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

SUMMARYUsing Leptochloa fusca (L.) Kunth (Kallar grass) plants, the distrihution of Cl", NO.,-, H.^PO^', SO;^" and malate between leaves of various ages has been studied. Plants grown in a reclaimed, salt-affected field, in solution culture and in soil at 10, 100 and 125 mM NaCl have been analyzed. Apparently due to excretion by salt secreting glands on L. fusca leaves and to phloem export, Cr concentrations did not increase strongly with leaf age. On a leaf f. wt basis, chloride secretion was constant over the series of increasingly aged mature leaves. If it was related to the chloride increments in the leaves, chloride secretion increased strongly from younger to mature leaves and reached between ISO and 200% of the concurrent Cl' deposition in the lamina. Changes in the tissue concentrations of nitrate and phosphate with leafage showed a maximum in recently matured leaves. Decreases in older leaves were attributed to nitrate reduction and export of reduced nitrogen and to retranslocation of phosphate. In leaves of field-grown L, fusca nitrate was non-detectable. Sulphate and malate concentrations in laminae continued to increase from the youngest to the oldest leaves. The increasing negative charge resulting from these increases in divalent anions can be accounted for by the loss of charge occurring in connection with reduction of nitrate and export of phosphate. Higher external salinity led, apart from increases in tissue Cl", to noticeable decreases in tissue nitrate and phosphate but not in sulphate and malate concentrations, the latter being even increased at higher external NaCl. The observed changes in anion concentrations are compared with and discussed in relation to changes found in Ricinus communis and in Atriplex hortensis.

Leptochloa fusca (L.) Kunth and Atriplex hortensis (L.) were grown on quartz sand or in liquid culture in the presence of varied concentrations of NaC1. Xylem sap was collected as (a) root pressure exudate, in L. fusca even at 100 mM NaC1, (b) by applying pressure to excised roots of L. fusca and (c) from leaves of the whole plant growing in quartz sand by pressurizing the root system. The latter procedure failed in L. fusca due to the passage of air and soil solution into the leaves. This was caused by an extensive aerenchyma in root cortex. In Atriplex hortensis remarkably high pressures were required to induce a flow of sap. The mineral cation and anion and the amino acid composition of the xylem sap obtained by the different methods was measured and is examined in view of using it for determining the flows of minerals in the whole plant and in relation to the effects of salinity. The spacious aerenchyma in roots of L. fusca has been found to persist also after prolonged exposure to dry air.