Dependence of Calcium Transport into Strawberry Leaves on Positive Pressure in the Xylem

Strawberry plants were cultured in concentrated and dilute nutrientsolutions by day and night, factorially. Guttation decreased,leaf tipburn increased and calcium in emerging leaves was reducedwhen solutions were more concentrated at night. Nutrient concentrationin the daytime was much less important for these responses.The effects were similar when the more concentrated solutioncontained additional Ca²⁺, NO₂^–, Cl^– and SO₄^2–or extra of all the major nutrients in the same proportions.When the solution was made stronger by adding extra Mg²⁺, NO₂^–,Cl^– and SO₄^2– the guttation, tipburn and calciumdifferences were basically similar to those in the previousexperiment but with an added effect explained by a competitivesuppression of calcium uptake caused by the extra magnesium.Thus, both nutrient strength and cation balance are importantfor preventing strawberry leaf tipburn. The results accord with the hypothesis that calcium translocationinto pre-emerged strawberry leaves depends on the attainmentof a positive water pressure in the xylem at night, when transpirationlosses are minimal. Fragaria ananassa Duchesne, Strawberry, calcium, tipburn, root pressure, nutrient concentrations