SUMMARYUsing 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 Beld, 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 leafage, 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.

SUMMARYAn empirically based modelling technique, based on the relative immobility of Ca^+ in phloem, was used quantitatively to describe uptake, flow in xylem and phloem, and partitioning of K*, Na', Mg'^^, and Cr for a 13-d period at the end of vegetative growth of the main shoot in Leptochloa fusca (L.) Kunth grown in presence of 100 mM NaCl. The model incorporated data on net inerements of the ions in the root, the stem, individual leaf sheaths and laminae (blades), and tillers, secretion of salt by glandular hairs on sheaths and laminae, and the molar ion:Ca ratios in the xylem sap. Molar ratios of uptake of Na:Cl:K were 1-27:112:1, indicating an uptake selectiyity of 11-3 in favour of K+ against Na+. The flow pattern of K+ in the main shoot featured relatively low permanent deposition (22 % of the intake into the shoot in the stem axis and 10 % in leaves) but a high return flow via phloem to the root (67%) followed by cyelingof K'. In the whole plant a large share (72 "") of K* uptake was utilized for growth of tillers but K' cycling from shoot to root amounted to 96 "o of uptake. The flow pattern of Na'^ featured a somewhat smaller commitment (62 %) to deposition in tillers. In the main shoot 33 % of Na"' intake was deposited in the stem and 35 % in leaves. In these the sheaths incorporated by far the larger (2-8-fold) share compared with the laminae. Of the total Na' intake, 9% was excreted by salt glands (3-3-fold more by laminae than sheaths) and only 31 % was translocated to the root via phloem. Flows and partitioning of Cr were similar to those of Na"^, but phloem transport was larger (60% of intake into the main shoot) than that of Na+. The flow patterns are discussed in relation to changes in ion concentrations of leaves with leafage and in relation to snlmity tolerance. It is suggested that besides salt secretion a high efficiency in K* utilization contributes to the performance of this halophyte in presence of salt

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An experiment was conducted to determine the effect of water stress on nutritional changes in tolerant (DS-4 and Chakwal-86) and susceptible (DS-17 and Pavon) genotypes in lysimeters. The stress was imposed at different growth stages (preanthesis, post-anthesis, terminal drought). The biomass (dry weight) and Ca, Mg and P concentration decreased with water stress in all the wheat genotypes. However, the tolerant genotypes had less reduction than susceptible at all the treatments. Potassium increased in all wheat genotypes due to water stress and was higher in tolerant than susceptible genotypes. Sodium content was not affected by water stress.

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