Germination and initial development of Simira gardneriana seedling under water stress and at different temperatures/Germinacao e desenvolvimento inicial de plantulas de Simira gardneriana sob estresse hidrico e em diferentes temperaturas

The germination of seeds is affected by many factors, including water availability and temperature. This study aimed to evaluate the effects of water stress and different temperatures on germination and initial development of S. gardneriana M. R. Barbosa & Peixoto seedlings. The experiment was carried out in a completely randomized design, in a 7 x 4 factorial scheme, with seven potentials (0; -0.1; -0.2; -0.3; -0.4; -0.5 and - 0.6 MPa) and four temperatures (25, 30, 35 and 20-30 [degrees]C), with four replicates of 25 seeds. The analyzed variables were germination, percentage of normal seedlings, germination speed index, seedling length (shoot and root) and dry weight (shoot and root). There is a decrease in the germination and vigor of the seeds as the water potential decreases, being less affected under the temperature of 25 [degrees]C and very accelerated at 35 [degrees]C. The tolerance of S. gardneriana seed germination to water stress is variable between the temperatures and limiting to the formation of normal seedlings from the potential -0.5 MPa at temperatures of 25 to 30 [degrees]C and -0.4 and -0.2 MPa for 20-30 and 35 [degrees]C, respectively. Key words: Rubiaceae Caatinga osmotic potential forest species A germinacao de sementes e afetada por varios fatores destacando-se a disponibilidade de agua e a temperatura. Objetivou-se avaliar o efeito do estresse hidrico e diferentes temperaturas na germinacao e no desenvolvimento inicial de plantulas de S. gardneriana M. R. Barbosa & Peixoto. O experimento foi realizado sob delineamento inteiramente casualizado, em esquema fatorial 7 x 4 sendo sete potenciais (0; -0,1; -0,2; -0,3; -0,4; -0,5 e - 0,6 MPa) e quatro temperaturas (25, 30, 35 e 20-30 [degrees]C), com quatro repeticoes de 25 sementes. As variaveis analisadas foram germinacao, porcentagem de plantulas normais, indice de velocidade de germinacao, comprimento de plantulas (parte aerea e raiz) e massa seca (parte aerea e raiz). Ocorre diminuicao na germinacao e no vigor das sementes a medida que decresce o potencial osmotico sendo menos afetados sob a temperatura de 25 [degrees]C e bastante acelerados na de 35 [degrees]C. A tolerancia da germinacao de sementes de S. gardneriana ao estresse hidrico e variavel entre as temperaturas e limitante na formacao de plantulas normais a partir do potencial -0,5 MPa sob as temperaturas de 25 e 30 [degrees]C e de -0,4 e -0,2 MPa para as de 20-30 e 35 [degrees]C, respectivamente. Palavras-chave: Rubiaceae Ca