Lecture #6 Plant Responses

Question 1

Characteristics of seeds that germinated in the dark underground

Answer 1

shoot supported by soil and does not need a thick stem
Allocates as much energy as possible to elongation of stems
Shoots do not have leaves because they would hinder soil penetration
Production of chlorophyll is unnecessary
Extensive root system is not required

Question 2

What is greening

Answer 2

When a shoot reaches the sunlight and the elongation rate of the stems slows down, the leaves expand l, roots elongate, and the entire shoot begins to produce chlorophyll

Question 3

What are the three stages of cell signal processing

Answer 3

1. reception (between cell wall and cytoplasm)
2. Signal transduction (in cytoplasm)
3. Response (in cytoplasm)

Question 4

What is phytochrome

Answer 4

The receptor for greening in plants which consists of a light absorbing pigment attached to a protein located in the cytoplasm

Question 5

What led to the discovery of plant hormones

Answer 5

Research on how plants grow toward light

Question 6

what is a tropism

Answer 6

growth response toward or away from stimuli

Question 7

what is phototropism

Answer 7

growth of a shoot toward light

Question 8

What is coleoptile

Answer 8

sheath that encloses shoot of a grass seedling (curves growth toward light)

Question 9

what is an auxin

Answer 9

substance that promotes elongation of coleoptiles

Question 10

What is indoleacetic acid (IAA)

Answer 10

natural auxin occurring in plants

Question 11

What is a major site of auxin synthesis

Answer 11

the apical meristem of a shoot

Question 12

How is auxin transported in growing shoots

Answer 12

unidirectionally from the apex down to the shoot

auxin is anion inside cell, neutral outside

movement facilitated by proton pumps

Question 13

What is the acid growth hypothesis

Answer 13

auxin Stimulates plasma membrane proton pumps which lowers the pH in the cell wall and increases the H+ gradient across the membrane which in turn increases the voltage

Question 14

What are Expansin enzymes

Answer 14

Enzymes that are activated by lowering the pH and they break cross-links between cellulose microfibrils allowing the cell to elongate

Question 15

Synthetic auxins We’re widely used as

Answer 15

Selective herbicide’s Because they also alter gene expression rapidly

Question 16

Cytokinins

Answer 16

Interact with auxins to stimulate cell division and differentiation

The inhibit protein breakdown by stimulating or nay and protein synthesis and by mobilizing nutrients from surrounding tissues

also Slow deterioration of leaves on plants

Question 17

Gibberellins

Answer 17

Stimulate growth in leaves and stems but have little effect on route growth

Mix grapes grow larger and the Internodes of the grape bunch elongate which allows more air circulation

Question 18

Abscisic Acid

Answer 18

Slows down growth
Causes seed dormancy
enables to withstand drought
produces ethylene in stresses

Question 19

The triple response

Answer 19

cause by ethylene, stem elongation slows, stem thickens, grows horizontally

Question 20

Why does food go bad quickly when near a ripe banana

Answer 20

Ethylene triggers ripening of fruit and is a gas so the signal to ripen spreads from fruit to fruit

Question 21

Abscission

Answer 21

Loss of leaves in autumn

Question 22

Apoptosis (programmed cel death)

Answer 22

Active expression of new jeans which produces enzymes that break down many chemical components, controlled by change in the balance of ethylene and auxin (more ethylene)

Question 23

Action spectrum

Answer 23

Wavelengths of light that trigger physiological responses