Evaluation the effect of three <em>in vitro </em>culture conditions in the quality of sugar cane plants propagated in Temporary Immersion Bioreactors

Abstract

Structural and functional deficiencies that affect survival during acclimatization are present in micropropagated plants. The current study was carried out to determine the effect of three in vitro culture conditions (autotrophic, mixotrophic and moderate mixotrophic) on the morph-physiological and biochemical behavior of plantlets of sugar cane propagated in Temporary Immersion Bioreactors (BIT). Morphological and physiological indicators and key enzymes of carbon metabolism were evaluated. Plantlets that were subjected to autotrophic conditions did not survive due to the stress caused by the absence of sucrose in the culture medium. For this reason it could not be evaluated. The best results were obtained for the condition of moderate mixotrofical. In this case, the morphological variables, height of the plants, fresh weight and dry weight, responded positively. It was minimum the answer of the net photosynthesis in vitro and increased it notably from the second week of acclimatization. Plants with a mixotrophic growth showed very high values of transpiration and estomatic conductance at the beginning of the elongation and during the first week of acclimatization. This group of plants took a longer time than the rest in achieving the control of the loss of water and in reaching a functional stability. Plants that showed a bigger activity of pyruvate kinase were those coming from mixotrophic conditions. An inverse behavior was observed in the phosphoenolpyruvate carboxylase. The activities of syntase sucruse and the neutral invertase were superior for the mixotrofic conditions. Key words: autotrofic, enzymes, mixotrofic, photosynthesis