The objective of the research was to evaluate the use of photoselective plastic shadenet and the effect of plant growth retardant paclobutrazol drench at different concentrations (0; 0.25; 0.50; 0.75 e 1.0 mg L-1 of substrate) on potted plants of sunflower cv Sunbright Supreme grown under protected environment. Two greenhouses were covered with transparent polyethylene film, 0,1 mm thick, and at one of them, the plastic film was applied over a blue photoselective plastic shadenet (30% of shading). Microclimatic and agronomic parameters were evaluated. The solar radiation was reduced by 27.5 % when the shadenet was used, which resulted in a very low influence on the air temperature and humidity in the shelter. Further, the use of the shadenet did not reduced plant height and did not influenced inflorescence diameter, the number of leaves per plant and the interval from transplant to flowering. Nevertheless, paclobutrazol substrate drench decreased plant height, leading to more compact plants that can be grown and commercialized in pots, without any loss to plant quality, since the inflorescence diameter was not affected. The use of the growth retardant delayed the flowering according to the drench concentration, but not exceeding one week.
photoselective plastic shadenet; plant growth retardant; Helianthus annuus; greenhouse
