Plant Growth and Development Test - 26

Answer: (B) NAA

Ethylene is a small hydrocarbon gas as well as a phytohormone. Some fruit will produce ethylene as ripening begins. Apples and pears are examples of fruit that produce ethylene with ripening. Ethylene is responsible for the changes in texture, softening, color, and other processes involved in ripening. Ethylene gas is used commercially to ripen tomatoes, bananas, pears, and a few other fruits postharvest. 

A) Correct option (D)
B) Explanation of the correct option

• Cytokinin (CK) is a plant hormone.
• It promotes cell division and delays senescence in plants.
• It improves nutrient mobilization and thus delays leaf senescence.
• When applied externally, it mobilizes nutrients towards sites of application.
• It also promotes stomatal opening along with the auxin hormone.
• It also breaks the dormancy of seeds and induces seed germination. 

• Auxins promote stem elongation, inhibit growth of lateral buds (maintains apical dominance). They are produced in the stem, buds, and root tips. Example: Indole Acetic Acid (IA).
• The gibberellins are named GA1 through GAn in order of discovery. Gibberellic acid, which was the first gibberellin to be structurally characterized, is GA3.
  
• Zeatin is a cytokinin derived from adenine, which occurs in the form of a cis- and a trans-isomer and conjugates. Zeatin was discovered in immature corn kernels from the genus Zea. It promotes growth of lateral buds and when sprayed on meristems stimulates cell division to produce bushier plants. W
• Abscisic acid (ABA), or Dormin is a plant hormone. ABA functions in many plant developmental processes, including seed and bud dormancy, the control of organ size and stomatal closure.

• Seedless watermelon plants are grown from seeds. The seeds are produced by crossing a diploid parent with a tetraploid parent to produce triploid seeds. When sprayed on flowers, any of the plant hormones gibberellin, auxin and cytokinin could stimulate the development of parthenocarpic fruit.
• Abscisic acid inhibits germination of mature Arabidopsis seeds by limiting the availability of energy and nutrients. The addition of abscisic acid (ABA) to mature non-dormant seeds inhibits their germination

Auxins inhibit growth. Auxins can be used to control the growth of weeds.

In term morphogenesis, morphe means shape and genesis means creation. So morphogenesis is defined as the biological process that causes an organism to develop its shape.  In plants, growth occurs during cell division, cell elongation and cell differentiation. The auxin produced by the apical bud (or growing tip) diffuses downwards and inhibits the development of ulterior lateral bud growth, which would otherwise compete with the apical tip for light and nutrients.  Also cytokinin stimulates morphogenesis (shoot initiation/bud formation) in tissue culture.

Berry size of many seedless table grape cultivars can be substantially increased by applying gibberellic acid.