Question

Phytohormones are
A. Chemical regulating flowers
B. Chemical regulating secondary growth
C. Hormones regulating growth from seed to adulthood
D. Regulators synthesized by plants and influencing physiological processes

Answer 1

Hint: Phytohormones are chemical messengers that coordinate cellular activities. Phytohormones or plant hormones are present in small organic molecules or substances.

Complete answer:
Phytohormones are the chemical messengers that coordinate cellular activities of plants. Plant hormones control different aspects of plant growth and development such embryogenesis, regulation of organ size, pathogen defense etc.
All plant cells do not respond to hormones, but those that do are programmed to respond at specific points in their growth cycle. Plants need hormones at specific times and at specific locations. They disengage the effects of hormones when they are not required. The production of hormones occurs very often at sites of active growth within the meristems, before cells have fully differentiated.
Functions:
Regulation by phytohormones: Phytohormones regulate trichome initiation and growth.
Growth and morphogenesis: Plant growth regulators (PGRs) include diverse classes of chemicals that will be considered traditional or nontraditional and which are generally active at very low concentrations. The foremost classes of traditionally accepted plant growth regulators are auxins, cytokinins, gibberellins, abscisic acid, ethylene, and therefore the brassinosteroids.
Direct plant growth promotion: Phytohormone production is one amongst the mechanisms by which PGPR can promote plant growth.

Therefore, the correct answer is D, regulators synthesized by plants and influencing physiological processes.

Note:
The phytohormone hydroxy acid (SA) plays important roles within the regulation of responses to biotic and abiotic stress, further as developmental processes, but the foremost extensive research has been focused on characterization of SA signaling in plant–microbial pathogen interactions. In response to pathogen infection, plants activate SA biosynthesis, which is important for defense responses, like pathogen-associated molecular pattern, triggered immunity, effector-triggered immunity, and establishment of systemic acquired resistance.