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Effects of interrupted K + supply on growth and uptake of K + , Ca 2+ , Mg 2+ and Na + in spring wheat
Author(s) -
Jensén Paul
Publication year - 1982
Publication title -
physiologia plantarum
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.351
H-Index - 146
eISSN - 1399-3054
pISSN - 0031-9317
DOI - 10.1111/j.1399-3054.1982.tb00336.x
Subject(s) - shoot , divalent , nutrient , chemistry , dry weight , horticulture , biology , organic chemistry
Effects of interrupted K + supply on different parameters of growth and mineral cation nutrition were evaluated for spring wheat ( Triticum aestivum L. cv. Svenno). K + (2.0 m M ) was supplied to the plants during different periods in an otherwise complete nutrient solution. Shoot growth was reduced before root growth after interruption in K + supply. Root structure was greatly affected by the length of the period in K + ‐free nutrient solution. Root length was minimal, and root branching was maximal within a narrow range of K + status of the roots. This range corresponded to cultivation for the last 1 to 3 days, of 11 in total, in K + ‐free nutrient solution, or to continuous cultivation in solution containing 0.5 to 2 m M K + . In comparison, both higher and lower internal/external K + concentrations had inhibitory effects on root branching. However, the differing root morphology probably had no significant influence on the magnitude of Ca 2+ , Mg 2+ and Na + uptake. Uptake of Ca 2+ and especially Mg 2+ significantly increased after K + interruption, while Na + uptake was constant in the roots and slowly increased in the shoots. The two divalent cations could replace K + in the cells and maintain electroneutrality down to a certain minimal range of K + concentrations. This range was significantly higher in the shoot [110 to 140 μmol (g fresh weight) −1 ] than in the root [20 to 30 μmol (g fresh weight) −1 ]. It is suggested that the critical K + values are a measure of the minimal amount of K + that must be present for physiological activity in the cells. At the critical levels, K + ( 86 Rb) influx and Ca 2+ and Mg 2+ concentrations were maximal. Below the critical K + values, growth was reduced, and Ca 2+ and Mg 2+ could no longer substitute for K + for electrostatic balance. In a short‐term experiment, the ability of Ca 2+ to compete with K + in maintaining electroneutrality in the cells was studied in wheat seedlings with different K + status. The results indicate that K + , which was taken up actively and fastest at the external K + concentration used (2.0 m M ), partly determines the size of Ca 2+ influx.