LIGHT QUALITY AFFECTS PHOTOSYNTHESIS AND LEAF ANATOMY OF BIRCH PLANTLETS IN-VITRO

Cultures in vitro of Betula pendula Roth were subjected to light of di fferent spectral qualities. Photosynthetic capacity was highest when t he plantlets were exposed to blue light (max recorded photosynthesis, 82 mu mol CO2 dm(-2) h(-1)) and lowest when irradiated with light high in red and/or far-red wave lengths (max recorded photosynthesis, 40 m u mol CO2 dm(-2) h(-1)). Highest chlorophyll content (2.2 mg dm(-2) le af area) was found in cultures irradiated with blue light, which also enhanced the leaf area. Morphometric analysis of light micrographs sho wed that the epidermal cell areas were largest in plantlets subjected to blue light and smallest in those subjected to red light. Morphometr ic analysis of electron micrographs of palisade cells, showed that the functional chloroplast area was largest in chloroplasts of leaves sub jected to blue light and smallest in those exposed to red light. We su ggest that light quality affects photosynthesis both through effects o n the composition of the photosynthetic apparatus and on translocation of carbohydrates from chloroplasts.