INFLUENCE OF REDUCTION OF ENHANCED MOUNTAIN UV-RADIATION ON THE PHOTOSYNTHESIS AND GROWTH OF CULTURED C₃-PLANTS

Valery Yu. Lyubimov , Alexander E. Kalevich, Institute of Soil Science and Photosynthesis RAS, Pushchino, Moscow Region, 142292 Russia.
Said Shomansurov, Pamir Biological Institute Tajik AS, Khorog, Tajikistan.

Key words: C₃-plants, hormones, Pamir, photosynthesis, productivity, UV-radiation.

Abstract
        Investigation was carried out with small radish (Raphanus sativus L.), pot marigold (Calendula officianalis L.), red pepper (Capsicum annuum L.), and bulb onion (Allium cepa L.). Plants were grown at the high mountain place (Pamir, near Khorog, 2320 m over sea level) under free sky (FS), under usual polyQ-film (UF), and under transforming polyQ-film (TF). Last one captures from 60 to 30% of UV-radiation (from 300 to 400 nm resp.) and effectively transforms it to visible light (600-700 nm). Under light condition using the UF the photosynthetic rate (¹⁴CO₂-assimilation per leaf fresh weight) of all species was similar (± 3-5%) to this one under FS. The small radish and pot marigold which were grown under TF exhibited the enhanced photosynthetic assimilation of ¹⁴CO₂ (+20%), red pepper exhibited the decreased assimilation (-22%) and bulb onion did not changes the photosynthetic rate. There was qualitative correlation between photosynthetic activity and growth of plants: the height of small radish and pot marigold plants were increased by 20 and 95%, respectively. The height of red pepper plants was reduced not significantly changed (-6%) and the height of bulb onion plants was reduced by 24%. These changes of plant growth and productivity parameters it seemed are associated with changes of hormonal status of plants. Reduction of the natural enhanced UV-radiation leads to complex changes in photosynthesis, hormonal status and growth of cultured plants.