Seasonality and growth rings in lianas of Bignoniaceae
Lima AC; Pace MR; Angyalossy V
Trees - Structure and Function
Lianas are one of the most important components\nof tropical forest and yet one of the most poorly\nknown organisms. Therefore our paper addresses questions\non the environmental and developmental aspects that\ninfluence the growth of lianas of Bignoniaceae tribe\nBignonieae. In order to better understand their growth we\nstudied the stem anatomy seasonality of formation and\ndifferentiation of secondary tissues and the influence of the\ncambial variant in xylem development on a selected species:\nTynanthus cognatus. Afterwards we compared the\nresults found in T. cognatus with 31 other species of\nBignonieae to identify general patterns of growth in lianas\nof this tribe. We found that cambial activity starts toward\nthe end of the rainy season and onset of the dry season in\ncontrast to what is known for tropical trees and shrubs.\nMoreover their pattern of xylem formation and differentiation\nis strongly influenced by the presence of massive\nwedges of phloem produced by a variant cambium. Thus\nthe variant cambium is the first to commence its activity\nand only subsequently does cambial activity progress\ntowards the center of the regular region leading to the\nformation of confluent growth rings. In summary we\nconclude that: the cambium responds to environmental\nchanges; the xylem growth rings are annual and produced\nin a brief period of about 2 months something that may\nexplain why lianas possess narrow stems; and furthermore\nphloem wedges greatly influence cambial activity.