Crescimento, composição química e desempenho fisiológico de sementes de trigo submetido a regulador de crescimento

Abstract

This work aimed to evaluate the growth of wheat plants subjected to the application of growth regulator and fertilization for high yields, as well as, chemical composition and physiological quality of seeds produced. The variety used was OR Topázio and the growth regulator was trinexapac-ethyl, via leaf application. On chapter I, the experiment was performed on greenhouse and the experimental design was completely randomized, factorial 5x8 (five doses and eight harvest dates) with four repetitions. Total dry matter, dry matter production rate, relative growth and net assimilation rates, leaf mass ratio, leaf area ratio and leaf area index were evaluated. The conversion efficiency of solar energy, assimilate partitioning, harvest index, plant height, seedling emergence and speed of emergence index were determined. On chapter II, the experiment was performed under completely randomized experimental design using five treatments and four repetitions, being evaluated germination and first count of germination, speed of germination index, seedling dry matter, electrical conductivity and accelerated aging. On chapter I, total dry matter allocation, relative growth rate, plant height and harvest index were reduced, with variable intensity, according to the growth regulator dose. The net assimilation rate was reduced in plants subjected to 400, 600 e 800 mL ha-1; leaf mass ratio and leaf area ratio were superior when doses of 400 and 800 mL ha-1 were used. The seedling emergence and the speed of emergence index were not affected by the action of the growth regulator. On chapter II, germination and first count of germination increased until the higher dose. Electrical conductivity after three hours of imbibition was reduced starting from the dose of 600 mL ha-1. The starch content increased until the dose of 448 mL ha-1; the amino acids up to the dose of 243 mL ha-1 and the protein content to the dose of 417 mL ha-1. There was a decrease on total soluble sugars content with the increase of growth regulator dose. Therefore, plants subject to the application of trinexapac-ethyl feature differential responses on growth and assimilate partitioning, lower harvest index and plant height. Seeds produced by these plants possess higher germination, vigor expression and starch, protein and amino acids contents, however, lower content of total soluble sugars.