Plant hormones: Name the organic substances that control plant growth and development in very small amounts. Full question: Organic substances which, even in very small concentrations, regulate growth and development in plants are called what? Choose the correct option.

Given data

• Tiny amounts of organic substances regulate plant growth and development.

Concept/Approach
Phytohormones (plant growth regulators such as auxins, gibberellins, cytokinins, ethylene, abscisic acid) are endogenous, signal-like molecules that control division, elongation, differentiation, and development at very low concentrations.

Option analysis
Vitamins and enzymes are essential but are not the primary regulatory signals of plant morphogenesis in minute amounts; alkaloids and carbohydrates are not regulatory signals.

Final Answer
Phytohormones (plant growth regulators).