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The increasing demand for irrigation water to secure food for growing populations with limited water supply suggests re-thinking the use of non-conventional water resources. The latter includes saline drainage water, brackish groundwater and treated waste water. The effects of using saline drainage water (electrical conductivity of 4.2–4.8 dS m−1) to irrigate field-grown tomato ( Lycopersicon esculentum Mill cv Floradade) using drip and furrow irrigation systems were evaluated, together with the distribution of soil moisture and salt. The saline water was either diluted to different salinity levels using fresh water (blended) or used cyclically with fresh water. The results of two seasons of study (2001 and 2002) showed that increasing salinity resulted in decreased leaf area index, plant dry weight, fruit total yield and individual fruit weight. In all cases, the growth parameters and yield as well as the water use efficiency were greater for drip irrigated tomato plants than furrow-irrigated plants. However, furrow irrigation produced higher individual fruit weight. The electrical conductivity of the soil solution (extracted 48 h after irrigation) showed greater fluctuations when cyclic water management was used compared to those plots irrigated with blended water. In both drip and furrow irrigation, measurements of soil moisture one day after irrigation, showed that soil moisture was higher at the top 20 cm layer and at the location of the irrigation water source; soil moisture was at a minimum in the root zone (20–40 cm layer), but showed a gradual increase at 40–60 and 60–90 cm and was stable at 90–120 cm depth. Soil water content decreased gradually as the distance from the irrigation water source increased. In addition, a few days after irrigation, the soil moisture content decreased, but the deficit was most pronounced in the surface layer. Soil salinity at the irrigation source was lower at a depth of 15 cm (surface layer) than that at 30 and 60 cm, and was minimal in deeper layers (i.e. 90 cm). Salinity increased as the distance from the irrigation source increased particularly in the surface layer. The results indicated that the salinity followed the water front. We concluded that the careful and efficient management of irrigation with saline water can leave the groundwater salinity levels unaffected and recommended the use of drip irrigation as the fruit yield per unit of water used was on average one-third higher than when using furrow irrigation. [ABSTRACT FROM AUTHOR]

Salinity and waterlogging interact to reduce growth of poorly adapted species by, amongst other processes, increasing the rate of Na+ and Cl− transport to shoots. Xylem concentrations of these ions were measured in sap collected using xylem-feeding spittlebugs (Philaenus spumarius) from Lotus tenuis and Lotus corniculatus in saline (NaCl) and anoxic (stagnant) treatments. In aerated NaCl solution (200 mM), L. corniculatus had 50% higher Cl− concentrations in the xylem and shoot compared with L. tenuis, whereas concentrations of Na+ and K+ did not differ between the species. In stagnant-plus-NaCl solution, xylem Cl− and Na+ concentrations of L. corniculatus increased to twice those of L. tenuis. These differences in xylem ion concentrations, which were not caused by variation in transpiration between the two species, contributed to lower net accumulation of Na+ and Cl− in shoots of L. tenuis, indicating that ion transport mechanisms in roots of L. tenuis were contributing to better ‘exclusion’ of Cl− and Na+ from shoots, compared with L. corniculatus. Root porosity was also higher in L. tenuis, due to constitutive aerenchyma, than in L. corniculatus, suggesting that enhanced root aeration contributed to the maintenance of Na+ and Cl− ‘exclusion’ in L. tenuis exposed to stagnant-plus-NaCl treatment. Lotus tenuis also had greater dry mass than L. corniculatus after 56 d in NaCl or stagnant-plus-NaCl treatment. Thus, Cl− ‘exclusion’ is a key trait contributing to salt tolerance of L. tenuis, and ‘exclusion’ of both Cl− and Na+ from the xylem enables L. tenuis to tolerate, better than L. corniculatus, the interactive stresses of salinity and waterlogging. [ABSTRACT FROM PUBLISHER]

