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CROP PHYSIOLOGY & METABOLISM

Sorghum and Salinity

I. Response of Growth, Water Relations, and Ion Accumulation to NaCl Salinity

^a Department of Botany, Faculty of Science, Maseno University, P.O. Private Bag, Maseno, Kenya
^b Department of Plant Physiology, University of Bayreuth, Universitätstraße 30, 95440, Bayreuth, Germany

^* Corresponding author (erwin.beck{at}uni-bayreuth.de)

	ABSTRACT

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Crops grown in salt affected soils may suffer from drought stress, ion toxicity, and mineral deficiency leading to reduced growth and productivity. The present study was conducted to determine how salinity affects growth, water relations, and accumulation of cations of nutritional importance in various organs of grain sorghum [Sorghum bicolor (L.) Moench]. Two Kenyan sorghum varieties, Serena and Seredo, were grown in a greenhouse in quartz sand supplied with a complete nutrient solution to which 0 (control), 50, 100, 150, 200, and 250 mM NaCl was added. The 250 mM NaCl treatment significantly reduced the relative shoot growth rates, measured 25 d after the start of salt application, by 75 and 73%, respectively, for Serena and Seredo, and stem dry weight by 75 and 53%. In a similar way, young leaves were affected, with leaf blades of both varieties being reduced by 67% while sheaths were reduced by 83 and 87% for Serena and Seredo, respectively. Leaf water potential, osmotic potential, leaf pressure potential, and relative water content significantly declined with increasing salt stress. Roots and stems accumulated substantial amounts of sodium, saturating at 150 mM external NaCl. Accumulation of K⁺ and Ca²⁺ in the roots, stems, and leaves was strongly inhibited by salinity. Magnesium concentration of the roots was minimally impaired but that of the stems and leaves was strongly affected. Leaves continuously accumulated sodium, which was preferentially deposited in the sheaths. Mature leaves contained more Ca²⁺ and Mg²⁺ than young ones. The two sorghum varieties appear to sequester Na⁺ predominantly in roots, stems, leaf sheaths, and older leaf blades sparing the growing tissues as a salt tolerance mechanism. Nevertheless, greatly reduced concentrations of Ca²⁺, K⁺, and Mg²⁺ in leaves under salinity could cause cation deficiency which reduces plant growth.

Abbreviations: ANOVA, analysis of variance • DASA, days after start of salt application • RSGR, relative shoot growth rate • RWC, relative water content

	INTRODUCTION

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SORGHUM is often grown in areas of relatively low rainfall, high temperatures and saline soils (Boursier and Läuchli, 1990). The effect of salinity on plant growth is a complex syndrome that involves osmotic stress, ion toxicity, and mineral deficiencies (Hasegawa et al., 2000; Munns, 1993, 2002; Neumann, 1997; Yeo, 1998). These effects are still not well understood. According to Munns (1993)(2002), osmotic stress is effective in the beginning (hours to few days) of exposure to salt, and ion toxicity becomes important in affecting plant growth after prolonged exposure. However, this hypothesis is still a matter of debate. Pardossi et al. (1998) stated that water stress is one of the first and most evident effects of salinity and that the determination of water relations is therefore critical for any study of plant resistance to salinity. Water stress may, however, continue to contribute to growth inhibition also during long-term exposure to salt (Hu and Schmidhalter, 1998; Munns, 2002; Neumann, 1997; Shalhevet and Hsiao, 1986).

There are various ways by which plants can keep endogenous levels of ions like Cl^– and Na⁺ low. Reduced influx at the root cell plasma membrane, efflux from roots, and retranslocation from the leaves to roots are possible mechanisms (Erdei and Taleisnik, 1993; Koyro, 1997). In addition, salt tolerance during accumulation of Na⁺ and Cl^– at the cellular level can be achieved through loading in vacuoles (Ashraf et al., 2001; Schachtman and Munns, 1992). Sequestration of Cl^– and Na⁺ in the leaf sheath of grasses is another mechanism of salt tolerance (Greenway, 1962; Boursier et al., 1987).

The partitioning of cations including K⁺, Ca²⁺, and Mg²⁺ in leaf tissues is not so well known. This limits our knowledge of the effects of salinity on the nutritional status of the plant. For example, Boursier and Läuchli (1990) found a higher concentration of K⁺ in the leaf sheath of salt-stressed sorghum plants and suggested that it acts as a counter ion to the high concentration of Cl^–. This is, however, not generally conclusive because Boursier and Läuchli (1990) did not consider age-dependent effects.

