VARIATIONS IN SAPWOOD STARCH LEVELS IN SOME AUSTRALIAN FOREST SPECIES

SUMMARY Variations in the sapwood starch levels have been investigated in some Eucalyptus spp. and Angophora costata (Gaertn.). J. Britt. in relation to season and to regeneration after defoliation. Starch was estimated by iodine spectrophotometry. During the period of regeneration following defoliation starch levels were reduced. The reduction in starch was significantly greater than seasonal changes. The extent of the starch loss appeared to be related to the severity of the defoliation. In Angophora costata sapwood starch levels approached their minimum values at approximately 100 days after spring defoliation. Sapwood of trees which had died after defoliation showed nil starch content. Death of trees after repeated insect defoliation could be due to the exhaustion of starch reserves to a level which, in the absence of a photosynthetic organ, does not support respiration or growth.