Desenvolvimento morfológico de folhas de Hevea brasiliensis Muell. Arg. e H. pauciflora Muell. Arg. submetidas a dois regimes hídricos

Abstract

In rubber trees the morphological characteristics related to foliar ontogeny were influenced by a water stress regime. For Hevea brasiliensis and H. pauciplora water stress provoked a significant reduction in 1) number of leaves, 2) lenght of the central leaflet, 30) leaf dry wight., 4) leaf wet weight, 5) class of angle, between petiole and leaflet and 5) grafted sprout size. Under the two different experimental water regimes little difference was found in thickness of leaf anatomical tissues, probably because the water stress was applied for a short period and because ambient conditions have little effect on development of the these tissues. Nonetheless, H. pauciflora tends to show greater resistance to water loss in comparison with H. brasillensis (clone IAN 873), and also has more xeromorphic leaver. Physiologic age of rubber tree leaves did not correlate well with either the class of angle between petiole and leaflet or the plastochron index. It was possible, however, to determine the reference value (R = 50.0 mm) for the rubber tree. Plants under water stress showed a lower rate of leaf emergence as the graft sprouted. The class of angle between the petiole and leaflet was significantly affected by ambient conditions.