Sodium chloride reduces the growth of rice seedlings, which accumulate excessive concentrations of sodium and chloride ions in their leaves. In this paper, we describe how silicon decreases transpirational bypass flow and ion concentrations in the xylem sap in rice ( Oryza sativa L.) seedlings growing under NaCl stress. Salt (50 mM NaCl) reduced the growth of shoots and roots: adding silicate (3 mM) to the saline culture solution improved the growth of the shoots, but not roots. The improvement of shoot growth in the presence of silicate was correlated with reduced sodium concentration in the shoot. The net transport rate of Na from the root to shoot (expressed per unit of root mass) was also decreased by added silicate. There was, however, no effect of silicate on the net transport of potassium. Furthermore, in salt-stressed plants, silicate did not decrease the transpiration, and even increased it in seedlings pre-treated with silicate for 7 d prior to salt treatment, indicating that the reduction of sodium uptake by silicate was not simply through a reduction in volume flow from root to shoot. Experiments using trisodium-8-hydroxy-1,3,6-pyrenetrisulphonic acid (PTS), an apoplastic tracer, showed that silicate dramatically decreased transpirational bypass flow in rice (from about 4.2 to 0.8%), while the apparent sodium concentration in the xylem, which was estimated indirectly from the flux data, decreased from 6.2 to 2.8 mM. Direct measurements of the concentration of sodium in xylem sap sampled using Philaenus spumarius confirmed that the apparent reduction was not a consequence of sodium recycling. X-ray microanalysis showed that silicon was deposited in the outer part of the root and in the endodermis, being more obvious in the latter than in the former. The results suggest that silicon deposition in the exodermis and endodermis reduced sodium uptake in rice ( Oryza sativa L.) seedlings under NaCl stress through a reduction in apoplastic transport across the root. [ABSTRACT FROM AUTHOR]

Bicellular microhairs are present on the surfaces of leaves of grasses with the exception of the Pooideae. In some halophytic grasses, these glandular hairs secrete salt, suggesting the intriguing question ‘can the microhairs of grasses that do not normally encounter salinity also secrete salt?’ Microhairs were counted in replicas of the adaxial and abaxial surfaces of leaves of various ages of maize plants growing either in the absence of salt or in the presence of 40, 80 or 120 mM NaCl. The number of microhairs per unit area of adaxial leaf surface of the youngest leaf almost doubled as the salinity increased from zero to 120 mM NaCl; on the abaxial surface, the number of microhairs increased by 50%. Spraying this leaf with benzyl adenine (BA) caused, when averaged across salinities and surfaces, a 32% increase in the number of microhairs. Salinity reduced leaf area but in all the salinity treatments, spraying with BA increased the total number of microhairs per leaf. Washing leaves of plants provided estimates of the loss of salt from those leaves. There were large differences between the Na:K molar ratios in the washing solution and the leaf tissue, indicating a high selectivity for sodium over potassium for loss from the leaf. BA did not influence the efficiency of salt loss, expressed per microhair, at any salinity level, but did increase loss per leaf. Thus, BA increased salt loss from plants due to its influence on the number of microhairs and leaf area, but not due to its effect on the efficiency of the secretion process per se. [ABSTRACT FROM AUTHOR]

Salinity is an ever‐present threat to crop yields, especially in countries where irrigation is an essential aid to agriculture. Although the tolerance of saline conditions by plants is variable, crop species are generally intolerant of one‐third of the concentration of salts found in seawater. Attempts to improve the salt tolerance of crops through conventional breeding programmes have met with very limited success, due to the complexity of the trait: salt tolerance is complex genetically and physiologically. Tolerance often shows the characteristics of a multigenic trait, with quantitative trait loci (QTLs) associated with tolerance identified in barley, citrus, rice, and tomato and with ion transport under saline conditions in barley, citrus and rice. Physiologically salt tolerance is also complex, with halophytes and less tolerant plants showing a wide range of adaptations. Attempts to enhance tolerance have involved conventional breeding programmes, the use of in vitro selection, pooling physiological traits, interspecific hybridization, using halophytes as alternative crops, the use of marker‐aided selection, and the use of transgenic plants. It is surprising that, in spite of the complexity of salt tolerance, there are commonly claims in the literature that the transfer of a single or a few genes can increase the tolerance of plants to saline conditions. Evaluation of such claims reveals that, of the 68 papers produced between 1993 and early 2003, only 19 report quantitative estimates of plant growth. Of these, four papers contain quantitative data on the response of transformants and wild‐type of six species without and with salinity applied in an appropriate manner. About half of all the papers report data on experiments conducted under conditions where there is little or no transpiration: such experiments may provide insights into components of tolerance, but are not grounds for claims of enhanced tolerance at the whole plant level. Whether enhanced tolerance, where properly established, is due to the chance alteration of a factor that is limiting in a complex chain or an effect on signalling remains to be elucidated. After ten years of research using transgenic plants to alter salt tolerance, the value of this approach has yet to be established in the field. [ABSTRACT FROM PUBLISHER]

