In a study w ith the objective of controlling the natural precocious flowering in pineapple 'Perola', the plants treated with the 2-(3-chlorophenoxy) propionic acid - CPA (50 and 100 mg L-1, 3 applications) showed some internal and external modifications in the leaves. The young 'E' and 'F' leaves presented small constrictions on the central portion of their limbs, while on the 'C' and 'D' ones, those constrictions were observed near to their bases. At about 5-10 cm from that point emerged some structures similar to a callus, on which originated adventitious roots. The central rosette showed shorter and wider leaves. Anatomical cuttings of the leaves, observed under optical microscope (40X), showed that the adventitious roots were originated from meristems found in the vascular bundles (xylem and phloem), and that the anatomical structure of the leaves, on the constriction points, was not modified. Assimilative parenchyma was observed on the cortex of those adventitious roots, suggesting that this tissue carried on photosynthesis. The localization of the adventitious roots corresponded probably to the point of accumulation of the applied product on the leaves. Those effects suggest the possibility of CPA use in studies of rooting induction in conventional vegetative propagation and micropropagation, and in callus formation "in vitro". And also, to guide new studies on natural flowering inhibition and its practical use, in order to avoid damage to the plants.
Ananas comosus; growth regulator; adventitious roots
