Effect of paclobutrazol as regulator of growth in production of flowers of sunflower in cultivo hidropônico

This work had the aim of studying the effects of a growth regulator (paclobutrazol) on the growth and the production of sunflowers in vases, with hidroponic solution. Two sunflower genotipes were used (BRS Oásis and Helio 358), combined with sixpaclobutrazol doses (0;0,5;1;2;4 and 6 mg.L-1) and inert substratum of silex ground. The nutritious solution was a Hoagland modified (EPSTEIN & BLOOM, 2004) and the plants were maintained under constant aeration. To evaluate the effects of the paclobutrazol on the growth of the plants (final height and head diameter), the variables were submitted to the variation analysis (F tests) , being used routines of the system SAS/STAT, being applied, for the significant values at 5% of probability and the lineal and not lineal regression for the analysis of the parameters checked, in function of the growth regulator doses. The analysis of the data allowed to conclude that there is effect of the paclobutrazol on the growth and on the production of sunflowers, reducing the final height of the plants and head diameter, and the high doses caused deformations in the plants and bad formation in the flowers. Helio 358 presented to be more adequate for the ornamental production, being the best dose between 1 and 2 mgL-1de paclobutrazol.

Paclobutrazol; head diameter; plant height; Helianthus annuus

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