Production of grain legumes is severely reduced in salt‐affected soils because their ability to form and maintain nitrogen‐fixing nodules is impaired by both salinity and sodicity (alkalinity). Genotypes of chickpea, Cicer arietinum, with high nodulation capacity under stress were identified by field screening in a sodic soil in India and subsequently evaluated quantitatively for nitrogen fixation in a glasshouse study in a saline but neutral soil in the UK. In the field, pH 8·9 was the critical upper limit for most genotypes studied but genotypes with high nodulation outperformed all others at pH 9·0–9·2. The threshold limit of soil salinity for shoot growth was at ECe 3 dS m–1, except for the high‐nodulation selection for which it was ECe 6. Nodulation was reduced in all genotypes at salinities above 3 dS m–1 but to a lesser extent in the high‐nodulation selection, which proved inherently superior under both non‐saline and stress conditions. Nitrogen fixation was also much more tolerant of salinity in this selection than in the other genotypes studied. The results show that chickpea genotypes tolerant of salt‐affected soil have better nodulation and support higher rates of symbiotic nitrogen fixation than sensitive genotypes. [ABSTRACT FROM PUBLISHER]

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In a previous study on the effects of N-supply on leaf cell elongation, the spatial distribution of relative cell elongation rates (RCER), epidermal cell turgor, osmotic pressure (OP) and water potential (Ψ) along the elongation zone of the third leaf of barley was determined (W. Fricke et al. 1997, Planta 202: 522–530). The results suggested that in plants receiving N at fixed relative addition rates (N-supply limitation of growth), cell elongation was rate-limited by the rate of solute provision, whereas in plants growing on complete nutrient solution containing excessive amounts of N (N-demand limitation), cell elongation was rate-limited by the rate of water supply or wall yielding. In the present paper, these suggestions were tested further. The generation rates of cell OP, turgor and Ψ along the elongation zone were calculated by applying the continuity equation of fluid dynamics to the previous data. To allow a more conclusive interpretation of results, anatomical data were collected and bulk solute concentrations determined. The rate of OP generation generally exceeded the rate of turgor generation. As a result, negative values of cell Ψ were created, particularly in demand-limited plants. These plants showed highest RCER along the elongation zone and a Ψ gradient of at least −0.15 MPa between water source (xylem) and expanding epidermal cells. The latter was similar to a theoretically predicted value (−0.18 MPa). Highest rates of OP generation were observed in demand-limited plants, with a maximum rate of 0.112 MPa · h−1 at 16–20 mm from the leaf base. This was almost twice the rate in N-supply-limited plants and implied that the cells in the leaf elongation zone were capable of importing (or synthesising) every minute almost 1 mM of osmolytes. Potassium, Cl− and NO3 − were the main inorganic osmolytes (only determined for demand-limited plants). Their concentrations suggest that, unlike the situation in fully expanded epidermal cells, sugars are used to generate OP and turgor. Anatomical data revealed that the zone of lateral cell expansion extended distally beyond the zone of cell elongation. It is concluded that leaf cell expansion in barley relies on high rates of water and solute supply, rates that may not be sustainable during periods of sufficient N-supply (limitation by water supply: Ψ gradients) or limiting N-supply (limitation by solute provision: reduced OP-generation rates). To minimise the possibility of growth limitation by water and osmolyte provision, longitudinal and lateral cell expansion peak at different locations along the growth zone. [ABSTRACT FROM AUTHOR]

