Phenotypic characterization of photomorphogenic responses during plant development.

Light is one of the most important exogenous factors regulating plant development throughout the entire life cycle. Light is involved in the breaking of seed dormancy, the regulation of photomorphogenic seedling development, the adaptation of plant morphology toward spectral composition of incident light, and the transition to flowering. Plants have evolved with several photoreceptor families that sense UV-A, blue, red, and far-red light. Here, basal methods to measure light-regulated changes in plant morphology and pigment accumulation will be described. The methods include the determination of apical hook angle and cotyledon opening, the measurement of stem elongation, the determination of leaf surface area, the measurements that characterize light-controlled transition to flowering, and the determination of anthocyanin and chlorophyll accumulation. Furthermore, different light programs are listed that can be used to test for the functional involvement of separate light response modes controlling photomorphogenic plant development.