Morphological, anatomical and physiological features of assimilation apparatus changes in Prunus armeniaca L infected by Plum pox virus

摘要

The southern coast of the Crimea refers to an arid climate zone with unstable moisture. Under these conditions drought and disease resistance, heat tolerance should be considered as the main criteria for apricot plants' normal growth and development.The objective of the present study was to identify the effects of apricot plant assimilation apparatus changes on the structural and physiological characteristics associated with the appearance of Plum pox virus (PPV) symptoms. Four apricot cultivars andone form were investigated in late July 2017 (the average daily air temperatures were 24-28°C, the maximum was 35.6°C, relative air humidity was 24-57%, the supply of productive moisture in soil was 38-49 mm (25-37% MR - moisture retention). The mainsymptoms of PPV were revealed in 10-40% of leaves and up to 30% fruits. Leaf blade structure in the damaged cultivars was characterized by decrease of a leaf size and thickness ('Iskorka Tavrydy' - from 220±17 to 174±11 mum) as well as palisade tissue('Iskorka Tavrydy' and 'Salyeri 99-266' were 24-30%), and increase of intercellular spaces in spongy parenchyma in 'Ananasniy Ukrainskiy". In 'Khersonskiy-23' and 'Salyeri 99-266' increase of stomata number 1.5-2 times was noted in the damaged plants. Evaluation of a photosynthetic apparatus activity demonstrated photoinhibition in leaves with the visible symptoms in 'Khersonskiy-23','Iskorka Tavrydy' and 'Salyeri 99-266' [F_(m (maximum fluorescence))-F_(st (stationary fluorescence))]/F_m =0.52-O.58 approximate units. The total water content in leaf tissues was 62-68%. Water deficiency was 14-23% (maximum in damaged cultivars 'Khersonsltiy-26' and 'Iskorka Tavrydy'). Thus, the indicated morphological, anatomical and physiological changes have decreased the resistance to hydrothermal stress and deteriorated of functional state of the damaged apricot plants.