A. Saeed Bhatti

Na+ and Cl−: Leaf extrusion, retranslocation and root efflux in diplachne fusca (kallar grass) grown in NaCl

Abstract Groups of “Kallar”; grass plants were subjected to various treatments of 100 mM NaCl simultaneously labelled with 22Na+ and 36Cl−. On the basis of the specific activity, the distribution of Na and Cl− in the tissue was followed during and after treatment, i.e. after transfer of some groups to an identical but inactive solution. Sequential collections of leaf washes showed that both Na and Cl− were extruded at a somewhat constant rate. Leaf sheaths accumulated more Na+ and Cl− than the leaf blades and the amounts of Na+ and Cl− in the leaf sheaths as a percentage of their total plant content (i.e. 28% and 31%) approximated the amounts of Na and Cl− extruded by the leaves (i.e. 23%). Moreover, almost equivalent amounts of Na+ (21%) and Cl− (29%) were removed by root efflux which continued even several days after transfer of the plants to the inactive, saline solution. Part of the Na+ and Cl− was retranslocated from the tops to the roots and was attributed to phloem export. Tolerance of Kallar grass...

Time sequence studies on uptake and distribution of Na+ and Cl– in diplachne fusca (Kallar grass) grown in NaCl

Abstract The time sequence of uptake and distribution of labelled Na and Cl– in osmotically adjusted “Kallar”; grass was studied at low (10 mM) and moderately high salinity (100 mM) in nutrient solutions. Increasing NaCl raised the concentrations of Na+ and Cl– in the tissue of tops and roots but had little or no effect on plant growth. On the leaves no toxic symptoms were obvious, not even in plants grown at salt stress of 200 mM NaCl. In all treatments, the young and the old leaves extruded 30–60% and 30–70% of their total Na+ and Cl–. As the amounts of Na+ and Cl– in the tissue increased with time, their extrusion also increased, however, as a proportion of the total Na+ and Cl– it did not change much with time. Autoradiographs revealed that the extruded salts were distributed equally on the upper and lower surface of all leaves, parallel to veins. There seemed to be a more intense distribution of Na+ and Cl– in the leaf sheaths as well as in the apical region of the roots. However, the net transfer ra...

Collection and composition of xylem sap and root structure in two halophytic species

Leptochloa fusca (L.) Kunth and Atriplex hortensis (L.) were grown on quartz sand or in liquid culture in the presence of varied concentrations of NaCl. Xylem sap was collected as (a) root pressure exudate, in L. fusca even at 100 mM NaCl, (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.

Response of corn to micronutrients (Zn and Cu) on a saline soil. I. Growth and ionic relationships

SummaryResponse of corn to Zn and Cu on a salinized soil in pots has been studied. Zinc increased the dry weights of tops and roots at all levels of NaCl+CaCl2. Increasing Zn level increased the weights considerably at 10 mM NaCl+CaCl2. Copper increased the weight of tops at 10 mM NaCl+CaCl2: it had little effects on plant weights at 50–125 mM NaCl+CaCl2. The growth response of plant to low Cu was somewhat similar to that of higher Zinc.NaCl+CaCl2 treatments, in general, increased Zn concentrations in tops as well as roots. At low Zn application, Zn concentrations in the tops were higher than those in the roots but at high Zn application, the concentrations of Zn in tops were similar to those in the roots.NaCl+CaCl2 treatments increased Cu concentrations in the tops to a slight extent but had a depressive effect on those in the roots. Copper concentrations in the tops were, however, much below those in the roots. The greater retention of Cu in the roots remains to be explained.

Secretion and uptake of salt ions by detached Leptochloa fusca L. Kunth (Kallar grass) leaves

Abstract Data on time dependence of secretion of ions by detached Leptochloa fusca leaves showed a massive linear secretion of Na and Cl over 24 hr. Secretion of K and Ca was very low and could not be detected before 2 or 6 hr, respectively, thus indicating a strong selectivity operating for the secretion of Na. The detached leaves secreted much larger quantities of salt than the intact leaves. Light stimulated the secretion of Na and Cl by detached and intact leaves at 10 and 100 mM NaCl; chilling the plant roots decreased the secretion of Na and Cl and their contents in leaves at low and high NaCl concentrations. The presence of DNP around the roots increased the secretion of Na and Cl by the leaves; at a high concentration of DNP, the secretion decreased while concentrations of Na and Cl in the leaves increased. The high K/Na ratios in Kallar grass leaves are postulated to have arisen independently of the high K: low Na affinity observed in the roots. Studies are now underway to determine flow rates of K and Na via phloem and xylem in the shoot to assess Na selectivity for secretion in situ .

Some leaf structures related to salt regulation in kallar grass [Leptochloa fusca (L.) kunth]∗

Abstract The Kallar grass leaf is linear with spiny surfaces. On its margins were found spines with a broad base, and on the upper and the lower surface, vesicles or swollen epidermal hairs with pointed, capped ends. On cellulose‐acetate film moistened with acetone and pressed against the leaf surface, the vesicles appeared as bladder‐like structures located above the epidermis. More vesicles were found on the upper than on the lower surface. In young field plants, the vesicles of the sheath were less developed and fewer in number than those of the blade. Vesicles in the leaf sheath were found largely on the lower (outer) surface. Using a pressure probe, he vesicles were found to contain sap and a turgor pressure of about 0.3 MPa which decreased with 100 mM NaCl and 10 mM PEG 6000. The sheath cells which were chlorophyllous, larger and rectangular, had a turgor pressure of about 0.1 MPa, which was either little affected or was increased when the leaf sheath was exposed to 100 mM NaCl or PEG 6000. The impo...

Treatment of cotton seeds for germination

Effects of H2SO4, H2O2, C2H5OH and of acetone on germination of cotton seeds and on the growth of seedling root were studied under laboratory conditions. H2SO4 or H2O2 hastened germination but decreased the ultimate number of seeds germinated. Higher temperature (27°C) hastened germination and increased the number of seeds germinated. Root length remained unaffected by treatments at room temperature while H2SO4 or H2SO4/H2O2 substantially decreased it at 27°C.