ABSTRACT
INTRODUCTION Lighting for plant cultivation based on broad-spectrum natural sunlight and conventional artificial sources, which have inherently been designed for visual applications, is neither spectrally optimal nor energetically effective. Basically, plants require light in the vicinity of 660 urn for photosynthetic processes, which are due mainly to absorption in chlorophyll, blue light (-450 nm) to maintain healthy plant growth, and near-IR light in the vicinity of 735 nm for photomorphogenetic purposes. The rest part of broad spectra is utilized inefficiently. Also, most of the present artificial light sources used in plant cultivation contain mercury. Light-emitting diodes (LEDs) with narrow-band spectrum already available in the entire visible, near IR, and near UV range provide an alternative basis for plant cultivation lighting. LED-based illuminators can benefit in reduced power consumption and possibility of control over plant photomorphogenesis and offer mercuryfree greenhouse technology with low-voltage control. Although feasibility of LED-based plant growth technology has been already demonstrated [1-3], wide application of solid-state lighting in horticulture is hindered by low power of LEDs and lack of basic knowledge in plant photophysiology. Here we report on a solid-state lighting facility based on advanced high-power LEDs and its application for study of photophysiological processes in common vegetables such as reddish, lettuce, and onion. In particular, effect of spectral composition of light and circadian regime of illumination on concentration of chlorophyll a and 6, carotinoids, phytohormones, and photosynthetic pigments as well as on photosynthetic productivity was demonstrated.
