#tropisms

[dabiconcordia]

“Tell me why the stars do shine, Tell me why the ivy twines, Tell me what makes skies so blue, And I'll tell you why I love you. Nuclear fusion makes stars to shine, Tropisms make the ivy twine, Rayleigh scattering make skies so blue, Testicular hormones are why I love you. ” ― Isaac Asimov

[biostudyblog]

Plant Facts! Part 2

There are 3 main types of plant tissue:

Dermal tissue- the outer protective coating. This is usually made up of a single layer of epidermal cells. The cuticle then covers this tissue with cutin. Some leaves also have spikelike projections called trichomes. The epidermis typically does not have chloroplasts, however guard cells are a noteable exception to this rule.

Vascular tissue- this tissue transports water and nutrients. There are 2 kinds: xylem (made of tracheids and vessel elements) and phloem (made of sieve tube elements and companion cells) more on them later.

Ground tissue- This includes all tissue that is not encapsulated by dermal or vascular tissue. There are 3 major types: parenchyma, collenchema, and sclerenchyma cells.

Parenchyma cells resemble the traditional plant cell. They add support and are found as mesophyll cells, epidermal cells etc. Collenchyma cells do not have secondary cell walls. A noteable example are the strings on celery. Sclerenchyma cells have thick primary and secondary cell walls, with the addition of lignin. They exist purely for support.

Xylem

As mentioned before, xylem is made of tracheids and vessel elements. The secondary cell walls have the addition of lignin to provide support. Xylem makes up wood. Xylem carries nutrients and water up from the soil without energy. They do this via transpirational pull and cohesion tension. Cohesion is the tendency of a molecule to be attracted to itself.

The transpirational pull-cohesion tension theory says: For each molecule of water that evaporates from a leaf by transpiration, another molecule is drawn in by the root to replace it.

How weather impacts transpiration:

High humidity slows transpiration

High wind increases transpiration

Increased light intensity increases transpiration

(Not weather) Closed stomates stop transpiration

Phloem

As mentioned before, phloem is made of sleeve tube elements, and companion cells. It transports sugar from the leaves to the plant body via translocation. This process requires energy.

Plant Reproduction

Firstly, plants can reproduce asexually. They can clone themselves, or use a method called vegetative propogation. This is noted in grafting, cuttings, bulbs, and runners.

Flowers are the sexual organs of the plant. They are hemaphrodites, meaning they contain reproductive organs of both males and females.

My diagram is very messy. I’m very sorry. I’ll probably fix it at some point.

Pollination marks the beginning of reproduction. 1 pollen grain contains 3 haploid nuclei. 1 is a tube nucleus and 2 are sperm nuclei. The pollen grain attaches to the stigma. It germinates, creating a tube running down the style, into the ovary. The sperm will enter the ovule bia the micropyle. One sperm will fertilize the egg and become the embryo (2n). The other will fertilize the polar bodies, to become the triploid endosperm/cotelydon. (3n) This is the food for the embryo. This process is known as fertilization.

The ovule becomes the seed, and the ovary becomes the fruit. In monocots, the food remains in the endosperm? however in dicots, the food reserves are moved to cotelydons. The embryo is made of 3 parts; the hypocotyl, (the lower stem/roots), the epicotyl (the upper stem) and the radicle (embryonic root, the first to emerge from the seed)

The sexual lifespan of a plant is marked by the alternation of generations, meaning it alternates between the haploid generation and diploid generation.

The gametophytes (n) produce gametes that fuse during fertilization to become (2n) zygotes. Each zygote becomes a sporophyte through mitosis, which become haploid spores through meiosis. Via mitosis, each haploid spore becomes a gametophyte.

Here’s some vocab !

Antheridium- Structure that produces sperm, develops on the gametophyte

Archegonium- Structure that produces eggs, develops on the gametophyte

Gametophyte- Haploid adult plant

Megaspores- Made by female cones, become female gametophytes

Microspores- Made by male cones, become male gametophytes

Protonema- Branching, 1 cell thick filaments, made by germinating moss spores, become the moss gametophyte

Sporangia- Found on the tip of a mature sporophyte, where meiosis occure, creating haploid spores

Sporophyte- Diploid adult plant

Sori- Raised sports under sporophyte ferns, clusters of sporangia

In bryophytes like moss, the gametophyte is the dominant generation. The sporophyte receives its nutrients from the gametophyte generation, which gains its nutrients from photosynthesis.

