Effects of the Gas Exchange Rate in the Culture Vessels on the Photosynthesis and the Carbon Metabolism of Micropropagated Fruit Plantlets (Apple Rootstock MM 106)

ABSTRACT

The specific in vitro conditions cause a modified structure and physiological functions of the photosynthetic apparatus which result in poor survival rate of plantlets during acclimatization. The type of vessel closure affects the gaseous composition and hence affects the growth of plantlets in culture. In tightly closed vessels concentrations of metabolically generated gases increase because their rate of diffusive escape is depressed. Different approaches have been proposed to enhance the photosynthetic ability of plants in vitro in striving to favour the success of further acclimatization to conditions ex vitro. The aims of the present research are to find the closure material which is gas permeable and to study the effect of the improved gas exchange on the growth and the photosynthetic ability of the micropropagated apple rootstock MM 106. The polyester wool—one of the tested types of closure, provides good gas exchange rate and preserves the culture from contamination. The data of this investigation show that there is a positive correlation between the improved gas exchange and accumulation of dry matter, light harvesting pigments as well as the ability of plantlet to assimilate ¹⁴CO₂. In plantlets, cultured with polyester wool, the relative part of the labelled low -molecular photosynthetic products (sugars, amino acids, organic acids) decreases, while the part of labelled high-molecular fractions (lipids, pigments and starch) increases. The improvement of gas exchange leads to rise of the content of sorbitol and the ratio sorbitol: saccharose. This might be a sign of a better carbon metabolism of in vitro cultivated apple root-stock MM 106.