The two varieties of sorghum used in the present study, Serena and Seredo, are improved hybrids recommended for drought-prone areas in East Africa. However, the salt tolerance mechanisms of these varieties have not been studied. The objective of this research was to quantify plant growth, water relations and ion concentrations of roots, stems, leaf blades, and sheaths of the two Kenyan sorghum varieties in relation to various concentrations of NaCl. In addition, NaCl effects on the allocation of K⁺, Ca²⁺, and Mg²⁺ ions to the plant organs were measured. In an accompanying paper (Netondo et al., 2004), the influence of salt stress on gas exchange and photosynthesis is described.

	MATERIALS AND METHODS

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Plant Growth and Salt Treatment
Two Kenyan varieties of sorghum, Serena and Seredo were grown in quartz sand in 1.5-L plastic pots, in the greenhouse of the University of Bayreuth, Germany, between October 1997 and January 1998. Five seeds were planted in each pot and after 5 d, the seedlings were thinned to one plant per pot. During the first 7 d, pots were watered twice daily with deionized water. Thereafter, nutrient solution was supplied instead of water. The nutrient solution was prepared according to Maas et al. (1986) and contained 2.5 mM Ca(NO₃)₂, 3.0 mM KH₂PO₄, 1.5 mM MgSO₄, 0.1 mM KNO₃, 0.1 mM Fe-EDTA, 0.023 mM H₃BO₄, 0.005 mM CuSO₄, and 0.01 mM H₂₄Mo₇N₆O₂₄.4H₂O. The pH was adjusted between 6 and 6.5 using 0.1 mM KOH or H₂SO₄. The exposed sand surface of pots was covered with aluminum foil to prevent growth of algae.

Natural illumination was augmented for 12 h per day with light with tungsten lamps, giving an average PAR of 350 to 400 (maximum 600 at midday) µmol quanta m^–2 s^–1. Day and night temperatures in the greenhouse were programmed at 34 and 24°C, respectively, with a transition period of between 1 and 2 h. Recorded temperatures averaged 33.7°C (day) and 23.2°C (night). The relative humidity was set at 30% for days and 85% for nights, and the recorded values ranged between 32 and 80%. These conditions are similar to field conditions in Kenya, except light intensity, which is normally higher than 600 µmol quanta m^–2 s^–1.

Salt treatment started 14 d after planting. Sodium chloride was added in five concentrations of 50, 100, 150, 200, and 250 mM to the nutrient solution. These corresponded to electrical conductivities of 3.42, 6.74, 9.66, 12.40, and 15.01 dS m^–1, respectively. The control was irrigated with NaCl-free nutrient solution, whose electrical conductivity was 0.01 dS m^–1. To avoid osmotic shock, saline treatment was imposed incrementally, increasing the concentration by 50 mM every second day until the final concentration was reached. Pots were irrigated twice per day with nutrient solution and the excess was allowed to drain into collecting pans.

Measurement of Plant Growth
Dry weights of shoots were measured 1, 9, 17, and 25 d after the start of salt application (DASA) corresponding approximately to growth stages 0, 1, 2, and 3, described by Vanderlip (1993). Shoots were cut at the sand surface and dry weights were obtained after drying at 75°C for 72 h. Relative shoot growth rate (RSGR) was calculated according to Kingsbury et al. (1984) as:

where w₁ and w₂ are dry weights in grams obtained at times t₁ and t₂, respectively. Roots were harvested together with shoots 25 DASA and dried at 75°C for 72 h and the whole plant dry weight was determined. Five leaves of different ages were harvested 25 DASA, namely leaf number 5 (oldest) to number 9 (youngest). They were separated into blades and sheaths, dried at 75°C for 72 h, and weighed. The roots, stems, leaf blades, and leaf sheaths were used to determine element ion concentration as described below.

