Ion distribution in relation to leaf age in Leptochloa fusca^* (L.) Kunth (Kallar grass): I. K, Na, Ca and Mg

Using Leptochloa fusca (Kallar grass) plants, the distribution of K, Na, Mg and Ca between leaves of various ages has been studied. Plants grown in a salt-affected, reclaimed field, in a solution culture and in soil in pots at 10, 100 and 125 mM NaCl have been analyzed. Despite the presence of salt-secreting glands on Leptochloa fusca leaves, Na concentrations increased strongly with leaf age, while K concentrations were highest in young leaves and decreased with increasing leaf age. This was due to K retranslocation, which was clearly intensified at higher external NaCl concentration. The data point to the importance of K recycling in this halophyte and also to the use of Na by this salt-secreting species for turgor maintenance in mature and old leaves. Both Mg and particularly Ca concentrations increased with leaf age, indicating that xylem import surpassed phloem export even for the phloem-mobile ion, Mg. In young leaves, Mg concentrations exceeded those of Ca.