” and the room groaned, Ahoska couldn't help but huff in amusement, at least her mene didn’t need to take an exam about it tomorrow she was getting increasingly nervous about the whole office.

“It’s similar enough” she said waving her stylish, she drew a circle and labeled the top diploid and the bottom half lid. “If you remember, angiosperms are sporophyte dominant. So the diploid stage is bigger” she explained as she drew a little flower at the top, she labeled the ovary ovule and anther, then drew the male sporangia much larger, and drew a microsporocyte common from it, she also drew the megasporocyte much larger next to it. “The sporangia surround the gametes, and after meiosis there are 4 microspores” she drew this and then drew the pollen grain landing on the gametophyte, she made a little wiggle down from the plen grain and reaching towards the egg “they make a spleen tube so the sperm can travel from the pollen to the egg” she drew this and then traced an arrow away from it and wrote double fertilization “double fertilization is when thee ends up with an endosperm nucleus and a zygote this then develops into a seed and seedling and back around it goes.” she was scared, and continued.

“In meiosis there end up being 4 haploid megaspores, which make 3 megaspores degenerate and leave one megaspore behind, it undergoes mitosis three times and ends up with 8 haploid cells, then two dissolve and we geta 7 celled female gametophyte” the men huffed at her, confused but said nothing. She moved on to seeds ``dicots seeds often have an epicotyl which is a portion of the embryonic stem, seeds can become dormant and dry, but they do need water to sprout. Monocot and dicot seeds are different. Monocot seeds have an epicotyl within a first bud, they’ll typically shoot up straight from the seed. Fruits are basically ovaries that form around the seeds, although sometimes they come from other portions, they’re designed to help with seed dispersal, to attract animals or some other such thing.” the second chapter had gone much faster than the first so Ahoka smiled as she wrapped it up “plants can also have asexual reproduction, some roots stems and leave can function as reproductive structures, and somatic embryos can develop at the edges of plants, that’s not to emotion apomixis which is where fruits and seeds are produced in the absence of fertilization. Once again Ahoska took a breath and moved on, there was more to deal with flowers.

“Here’s some of the differences between monocots and dicots, the embryos of monocots have one cotyledon, they have scattered vascular tissues in their stems and their leaf veins are usually parallel, they’ve got fibrous roots and have floral organs in sets of threes. Whereas dicots have cotyledons, vascular tires in a concentric circle, veins that form a network, a taproot and flowers in multiples of four or five organs.” she yawned despite herself, and moved right along “plants have distinctive architecture, they have a shoot system which are the leaves and stems and also a root system.”

“Let me guess, that contains the roots?” Fives snarked

“Yeah, got an idea of what the roots do?”

“They help the plant get water and nutrients?” Echo offered

“They act as stabilizers?” Wraith asked.

“Yes to both they also store the products of photosynthesis and increase surface area. Primary growth is lengthening of shoots and roots whereas secondary growth comes later and is an increase in thickness.”

“There are also different types of tissues in plants, there’s the parenchyma which are the most abundant and have thin cell walls, they can photosynthesise the collenchyma which have thick cell walls and provide support then there’s sclerenchyma which have thick cell wall reinforced with lignin. We already covered the xylem and the phlegm so I’m not going over that again. Going back to the monocot vs dicot dichotomy we can see that monocot stems have vascular bundles that kinda look like little faces, and their roots are kinda circular whereas the stem from dicots form a lateral ting and look more like ovals whereas their roots form a distinctive x shape roots have a pith xylem phloem a previccle endodomers a cortex and epidermis, although a monocot root salsa has a stele” she sighed

“We’re moving on to angiosperm nutrition, remember angiosperm means covered seeds so it’s stuff that has its seeds covered, this is the group that includes flowers. Now plants, well most of them, are autotrophs. They have limiting factors, light for energy, carbon fixing from the atmosphere, hydrogen and oxygen from water, nitrogen from the soil well from the bacteria and fungi and also phosphorus and other such mineral nutrients. That said, not every plant is an autotroph, there are some parasitic plants, which I think are pretty neat. Ahsoka flicked her wrist and prompted the projector to display a list “here’s some essential elements that plants need, they can be divided into macronutrients and micronutrients, which means the plants need at least one g per kg of dry plant mass. These include carbon which is a component of all organic columles, and oxygen which is also a component of organic molecules, and hydrogen, they also need nitgorgen while we’r ein the acronym they also need phosphorus and sulfur, if you remember the acronym CHNOPS carbon hydrogen nitrogen oxygen phosphorus sulfur then you remember that living things need CHNOPS, although plants also need potassium which is important in iconic ballance, calcium which is a component of cell walls and magnesium which is a part of chlorophyll. Plants also need micronutrients less than .1 g per kg, these include chlorine ironmagnesese boron zinc sodium and copper, fertilizer can provide these nutrients but you don’t want to add too much or it may result in blooms'' with a Sigh Ahsoka continued “soil is important for growing plants, they have a lot of comprent, living things like plant roots bacteria and such and nonliving things like rock fragments, it’s important to understand the difference in types of soil they have sand which is the largest piece, silt which is smaller and clay which is the smallest, it also has bacteria, fungi, roots and root hairs, and air and water. If the soil is too thick with water plants can die. Soil with organic matter is called humus, and humus which is a good food sources, there are also types of sil, sandy soil which is proosu and allows air and water, silty clay souls which retain more water and minerals and loam soils which combine the aeration benefits of sand with the water and iron retention of silty clay soils, soils are also a part of nitrogen fixation because mycorrhizae is a fungus that grows on the roots of plants and helps the plant get nutrients, there’s also nitrogen fixing nodules which are bacteria in a symbiotic relationship with plant roots. Nitrogen must be fixated, going from atmospheric nitrogen to NH4+ or ammonium, then from that to NO2 and then NO3 then from there to organic nitrogen and then to ammonia and then NO3 back to atmospheric nitrogen, this process has steps called Nitrogen fixation nitrification assimilation ammonification and denitrification. Nitrogen fixing nodules are bacteria this is because bacteria is the thing that can fix nitrogen.” Ahsoka scrolled on her datapad for a few moments before she continued

