Inhibition of cambial activity inAbies balsameaby internal water stress: role of abscisic acid

摘要

In experiments with attached and detached shoots of balsam fir,Abies balsameaL., synthetic (plusmn;)abscisic acid (ABA) (1) reduced photosynthesis and transpiration by inducing stomatal closure, (2) inhibited indoleacetic acid (IAA) - induced cambial activity in photosynthesizing and non-photosynthesizing shoots, and (3) inhibited the basipetal movement of 14CIAA. Neither gibberellic acid nor kinetin counteracted the inhibitory effect of (plusmn;)ABA on IAA-induced cambial activity. In addition it was demonstrated that increasing the internal water stress increased the level of endogenous ABA in the phloemndash;cambial region of bark peelings and decreased the basipetal movement of 14CIAA through branch sections. On the basis of these findings it is proposed that internal water stress inhibits cambial activity, partly through increasing the level of ABA; the ABA acts to decrease the provision of carbohydrates and auxin that are required for cambial growth.