SALT STRESS ON THE PHYSIOLOGICAL QUALITY OF Cryptostegia madagascariensis Bojer ex Decne. SEEDS

Abstract

A esp\ue9cie Cryptostegia madagascariensis Bojer ex Decne. foi introduzida no Brasil com fins ornamentais, mas, atualmente, \ue9 uma invasora do bioma Caatinga. Apesar de sua elevada capacidade de ocupa\ue7\ue3o de \ue1reas alteradas do referido bioma, h\ue1 car\ueancia de informa\ue7\uf5es sobre esta esp\ue9cie, particularmente em rela\ue7\ue3o \ue0 capacidade de suas sementes germinarem em condi\ue7\uf5es adversas. O objetivo deste trabalho foi avaliar a germina\ue7\ue3o de sementes e o crescimento inicial de pl\ue2ntulas de Cryptostegia madagascariensis em fun\ue7\ue3o da salinidade em diferentes temperaturas. O experimento foi realizado seguindo um delineamento inteiramente casualizado, com os tratamentos distribu\ueddos em esquema fatorial 6 x 3, sendo seis n\uedveis de salinidade promovidos pelo cloreto de s\uf3dio (NaCl): 0,0 (controle); 2,0; 4,0; 6,0; 8,0 e 10,0 dS m-1; e tr\ueas temperaturas: 25 e 30\ub0C constantes e alternada de 20-35\ub0C. A qualidade fisiol\uf3gica das sementes foi avaliada pelas seguintes vari\ue1veis: germina\ue7\ue3o, primeira contagem e \uedndice de velocidade de germina\ue7\ue3o, comprimento e massa seca de ra\uedzes e do hipoc\uf3tilo. Os resultados obtidos indicam que h\ue1 elevada probabilidade de germina\ue7\ue3o de sementes de Cryptostegia madagascariensis submetidas a estresse salino em temperatura constante de 30\ub0C e alternada de 20-35\ub0C, o que potencializa o seu car\ue1ter invasor.The Cryptostegia madagascariensis Bojer ex Decne. species was introduced in Brazil with ornamental purposes, but currently, it is invasive in the Caatinga biome. Despite its high level of occupancy of altered areas of Caatinga, there is lack of information about this species, particularly in relation to the capacity of its seeds to germinate in adverse conditions. The objective of this study was to evaluate seed germination and the initial seedling growth of Cryptostegia madagascariensis in function of salinity at different temperatures. The experiment was conducted following a completely randomized design, with treatments arranged in a 6 x 3 factorial design with six salinity levels promoted by sodium chloride (NaCl): 0.0 (control); 2.0; 4.0; 6.0; 8.0 and 10.0 dS m-1 and three temperatures: 25 and 30\ub0C constant and alternating 20-35\ub0C. The physiological quality of seeds was evaluated using the following variables: germination, first count and the speed of germination index, length and dry weight of roots and hypocotyl. The results indicate that there is high probability of seed germination of Cryptostegia madagascariensis subjected to salt stress at constant temperature of 30\ub0C and alternating 20-35\ub0C, which enhances its invasive character