An analysis of the frequency of occurrence of chloroplasts, mitochondria and microbodies in leaf cells of the halophyte Sueda maritima (L.) Dum, showed a remarkable increase (almost a doubling) in the number of mitochondria per cell section when plants were grown in saline (340 mol m−3 NaCl) as opposed to non‐saline conditions. Chloroplast and microbody volume per cell increased under saline conditions, but number per cell was insensitive to salt. Chloroplasts contained a greater number of starch grains in plants grown under saline as compared to non‐saline conditions and, under both conditions, were closely associated with the cell wall adjacent to the intercellular spaces. The implications for growth, photosynthesis and respiration are discussed. [ABSTRACT FROM AUTHOR]

Visual damage is commonly used as the criterion for assessment of salinity resistance in rice breeding programmes. The use of other indicators, such as sodium uptake, is being evaluated: a correlation between initial sodium uptake to the third leaf and varietal survival was established and the physiological basis of this examined. Chlorophyll was used as an indicator of metabolic status and the relationship between leaf sodium and chlorophyll concentrations investigated for nine varieties differing in their resistance to salinity. By sampling a population of leaves having a wide range of salt concentrations, inverse relationships between chlorophyll and sodium concentrations were established. The salt concentration in the leaf tissue which causes equivalent toxicity (50% loss of chlorophyll) differed 3‐fold amongst these varieties. Varieties showing the greatest tolerance to salt within the leaves were not necessarily those showing the greatest overall phenotypic resistance to salinity. The enzymes malate dehydrogenase and nitrate reductase were activated equally by sodium and potassium ions at 60–80 mol m−3 in both control and saline grown plants and severely inhibited at higher concentrations. If all the salt in the tissue of leaves with 50% chlorophyll remaining was in solution and uniformly distributed the concentration would be 135–500 mol m−3. This is improbable and some level of compartmentation is likely. [ABSTRACT FROM AUTHOR]

Oryza sativa L. (rice) is a salt-sensitive crop species which is relatively ineffective in controlling the influx of sodium and chloride ions to the shoot Nonetheless there is considerable varietal and individual variability in salinity resistance, much of which must derive. Therefore, from differences in the fazes and subsequent effects of saline ions after they have entered the plant The destination of sodium ions within the plant has been investigated, in saline conditions, by examining the time-course of sodium ion concentrations in different leaves of four varieties and breeding lines of rice of differing salinity resistance. Radionuclide tracers were employed to study short term effects and the degree of retranslocation of these sodium ions. Sodium was not distributed uniformly but accumulated in the older leaves before the younger ones. At least some leaves were maintained at sub-lethal salt concentrations in at least the more salt resistant varieties. Radionuclide tracer studies showed that the discontinuous distribution of sodium (from leaf to leaf) is constitutive, and cannot be explained by time of exposure or differential leaf growth rates, and that significant quantities of sodium were not subsequently retranslocated, either within the plant or to the root medium. [ABSTRACT FROM AUTHOR]

The role of phosphorus application on growth and yield of rice under saline conditions was studied in a set of two experiments, one in nutrient and the other in soil culture. In experiment 1, the effect of inorganic phosphate (P1) on the growth and ionic relations of four rice cultivars, varying in salt tolerance and phosphorus use efficiency, grown in nutrient solution with and without 50 mol m-3 NaCl was measured in a 2 week trial. The growth of all rice cultivars was affected to different degrees due to external Pi in the presence of salt. External Pi concentration up to 100 µM in the presence of NaCl caused stimulation of all growth parameters (shoot, root, tillering capacity), above this concentration Pi had an inhibitory effect. Salt-induced P toxicity was exhibited at a much lower Pi concentration (10 µM) by the salt sensitive cultivar. Increasing the supply of phosphorus (from 1 to 100 µM Pi) to the saline medium tended to decrease the concentrations of Na+ and Cl-1 in all cultivars except IR 1561. Shoot concentrations of these saline ions were much lower In the salt tolerant and moderately salt tolerant rice cultivars. Shoot P and Zn concentrations showed an increasing trend in the presence of external Pi and salt in the rooting medium but most strikingly P: Zn ratio was lower in salt tolerant and moderately salt tolerant cultivars. Significantly higher concentrations of Na+, P and Cl- , and lower concentrations of Zn, were determined in the shoots of salt sensitive cultivars when exposed to salt stress in the presence of Pi. Results were confirmed in naturally salt-affected soils of two different types (saline-sodic and saline) where paddy yield of NIAB 6 (salt tolerant) and IR 1561 (salt sensitive) showed improvement through moderate phosphorus supply (18 kg P ha-1). [ABSTRACT FROM AUTHOR]

