Trocas gasosas e fluorescência em maracujazeiro amarelo sob salinidade da água e adubação nitrogenada.

Abstract

The stress caused by the salinity of the irrigation water decreases the physiological activities, reflecting directly on the success of crop production in general, such as yellow passion fruit. With the possibility of attenuation of the effects of saline stress on nitrogen fertilization. In this context, the objective was to evaluate responses related to gas exchange and photosynthetic efficiency in yellow passion fruit seedlings irrigated with salinized water and nitrogen doses. The experimental design was randomized blocks with the treatments arranged in subdivided plots, in a 5 x 5 factorial scheme with five irrigation water salinity levels (ECa) (0.3, 1.0, 1.7, 2.4 and 3.1 dS m-1) and five doses of nitrogen fertilization (subplot) (60, 80, 100, 120 and 140%), as recommended by 300 mg of N dm-3, with five replicates and one plant per plot, in citrus-type tubes with a capacity of 3,780 ml using lysimeters with drains at the bottom for irrigation management and leaching of excess salts. The treatments were started at 40 days after sowing (DAS) and ending at 70 DAS. The gaseous exchange and chlorophyll a fluorescence variables were measured at 55 and 70 DAS. Os dados obtidos foram submetidos à análise de variância, teste F, com análise de regressão (linear e polinomial). The highest photosynthesis value was 13,765μmol obtained as a function of the salinity of 1,0 dS m -1 and 120% N. The salinity caused reduction in gas exchange and fluorescence of chlorophyll a at 55 DAS, and the effect was attenuated by nitrogen fertilization until the salinity of 2,4dS m-1.