The most common example being indole acetic acid iaa

Plant Growth Hormones

Chukwuma Eke

Seed: A seed is a small embryonic plant enclosed in a covering called the seed coat, usually with some stored food. It is the product of the ripened ovule of gymnosperm and angiosperm plants which occurs after fertilization and some growth within the mother plant.

Seedling: A seedling is a young sporophyte developing out of a plant embryo from a seed.

Hypocotyl: In the developing embryo, the hypocotyl is the embryonic axis that bears the seedling leaves (cotyledons).

Epicotyl: An epicotyl is important for the beginning stages of a plant's life. It is the region of a seedling stem above the stalks of the seed leaves of an embryo plant.

Gravitropism: Gravitropism, also called geotropism, where geo- means the earth, and tropism refers to turning, is the growth of a plant's organ or change in the direction of its growth in response to gravity.

Apical Dominance: In botany, apical dominance is the phenomenon whereby the main, central stem of the plant is dominant over i.e., grows more strongly than other side stems; on a branch the main stem of the branch is further dominant over its own side twigs.

2.The most important differences between auxin and gibberellin are that auxin promotes the growth of shoot whereas gibberellin is involved in the elongation of the stem, flowering and seed germination. Auxin plays a major role in apical dominance
whereas gibberellin has no role in apical dominance.

Applying Your Knowledge

The receptor responding to light contains a pigment component like phytochrome.

Phytochrome is a receptor protein and is sensitive to red light. Phototropic is a receptor protein sensitive to blue light. The phytotropin pigment of photo receptor changes its shape or conformation in response to blue light wavelength. The changing of the shape causes transfer of the phosphate group from ATP to protein component of photo receptor. The phosphorylated photo receptor thus triggers the transduction pathway and leads to the entry of light in to the cell.

Cytokinin’s - prevent the yellowing of lettuce leaves

Auxins - to prevent leaf and fruit abscission (drop)

crop, it does not cross-pollinate with other wheat varieties. To produce hybrids,

plant breeders have had to sterilize the anther in order to get plants to cross-