Summary

This chapter traced the journey of a plant from a dormant seed to a mature, developed individual capable of flowering. Germination begins with imbibition and enzyme activation and, depending on whether the hypocotyl or the epicotyl elongates, follows either the epigeal pattern (cotyledons raised above the soil, as in gram) or the hypogeal pattern (cotyledons remaining below the soil, as in maize). Growth itself is an irreversible increase in size, made indeterminate in plants by the presence of meristems, and every growing cell passes through a meristematic, an elongation and a maturation phase; growth rate can follow either a simple arithmetic pattern or, far more commonly, a geometric pattern that, under the resource limits of a natural environment, plots as the characteristic sigmoid growth curve. Growth further requires favourable water, oxygen, nutrient, temperature and (for many responses) light conditions to proceed at all.

Cells differentiate into specialised, function-specific types as they mature; some already-differentiated mature cells, such as the interfascicular and cork cambium, can dedifferentiate and regain the capacity to divide, and the cells they in turn produce can redifferentiate into a specific mature type once again -- a connected cycle that, together with growth and eventual senescence, makes up the full developmental sequence a plant cell can follow, governed jointly by intrinsic genetic and hormonal signals and extrinsic environmental conditions, and capable of producing genuinely plastic outcomes such as heterophylly. …