Indução de tolerância à deficiência hídrica na germinação e crescimento inicial de melão.

Abstract

In melon, some substances can collaborate by improving the efficiency of metabolic processes or acting directly on metabolic routes of response to the unfavorable environment, allowing adaptations to environmental changes, such as salicylic acid and gibberellin. In this context, the objective was to evaluate the quality and vigor of melon seeds pretreated with salicylic acid (SA), gibberellic acid (GA3) and cold shock (CS), and then subjected to water stress conditions. In the first experiment, the seeds were pre-treated in eight conditions, being P1 (control), P2 (CS), P3 (SA), P4 (SA + CS), P5 (GA3), P6 (GA3 + SA), P7 (GA3 + CS) and P8 (GA3 + SA + CS) and physiological quality (germination test, first germination count and germination speed index) and enzymatic activity (ascorbate peroxidase, catalase, phenol peroxidase activity) were evaluated , protein quantification, SDS-PAGE denaturing electrophoresis and lipase) in a completely randomized design and compared by the Tukey test at 5% probability. Salicylic acid inhibits the germination of melon seeds and the cold thermal shock, potentiates it. Gibberellin associated with cold shock induces germination of melon seeds. The second experiment conducted in a completely randomized design in a factorial scheme 2 (seeds without any pretreatment and seeds pretreated with gibberellin and cold shock) x 4 (four osmotic potentials 0.0; -0.3; -0.6 and -0.9 Mpa and in the evaluation of the emergence of the plants the water retention capacity in the sand of 100, 80, 60, and 20%), using four repetitions. The physiological quality of seeds and initial seedling growth were evaluated using the germination pattern, first count and germination speed index, radicle length, seedling emergence, seedling emergence index, shoot length and dry mass and the root. The data obtained were subjected to analysis of variance and when significant, the means of the qualitative factor were compared by the Tukey test at 5% probability. As the water holding capacity in the sand increases, the vigor of the seeds and seedlings of Yellow Melon decreases. Gibberellic acid + cold shock does not induce resistance to water stress. The seeds without pre-treatment resist up to -0.3 Mpa and 40% of the water retention capacity in the sand.