PLANT HORMONE

Auxin

This hormone is present in the seed embryo, young leaves, and apical buds' meristem.

Functions of Auxins

• Auxins are hormones produced in immature parts of plants that stimulate growth.
• Stimulation of cell elongation, cell division in cambium, differentiation of phloem and xylem, root initiation on stem cuttings, lateral root development in tissue culture
• Delaying leaf senescence
• Suppression of lateral bud growth when supplied from apical buds
• Inhibition or promotion of fruit and leaf abscission through ethylene stimulation
• Fruit setting and growth induced through auxin in some plants
• Auxin can delay fruit ripening
• In Bromeliads, the auxin hormone promotes flowering
• Stimulation of flower parts, femaleness of dioecious flowers, and production of high concentration of ethylene in flowering plants

Cytokinin

They are synthesized in roots and then transported to other parts of the plant.

Functions of Cytokinins

• Stimulation of cell division, growth of lateral buds, and apical dominance
• Stimulation of shoot initiation and bud formation in tissue culture
• Leaf cell enlargement that stimulates leaf expansion
• Enhancement of stomatal opening in some plant species
• Etioplasts converted into chloroplasts through stimulation of chlorophyll synthesis.

Ethylene

Ethylene is present in the tissues of ripening fruits, nodes of stems, senescent leaves, and flowers.

Functions of Ethylene

• Leads to release of dormancy state
• Stimulates shoot and root growth along with differentiation
• Leaf and fruit abscission
• Flower induction in Bromeliad
• Stimulation of femaleness of dioecious flowers
• Flower opening is stimulated
• Flower and leaf senescence stimulation
• Stimulation of Fruit ripening

Abscisic Acid

Abscisic acid is found mostly near leaves, stems, and unripe fruit.

Functions of Abscisic Acid

• Stimulation of closing of stomata
• Inhibition of shoot growth
• Inducing seeds for synthesizing storage of proteins

Gibberellin

Gibberellins are present in the meristems of apical buds and roots, young leaves, and embryo.

Functions of Gibberellins

• Stimulates stem elongation
• Leads to development of seedless fruits
• Delays senescence in leaves and citrus fruits
• Ends seed dormancy in plants that require light for induction of germination