Tag: plants and animal hormones

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Multiple choice biology chemical coordination in plants cytokinins plant hormones plants and animal hormones

The first cytokinin was discovered by 

  1. Skoog

  2. Went

  3. Addicott

  4. Miller
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation
The first cytokinin was isolated from herring sperm in 1955 by Miller. This compound was named as kinetin because of its ability to promote cytokinesis. Natural cytokinins are synthesized in regions where rapid cell division is occurring. e.g., root apices, developing shoot buds, young fruits etc.
Cytokinins overcome apical dominance. They promote nutrient mobilization that help in delay of leaf senescence.
Thus, the correct answer is option D.
Multiple choice biology chemical coordination in plants cytokinins plant hormones plants and animal hormones

Which of the following induces morphogenesis in tissue culture?

  1. Gibberellin

  2. Cytokinin

  3. IAA

  4. Ethylene
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

During the 1940s and 1950s, researchers were trying to find substances that might induce plant cells to divide in tissue culture, a technique in which cells are isolated from plants and grown in a nutrient medium. They discovered that cells would not divide without a substance found in coconut milk. Because coconut milk has a complex chemical composition, investigators did not chemically identify the division-inducing substance for some time. Finally, researchers isolated an active substance from a different source, aged DNA from herring sperm. They called it cytokinin because it induces cytokinesis, or cytoplasmic division. In 1963, researchers identified the first plant cytokinin, zeatin, in corn. Since then, similar molecules have been identified in other plants. Biologists have also synthesized several cytokinins. Cytokinins are structurally similar to adenine, a purine base that is part of DNA and RNA molecules.
Morphogenesis means generation of proper morphological form of a plant body. Cytokinins promote cell division and differentiation of young, relatively unspecialized cells into mature, more specialized cells in intact plants (morphogenesis). They are a required ingredient in any plant tissue culture medium and must be present for cells to divide. In tissue culture, cytokinins interact with auxin during the formation of plant organs such as roots and stems. For example, in tobacco tissue culture a high ratio of auxin to cytokinin induces root formation, whereas a low ratio of auxin to cytokinin induces shoot formation. Cytokinins and auxin also interact in the control of apical dominance. Here their relationship is antagonistic: auxin inhibits the growth of axillary buds, and cytokinin promotes their growth.

Multiple choice biology chemical coordination in plants cytokinins plant hormones plants and animal hormones

Richmond-Lang effect is shown by

  1. Auxins

  2. Sugars

  3. Kinetin

  4. Gibberellins
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Kinetins are a type of phytohormone (cytokinin). One of the important physiological effect of cytokinins is that they delay senescence. This delay in senescence of mature plant parts is known as Richmond Lang effect.

Thus, the correct answer is option C.

Multiple choice biology chemical coordination in plants cytokinins plant hormones plants and animal hormones

Hormone concerned primarily with cell division is 

  1. GA$ _{3}$

  2. IAA

  3. NAA

  4. Cytokinin
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Cytokinin is a type of phytohormone. It encourages the process of cell division and cell differentiation. They promote cytokinesis, and so the term 'Cytokinin'. They affect apical dominance and axillary bud growth.

So, option D " Cytokinin" is the correct answer.

Multiple choice biology chemical coordination in plants cytokinins plant hormones plants and animal hormones

The hormone present in higher concentration in fruits and seeds is

  1. Auxin

  2. Gibberellin

  3. Cytokinin

  4. Ethylene
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Auxin promotes stem elongation. It is present in high concentration in apical meristem. Gibberellin controls shoot elongation, seed germination and delay the senescence in leaves and fruit. Cytokinin promotes cell growth and division. It is present in higher concentration in developing areas such as young fruits and seeds. Ethylene helps in fruit ripening, senescence and abscission.

Thus, the correct answer is option C.

Multiple choice biology chemical coordination in plants cytokinins plant hormones plants and animal hormones

Choose the right from the following.

i. In light, hormone auxin, helps the cells to grow longer in plants .
ii. Plant hormone gibberellins helps in growth of a stem.
iii. Cytokinins inhibits cell division.
iv. Abscisic acid promote growth in plants.

  1. Option i and iii are correct.

  2. Option ii and iv are correct.

  3. Option i and ii are correct.

  4. Option i and iv are correct.
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Plants have certain chemical substances in them that transmit messages for maintaining different functions of the body. 

One of the important function of auxins is that they help in the growth of the plants in the din growth like the growth of the stem.
Gibberellins help in the growth of different plant parts like stems.
Cytokinins help in cell division and differentiation, and so option iii is incorrect.
Abscisic acid retards plant growth, so option iv is also incorrect. 
So, option C " Option I and ii are correct" is the correct option.

Multiple choice biology chemical coordination in plants cytokinins plant hormones plants and animal hormones

The plant hormone that promote cell division

  1. Abscisic acid

  2. Auxins

  3. Gibberellins

  4. Cytokinins
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Abscisic acid is a plant growth hormone involved in seed dormancy and responses of plants to stress. This makes option A incorrect. Auxins promote the formation of lateral and adventitious roots, regulate the flower bud development and induce vascular differentiation. This makes option B incorrect. Gibberellins are responsible for stem elongation, breaking seed dormancy, mobilization of endosperm reserves as well as regulate sex determination, flower initiation and fruit set. This makes option C incorrect. Cytokinins are the plant growth hormones that regulate the cell division in root and shoot of the plant both in vivo and in vitro. They do so by regulating the controls that govern the transition of the cell from one stage of the cell cycle to the next one. This makes option D correct. 

Multiple choice biology chemical coordination in plants cytokinins plant hormones plants and animal hormones

The growth regulator that retards ageing of plant organs is

  1. Auxin

  2. Gibberellin

  3. Cytokinin

  4. Abscisic acid
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Cytokinin is the plant growth regulator which promotes cell division. The hormone retards the process of ageing which is known as senescence. There is stimulation for the production of chlorophyll and the fruits and leaves are prevented from falling. There is breaking of the bud dormancy which allows reproductive growth in the plants.

Thus, the correct answer is option C.