In seedless, vascular plants, like ferns, the sporophyte generation is much larger than that of a bryophytes, and is independent. Both generations sustain themselves via photosynthesis

In advanced, vascular, seed plants, the sporphyte generation is much more dominant. In angiosperms, the gametophyte generation exists within the sporophyte generation and completely depends upon the gametophyte generation. In gymnosperms, the gametophyte generation comes from haploid spores within the sporangia.

Plant Hormones!

Hormones are responsible for coordinating growth, development, and response to stimuli. Some noteable hormones are:

Auxins

Phototropisms (a plants tendency to lean toward light) occur due to an unequal distribution of auxins

They enhance apical dominance (the tendency of a plant to grow vertically, not laterally). The terminal bud suppresses lateral growth by suppressing the growth of axial buds.

They stimulate stem elongation and growth by softening the cell wall

They were the first plant hormone found

Includes Indoleacetic acid (IAA) -naturally occuring and 24-D - man made weed killer

They are used as rooting powder as they help roots develop quickly.

A man made form of auxins are sprayed on tomato plants. This induces fruit production without fertilization, thus creating seedless tomatoes (yum)

Cytokinins

As the name suggests, cytokinins induce cytokinesis and cell division.

They delay senescence (a nerdy way to saying aging) as they inhibit protein breakdown.

Gibberellins

Gibberellins promote stem and leaf elongation.

They induce bolting, which is the rapid growth of a floral stalk. This is something commonly seen on plants like broccoli, where the plant will rapidly shoot out of the ground.

Abscisic Acid (ABA)

Along with sounding really freaking cool, abscisic acid halts growth, closes stomates and causes seed dormancy

This is useful during times of great stress such as during a drought.

Ethylene

Ethylene is a gas that induces ripening (and rotting). It also stimulates the production of ethylene in other plants. Basically, they make things great for everyone, but also spoil everything (mood)

Finally: tropisms. Tropisms are when plants move away from or towards a stimulus. Some examples are : thigmitropisms (touch), geotropisms/gravitropisms (gravity), and phototropisms (light)

So how do auxins cause phototropisms? Auxins build up in the shaded part of the plant. They induce growth, thus the plant grows and becomes heavy on the shady area. Thus the plant will bend.

Geotropisms are caused by the interaction between auxins and statoliths (specialized plastids containing dense starch grains)

[robertsmithsonlibraryandbookclub]

Untitled Project: Robert Smithson Library & Book Club [Sarraute, Nathalie, Tropisms, 1963] Oil paint on carved wood, 2018

[greeniezona]

For International Women’s Day, a stack of #womenintranslation. This year I decided to restrict myself to books I’ve read and loved. I would enthusiastically recommend any of the books in this stack. Leave a comment if you see a book here you’d like to know more about! Or if you’d like me to pick one of these in particular to recommend to you. . . #nathaliesarraute #tropisms #mariajolas #cheri #thelastofcheri #colette #labastarda #trifoniamelibeaobono #lawrenceschimel #hildahilst #withmydogeyes #adammorris #kitchen #bananayoshimoto #meganbackus #memoirsofapolarbear #yokotawada #susanbernofsky #onlyinlondon #hananalshaykh #catherinecobham #thevegetarian #hankang #deborahsmith #thetenthousandthings #mariadermoût #hanskoning #sanaaq #mitiarjuknappaaluk #bernardsaladindanglure #peterfrost #translatedfiction https://www.instagram.com/p/BuwCoLFH-_-/?utm_source=ig_tumblr_share&igshid=10ou1a4sjr0lv

[greeniezona]

I missed a few days because the back-to-school crunch crunched me. But I’m back today with a little gem I discovered in a local used book store. To be honest, I picked it up nearly entirely for the book design, as I’d never heard of it before and am often extremely picky about short stories. But these are less short stories and more extremely distilled moments of emotion. . . #womenintranslation #womenintranslationmonth #witmonth #tropisms #nathaliesarraute #newdirectionspearl #mewdirectionspress #translatedfromfrench #mariajolas #translatedfiction #booksandtea

[cosmoread-blog]

Political

Tropisms: political offenses erode voter confidence

Donald Trump

#cosmoread: Heart, politics is a war of words. And sometimes, pithiest phrases made the biggest impact.

Donald Trump is shown as the primary drive, pounding offense stature between supporters of a candidate, another factor in the resonance chambers that social media can play out more strongly than ever to increase. Unfortunately,…

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