Lecture #6 Plant Responses Flashcards
Characteristics of seeds that germinated in the dark underground
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
What is greening
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
What are the three stages of cell signal processing
- reception (between cell wall and cytoplasm)
- Signal transduction (in cytoplasm)
- Response (in cytoplasm)
What is phytochrome
The receptor for greening in plants which consists of a light absorbing pigment attached to a protein located in the cytoplasm
What led to the discovery of plant hormones
Research on how plants grow toward light
what is a tropism
growth response toward or away from stimuli
what is phototropism
growth of a shoot toward light
What is coleoptile
sheath that encloses shoot of a grass seedling (curves growth toward light)
what is an auxin
substance that promotes elongation of coleoptiles
What is indoleacetic acid (IAA)
natural auxin occurring in plants
What is a major site of auxin synthesis
the apical meristem of a shoot
How is auxin transported in growing shoots
unidirectionally from the apex down to the shoot
auxin is anion inside cell, neutral outside
movement facilitated by proton pumps
What is the acid growth hypothesis
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
What are Expansin enzymes
Enzymes that are activated by lowering the pH and they break cross-links between cellulose microfibrils allowing the cell to elongate
Synthetic auxins We’re widely used as
Selective herbicide’s Because they also alter gene expression rapidly
Cytokinins
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
Gibberellins
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
Abscisic Acid
Slows down growth
Causes seed dormancy
enables to withstand drought
produces ethylene in stresses
The triple response
cause by ethylene, stem elongation slows, stem thickens, grows horizontally
Why does food go bad quickly when near a ripe banana
Ethylene triggers ripening of fruit and is a gas so the signal to ripen spreads from fruit to fruit
Abscission
Loss of leaves in autumn
Apoptosis (programmed cel death)
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)
Action spectrum
Wavelengths of light that trigger physiological responses