Variations in the lengths of fusiform cambial cells and vessel elements inKalopanax pictus

Samples of a mature specimen of Kalopanax pictus, a ring-porous hardwood, w ere studied to compare the respective lengths of fusiform cambial cells and vessel elements in the stem. The lengths of dormant and reactivated fusifo rm cambial cells were measured with a confocal laser scanning microscope in tissue that had been macerated by digestion with pectinase and in thick ta ngential sections. The lengths of early wood and late wood vessel elements were measured in tissues that had been macerated by Franklin's method. The vessel elements and fusiform cambial cells varied considerably in length wi thin individual samples. The mean length of early wood vessel elements corr esponded to that of fusiform cells in the dormant cambium but not in the re activated cambium. Significant differences were observed between the mean l engths of dormant and reactivated Fusiform cambial cells, between those of reactivated fusiform cambial cells and early wood vessel elements, between those of reactivated fusiform cambial cells and late wood Vessel elements, and between those of early wood and late wood vessel elements. The frequenc y distributions of lengths of cambial cells were bimodal and differed from those of vessel elements, which more closely resembled a normal distributio n. The proportion of shorter lengths was higher in the reactivated cambium than in the dormant cambium, the early wood and the late wood vessel elemen ts. Our results do not suppot the hypothesis that the lengths of early wood vessel elements in ring-porous hardwoods change during differentiation. Th e similar ranges of recorded lengths suggest that short and long vessel ele ments might be derived directly from short and long cambial cells, respecti vely. (C) 1999 Annals of Botany Company.