Ion distribution in relation to leaf age inLeptochloa fusca(L.) Kunth* (Kallar grass) II. Anions*^†

Abstract

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.

Partitioning and flows of ions and nutrients in salt‐treated plants ofLeptochloa fuscaL. Kunth

“…In the youngest laminae (leaves 8 and 9) the secretion rate relative to fresh weight was low and it increased to a fairly constant value in mature leaves. The rates found compare well with published data of Gorham (1987) (see discussion in Klagges et aL, 1993). Secretion from sheaths, occurring from the abaxial surface only, was around a third of that from laminae (Table 1) a fresh weight basis only one fourth.…”

“…The secretion of Na' by salt glands on the lamina and sheath of the series of differently aged leaves during the study period is given in Table 1; data for Cl" secretion have been presented in a previous paper (Klagges et al, 1993). In the youngest laminae (leaves 8 and 9) the secretion rate relative to fresh weight was low and it increased to a fairly constant value in mature leaves.…”

Mechanisms of Cl‐ transport contributing to salt tolerance

“…1987). Partitioning of Cl ‐ in the sheath versus laminae was also found for the salt‐tolerant grass Leptochloa fusca (Klagges et al. 1993) and for barley (Greenway 1962).…”

“…Possibly, this partitioning keeps potentially toxic levels of Claway from the primary sites of photosynthesis in the leaf, and is proposed to be important to salt tolerance of sorghum (Boursier et al 1987). Partitioning of Clin the sheath versus laminae was also found for the salt-tolerant grass Leptochloa fusca (Klagges et al 1993) and for barley (Greenway 1962). For other species, such as grapevines, petioles can also accumulate high Clconcentrations to protect the laminae (Downton 1977).…”

Flooding tolerance in halophytes

“…Although glands can secrete a range of ions (e.g. S. anglica ; Rozema et al ., 1991), phosphate was not secreted by glands of Leptochloa fusca (Gorham, 1987; Klagges et al ., 1993), supporting the view that phosphate (and other solutes) might be lost from submerged leaves via ‘leaching’ rather than secretion. These processes should be evaluated for a range of halophytes with and without salt glands.…”