Cultivo de pimentão em sistema hidropônico sob estresse salino

Abstract

The salinity of water in crop irrigation is one of the main limiting factors of agricultural production in the world. The effects of salt stress on the plants are growth reduction and production, as well as physiological and biochemical disorders, which affect the development of glycophyte species such as bell peppers (Capsicum annuum L.) The bell pepper ranks among the vegetables of greater importance in Brazil, both in quantity produced how much in nutritive quality and has good acceptance. Thus, this study aimed to evaluate the effects of salt stress on the growth variables, production, nutritional, physiological and biochimical in two bell pepper cultivars in hydroponic system. The experiment was conducted in a greenhouse located at the Deagri - UFRPE in the period from 6 October 2014 and 6 February 2015. Was used a randomized block design with factorial 5 x 2, the factors were: five salinity levels of the nutritive solution (2.0, 3.5, 4.5, 5.5 and 6.5 dS m-1) and two bell pepper cultivars, Bruno and Rúbia. The results demonstrated that the salinity of the nutritive solution affected the growth and production of both cultivars. The cv. Bruno had greater leaf area and fresh mass of the aerial part, while cv Rúbia stood out for higher productivity. The salinity reduces contents of phosphorus, potassium and sulfur and increased sodium and chlorine in the leaves of both cultivars. The cv. Rúbia proved more efficient in the ionic selectivity, being able to accumulate more potassium and calcium, as well as maintaining contents lower sodium and chlorine in the leaf tissue, compared to cv. Bruno. The cv. Rúbia production got higher fruits with 1.46 kg plant-1 against 0.83 kg plant-1 cv. Bruno. The cv. Rúbia was less affected in relation to the chlorophyll "a" content presenting unitary decrements of 3.8% per dS m-1, versus 6.8% of cv. Bruno. There was reduction in the gas exchange, in the soluble proteins and increased proline content, with increasing salinity of the nutritive solution, in both cultivars. On both cultivars the antioxidative defense system was activated. The cv. Rúbia showed higher APX activity that the cv. Bruno even in the lower salt level by showing up more acclimatized to the adverse effect of salinity.