ABSTRACT
Plant hormones and environmental factors play central roles in the regulation of growth, development, nutrient allocation, and source/sink transitions. The response and adaptation of plants are determined by complex interactions with metabolites, plant growth regulators, secondary messengers, and downstream defense and/or homeostasis genes. Plant hormones are small molecules that regulate plant growth and development, as well as responses to changing environmental conditions. Post-embryonic plant growth and development are sustained by the meristem, a source of undifferentiated cells that gives rise to the adult plant structures. The phytohormone auxin has been implicated in diverse developmental processes throughout the life cycle of plants, including apical dominance, tropic responses, vascular development, organ patterning, flower development, and fruit development. Cytokinins have the ability to induce plant cell division and were discovered in the 1950s. Salicylic acid is a phenolic compound widely distributed in plants. Plants are entrained by light intensity, spectrum, direction, and photoperiod.
