Question

What is the meaning of heterophylly?

Answer 1

Many aquatic and amphibious plant species, including those belonging to the Nymphaeales, Ranunculales, Saxifragales, Myrtales, Brassicales, Lamiales, and other orders, exhibit heterophylly. The morphological contrasts between submerged and terrestrial environments in these heterophyllous plants are striking.

Complete answer:
Heterophylly is a type of plasticity in which plants follow many paths in response to their surroundings. Cotton, coriander, larkspur, and buttercup plants have juvenile leaves that are completely different from mature leaves. Also, whether the plant is aquatic or terrestrial makes a difference.
Heterophylly can be defined as the presence of differently shaped leaves on the same or different stem of the same plant.
Variations in environmental conditions are known to cause plant species to respond. In reaction to such changes, many plant species can change their leaf shape. Heterophylly is a term used to describe a condition that occurs frequently in land plants. Heterophylly is hypothesised to be an adaptation process that permits plants to respond best to environmental variability in some instances. Many studies have recently looked into the presence of heterophylly in a wide range of plants. Phytohormones appear to regulate heterophylly in plants, according to several studies.
The regulation of heterophylly is influenced by a number of phytohormones. Gibberellic acid (GA) can cause floating plants to develop aquatic leaves in the two-headed water starwort Callitriche heterophylla (Callitrichaceae) and pond water starwort Callitriche stagnalis, while abscisic acid (ABA) can cause submerged plants to grow floating leaves in the two-headed water starwort Callitriche heterophylla (Callitrichaceae) and pond water starwort Callitriche stagnalis.

Note:-
McCallum (1902) was the first to investigate how environmental factors affect heterophylly. He discovered that when leaves are not submerged, marsh mermaid-weed, Proserpinaca palustris (Haloragidaceae), has a broad, serrated leaf shape and a well-developed vascular system, but when leaves are submerged, it has a dissected, thread leaf shape, lacks a xylem, and has a weak phloem under certain conditions.