Influence of Phloem Blockage on Cambial Growth of Sugar Maple

Abstract

Circular patches of bark were sugically isolated on the sides of sgar maple(Acer saccharum Marsh.) trees at breast height at various tiems during the dormant and growing seasson. Subsequently, samples of wood and attached bark were taken from isolated and control sites to determine the effects of isolation fo the bark on camila actitivty adn xylem and phloem development. in control sites cambial activtity and xylem and phloem develpment occurred normally. Isolation fo bark durign the dormant season(in Novemer, February or March) prevented initiation of cambial activity and xylemand phloem development in isiolated areas of half of the trees. Varying degrees of cambial activity and xylem and phloem devellpment were prevented. Isolation of bark after initiation of cambbial activtity and phloem differentiation but prior ot intiation of xylem diffentitation, resulted in the formation of very narrow xylem and phloem increments with atypically short vessel mbers and sieve-tube members, respectively. The xylem incrementrs consisted primarily of parenchyma cells. Isolation of bark after intiation of xylem differentiation resulted in curtailment of secondary wall formation in the last-formed part of many incresmnets . The last-formed sieve-tube memebers of corresponding phloem increments were atypically short. The atypically short cells inthe xylem and phloem of isolated areas reflected the effect of isolation on camial region viz., the subdivision fo all fusiform cells into strands of cells. Ultimately, the strands of short fusiform cells lapsed into maturitu ty, leavign only strands of parenchymatous elements between xylem and phloem.