plant hormones Flashcards
1
Q
What are plant growth regulators?
A
- Plant growth regulators are substances that coordinate plant growth, development, and responses to environmental stimuli.
- They include hormones such as Auxins, Gibberellins, Cytokinins, Abscisic acid, Jasmonic acid, and Ethylene.
2
Q
What are auxins and their primary roles?
A
- Auxins are the first plant hormones discovered.
- They are involved in apical dominance, cell elongation, gravitropism, and the remobilization of nutrients.
- They are produced in meristematic regions and growing organs.
3
Q
How are auxins produced and what are their forms?
A
- Auxins are synthesized from tryptophan in three steps.
- They exist in two forms:
Free form (active form, moves freely).
Conjugated form (inactive, released after enzymatic hydrolysis).
4
Q
What are gibberellins and their functions?
A
- Gibberellins are diterpenoid compounds involved in cell division and elongation, seed dormancy breakage, and bolting in response to long days.
- They are synthesized in developing seeds, fruits, and young leaves.
5
Q
How are gibberellins metabolized and transported?
A
- Gibberellins are synthesized from acetyl CoA via the mevalonic acid pathway.
- They are poorly understood in terms of transport and are found in both phloem and xylem.
6
Q
What are cytokinins and their roles?
A
- Cytokinins regulate the cell cycle, promote cell elongation, and delay senescence.
- They are mainly produced in the roots and work with auxins in morphogenesis.
7
Q
What is abscisic acid (ABA) and its role in plants?
A
- ABA regulates stomatal movement, seed dormancy, and inhibition of growth.
- It promotes water uptake by roots and induces resistance to water stress.
8
Q
What is ethylene and its physiological roles?
A
- Ethylene is a gaseous hormone produced by all plant organs.
- It regulates fruit ripening, senescence, flowering, stem elongation, and defense responses to stress.
9
Q
What is jasmonic acid and its effects on plants?
A
- Jasmonic acid is synthesized from linolenic acid.
- It induces resistance to insects and diseases, alters pollen development, and works in concert with ethylene to modulate responses to wounding.
10
Q
What is the role of PIN proteins in auxin signaling?
A
- PIN proteins are involved in auxin transport, orienting asymmetrically in plant cells.
- They help regulate polar auxin transport, a key mechanism in various physiological processes like apical dominance and cell elongation.
11
Q
What are the practical applications of gibberellins?
A
- Inducing parthenocarpic fruit production.
- Malting of barley by promoting fermentation and enzyme production.
12
Q
How is ethylene transported and what are its roles?
A
- Ethylene is transported as a volatile gas and soluble form in the phloem and xylem.
- It regulates ripening, senescence, flowering, and responses to stress and wounding.
13
Q
How do jasmonic acid and ethylene interact in plants?
A
- Jasmonic acid and ethylene work together to regulate responses to stress and pathogen attacks.
- They both promote defense mechanisms and influence plant growth and development.
