How do gibberellins and cytokinins regulate plant growth?

Gibberellins and cytokinins regulate plant growth by promoting cell division, elongation, and differentiation in various plant tissues.

Gibberellins (GAs) are a group of plant hormones that play a crucial role in promoting stem elongation, germination, flowering, and fruit development. They are produced in the roots and young leaves of plants. GAs stimulate cell elongation and division in the stem and leaves, which results in the overall growth of the plant. They also play a significant role in breaking seed dormancy and promoting germination by stimulating the synthesis of enzymes that break down the stored food in the seed. Furthermore, GAs are involved in the transition from vegetative growth to flowering. They do this by interacting with other hormones and signalling pathways to initiate the formation of flowers.

Cytokinins, on the other hand, are plant hormones that promote cell division, or cytokinesis, in plant roots and shoots. They are primarily produced in the root apical meristems and are transported to other parts of the plant where they stimulate cell division, leaf expansion, and the growth of lateral buds. Cytokinins also delay the ageing process in plants by inhibiting protein breakdown, promoting RNA and protein synthesis, and mobilising nutrients from the surrounding tissues to the site of action. This results in the delay of senescence, or ageing, in leaves and flowers, thereby extending their functional lifespan.

Both gibberellins and cytokinins interact with other plant hormones to regulate growth and development. For instance, the balance between cytokinins and auxins (another group of plant hormones) is crucial for determining whether a plant cell will differentiate into a root or a shoot cell. If the concentration of cytokinins is higher, the cell will become a shoot cell, and if the concentration of auxins is higher, the cell will become a root cell.

In summary, gibberellins and cytokinins are vital plant hormones that regulate various aspects of plant growth and development. They do this by promoting cell division, elongation, and differentiation, and by interacting with other hormones to control the overall growth pattern of the plant.