Citrus volkameriana Grown Under Salinity: Impacts on Soil Properties, Plant Growth, Leaf Physiological and Biochemical Indices and Nutrient Content

Abstract Salinity is a major constraint in many areas of the world where citrus trees are cultivated. Understanding the role and physiological functions of the rootstock used could provide valuable information for understanding salinity tolerance. For this reason, Citrus volkameriana plants were grown under four levels of sodium chloride salinity (0, 40, 80, and 120 mM) to assess possible effects on soil properties, plant growth, nutrition, biochemistry and physiology. Soil electrical conductivity increased with increasing salt concentration (8x) while potassium concentration increased up to 80 mM and subsequently decreased under 120 mM. Increased sodium and especially chloride concentration was detected in all plant parts (roots, stem and leaves). At the same time, the calcium concentration in the leaves was reduced under the two highest salinity levels. Plant growth was impaired, although the plant exhibited a high tolerance index of up to 80 mM. The photosynthetic capacity of the leaves was severely affected as well as leaf chlorophyll concertation, while sugar concentration in the leaves decreased only under the highest level (120 mM), where the highest proline concentration was also detected. Leaves exhibited reduced relative water content as well as high electrolyte leakage, with no signs of lipid peroxidation though, while neither the phenolic compounds nor the antioxidant capacity of the leaves significantly changed with salinity, which is a new finding regarding citrus response under saline conditions. Based on these results it seems that volkamer can be considered a valuable citrus rootstock under moderate salinity level though.