Tag: chemical coordination in plants

Questions Related to chemical coordination in plants

Which of the following is a growth inhibitor hormone?

biology chemical coordination in plants abscisic acid fruit plants: structure and function

  1. Cytokinin

  2. Gibberellin

  3. Auxin

  4. Abscisic acid

Show answer
Correct Option: D

The plant hormone that inhibits growth is called as

biology chemical coordination in plants abscisic acid fruit plants: structure and function

  1. Cytokinins

  2. Gibberellins

  3. Auxins

  4. Abscisic acid

Show answer
Correct Option: D
Explanation:

Auxin is the plant growth hormone that promotes lengthening and coordinates with other growth hormones to regulate growth; it also causes apical dominance. Cytokinin is the plant growth hormone that promotes cell division in shoot apical meristem and differentiation in root apical meristem. It works antagonistically to auxin to balance the growth with development in the shoot and root apex. Gibberellins are responsible for stem elongation, breaking seed dormancy, mobilization of endosperm reserves as well as regulate sex determination, flower initiation and fruit set. Abscisic acid is a plant growth hormone involved in seed dormancy by suppressing seed germination and growth as well as in responses of plants to stress. This makes option D correct. 

Select the wrongly paired one from the following.

biology chemical coordination in plants abscisic acid fruit plants: structure and function

  1. Companion - Helps in the cells tranlocation of phloem

  2. Antitranspirants - PMA in high concentation increase $CO _2$ and ABA which promote transpiration

  3. Mineral nutrient - available in both inorganic and organic forms to plants

  4. Photosynthetically active radiation - 400-700 nm of radiation of sunlight.

Show answer
Correct Option: B
Explanation:

Diffusion of CO$ _2$ into the leaf is decreased due to the closure of stomata and reduces the transpiration, which is done by antitranspirants.

So the correct option is 'Antitranspirants - PMA in high concentration increase CO$ _2$ and ABA which promote transpiration.'

The naturally occurring growth inhibitor is

biology chemical coordination in plants abscisic acid fruit plants: structure and function

  1. IAA (indoleacetic acid)

  2. ABA (abscisic acid)

  3. NAA (naphthalene acetic acid)

  4. GA (gibberellic acid)

Show answer
Correct Option: B
Explanation:
The naturally occurring growth inhibitor is ABA (abscisic acid).
Abscisic acid is a growth inhibitor which retards or suppresses growth and metabolism.
It induces bud dormancy in a number of plants. In perennial plants, ABA causes the active axillary buds to become dormant.
ABA maintains dormancy in many seeds.
It inhibits mitosis in vascular cambium.
It accelerates senescence in leaves
It functions as a stress hormone by inducing a temporary closure of stomata, to tide over adverse environmental conditions
It promotes abscission of leaves, flowers and fruits in most of the plants
It inhibits seed germination.
It delays cell division and cell elongation
It inhibits flowering except in some short day plants where it promotes flowering.
Thus, the correct answer is option B.

Which of the following induces dormancy?

biology chemical coordination in plants abscisic acid fruit plants: structure and function

  1. Auxin

  2. Cytokinin

  3. Both (A) and (B)

  4. Abscisic acid

Show answer
Correct Option: D
Explanation:

Abscisic acid (ABA) induces dormancy. Robinson and Warming (1964), isolated a substance responsible for dormancy in Acer pseudoplatanus, and named it as dormin. This hormone was similar to abscission It is a naturally occurring hormone that is present in all vascular plants and some mosses but is not present in bacteria, algae fungi and liverworts. This hormone is responsible for dormancy.

Thus, the correct answer is option D.

In autumn, leaf fall occurs because

biology chemical coordination in plants abscisic acid fruit plants: structure and function

  1. Formation of abscission layer at bases

  2. Leaf becomes heavy

  3. Leaf does not remain green

  4. Of low temperature

Show answer
Correct Option: A
Explanation:

By the end of summer, the leaves may be damaged by insects, disease or general wear and tear and ready for renewal. They are equipped to self-destruct. At the point where the leaf stem meets twig or branch is an array of cells called the abscission layer. As autumn days shorten, this layer begins to choke off the veins that move water into the leaf and food into the tree. Once the leaf is completely choked off, the layer becomes dry and flakey and, through decomposition, detaches the leaf from the tree.

So, the correct option is 'Formation of an abscission layer at bases'.

The following is a naturally occuring growth inhibitors ............

biology chemical coordination in plants abscisic acid fruit plants: structure and function

  1. IAA

  2. ABA

  3. NAA

  4. GA

Show answer
Correct Option: B
Explanation:

IAA, NAA - are several forms of auxin hormone which promotes plant growth. At the same time, GA is gibberellic acid which initiates shoot elongation. ABA is abscissic acid which is an inhibiting hormone which causes dormancy and also inhibits the longitudinal growth of plant.

Which of the following is true?

biology chemical coordination in plants abscisic acid fruit plants: structure and function

  1. ABA open stomata.

  2. ABA and cytiokinin does not effect on stomata.

  3. ABA open, cytokinin close stomata.

  4. ABA close and cytokinin open the stomata.

Show answer
Correct Option: D
Explanation:

ABA is an inhibiting hormone which helps in the closure of stomata. It thus helps in control of transpiration. Whereas cytokinin promotes the opening of stomatal pore. It also initiates mitotic cell divisions.

Match List I and List II and select the correct option.

   List I    List II
 A  Auxin  1  Herring sperm DNA
 B  Cytokinin  2  Inhibitor of growth
 C  Gibberellin  3  Apical dominance
 D  Ethylene  4  Epinasty
 E  Abscisic acid  5  Induces amylase synthesis
biology chemical coordination in plants abscisic acid fruit plants: structure and function

  1. A- 3, B- 1, C- 5, D- 4, E- 2

  2. A- 1, B- 2, C- 3, D- 4, E- 5

  3. A- 5, B- 4, C-2, D- 3, E- 1

  4. A- 2, B- 3, C- 1, D- 4, E- 5

Show answer
Correct Option: A
Explanation:

Auxin plant hormone induces apical dominance. Apical dominance is the growth of the shoot apex of plant. It increases the height of the plant.
Cytokinins were first discovered in 1955 as promoters of cell division in the DNA of Herring sperm. Since, that discovery many different compound with cytokinin activity have been discovered, both natural and synthetic (diphenylurea).
Gibberellin induces the synthesis of $\alpha$-amylase in the aleurone layers. GAs are plant hormones that regulate growth and influence various developmental processes, including stem elongation, germination, dormancy, flowering, sex expression, enzyme induction and leaf and fruit senescence.
Epinasty is the downward bending of a leaf or other plant part, resulting from greater growth of the upper side than of the lower side. Ethylene is the phytohormone which promotes epinastic movement in plants. It also promotes early ripening of fruits.

Abscissic acid promotes seed dormancy, inhibits seed germination, inhibits fruit ripening, induces stomatal closure, etc.
Thus, the correct answer is option A.

Which one of the following plant hormones (phytohormone) is known as a stress hormone?

biology chemical coordination in plants abscisic acid fruit plants: structure and function

  1. Gibberellins

  2. Kinetin

  3. Auxin

  4. Abscisic acid

Show answer
Correct Option: D
Explanation:

The synthesis of ABA is stimulated by drought, water logging and other adverse environmental condition. Therefore, it is also called as stress hormone. It is also called as 'growth inhibitor hormone', because it causes inhibition of seed germination, flowering and so on.