Inibição do florescimento natural de abacaxizeiro após a aplicação de reguladores de crescimento

Abstract

The natural flowering of pineapple is one of the major problems of culture, which can trigger on a uneven flowering generating losses for the activity. For that reason, two experiments were carried out in order to determine the effects of two growth regulators on vegetative characteristics, natural flowering and quality of 'Pérola', 'Vitória' and 'IAC Fantastico' pineapple fruit. The experiments were conducted in the experimental area in Janaúba city, state of Minas Gerais. The culture was planted in double rows spaced at 0.9 x 0.4 x 0.3 m. The first experiment was arranged in a randomized block design using the regulator growth 1-methylcyclopropene. The vegetative growth evaluations were conducted in split plot scheme in space and time ( 5 x 3 x 8 ) with four replications, with five treatments concerning concentrations of 1-MCP, T1: control, 0.00 mgL-1; T2: one weekly application, totaling eight applications at a concentration of 37.5 mgL-1; T3: one application every 14 days, totaling four applications at a concentration of 75 mgL-1; T4: a weekly application, totaling eight applications at a concentration of 75 mgL-1; T5: an application every 14 days, totaling four applications at a concentration of 150 mgL-1, in the plot, three commercial pineapple cultivars ('Pérola', 'Vitória' and 'IAC Fantastico') in the subplot, and nine times of evaluation in the subplot. For the percentage of natural flowering, mortality of plants and fruit quality, the scheme was split plot in space (5 x 3), with four replications, with five treatments concerning to concentrations of 1-MCP in the parcel; three commercial pineapple cultivars ('Pérola', 'Vitória' and 'IAC Fantastico') in the subplot. The second experiment was conducted in a randomized block design using the growth regulator 2-(3- chlorophenoxy) propionic acid. The evaluations of vegetative growth were conducted in split plot scheme in space and time (5 x 2 x 10) with four replications, with five treatments concerning to ACP concentrations, 0, 30 , 90 , 120 and 150 mgL-1 with applications every 14 days totaling four applications, in the plot; two commercial pineapple cultivars ('Pérola' and ' Vitória') in the subplot and ten times of evaluations in the subplot. For the percentage of natural flowering, mortality of plants and fruit quality, the scheme was split plot in space (5 x 2), with four replications, with five treatments concerning concentrations of ACP in the parcel; two commercial cultivars of pineapple ('Pérola' and ' Vitória') in the subplot. Each plot consisted of 60 plants, 20 plants of each cultivar, in which all the plants were used for evaluation of the experiment. The evaluated characteristics were: stem diameter at ground level; length of the D leaf; number of leaves adding leaves grown every month; natural flowering in the first and second year after planting and the total accumulated; Accumulated accumulated mortality of plants; average fruit weight with and without crown; fruit length with and without crown; average fruit diameter; fruit firmness; soluble solids; titratable acidity; SS/TA ratio and hydrogen potential. In the first experiment, for stem diameter, leaf length and number of D leaf grown, it was observed a significant interaction of cultivars and assessment time in different concentrations of 1-methylcyclopropene (1-MCP). In the analysis of natural flowering and mortality of plants, there was a significant effect only on the characteristics of the cultivars studied. Application of 1-MCP had no significant effect, that may be due to the product formulation that when it is mixed with water it becomes a gas. In evaluating the fruit quality, it was found that there was isolated significant effect of treatments with 1-MCP and cultivars on the structural and physical-chemical characteristics of fruits, except for titratable acidity (TA), pH and SS / TA ratio. In the second experiment there was a significant interaction between evaluation periods (days after planting) and doses of ACP solution on the characteristics of vegetative development, with the decrease of plant development. Some phytotoxic effects on pineapple plants, such as anomalies and even plant death caused by ACP were observed. There was a lack of significant effect of the factors studied on the natural flowering in the first year and plant mortality. However, significant effect of concentrations of ACP on the natural flowering of the second year, the total accumulated natural flowering was observed. In the evaluation of structural and physical-chemical characteristics of fruits, there was no significant effect of concentrations of ACP and cultivars.