“We also need to cover diffusion, osmosis is diffusion but with water, there’s also facilitated diffusion that flows through a specific transport protein path and then active transport that requires energy. Secondary active transport requires energy in the first step but not in the second. There’s also three tissue level transport forms, the first is transmembrane, the second is symplastic which is like using the slow lane and then apoplastic which is much faster plants use bulk flow to transport water, bulk flow occurs using negative pressure and this is called the cohesion tension theory this is kind of like a straw, when water evaporates it creates a negative pressure and sucks more water up into its place, this is happening nearly constantly and allows the plant to transport water through its body with extreme efficacy. There are three factors to this, transportation cohesion and tension. Blue light is absorbed by a guard cell and activates H atpase, which then pumps protons and K and CL enter guard cells, then water enters by osmosis and increases turgor pressure which opens the stomata, so during the day water is transferred much faster. Some plants have adapted to drop all their leaves when water is unavailable so they can preserve water and not let it evaporate too fast. This can also happen seasonally in a process called leaf abscission.”

Finally she was onto the last lecture. This whole thing had been exhausting, and although there wasn’t nearly as much content as there was last time, it was still so much to cover.

“Plants have behavior” the little jedi announced “they can respond to changes, environmental cues like day lengths, they use receptors to sense environmental cues, and hormones for chemical signals, some of the plant behaviors include shoots growing towards the light or roots growing towards gravity, seed germination, seasonal flower production or protective responses cell communication happens by receptor activation, signal transduction and then cellular response. We also need to go over a list of hormones and what they all do.” with a breath Ahsoka pulled up her list “Auxins establish optical basal polarity, they’re often called a control hormone because they encourage a lot of stuff, they promote formation or doors and himiti leaf and fruit drop, they also help with fruit development, cytokines promote cell division and inference cells cephalization, gibberellins stimulate cell decision, and stem elongation and flowering, ethylene is the reason fruit goes bad so fast, it promotes seedling growth induces fruit ripening and plays a role in leaf and petal aging, abscisic acid slows or stops metabolism during stress it also induces bud and see dormancy and prevents germination in unfavorable condition brassinosteroids promote cell expansion”

“The effects of auxins can make plants bigger or taller, they can also help with phototropism, and gravitropism, so in other words movement, although auxins can inhibit cell elongation. In a curve the cells that elongate are on the outward edge. Cytokines are a part of cell division and they increase cttokensisis which is an important factor. Gibberellins are similar to dioxins but they also promote fruit growth and seed germination. Gibberellins are sprayed on fruits to get more product out of them. Ethylene is a gas and it promotes ripening, it’s how some fruit ripens and goes bad so fast. It also is involved in a positive feedback loop so the release of some amount of ethylene encourages more ethylene, ABA or abscicic ascid stops plant botabalsisum and bratheostariods induce vacule water intake and foster cell expansion.”

“Seeds can germinate in the presence of light, Pr absorbs red light and Pfr absorbs far-red light, if the sun is out then there’s plenty of red light and Pr switches to Pfr so the plant can germinate, in the presence of far red light the reverse happens plants can also respond to touch and curl up in a really cool way, plants are also chemical weapons, and they defend against predators by releasing a volatile chemical which then prompts the rest of the plants to produce the volatile chemical” Ahsoka paused for a moment, remembering the anecdote her professor had told her “scientists found this out during an experiment where they decided to simulate predation by getting a bunch of plants and whacking a few with a broom, or at least that’s the story I was told.'' There was laughter in the room, and the padawan took a breath before continuing. “There’s also ways for plants to defend against pathogens, plant pathogens produce compounds known as elicitors which promote infection they can feel these chemicals through the use of receptors, and then they can use mRNAs to destroy the nucleic acids and well as chemical defenses, these things can change things like strengthening plant cell walls, programed cell death or producing a compound that will kill the pathogen. A hypersensitive response is a local reaction to a pathogen attack that’s supposed to limit the progression of the disease, they can kill pathogens or stimulate the synthesis of chemicals, or induced programed cell death, killing sections to stage out the pathogen and protect the rest of the plant a systematic acquired resistance is an immune response of the WHOLE plant.” with a smile Ahsoka realized that she’d reached the last of her slides, and slumped in releaf.

“That’s all for now, with any luck I’ll pass this exam!” she chimed.

#college #study fic #wiring

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