POTASSIUM DEFICIENCY AND EXCESS IN GUAYULE. II. CATION-ANION BALANCE IN THE LEAVES

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Abstract
Cation-anion relationships were studied in expanding and mature leaves of guayule (Parthenium argentatum) plants which had received low, intermediate or high levels of K supply in each of 2 series of treatments differing in Ca and Na supply. The excess of cations over inorganic anions is not nearly balanced by ether-soluble organic acids. This discrepancy is largely accounted for by carbonate. Most of the carbonate is insoluble and is localized in the epidermal trichomes. Insoluble Ca concn. is closely related to insoluble carbonate concn. in the leaves. Values for these components are low in high K leaves. Oxalic acid could not be detected. Total organic acids and values for excess of cations over inorganic anions in the leaves were at least as high in low K as in intermediate K treatments of a given series, indicating that in guayule lack of sufficient organic acids to serve as buffers is not an early symptom of K deficiency. In expanding leaves soluble organic acids were related to excess of soluble cations. In these leaves soluble organic acids were high for high K leaves. Citric acid was relatively high in these leaves. In mature leaves, sap-soluble Ca was correlated with sap-soluble malic acid. Malic acid was lower in expanding leaves, but in these leaves, too, the highest malic acid concn. was found in leaves highest in Ca.