Seasonal changes and content of sodium in main organs of European plum trees (Prunus domestica L.), fruit size and yield as affected by rootstocks on acidic soil

In the present study, the seasonal changes of Na content of shoots, flower buds and flowers, and fruit weight and yield of two European plum cultivars ('Cacanska Lepotica' and 'Cacanska Najbolja') budded on Myrobalan (Prunus cerasifera Ehrh.) and Stanley rootstocks were analyzed after 6-8 years of planting on acidic sandy-loam soil. The Na content of the shoots and flower buds of each rootstock/cultivar combination varied during season, and the highest content in above organs was observed in May and August, respectively. The effect of rootstocks on the examined parameters was variable due to the strong rootstock/cultivar/year interaction observed. The shoots and flower buds of cultivars budded on Stanley and Myrobalan rootstocks gave the highest and lowest Na content, respectively, whereas the highest Na content in flowers registered in 'Cacanska Lepotica' on Myrobalan. The content of Na in the plum organs suggests the following trends: 1-year old shoots > 2-year-old shoots > flower buds > flowers. There were no statistically significant correlations among plum organs with respect to Na content. The Principal Component Analysis showed that Stanley rootstock had a higher Na accumulation and distribution capacity than Myrobalan rootstock in plum trees. Finally, content of Na in the main organs of plum trees and acidic soil have not a negative effect on fruit weight and yield of plum cultivars, since these properties were respectable.