Ecofisiologia de maracujazeiro gigante amarelo cultivado com águas salinas e adubação silicatada.

Abstract

The yellow passion fruit is considered one of the main fruit plants with high market value, which has aroused interest mainly for small and medium producers in the northeastern semiarid. However, in those regions it is often necessary to use waters with high concentrations of salts for irrigation. For the use of these waters, management strategies are often required, silicate fertilization, which presents itself as an alternative to mitigate this stress condition for plants. In this context, the objective was to evaluate the cultivation of yellow passion fruit irrigated with waters of different salinity associated to silicate fertilization. The experiment was carried out in 2 stages at Federal University of Campina Grande, Pombal - PB. The first stage was carried out in a greenhouse environment, where different levels of salinity and doses of silicon were tested in the production of yellow passion fruit seedlings, with a randomized block design, with a 5 x 5 factorial scheme, whose treatments consisted of five levels of electrical conductivity of irrigation water (0.3; 1.0; 1.7; 2.4 and 3.1 dS m-1) and five doses of silicate fertilization (0; 25; 50; 75 and 100g of potassium silicate / plant), with four replications and two plants per plot, totalizing two hundred experimental units. The salinity in the irrigation water reduced the photosynthetic pigments and the yield in photosystem II in yellow passion fruit plants. The silicate fertilization in the 75g plant-1 dose attenuated the deleterious effect of salt stress for the osmotic potential, chlorophyll b and carotenoids. The salt stress caused by the conductivity of water from 0.3 dS m-1 caused a decrease in the production of phytomass of passion fruit at 60 days after sowing, being the dry leaf phytomass highlighted as the most sensitive variable. The production of passion fruit seedlings with water salinity up to 3.1 dS m-1 obtained an acceptable Dickson quality index. The doses of silicate fertilizer softened the effect of saline stress only for the root / shoot ratio of giant yellow passion fruit plants. In the second trial, the experiment was carried out under field conditions. The experimental design was used in randomized blocks in a 5 x 2 factorial scheme, whose treatments consisted of five levels of electrical conductivity of irrigation water (0.3; 1.0; 1.7; 2.4 and 3.1 dS m-1) associated with two doses of silicate fertilization (150 and 300 g plant-1 of potassium silicate) with four replications. Saline stress provided a decrease in stomatal conductance, intercellular CO2 concentration, transpiration, instant water use efficiency and in the growth of passion fruit plants. The synthesis of chlorophyll a was inhibited by the increase in CEa from 0.3 dS m-1, however, the salinity of the water caused an increase in the levels of caratenoids and protoplasmic content; silicon had a significant effect on conductance, photosynthesis, water use efficiency, chlorophyll b, caratenoids and relative diameter growth rate.