Biostimulant Doses X Stress Conditions on the Germination and Seedling Characteristics of Sunflower Seeds

Considering the importance of sunflower crop and its versatility in the world market, this study aimed to evaluate the physiological quality of sunflower seeds subjected to different doses of biostimulant (0.009% kinetin, 0.005% indolebutyric acid and 0.005% gibberellic acid) under stress conditions. The experiment was carried out at the Federal University of Viçosa, using the cultivar Hélio 250. The studied factors consisted of biostimulant doses (0, 2, 3, and 5 mL kg-1), water retention capacities (40, 60 and 90%), and osmotic potentials (0.0, -0.2 and -0.4 MPa). Seeds were pre-soaked with solutions of 0.009% kinetin, 0.005% indolebutyric acid and 0.005% gibberellic acid for 4 hours and then tested for germination and vigour. The study was divided into three trials: 1. Biostimulant x field capacity; 2. Biostimulant x osmotic potential; both in a completely randomised design (CRD), with factorial scheme 5x3; and 3. Biostimulant x Temperature, in CRD, with a 5 x 2 factorial arrangement and four replications. After collection, data were tested by Analysis of Variance and regression in the statistical program SISVAR. Under the water and osmotic stress conditions, the biostimulant action was maximised, demonstrating superior performance in the doses of 3 and 4 mL. There was an increase for both the dry mass of the root at all doses of the biostimulant and for the dry mass of the area part in potentials -0.2 and - 04 in the use of PEG6000. The stress given by PEG 6000 promoted an increase in the dry mass of the root in all the doses of the biostimulant, and for the dry matter of the aerial part, there was a progressive increase of the potentials -0.2 and -0.4.