1977 Volume 45 Issue 4 Pages 349-361
In order to clarify the mechanism of necrosis development in the resistant host in response to chestnut gall wasps, polyphenoloxidase and some dehydrogenase activities in gall and healthy tissues of susceptible and resistant varieties were investigated histochemically.
In healthy tissues, polyphenoloxidase (PPO) activity was high in parenchymatous tissues surrounding vascular bundles but low in mesophyll tissues. In general, the activity in gall tissues was reduced as compared with healthy tissues of both susceptible and resistant varieties. But, PPO activity in gall tissues of resistant varieties was higher than that of the susceptible varieties. Also, boundary tissues intervened between healthy and gall tissues of the former varieties, and such boundary tissues consisting of parenchymatous cells around vascular bundles displayed a large increase in activity.
Reduction of tetrazolium salts in gall tissues of susceptible varieties was decreased by treatment with heating, freezing and enzyme poisons. This implies that the reduction is caused by coenzyme requiring enzymes. Dehydrogenase activity was also inhibited by 10-3M tannic acid or 0.4% tannins obtained from the resistant chestnut bark.
Dehydrogenase activity was low in normal young leaf tissues but very high, similar to apical tissue, in the infected tissues (gall tissues) of the susceptible varieties. by the parasite. However, dehydrogenase was not activated in those of the resistant varieties.
Healthy tissues were low in NADP-hydrogenase and glucose-6-phosphate dehydrogenase activity. However, as the normal tissues galled, the tissues of susceptible varieties showed high activities of NAD- and NADP-hydrogenase, glucose-6-phosphate dehydrogenase and iso-citrate dehydrogenase which might play important roles in the physiology of gall formation and nutrition supply for the parasite. On other hand, the tissues of resistant varieties were low in activity in coenzyme requiring enzymes.