Attempts to enhance the salt-tolerance of the cultivated tomato using the tolerance of related wild species of Lycopersicon Mill. have been unsuccessful commercially. An alternative approach is to attempt to accumulate physiological characters that contribute to tolerance within a genotype. We have investigated the relationships between tolerance and certain physiological characteristics in accessions of L. esculentum Mill., L. cheesmanii (Hook) C. H. Mull., L. pennellii (Correll) D'Arcy, L. peruvianum (L.) Mill. and L. pimpinellifolium Mill. with this aim in view. At a salinity equivalent to 40 % of that in an artificial seawater, the growth of young plants was ranked both in absolute terms (fresh weight, dry weight or the growth in area of a leaf that developed during the salt treatment) and relative to growth in a salinity 2 % of that of seawater. In absolute terms, two cultivars of L. esculentum ('Moneymaker' and 'Edkawy') performed about as well as L. pimpinellifolium and better than L. pennellii and L. cheesmanii: L. peruvianum showed the poorest tolerance. In relative terms, L. pimpinellifolium remained the most tolerant of the species, and L. peruvianum the most sensitive. L. cheesmanii was little more tolerant than L. peruvianum. The five species differed in their succulence and the Na : K ratio in leaves that developed during the treatment with salinity. Succulence was higher at low salinity in L. pennellii and L. cheesmanii than in the other species, but increased less on salinization. L. pimpinellifolium showed the greatest increase in succulence on salinization, a consequence of its low water content in 2 % seawater. Sodium concentrations increased dramatically in all five species on salinization : L. pimpinellifolium had the highest and L. esculentum the lowest values. [ABSTRACT FROM AUTHOR]

While members of the genus Oryza are very sensitive to salinity, salt concentrations as high as 20% of that of seawater had no adverse effect on the growth of the tropical wild rice (Porteresia coarctata Tateoka) in experiments undertaken in a greenhouse in the UK. P. coarctata plants accumulated sodium and chloride ions in the leaves, but maintained a Na: K ratio as low as (0.7, even after 6 weeks of growth in 25% artificial seawater (ASW) where the Na: K ratio was 34. This ability to maintain a high K: Na ratio in the leaves is in part a consequence of the secretion of ions from the leaves. The ratio of Na: K in the secreted salt (more than 5 for plants growing in 25% ASW) is similar to that measured by X-ray microanalysis in the vacuoles of hairs found in folds of the adaxial surface of the leaf lamina, suggesting that the secretions emanate from these hairs. The salt secreted by the hairs is an important factor in the salt-balance of the leaves: the consequences of these findings for the transfer of salt-tolerance from this species into cultivated rice are discussed. [ABSTRACT FROM AUTHOR]

Varieties (including designated cultivars) of Asian rice (a predominantly inbreeding species) show large individual variability in sodium transport and salinity resistance. Recurrent selection has been carried out over five generations with populations of Oryza saliva L. cv. IR36 and cv. IR20. Large numbers of individuals were exposed to a low concentration of NaCl in solution culture, and their sodium uptake determined non-destructively by sampling the third leaf. The range of sodium concentrations in the leaf was two or three orders of magnitude. Individuals showing both high and low extremes of sodium uptake were selected and allowed to self-pollinate. The sodium uptake by the progeny was measured in the same way, and the selection repeated. Significant differences in the frequency distribution of sodium transport between the selected lines were evident in both varieties after three cycles of selection. The lines continued to segregate in the fourth and fifth generations by which time the high and low selected lines showed substantial differences in sodium uptake. It is concluded that useful genetic diversity for sodium uptake and hence salt resistance exists within modern rice varieties. [ABSTRACT FROM AUTHOR]

