Tolerância de genótipos do algodão colorido ao estresse salino

Abstract

The use of some areas of arid and semi-arid regions goes onto obstacles as water salinity and sodium potentiality in use for irrigation. Saline stress caused by handling not always proper to irrigation is one of the most serious factors limiting culture growth and production, implying on morphological, metabolic and structural changes on plants. About this matter, this work has an aim to evaluate vegetative and physiologic behavior on four varieties and six strains of colored cotton, submitted to three different conditions of saline stress, in a screen house. The experiment was taken in the installations of the Department of Agricultural Engineering in the Technological Center and Natural Resources at UFCG (Federal University of Campina Grande), in a partnership with the State University and EMBRAPA Cotton, all of them located in the city of Campina Grande PB. The treatments got 10 x 3 factorial, constituted of 10 genotypes of colored cotton, (four varieties: BRS ruby, BRS sapphire, BRS green, BRS topaz, and six strains: CNPA/2009-06, CNPA/2009-11, CNPA/2009-13, CNPA/2009-50, CNPA/2009-27, CNPA/2009-42) and three conditions of salinity in the irrigation water, making use of salts NaCl, CaCl2.2H2O e MgCl2.6H2O, in the proportion 7:2:1, diluted in supplying water: 1) without stress, plants irrigated with supplying water with conductivity of 0.6 dSm-1 , during experimental time (up to 43 days after sowing (DAS); 2) usage of water with saline content de 2 dSm-1, in a period of time of 7 to 15 days after sowing (DAS), intensifying saline stress from the 16º DAS, with an increase to 10 dSm-1, until the end of the experiment at 43 DAS; 3) water with saline content of dSm-1 from 7 to 15 days after sowing (DAS), intensifying saline stress from 16º DAS, with an increase to 10 dSm-1 until the end of the experiment at 43 DAS. The experimental lineation was in randomized blocks, with three repetitions, constituting the portion of 10 288mL tubes, having one plant each. The work evaluated: emergency speed index of seedlings, number of leaves, plant height, stalk diameter, phytomass (dry matter of root, stalk, leaves and total plant phytomass), and gas changes (stomatal conductivity, transpiration, photosyntesis and inner carbon). The evaluations were begun on the 15 days and repeated at each 7 day. Obtained data were submitted to variance analyses 10 dSm-1. We checked out that saline stress causes physiological alterations expressed in reduction of the gas changes; the variety BRS sapphire is the most sensitive to saline stress; saline stress inhibits phytomass production of the varieties and strains studied in the cotton plant; varieties BRS green and BRS Topaz and strains CNPA/200906, CNPA/2009-27, CNPA/2009-42 e CNPA/2009-50 are the most tolerant to saline stress.