Respostas fisiológicas de plantas transgênicas de tabaco com alto acúmulo de prolina sob níveis de nitrogênio

Abstract

In this work, tobacco plants with a high proline accumulation due to the insertion of the VaP5CSF129A mutant gene on the control of the promoter constitutive CaMV 35S were used as a model to verify the effect of transgene overexpression on the uptake and utilization of N. The experiment was conducted in a greenhouse for a period of 30 days. The arrangement was completely randomized in the 2x5 factorial scheme, consisting of two genotypes (one transgenic event and one unprocessed control) and five nitrogen fertilization doses (ammonium nitrate (NO3NH4): 25, 50, 100, 200 and 400 kgN ha-¹), totaling 10 treatments with 4 replicates. The plants were evaluated for height, leaf number, dry mass, root/shoot ratio, chlorophyll content, free proline content, nitrogen content, total protein foliar content, carbon/nitrogen ratio and nutritional efficiency for N (Absorption efficiency - EAbs, leaf utilization - EUtil and plant use - EUN). The plants of the transgenic event with high proline accumulation were less efficient than the control plants in terms of nitrogen absorption (lower levels of N in root, leaves and role plant), which resulted in lower EAbs in these plants. For EUtil (given by the relation between leaf dry mass and N content in the plant) there was no difference between the transgenic and control genotypes. However, the transgenic plants presented lower EUN in comparison to the control plants. It was concluded that the use of tobacco plants with overexpression of the VaP5CS129A gene on control of the constitutive promoter CaMV 35S for a high proline accumulation does not present potential of direct use in agricultural systems, since the alteration of the biochemical balance between the metabolisms of nitrogen and carbon did not result in plants with higher EUN.