Significant varietal differences were apparent in the survival of seedlings of maize in saline conditions but only at relatively high external concentrations (200 mol m-3 NaCl), where there was a range from 0 to 66% survival, 25 d after salinization. For the varieties examined there was a strong negative correlation between Na concentrations in the third leaf and survival. Two resistant varieties (Across 8024 and Protador) and one salt-sensitive variety (LG11) were identified. The characteristics of ion accumulation were clearly different in salt-tolerant and salt-sensitive types, the difference becoming more pronounced with plant age. The distribution of ions, particular those of Na, K and Cl, was determined within subcellular compartments of roots cells using X-ray microanalysis of freeze-substituted tissue. Salinity induced a greater increase (about 1.7 times) in cytoplasmic Na concentration in the salt-sensitive variety (LG11) than in resistant varieties (Across 8024 or Protador). The mean K : Na ratio in the cytoplasm of the root cortical cells in the salt-resistant varieties grown for 15 d in saline conditions (100 mol m-3 NaCl) was twice that found for LG11. Sodium and Cl concentrations in the vacuoles decreased radially inwards from the epidermal cells in salt-treated roots of LG11. [ABSTRACT FROM AUTHOR]

Rates of ion transport and transpiration were measured during the day and night in whole seedlings of Suaeda maritima growing over a range of salinities, in order to calculate concentrations of sodium and potassium in the xylem during these periods. Mean sodium concentration in the xylem was maximal at 56 mol m-3 Na with an external salinity of 200 mol m-3 NaCl. The sodium concentration in the xylem was greater in the dark than in the light at all external salinities investigated. Comparison of the external sodium with that in the xylem indicated that sodium was more strongly excluded from the transpiration stream as salinity increased. The mean concentration of potassium in the xylem declined as external NaCl concentration increased, although selectivity for potassium increased at higher salinities. Results are discussed in relation to osmotic adjustment in S. maritima. [ABSTRACT FROM AUTHOR]

The effects of sodium chloride on the leaf ultrastructure and net photosynthesis of two varieties of rice (Oryza sativa L.), the land race Amber and the elite breeding line IR2153.26.3.5.2, were examined. Similar concentrations of salt in the leaf tissue had a greater effect in bringing about a disorganization of cellular structure and of decreasing net photosynthesis in Amber than in 1R2153.26.3.5.2. It is argued that these data support the view that rice varieties differ with respect to a cellular component of salt resistance. [ABSTRACT FROM AUTHOR]

Anatomy and ion concentrations have been studied in the roots of the halophyte Suaeda maritima (L.) Dum. growing in saline and non-saline conditions. The roots were fine with only three layers of conical cells. Salinization of the growth medium resulted in cellular vacuolation commencing closer to the apex than in non-salinized plants and led to an increase in root dimensions through increased cell (vacuole) size but not increased cell numbers: the Casparian strip developed much closer to the apex and was twice as long in salt-grown plants. Ion concentrations were determined in sections (1 mm) of root. The apical 1 mm was predominantly non-vacuolate, with a K+ concentration greater than 100 mol m-3 and a Na:K ratio less than 2, even when growing in 340 mol m-3 NaCl. The adaptive value of the anatomical observations are discussed and the ion concentration data assessed in relation to current concepts of the halophyte cell. [ABSTRACT FROM AUTHOR]

The effect of the Na/Ca ratio in the growth medium on the response of the salt-sensitive crop species Oryza sativa L. to NaCl salinity was investigated. No effects on growth or salt concentration in the shoot were found over a range of Na/Ca ratios (5 to 25) considered likely to be commonly encountered in saline situations in the field, and even at extreme Na/Ca ratios (100 to 500) there were only marginal increases in NaCl entry to the shoot. Increasing the Ca concentration in the growth medium over a wide range did not, therefore, ameliorate the effects of salinity on rice seedlings. Polyethylene glycol at low, osmotically negligible, concentrations reduced the movement of Cl to the shoot by 60 to 70% even in the presence of adequate (3.5 mol m-3)Ca. It is concluded that membranes of rice roots respond weakly to Ca and that they are capable of better permeability control than is evoked by Ca ions. The relevance of this to the salt sensitivity of rice is discussed. [ABSTRACT FROM AUTHOR]

