THE ECOPHYSIOLOGICAL REACTION OF SOME VARIETIES OF APPLE TREE, PEAR TREE AND QUINCE TREE TO THE PATHOGENIC AGENTS ATTACK

The research was carried out in 2004, on material from horticultural collections of the Didactical Station “Vasile Adamachi” within the University of Agricultural Sciences and Veterinarian Medicine of Ia i. The investigations were performed on three fruit tree species: Cydonia oblonga Mill., Pyrus communis L., and Malus domestica Borkh. and consisted in revealing the morphological symptoms induced by the attack of the pathogen Erwinia amylovora (Burrill 1882) Winslow et al. The biochemical (contents of water, assimilatory pigments and total mineral) and physiological analyses (intensity of photosynthesis, respiration and transpiration) were carried out on healthy and with different infection degree material of two varieties for each species: “Jonathan” and “Generos” (apple tree), “Williams” and “Argesis” (pear tree), “Mo na” and “De Hu i” (quince tree). The results revealed the correlation between the physiological alterations and the severity of the pathogenic attack: in weakly attacked (5 – 8% per tree) “Jonathan” (apple), “Argesis” (pear) and “De Hu i” (quince) samples we recorded high contents of water and minerals and an increase of the net photosynthesis intensity compared to the “Williams” (pear) variety and relatively strong bacterial attack (12%). Large differences between healthy and infected leaves were recorded in “Mo na” (quince) at a bacterial attack of 38%, which induced a decrease in pigment content (20%), net photosynthesis (50%), water content (76%), transpiration (38%), and an increase in respiration (117%).