Regulador de crescimento (cloreto de mepiquat) na embebição de sementes de algodão : crescimento e desenvolvimento inicial e produção

AUTOR(ES)
DATA DE PUBLICAÇÃO

2005

RESUMO

Ultra narrow row cotton production requires plants that do not exceed a certain height limit. Reduction in cotton plant height can be accomplished through genetic improvement, however, this is a slow and highly expensive technique. Another alternative to reduce the height of cotton plants, to facilitate crop management practices, is the use of growth regulators. The aim of the present study was to reduce the height of the cotton plants, starting at the seedling stage, as a way of increasing plant density using cotton seeds soaked in solutions with different concentrations of the growth regulator mepiquat chloride. The first experiment was conducted under greenhouse conditions in Londrina, PR, Brasil (23°29 S, 51°12 W), using plants of the cultivar IPR-120 planted in 2.5 L black plastic bags. A completely randomized factorial experimental design, comprising five mepiquat chloride concentration solutions (0; 0.5; 2.5; 5 e 7.5% (v/v)) and three soaking time intervals (3, 6 e 12h), was used. Each treatment was replicated five times. Evaluations were carried out weekly from emergence to the phenological stage F1 (first flower), 49 days of emergence. Compared to soaking in water, all treatments with mepiquat chloride solution reduced the height of the plant since its emergence. The statistical analysis revealed an interaction among the factors evaluated. It was also observed a reduction in the number of flower buds, branch, in the foliage, in the dry matter and in the insertion height of cotyledon node. In the second experiment the effect of soaking cotton seeds in mepiquat chloride solutions on plant height was evaluated under field conditions, in Londrina, PR. Cultivar IPR-120 seeds were soaked in solutions of five concentrations of mepiquat chloride (0; 0.5; 2.5; 5.0 e 7.5% (v/v)) and after emergence half of the experimental units was sprayed with the growth regulator and half was maintained without the product. A randomized block, arranged in a 5X2 factorial, design was used. Each treatment was replicated four times. It was observed that plant height was affect by the dose of mepiquat chloride used until the 31st day after emergence, not persisting thereafter. There was no interaction among the analyzed factors. The height of the cotyledon node was affected by the mepiquat chloride doses utilized on seed treatment, but not the height of insertion of the first productive branch, the total number of stem or the reproductive branch. However, there was an effect of the foliar applications on those parameters. There was no effect of the mepiquat chloride seed soaked treatment concentrations and of the foliar applications on the weight of cotton bolls.

ASSUNTO(S)

algodão - cultivo algodão - sementes agronomia. cotton growing cotton-seed.

ACESSO AO ARTIGO

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