Участие фенольных соединений в реакции грецкого ореха на затопление почвы (INVOLVEMENT OF PHENOLIC COMPOUNDS IN WALNUT TREES RESPONSES TO SOIL FLOODING)

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Walnut trees have been shown to be very sensitive to abiotic stresses, especially to soil hypoxia consequence of soil flooding or waterlogging. The aim of study was to search for correlation between polyphenols and tolerance to flooding stress. Two-three years old walnut trees, Juglans regia, J. nigra and interspecific hybrids, grown in pots were subjected to soil flooding in summer at full leaves expansion. In high sensitive J. regia trees, when flooded, the net CO2 assimilation rapidly decreased and 3-4 days of flooding were enough to block the recovery when soils was drained. In walnut hybrid (J. nigra x J. regia) and less sensitive J. regia genotypes, a longer resistance was observed; after 13 days of treatment leaves culd still be green and trees can recovered till to the normal photosynthesis when drained. J. nigra when flooded reduced net photosynthetic rate but maintained leaves without damages and with the capacity to recover CO2 assimilation. The data showed resistance of J. nigra and hybrid trees and of some J. regia genotypes to the stress. The HPLC analyses of polyphenols showed a modification of the patterns during the stress. The plants less tolerant to hypoxia have higher content of polyphenols distributed in a lot of compounds. Trees more tolerant, J. nigra, showed a very simple HPLC pattern. All samples contained juglone, more in less tolerant genotypes. Hydroxy juglone glucoside was detectable in all genotypes, but only in low quantity, it increased in trees with high resistance to hypoxia and decreased in J. regia. Less flooded tolerant J. regia genotypes have higher polyphenols and juglone content. The metabolism of hydroxyl juglone glucoside could be involved in a mechanism of juglone detoxification during the hypoxia to give stress tolerance.