Both cuticle and cell wall of the epidermal cells of leaves of Suaeda maritima showed a considerable increase in thickness (approximately 1.8 times) in plants grown in the presence of 0.34 M sodium chloride when compared with plants grown without added sodium chloride. Differences in the structure of the cuticle were also observed. The rate of transpiration in the dark was markedly reduced with increasing concentrations of salt in the external medium. Cuticular transpiration appears to be related to cuticular thickness and to fall with increasing salinity. [ABSTRACT FROM AUTHOR]

Salinity reduces fertility in rice (Oryza sativa L.) but little is known of the underlying cause(s). In order to determine the relative importance of pollen viability and stigmatic receptivity for seed setting, plants of the rice cultivar IR36 were treated with 'artificial' sea water (0, 10, 25 or 50 mol m-3 with respect to NaCI) from 1 month after germination until the main tiller flowered. As increase in the salinity in the medium resulted in a decrease in the number of fertile florets and in the viability of pollen as determined both by pollen germination and by pollen staining with the tetrazolium salt 3-(4,5-dimethyl-thyazolyl)-2,5-diphenyl monotetrazolium bromide. In order to assess the effects of salt on stigmas, seed production was measured for salt-grown and non-salt-grown female plants pollinated with viable pollen (from plants grown in the absence of salt). The percentage of seed set was reduced by 38% when the female plants were grown in 10 mol m-3Na and by 72% aat 25 mol m-3Na: no seed setting was recorded for plants grown in 50 mol m-3 Na. Comparisons between crosses involving male and female parents grown at different salinities indicated that effects on the female plants dominated those on pollinator plants. Mineral analysis of leaves of different ages showed that there was opposite to that of Na and Cl at all levels of applied salinity: K was maximal in the flag leaf, where Na and Cl were minimal. Analysis also revealed that there was an increase in the concentrations of Na Cl and a decrease in the concentration of K in the pollen grains and stigmas of plants subjected to saline conditions. Correlations between the concentration of Na and Cl in pollen and pollen staining and pollen germination in vitro suggest that Na and Cl per se were responsible for the poor viability. The change in ionic concentrations in pollen and stigmas was much larger than that in the younger leaves, and in particular very much larger than that in the lemmas and paleas. [ABSTRACT FROM AUTHOR]

When plants of rice (Oryza sativa L.) are subjected to mildly saline (50 mol m-3 NaCl) conditions, the leaves show symptoms of water deficit, even though ion accumulation has been more than sufficient to adjust to the decrease in external water potential. After a few days of exposure to salt, there is a negative correlation, in a population of leaves, between the leaf water concentration (g water per g dry weight) and their sodium concentration mmol Na per g dry weight). Ion concentrations in the cell walls and the cytoplasm of cells of plants grown in low salinity were measured by X-ray microanalysis. The NaCl concentration in solution in the apoplast was calculated to be around 600mol m-3 in leaves of plants whose roots were exposed to only 50mol m-3 NaCl. This constitutes strong evidence that an important factor in salt damage in rice is dehydration due to the extracellular accumulation of salt as suggested in the Oertli hypothesis. The implication, that changes in tissue ion concentration and solute potentials equivalent to the external medium is not evidence of plant osmotic adjustment to salinity, is discussed. [ABSTRACT FROM AUTHOR]

Cytoplasmic concentrations, fluxes of K[SUP+], Na[SUP+] and Cl and microsomal membrane lipids were investigated in a salt-sensitive and salt-resistant variety of Zea mays. The salt resistance of Protador relative to LG[SUB11] (salt-sensitive) appears to be related to higher K fluxes and cytoplasmic concentrations, and lower Na[SUP+] and Cl fluxes and cytoplasmic concentrations when grown in NaCl. There were no apparent differences in the simple chemical composition of root microsomal membrane lipids between the two varieties, neither were these affected by salt. [ABSTRACT FROM AUTHOR]

The effects of sodium chloride on water-use efficiency of a number of varieties of rice have been investigated. Sensitivity to salinity in rice arises in large part from excessive rates of sodium ion transport to the shoot consequent upon high rates of transpirational water loss. Varietal differences in water-use efficiency were found, these were greater when measured for whole shoots over a period of one week, than when made as instantaneous measurements on individual leaves. Salinity had rather little effect on water use efficiency but overall resistance of seedlings to salt was, in general, greater the greater the water-use efficiency. The reasons for the differences between varieties are discussed in terms of differences in growth pattern, among the seven varieties investigated, water-use efficiency and saltresistance were lower in dwarfed as opposed to nondwarfed varieties. [ABSTRACT FROM AUTHOR]

