EFFECT OF SUCROSE LEVEL ON THE PHOTOSYNTHETIC ABILITY OF IN VITRO CULTIVATED APPLE ROOTSTOCK MM 106

Abstract

The aim of the present research was to observe the effect of sucrose level in the nutrient media on the photosynthetic ability of in vitro cultivated apple rootstock MM 106. The plantlets in an elongation stage (hormone-free medium) were grown at different sucrose concentrations (0, 1, 2 and 4% w/v) in the medium and in vessels with two types of closures - tight closure (T - gas exchange rate of 0.013 volumes/hour) and gas-permeable closure (G - gas exchange rate of 3 volumes/hour). The net photosynthetic rate (light and CO 2 curves), chlorophyll fluorescence and chlorophyll content were observed. There was a positive correlation between sucrose concentration and accumulation of dry matter and light-harvesting pigments. However, the increased sucrose concentration leads to a decrease in the net photosynthetic rate (Pn) of the plantlets. Plantlets cultivated with gas-permeable closure without sucrose showed the highest value of the Genty-parameter and ETR. The highest increase of the leaf area was achieved in plantlets cultivated on medium with 1 % sucrose and gas-permeable closure. Results from this study showed that in vitro cultivated apple plantlets could develop a positive carbon balance at suitable parameters of environmental factors (mainly light intensity, CO 2 concentration and sucrose in the nutrient medium).