Annual Rhythm of Cambial Activity in Streblus Asper

Abstract

Cambial strueture and aetivity of Streblus asper Lour. vary with the loeal c1imate. The eells start swelling eady in May prior to the onset of peric1inal divisions whieh are most frequent in September. The cell division stops in Oetober indieating the approach of dormaney. During the growth season, initiation as well as eessation of the xylem produetion preeedes that of phloem. High temperatures induee the eambial reaetivation. Onee initiated, the aetivity eontinues at relatively low temperatures. Hot and moderately humid eonditions in June favour xylogenesis whereas phloem differentiation begins at relatively low temperature and high humidity in July. The eoneurrent differentiation of xylem and phloem has its peak in August-September. The size and relative proportion of eambial initials change with the season. Fusiform initials are shorter and broader during the rainy season (July-September) than during the rest of the year. Tetraseriate rays and tall rays outnumber the other types of rays throughout the year.