SALINITY AND SHADING EFFECTS ON LEAF WATER RELATIONS AND IONIC COMPOSITION OF STRAWBERRY PLANTS GROWN ON ROCKWOOL

Strawberry plants were grown in rockwool under glasshouse conditions at NaCl salinities of 2.6, 5.9 and 8.6 mS cm-1 and at total irradiances of 2.1 and 4.9 MJ m-2d-1. Increasing salinity and irradiance reduced leaf water potential (psiomega), osmotic potential (psipi) and turgor potential (psitau). There was an interaction between salinity and irradiance on psipi with the lowest psipi recorded for the unshaded leaves. Increased salinity altered the ionic composition of the leaf. Chloride concentration was increased from 0.03 to 0.61% (D.W.) while NO3 content in the leaf sap was reduced from 10.51 to 3.60 mg ml-1 as salinity increased from 2.6 to 8.6 mS cm-1. Expressed on a fresh-weight basis, the concentration of K was reduced at high irradiance whereas Ca and Mg were enhanced. On a dry-weight basis K, Na, Ca and Mg were unaffected by salinity treatment. Net photosynthesis was reduced by high salinity but only in plants grown in unshaded conditions.