Abstract
Plant photomorphogenesis is a complex of developmental and growth processes of light-mediated changes in plant morphology and structure, ontogenetic patterns as well as movements of plants, plant parts and/or organelles. During photomorphogenesis, plants respond to the quality, intensity and/or direction of radiation, to which they are exposed, by changes in plant development, growth and/or movement.
This is a completely separate process from photosynthesis where light is used as a source of energy and for building of plant biomass, while in photomorphogenesis radiation plays a role of a signal. Photomorphogenesis is mediated by a sophisticated network of photoreceptors, which can be responsive to different kind of radiation and interfere in their action on plant photomorphogenetic processes.
The most important families of photoreceptors are: 1) phytochromes sensing particularly in red visible light and being crucial in numerous photomorphogenetic processes; 2) cryptochromes, phototropins and recently discovered ZTL/FKF1/LKP2 proteins sense blue light and UV-A, while 3) very recently discovered UVR8 receptor percieve UV-B radiation. These photoreceptors interact in accord to orchestrate numerous developmental and physiological processes, e.g. germination, deetiolization, shade avoidance, phototropism, leaf development, flowering, movement of chloroplasts, to optimize their location in order to perceive the optimum irradiance, etc..
Due to photoreceptors, plants perceive their neighbours and can avoid shading by them through photomorphogenetic processes. In artificial greenhouse cultivation systems, it is possible to efficiently manipulate artificial radiation in order to optimize quality and quantity of plant biomass and yield.
Nowadays, due to technological progress it is possible to cultivate plants not only in winter but also in polar regions during polar night. We can also manipulate radiation quality (e.g. using LED lighting), to induce better plant resistance to both abiotic factors such as drought, herbivores or pathogens.
Also we can positively affect yield quality, e.g. to lower nitrates or increase anthocyanins in yield biomass. In addition, we can affect timing of flowering, seed germination etc.