Methods were developed for measuring water content of the free space of suspension cultured tobacco cells using 3H- or 14C-sorbitol. Sorbitol was not taken up by cells in significant quantities over the 3 min taken to label free space. Free space accounted for 50-60% of the water content of cell pellets irrespective of whether 3H- or 14C-sorbitol was used. 14C-insulin labeled 13.5% less of the water in cell pellets than 3H-sorbitol, probably due to inadequate penetration by insulin into the free space in the cell wall matrix and within clumps of cells. Measurement of free space is necessary for measuring growth on a fresh or dry weight basis, solute concentrations and parameters of water relations of cells. Techniques for making these measurements on tobacco cells were also developed in this study. Solutes were measured after extraction from cells by expressing sap or by boiling cells in ethanol. Similar solute concentrations were found using both methods of extraction. By expressing sap from cells grown in culture medium with an osmotic pressure of 0.24 MPa, the cells were found to have an internal osmotic pressure of 0.70 MPa. Glucose, fructose, sucrose, amino acids and K+ accounted for 60% of this osmotic pressure. Elastic moduli were estimated using the Boyle-Van't Hoff relationship after suspending cells in solutions with different osmotic pressures and assessing their water content or internal osmotic pressure. For two different lines of tobacco cells, elastic modulus varied between 1 MPa and 5.4 MPa at turgor pressures of 0.15-0.52 MPa (line 1) and between 0.2 MPa and 4.2 MPa at turgor pressures of 0.04 -0.26 MPa (line 2). [ABSTRACT FROM AUTHOR]

The effect of salinity on the growth and ion concentrations in a number of tobacco cultivars is described. Sodium chloride, at a concentration of 200 mol m-3, hardly affected the fresh weight, but significantly reduced the dry weight. The difference in the response of fresh and dry weights to salt was due to a change in succulence (water per unit leaf area); the latter increased with increasing leaf Na+ and Cl- concentration. Under saline conditions, increasing the external Na+ Ca- ratio by decreasing the Ca2+ concentration increased the accumulation of Na+ and Cl- into the leaf tissue. [ABSTRACT FROM AUTHOR]

The starch concentration in mature leaves of the halophyte Suaeda maritima increased from 4.7 to 7.3 mg mg-1 chlorophyll when sodium chloride (680 mol m-3 was added to the solution in which the plants were grown. This effect of salinity on the starch: chlorophyll ratio was greater in young than in old leaves. Electron micrographs showed the starch to be in the chloroplasts and this was confirmed by measurements on isolated chloroplasts. Total phosphorus concentration (mg mg-1 chlorophyll) in leaves of all ages from plants of S. maritima decreased on salinization of the growth medium suggesting an inverse relationship between phosphorus and starch concentrations. However, although leaf starch concentration varied with leaf age, phosphorus concentration did not. The cause of starch accumulation in chloroplasts at salinities which are optimal for growth (340 mol m-3) remains unclear. [ABSTRACT FROM AUTHOR]

Varieties of rice differ in their resistance to sodium chloride salinity. Within varieties, which are not homozygous lines, there is very high variability in sodium uptake and in survival under saline conditions by the individual plants. This is in contrast with the relative uniformity in (for example) potassium uptake, dry wt and transpiration rate. There is a negative correlation between sodium (and chloride) accumulation by individual plants and their survival in saline conditions, demonstrating that variability amongst individuals fits the same pattern as has become generalized for varietal differences in glycophyte species. Possible reasons for this variability in sodium and chloride uptake within varieties, and its relevance to selecting salt-resistant varieties of rice, are discussed. [ABSTRACT FROM AUTHOR]

Chloride has been localized in leaf cells of Suaeda maritima by the silver precipitation technique. The major site of precipitation was the cell vacuole although deposits were found at other sites, particularly in the chloroplasts of plants grown without salt. Considerable loss of chloride from the tissue occurred during the preparative procedure and the validity of the technique is discussed. [ABSTRACT FROM AUTHOR]