1. Which of the following processes is not directly involved in auxin-mediated c
ID: 166643 • Letter: 1
Question
1. Which of the following processes is not directly involved in auxin-mediated cell expansion?
(a) Acidification of cell walls
(b) Decreased cellular solute potential
(c) Cellular nitrate (NO3-) accumulation
(d) Production of cellulose microfibrils
2. If you wanted to extend the life span of a tree leaf, you would:
(a) Decrease the amount of auxin in the leaf tissue
(b) Increase the amount of brassinosteroids in the leaf tissue
(c) Increase the ratio of ethylene to cytokinins in the leaf tissue
(d) Decrease the ratio of ethylene to cytokinins in the leaf tissue
3. Which of the following hormone is most directly involved in plant pathogen responses:
(a) Abscicic acid
(b) Auxin
(c) Ethylene
(d) Gibberellins
(e) Systemin
Explanation / Answer
1. Auxins promote elongation or expansion of cells by acidification of cellwall. This cause loosening of primary cellwall and cellwall becomes more plastic or stretchable. The water moves into the cellwall causing the cells to expand. As a result, the microfibrils in cellwall become loose allowing the solutes. Therefore, option c is correct.
2. Cytokinins are the plant hormones that delay senescence of plant tissues. Excessive ethylene hormone in plants decreases the leaf expansion. Brassinosteroids are polyhydroxy steroids produced in plants and inhibit the abscission of leaf. Therefore, lifespan of leaf can be increased by decreasing the ratio of ethylene to cytokinins in the leaf tissue. Option d is correct.
3. Plant immune system is activated by Ethylene and provide plants to gain resistance against the pathogens. systemins are plant proteins that provide resistance against the pathogens. Option e is correct.
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