Water Relations
Leaf water relations were measured 25 DASA on the third youngest fully expanded leaf blade counted from the top. Measurements were performed between 1000 and 1400 h. Leaf water potential (_w) was measured with four replicates in situ with a leaf psychrometer attached to a microvoltmeter (L-51 and HR-33T; Wescor Inc.; Logan, UT). The psychrometer was calibrated with various NaCl concentrations according to Lang (1967). After water potential measurement leaves were ground in liquid nitrogen and then centrifuged at 14 000 g for 30 min to extract cell sap. Osmotic potential () of the cell sap was determined with the Wescor psychrometer. A drop of the sap was placed on a filter paper disc and then measured. Pressure potential () was calculated as the difference between _w and .

Relative water content (RWC) was determined from leaf discs with a diameter of 16 mm, excluding the major rib. Discs were weighed and then immediately floated on double distilled deionized water in a Petri dish. In this way, leaves were saturated with water for 24 h in the dark at 4°C. Turgid weights of leaf discs were obtained after removing superficially adhering droplets. Dry weights of discs were measured after drying at 75°C for 48 h. Relative water content of the discs was calculated as RWC = (f.wt – d.wt)/(t.wt – d.wt) (Jones and Turner, 1978) where f.wt, d.wt, and t.wt are the fresh, oven dry, and turgid weights, respectively.

Element Analysis
Inorganic solute concentrations were measured with four replicates of the roots, stems, leaf blades, and leaf sheaths, which were harvested 25 DASA. Five leaves of different ages as described above were used for elemental analysis. Samples were weighed, carefully rinsed with distilled deionized water, and then dried at 75°C for 72 h. Dry samples were milled in a Retsch mill type MM2 (Retsch GmbH and Co. KG 5637 HAAN 1, Federal Republic of Germany) before acid digestion in 1 mL of 65% (v/v) ultra pure nitric acid at 270°C for 6 h. Concentrations of Na⁺, K⁺, Ca²⁺, and Mg²⁺ were estimated by atomic absorption spectrophotometry (Perkin–Elmer Atomic Absorption Spectrophotometer, Model 5000; Perkin–Elmer; Norwalk, CT).

Statistical Analysis
The experiment was a completely randomized design of six salt levels, two varieties, and four replicates. Analysis of variance (ANOVA) was performed by Minitab statistical program (Minitab Inc., State College, PA). Two or more levels of classification were used depending on the variables involved such as variety, salinity, and leaf number (tissue). Means were separated using the least significant difference (LSD) test at 5% level. LSD (0.05) values were compounded from ANOVA computations as opposed to paired comparisons (Sokal and Rohlf, 1995). For statistical comparisons the LSD (0.05) value can be used to compare the difference between any combination of two means within a table or figure. The variety by salinity level interactions were significant at P 0.05 for all the ANOVA analyses where LSD (0.05) value has been presented.

	RESULTS

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Effect of Salinity Stress on Plant Growth
Salt strongly inhibited plant growth (Fig. 1) . Treatment with 250 mM NaCl caused 75 and 53% reduction in stem dry weight for Serena and Seredo. The decrease in stem dry weight with increasing salt stress was nearly linear for Serena. Relative shoot growth rates were not significantly (P > 0.05) affected during the first 2 wk of salt treatment (Table 1). There was a significant (P 0.05) effect of salt in the third week, where 250 mM NaCl induced a reduction of RSGR by about 75% for Serena and 73% for Seredo.

View larger version (24K): [in this window] [in a new window]   Fig. 1. Effects of increasing NaCl concentration in the irrigation medium on plant dry weight of sorghum varieties Serena and Seredo. Means of 4 replicates ±SD. [LSD (0.05) = 0.45.]

View larger version (45K): [in this window] [in a new window]   Fig. 2. Effects of increasing NaCl concentration in the irrigation medium on dry weight of leaf blades (A and B) and leaf sheaths (C and D) of sorghum varieties Serena and Seredo. Means of 4 replicates ±SD. Leaf 5 is the oldest and leaf 9 is the youngest. [LSD (0.05) = 0.08.]

Effect of Salinity Stress on the Concentration of Mineral Ions
The Na⁺ concentration was highest in roots and decreased in the following sequence: stem, leaf sheath, and leaf blade (Fig. 3) . The root and stem Na⁺ concentration became saturated at about 150 mM external NaCl and did not substantially increase at higher salt concentrations. Seredo accumulated significantly (P 0.01) higher Na⁺ concentration in stems than did Serena at 150, 200, and 250 mM.

