Plant Hormones and Their Roles in Growth and Development

Auxin

Apical meristems, buds, young leaves; promotes cell elongation, root development, and plant responses to light and gravity.

Cytokinins

Promote cell division, cell differentiation, shoot formation, and delay leaf senescence; synthesized mainly in the roots and transported upward through the xylem.

Gibberellins

Stimulate seed germination, flowering, and stem elongation; produced in young tissues, seeds, and developing fruits.

Abscisic Acid

Helps leaves respond to water loss, prevents seeds from germinating while still on the plant, and promotes fruit abscission.

Ethylene

Stimulates the ripening of green fruits and fiber production for defense in response to mechanical stress; it is a gas that diffuses throughout the plant.

Phototropism

Growth toward light, where auxins accumulate on the shaded side of the plant, promoting growth and bending toward the light source.

Environmental Signals

Factors like light, temperature, and water availability that can trigger the production of various plant hormones.

Developmental Stage

The phase in a plant's life cycle that influences hormone synthesis, such as gibberellins for flower development.

Hormone Interaction

The interplay between different hormones, such as auxins and cytokinins, that regulates cell division and differentiation.

Differentiation

The process where cells develop different forms adapted to specific functions.

Development

The coordination of growth and differentiation of a single cell into multicellular tissues and organs.

High Auxin, Low Cytokinin

Promotes root formation and root development.

High Cytokinin, Low Auxin

Promotes shoot formation.

Plant Breeding

The process of selecting plants for desirable traits, such as early flowering.

Early Flowering

Breeders select for varieties of crops with altered sensitivity to gibberellins for more precise control over flowering time.

Drought Resistance

Hormone manipulation, particularly ABA, synthesized in response to environmental stresses like drought or high salinity.

Resistant Varieties

Plants bred or genetically edited to withstand environmental stresses.

Gene Editing

A technique used in plant breeding to alter specific traits, such as flowering time or drought resistance.

Selection for Responsiveness

Choosing plants that are naturally more responsive to gibberellins for breeding purposes.

Crossing

The process of breeding two varieties of plants to combine desirable traits.