Trocas gasosas e crescimento do abacaxizeiro "pérola" adubado com nitrogênio e potássio

Abstract

Despite the importance of nitrogenous fertilizers and potassic for pineapple are no data on its effects on the physiological behavior of the culture. This study aimed to evaluate the physiological responses and the vegetative growth of the pineapple 'Pearl', on the basis of nitrogen and potassium fertilization, the soil and climatic conditions of tableland Paraibanos. The experiment was conducted under rainfed conditions in Ultisol the municipality of Itapororoca between December 2014 and December 2015. The experimental design was randomized blocks, with six treatments and three replications, totaling 18 experimental units. The treatments resulted from combinations of doses of N and K considered low (50 kg/ha of N and 50 kg/ha of K2O), medium (300 kg/ha of N and 300 kg/ha of K2O) and high (700 kg/ha N and K2O). Type seedlings were used 'puppy', planted in the system of double rows, spaced 0,80 x 0,40 x 0,40m. 180 days after planting (dap) the vegetative growth of variable number of leaves were evaluated (NF), plant height (AP), length (COM), median width (LAR) and leaf area 'D'. And to 330 dap the fresh weight of leaf 'D'. At 180 and 270, dap were certain physiological variables intercellular CO2 concentration (Ci), stomatal conductance (gs), transpiration rate (E), net photosynthesis (A) and efficiency in water use (USA).From the results it was observed that with the exception of stomatal conductance, the doses of N and K influenced all studied physiological variables, especially the 180 dap. Plants fertilized with the highest doses of N and K2O (700 kg/ha) exhibited lower transpiration rate. The combination of 300 kg/ha N and 700 kg/ha K2O and 50 kg/ha N and 300 kg/ha K2O resulted in higher net photosynthesis. The highest proportion of K with respect to N, contributed significantly to the improvement in gas exchange Doses of N and K did not influence the vegetative growth variables to 180 dap, as well as the weight of leaf 'D' in time of floral induction.