View larger version (65K): [in this window] [in a new window]   Fig. 3. Effects of increasing NaCl concentration in the irrigation medium on concentration of sodium ions of roots (A), stems (B), leaf blades (C and D), and leaf sheaths (E and F) of sorghum varieties Serena and Seredo. Means of 4 replicates ±SD. [LSD (0.05) = 161.3 (A), 184.4 (B), 16.9 (C and D), and 32.2 (E and F)].

There was a significant (P 0.01) decrease in K⁺ concentration in roots and stems with increasing salinity (Fig. 4) . As with the accumulation of Na⁺ in organs, this decrease was observed only up to 150 mM NaCl treatment, where saturation was achieved. Data also show that Seredo accumulated slightly more K⁺ at 0 (control), 50, and 100 mM external NaCl in roots and at 50 and 100 mM in stems, but the differences were not significant. There was no effect of NaCl on K⁺ concentration in leaf blades (data not shown), whereas in leaf sheaths, K⁺ concentration declined with increasing NaCl from 0 mM to 100 mM. Beyond 100 mM NaCl, no significant further decrease of the K⁺ concentration was observed. Concentrations of K⁺ in leaf blades and sheaths were similar for the different salinity treatments and leaf ages. However, some increases in K⁺ concentration with advancing leaf age were observed in the blades at 100 and 250 mM for Serena and at 100, 200, and 250 mM NaCl for Seredo. In contrast to the sheaths of Serena, those of Seredo showed an increase in K⁺ concentration with increasing leaf age at 0, 50, and 100 mM NaCl. Considering the whole plant, leaves (blades and sheaths) contained much higher K⁺ concentration than roots and stems.

View larger version (45K): [in this window] [in a new window]   Fig. 4. Effects of increasing NaCl concentration in the irrigation medium on concentration of potassium ions of roots (A), stems (B), and leaf sheaths (C and D) of the sorghum varieties Serena and Seredo. Means of 4 replicates ±SD. [LSD (0.05) = 12.5 (A), 11.6 (B), and 303.3 (C and D)].

View larger version (65K): [in this window] [in a new window]   Fig. 5. Effects of increasing NaCl concentration in the irrigation medium on concentration of calcium ions of roots (A), stems (B), leaf blades (C and D), and leaf sheaths (E and F) of sorghum varieties Serena and Seredo. Means of 4 replicates ±SD. [LSD (0.05) = 19.9 (A), 10.8 (B), 55.4 (C and D), and 17.0 (E and F)].

View larger version (67K): [in this window] [in a new window]   Fig. 6. Effects of increasing NaCl concentration in the irrigation medium on concentration of magnesium ions of roots (A), stems (B), leaf blades (C and D), and leaf sheaths (E and F) of sorghum varieties Serena and Seredo. Means of 4 replicates ±SD. [LSD (0.05) = 21.5 (A), 29.1 (B), 51.5 (C and D), and 50.6 (E and F)].

	DISCUSSION

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Leaf water potential decreased (numerically) with increasing salt stress, implying that there was reduction of turgor and that plants suffered from restricted water availability to cells (Greenway and Munns, 1980; Munns et al., 2000; Munns, 2002; Neumann, 1997). A decrease in turgor under salinity conceivably reduces expansive growth (Munns et al., 2000). The observed decrease in leaf water potential with increasing salinity ceased at external salt concentrations above 100 mM NaCl, which suggests an onset of osmotic adjustment. This possibility was indicated by the concomitant numerical drop of osmotic potential with increase in solute concentration (Table 2; Plaut and Federman, 1991; Shalhevet and Hsiao, 1986; Turner and Jones, 1980). Various organic and inorganic solutes such as K⁺, Na⁺, Cl^–, proline, and glycinebetaine have been reported to contribute to such osmotic adjustment (Saneoka et al., 2001; Weimberg et al., 1984; Yang et al., 1990). In the experiment reported here only the Na⁺ concentration showed this effect (Fig. 3).

