In potato crop, the excessive leaf growth in the later stages of the cycle can negatively affect the tuber yield. Under these conditions, the use of retarders or plant growth regulators can be an alternative to improve the yield of crop, by reduce plant height and to increase the allocation of dry matter (DM) for growing tubers. Thus, the aim of this study was to evaluate the effect of plant growth regulators mepiquat chloride, chlormequat chloride, placobutrazol, and prohexadione-calcium in the accumulation of DM, yield and quality of tubers of potato cv. Agata. The experiment will be carried out in the experimental design of randomized blocks, in factorial scheme of 4x5+1, with four replications. The treatments are represented by four plant growth regulators (mepiquat chloride, chlormequat chloride, placobutrazol, and prohexadione-calcium) applied at rates of 25, 50, 100, 200, and 400 g ha-1, besides the control treatment (no application of plant growth regulator). The plots will be composed of five 5-m-long rows of plants. The following variables will be evaluated in the tuber bulking stage (70 DAP): a) number of stems per plant and length of the longest stem; b) number of leaves per plant; and c) leaf area and leaf area index. Before the crop desiccation will be determined the DM accumulation in shoots, tubers and whole plant. In the harvest will be evaluated: a) number of tubers per plant, incidence of misshapen tubers and tuber mean weight; b) yield and classification of tubers produced; c) tubers shape index; d) percentage of DM in tubers; and e) firmness of tubers. The data will be submitted to ANOVA. The means of the plant growth regulators are compared by LSD test (pd0.05), while the effects of rates of plant growth regulators will be assessed by regression analysis (pd0.05).
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