T.+Angiosperms+Responses+(39)

= __**Angiosperm Response to Internal and External Stimuli (Chapter 39: Sections 39.2 - 39.4) **__ toc=

Quick Quizzes covering Most of the Basics:
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**Plant Hormones and their Functions**
**__Auxin:__** This hormone is present in the seed embryo, young leaves and apical buds meristem Functions: **__Cytokinin:__** Cytokinins are synthesized in roots and then transported to other plant parts Functions: **__Gibberellin:__** The gibberellins are present in the meristems of apical buds and roots, young leaves, embryo Functions: **__Abscisic Acid:__** Absicisic acid is found mostly near leaves, stems, unripe fruit Functions: **__Ethylene:__** Ethylene is present in the tissues of ripening fruits, nodes of stems, senescent leaves and flowers Functons:
 * Stimulation of cell elongation; cell division in cambium, differentiation of phloem and xylem, root initiation on stem cuttings, lateral root development in tissue culture
 * Delaying leaf senescence
 * Suppression of lateral bud growth when supplied from apical buds
 * Inhibition or promotion of fruit and leaf abscission through ethylene stimulation
 * Fruit setting and growth is induced through auxin in some plants
 * Auxin can delay fruit ripening
 * In Bromeliads, the auxin hormone promotes flowering
 * Stimulation of flower parts, femaleness of dioecious flowers and production of high concentration of ethylene in flowering plants.
 * Stimulation of cell division, growth of lateral buds and apical dominance
 * Stimulation of shoot initiation and bud formation in tissue culture
 * Leaf cell enlargement that stimulation of leaf expansion
 * In some plant species, enhancement of stomatal opening
 * Etioplasts are converted into chloroplasts through stimulation of chlorophyll synthesis.
 * Stimulates stem elongation
 * Gibberellin can lead to development of seedless fruits
 * It can delay senescence in leaves and citrus fruits
 * It can end seed dormancy in plants that require light for induction of germination
 * Stimulation of closing of stomata
 * Inhibition of shoot growth
 * Inducing seeds for synthesizing storage of proteins
 * Ethylene leads to release of dormancy state
 * It stimulates shoot and root growth along with differentiation
 * Leaf and fruit abscission
 * Flower induction in Bromiliad
 * The femaleness of dioecious flowers is stimulated
 * Flower opening is stimulated
 * Flower and leaf senescence stimulation
 * Fruit ripening is stimulated by ethylene

This is an organized chart with the plant hormones and their organized functions organized by organ/structure affected.

This is a link to a quick summary of the functions of each of the 5 plant hormones. (if not accessible, copy+paste [])

Quizzes
Quiz Yourself With This Quizlet - LOTS of information in Definitions! [|If you want good flashcards, click here!] or just copy & paste : []

I CAN'T BELIEVE SOMEBODY MADE THIS! [|Zombie Boxing: Plant Hormone Quiz] or copy & paste : []

Videos
media type="youtube" key="ZbRiKlIYa-k" height="402" width="402" align="left"

Description: A Brightstorm video about the different __plant hormones and their functions__.

media type="youtube" key="NdA11OalmSQ" height="315" width="420" Description: Part 1 of a Great Video about Plant Hormones : Auxin, Gibberellins and Etheylene (the guy's got an interesting accen too!)

media type="youtube" key="pgsorDGvr1I" height="315" width="420" Description: More From Plant Hormones Video (another part is under Target IV. d)

media type="youtube" key="VZAKr6sLJIQ" height="315" width="420" Description: All you ever wanted to know about Auxin....and then a little more :)

media type="youtube" key="mWmkZILCjEU" height="315" width="420" Description: Gibberellin! What it is...what it does...before & after pictures of its effects...etc :)

media type="youtube" key="so1hYe-zXik" height="315" width="420" Description: Cute and Informative video about Abscisic Acid! media type="youtube" key="e9cRYCm6YaM" height="315" width="420" Description: Kind of cheesy....but hey, they do put in a lot of information about Cytokinin!

media type="youtube" key="pg7BvFHaw74" height="315" width="420" Description: Last cheesy yet informative video covering Ethylene!

Quick Quiz:[|this quiz will help you... just saying] or copy and paste this: []

This is a link to a **brief animation** about __auxin (IAA) and its effect on a plant's growth__. It includes a **short quiz** at the end of the animation. (if not accessible, copy+paste [])

A link to a small crossword puzzle about [|plant hormones]. Just the bold words from 39.2

Thisis a link to basic Quizlet flashcards with __vocab from plant hormones and tropic reactions__. (if not accessible, copy+paste [])

**Gravitropism, Thigomotropism, Hydrotropism, and Phototropism (Target IV. c., Section 39.4)**
//Warning: Answers to previous questions may be found in later sections, CHECK YOUR ANSWERS AS YOU GO!//

__Quick Matching__
Term 1. Gravitropism 2. Hydrotropism 3. Thigmotropism 4. Phototropism Definition: Directional growth in response to: a. Water b. Light c. Gravity d. Mechanical (physical contact) Answers (highlight): 1. c. 2. a. 3. d. 4. b.

