Question

Genetically dwarf plants can be induced to grow tall by using
A. Auxins
B. Cytokinins
C. Gibberellins
D. Phycobillins

Answer 1

The genetically dwarf plants have inheritably small height. These dwarf plants can be induced to grow tall using some growth hormones or growth factors. The growth factors are naturally occurring chemical substances in plants. These help in various functions in plants. They cause stem elongation, cell differentiation, cell division, etc. The growth hormone used to induce plants to grow tall is present in most actively growing parts of the plant.

Complete answer: Plant hormones are chemical messengers that induce the plant cells to undergo required changes. These chemicals induce plant growth, flowering, stem and root elongation, fruiting, etc. In the plant tissue culturing technology, various plant types are grown and various plant hormones are experimented on them to know their effect.
-Genetically dwarf plants are inheritably smaller in height as compared to normal plants. To increase their height and induce more cell division so that more longitudinal growth can take place, scientists use Gibberellins.
-Gibberellins are one of the longest classes of plant hormones. These are majorly involved in breaking seed dormancy and initiate shoot growth. Gibberellin induces cell division and cell elongation. This results in longitudinal growth of stem that makes dwarf plants grow taller.
-Also, the gibberellins are present in the most actively growing regions of the plants, like shoot apex and tips. Due to their presence in apical regions, they elongate the cells and induce them to divide rapidly. This causes plants to grow taller longitudinally.
-Auxins are plant hormones that help in cell elongation and cell differentiation. Differentiation results in specialization in the functioning of particular cell types. Thus, auxins are used where differentiation of plant callus is required to form a plant.
-Cytokinins are also plant hormones that help in cell division. But it has no role in inducing longitudinal growth in plants. It may be used in callus formation from plant cells in tissue culture techniques. Phycobilins are chemical pigments that are found in cyanobacteria. These pigments capture the light energy that further aids in photosynthesis in these bacteria.
Therefore, we can conclude from the above discussion that the right answer is option C, Gibberellins.

Note: Gibberellins are also involved in various germination processes. They induce seed germination along with providing nutrition to the growing seedling. Gibberellins are produced under cold conditions. They are actively secreted and functional at lower temperatures.