Reguladores de crescimento na inibição da floração abacaxizeiro cv. pérola

Abstract

Natural flowering in pineapple is very inconvenient and has caused, with increasing intensity, significant losses in all producing regions around the world. The objective of this work was to determine the role of substances which inhibit the vegetative growth of the plant, in different seasons of the year, on the inhibition, reduction or delay of the natural flowering of pineapple, cv. Perola. Three experiments were conducted at the experimental field of Embrapa Cassava and Tropical Fruit Crops, in Cruz das Almas, Bahia, during the years of 1995-1999. Urea — U (foliar, 5 %, and solid, 1,5 g/plant) and the following growth substances were used: 2-(3-chlorophenoxy) propionic acid — ACP (45 to 300 mg L-1), paclobutrazol — PCB (77.4 to 320 mg 1,4), mepiquat chloride — CM (60 to 480 mg L"1), gibberelic acid - GA3 (30 and 60 mg L"1 ), tebuconazole — TBZ (60 to 180 mg L"1 ) and propaconazole — PPZ (120 mg L"1 ). The treatments were applied as two to four equally split applications, fortnightly (early in the morning), from April to July, which comprises the critical period for natural flowering in the region. The results obtained have shown that ACP and PCB are capable of inhibiting, reducing and delaying the natural flowering of pineapple, in the concentrations of 50 to 240 mg 1 -1, and also affecting the leaf mass, slip production and fruit harvesting period. The better results were obtained when the growth regulators were applied during the months of April and May. The other products did not affect the natural flowering of pineapple, neither the other variables studied. However, the variation observed in the effects and efficiency of the used growth regulators indicates the necessity of validating the most effective treatments under the environmental and cultural conditions in the other producing regions of the country, and also with other cultivars, mainly the `Smooth Cayenne'. The selected growth regulators can be used in studies about the mechanisms of the flowering initiation in pineapple.