Influência da temperatura e da salinidade em suas espécies de cactáceas endêmicas da caatinga.

Abstract

Arid and semi-arid environments around the world, several species of cactus are found. In Brazil, we can highlighted the Caatinga Biome, where many cactus endemic species are found. Cereus jamacaru DC., and Pilosocereus gounellei (A. Weber ex K. Schum.) Bly. ex Rowl. Are two important species that offer alternative resources, being used to several purposes. Studies about cactus germination front the abiotic factors are essencials, because they help the to understand its morphology and physiology, and contributed by conervation and preservation in the arid and semi-arids environments. Thus, the present study aims to evaluate responses of the germination of C. jamacaru and P. gounellei submitted to different temperature and salinity gradients. Parameters of germination used were: mean germination time (MGT), germinability (G%), germination speed index (GSI) and germination synchrony index (E). In the germination tests were compared with six temperatures (15, 20, 25, 30, 35 and 40 ºC) and six salts concentrations of NaCl p/v (0, 16, 25, 33, 41 and 49 mMol.L-1) under 12h of fotoperiod. The experiments were conducted in completely randomized design (2 species x 6 temperatures x 6 salinities), resulting in 36 treatments with 6 repititions of 300 seeds, being 150 C. jamacaru and 150 to P. gounellei. ANOVA factorial was applied to verify the principals differences between interactions, being applied post-hoc Tukey HSD to verify differences between means. The results have show diferences to all parameters of germination, between species, temperature and interaction species x temperature (p < 0,0001). C. jamacaru have shown higher values of germination, but with greater sensitivity in more extreme temperatures (15, 35 and 40 ºC). However, P. gounellei, although presenting lower germination values, showed higher temperatures (35 and 40 º C), showing good germination parameters. The germinative responses of C. jamacaru and P. gounellei appear to demonstrate a broad tolerance to salinity. While, to temperature C. jamacaru, although showing greater germinative power, showed lower tolerance to the extreme temperatures (15, 35 and 40 ºC). Differently, from P. gounellei that presented greater resistamce to the 35 and 40 ºC temperatures.