SEASONAL VARIATIONS IN CAMBIAL ANATOMY OF PLANTATION-GROWN <em>AZADIRACHTA</em> <em>EXCELSA</em>

Abstract

WANG KH, NOBUCHI T, ABDUL AZIM AA & SAHRI MH. 2013. Seasonal variations in cambial anatomy of plantation-grown Azadirachta excelsa. Tropical trees do not have clear growth rings as they do not show clear radial growth periodicity. It is important to investigate the cambial structure and anatomical characteristics of cells derived from cambium in order to understand the characteristics of radial growth periodicity. A comparison of the anatomical characteristics of cambium in Azadirachta excelsa was carried out between actively and non-actively growing seasons. Wood blocks comprising bark, cambium and wood were collected from a living tree. Sections were cut from epoxy-embedded block using a microtome. A periodic acid-Schiff’s method was used for staining. The results revealed that the average numbers of cambial and enlarging cambial zone cells varied at different months. During the wet season, the cambium formed high number of wood cells. During the dry season, from November till February, the cambium was inactive. The cambial zone was active for most period of the year. This finding indicates that the cambial growth of A. excelsa is sensitive to environmental factors, particularly rainfall.