__Fill in the Blank__
Highlight to see answers. __Word Bank__ ethylene, elongation, nastic, denaturing, chaperonins, leaf, away, heat-shock proteins, auxin, statolith, root cap, towards, thigmomorphogensis, evaporative cooling, air spaces, oxygen, stomata, gradient, action potential, cortex, water potential, __Gravity as a Stimulus:__ __Mechanical Stimuli:__ Changes in form in response to physical contact are known as thigmomorphogenesis. Non-oriented responses to stimuli are known as nastic responses. An example of this type of response is the folding of the leaflets on the compound leaf of //Mimosa pudica// in response to contact. The leaflets have special motor cells that quickly lose water and thus **turgo**r and also transmit the stimulus throughout the plant via electrical impulses called action potential. An example of thigmotropism is the coiling of vine tendrils around objects that they touch. The coiling is produced by different amounts of growth on the cells on opposite sides. __Water as a Stimulus:__ While there are some examples of **hydrotropism**, such as the **negative hydrotropism** of some plant roots turning away from drier soil to find wetter soil, most responses are **nastic**. For example, in a drought, the leaf organs of plants reduce the **transpiration** of water by closing the stomata when **guard cells** lose turgor from water loss, wilting to reduce surface area, and limiting growth with the increase of abscisic acid (and because of the water shortage). Only the roots in wetter (and usually deeper) soil continue to grow. When an area floods, water fills the air spaces in soil, reducing the oxygen available to root cells needed for **cellular respiration**. The plant responds with the production of the hormone ethylene to signal **apoptosis** (programmed cell death) in certain root cortex cells to leave air tubes to transport the necessary gas to the underwater roots. __Salt Stress:__ Salts affect plants by decreasing the water potential of the soil, causing the water gradient to lower and slowing the rate of water intake. Sodium and other ions may also be toxic to the plants at high concentrations. __Heat Stress:__ Heat damages plants by denaturing enzymes. Transpiration can reduce the temperature with evaporative cooling, but the plant must also conserve water which is lost at a relatively high rate on a hot, dry day. Many plants synthesize heat-shock proteins that protect other proteins from heat stress. Some of these proteins are chaperonins that help other proteins maintain their folded shape.
 * Positive gravitropsim** is directional growth towards the Earth; **negative gravitropism** is directional growth away from the Earth. The hormone auxin plays a key role in directing the response. One explanation is the "falling statolith "  hypothesis which claims that special plastids with dense starch grains fall to the bottom of root cap cells, triggering a biochemical response that transports the hormone to the cells, causing localized elongation that forces the root to grow downwards. However, this explanation is being questioned because some plants without these organelles still exhibit gravitropsim, although the density of the special plastids may amplify the sensing of gravity. An example of **gravitropism** is the growth of shoots upwards and orientation of roots downwards even if the plant is turned "upside-down."

__Phototropism__: directional growth in response to light Figure 39.18 in textbook
 * __Blue-Light Photoreceptors__: include **cryptochromes** (proteins involved in stem elongation inhibition in reponse to light), **phototropin** (a kinase involved in directing phototropic curvatures), and **zeaxanthin** (a carotenoid-based molecule involved in directing stomatal response to light)
 * __Phytochromes__: red-light photoreceptors

Quizzes, Flashcards
This is a link to a **short basic quiz** on __plant tropic responses__. (if not accessible, copy+paste [])

This is a link to some flashcards regarding plant tropic responses (useful if you want to quiz yourself on the definitions!) (if not accessible, copy+paste [])

Videos, Links
media type="youtube" key="zctM_TWg5Ik" height="315" width="420" Description: A short video explaining phototropism and Auxin (IAA)'s role in phototropism!

A website explaining gravitropism in plants. []

Website that has a basic overview of almost this entire section. []

Phytochromes & Photoperiodism (Target IV. c., Section 39.3)
media type="youtube" key="vevavE61kg4" height="315" width="420" Description: Leaf movement of a bean plant grown under a light and day cycle of 12 hours light/ 12 hour dark (5 am to 5 pm light). The video demonstrates movement to the downward sleep position, then waking of the leaves to an open position. This process is controlled by a circadian clock.
 * Bean Plant Video**

This is a link to a **brief animation/explanation** of __photoperiodism and phytochrome's role in photoperiodism__. It includes several questions during the animation, as well as a separate quiz after playing the animation. (if not accessible, copy+paste [])

[|This] is a link to a **brief animation** describing __phytochrome's structure and function, as well as its impact on seed germination__. (if not accessible, copy+paste [])

media type="youtube" key="dju6tTb55Fw" height="315" width="420" Here's a video about mechanisms of timing and control. The plant part starts at around two minutes in.

Summary and Relevance of Coleoptile Experiments (Target IV. d., Section 39.2)
Coleoptile: the protective sheath covering a grass stem at the tip

The Darwins' Experiment



media type="youtube" key="4-2DZo2ppAY" height="315" width="420" Description: A short video explaining the discovery of Auxin and the preceding coleoptile experiments

Good description of the discovery of plant hormones through the Darwin, Boysen-Jensen, and Went experiments. Also discusses the 5 major plant hormones and their functions, relating to Target IV a. [|http://www.plant-hormones.info/auxins.htm#] Animation and Simplified Explanation of Experiment: early Darwin version [|There's also a quiz included!] or: []

media type="youtube" key="GAD3LzmVEXw" height="315" width="420" Description: Guy With Accent Plant Hormones Video and the Discovery of Auxin

Went's results first discovering the presence of plant hormones, based on earlier coleoptile experiments by the Darwins and Boysen-Jensen

The "Tickle Me Plant" media type="custom" key="12015717" Scientific Name: Mimosa Pudica

Here's a practice test on the stuff from chapter 39. []