Sodium was the major cation that accumulated in roots and stems as salinity increased. The preferential accumulation in roots over shoots may be interpreted as a mechanism of tolerance in at least two ways. First, maintenance of a substantial potential for osmotic water uptake into the roots and second, restricting the spread of Na⁺ to shoots (Renault et al., 2001). Our results also show that Na⁺ concentration saturated in both the roots and stems at around 150 mM external salt concentration. This is in contrast to the findings of Weimberg et al. (1984) who found a continuous increase. Our plants, however, adjusted to the salt over a longer period (25 d), than those in the experiments of Weimberg et al. (1984) which were exposed for only 9 d. High Na⁺ concentration strongly inhibited uptake and accumulation of K⁺ and Ca²⁺ and to a lesser extent of Mg²⁺ by roots. Because K⁺ is a macronutrient involved in turgor control, inhibition of K⁺ uptake should stunt growth (Renault et al., 2001). Decreased root Ca²⁺ concentration has also been observed by Colmer et al. (1994)( 1996). High Na⁺ levels in the external medium greatly reduce the physicochemical activity of dissolved calcium (Cramer and Läuchli, 1986) and may thus displace Ca²⁺ from the plasma membrane of root cells (Cramer et al., 1985). In turn, displacement of Ca²⁺ from root membranes by Na⁺ affects Na/K uptake selectivity (Cramer et al., 1985) in favor of sodium. A low Ca²⁺ concentration under saline conditions may severely affect the functions of membranes as barriers to ion loss from cells (Boursier and Läuchli, 1990).

Preferential accumulation of Na⁺ in sheaths over leaf blades (Fig. 3) is one mechanism of salt tolerance exhibited by grasses. Exclusion of Na⁺ from leaf blades protects the delicate photosynthesizing tissues as much as possible from the potentially toxic ion. However, Na⁺ concentration in blades and sheaths continued to rise in proportion to the increase in NaCl treatment. This result was contrary to the hypothesis that there is an optimum level where Na⁺ saturates in the sheath (Boursier et al., 1987; Schachtman and Munns, 1992). A sudden rise in Na⁺ concentration in leaf blades beyond 150 mM NaCl was not accompanied by a saturation of the Na⁺ concentration in the sheath, which would be expected if the sheath acts as a Na⁺ buffer for the blades. Results also indicate that Na⁺ preferentially accumulated to higher concentrations in older leaf blades and sheaths, especially in treatments of 150 mM NaCl and above. This phenomenon is common in glycophytes (Greenway and Munns, 1980; Munns and Termaat, 1986; Nakamura et al., 1996) and could be explained by the fact that older leaves have been exposed to salt for a longer time period than the younger ones. In addition their vacuoles are bigger and thus can accumulate more Na⁺ than those of younger leaves. Accumulation of Na⁺ in vacuoles of older leaves could mitigate the Na⁺ pressure on the younger tissues and help maintain their growth.

Increased NaCl treatments reduced K⁺ concentrations in leaf sheaths but not in leaf blades (data not shown). However, overall K⁺ concentrations in leaf tissues were still high as compared with that of roots and stems. Therefore, severe potassium deficiency is unlikely to occur, at least in sorghum leaves, even at high salt concentrations. The results also show that there was no significant difference in K⁺ concentrations in sheaths and blades contrary to the findings of Boursier and Läuchli (1990) who observed a significantly higher concentration of K⁺ in sheaths as compared with leaf blades of sorghum. This difference would imply the sheaths were not controlling the entry of K⁺ into the leaf blades.

Our study shows a proportional reduction of Ca²⁺ concentration in all plant parts as external NaCl increased (Fig. 5). This is characteristic of Ca²⁺, whose transport is known to be affected by NaCl. The ionic interaction, particularly with Na⁺ leads to low Ca²⁺ concentration in the xylem fluid, and in turn, to a lower supply of Ca²⁺ to the leaf tissues.

Leaf blade tissues had substantially higher Ca²⁺ concentrations than leaf sheaths as has been observed also for other sorghum varieties (Boursier and Läuchli, 1990). Presumably, there is less absorption and retention of Ca²⁺ in sheaths as it passes from the stem to the leaf blade. There was an increase in Ca²⁺ concentration with increasing leaf age. This may reflect a higher proportion of cell wall and concomitant Ca²⁺ concentration of mature leaves or greater deposition via transpiration.

The data on Mg²⁺ concentration in roots show no clear-cut decline with increasing salinity, again contrary to some earlier reports (Boursier et al., 1987; Grieve and Maas, 1988). Our results therefore suggest that Na⁺ does not exclude Mg²⁺ from uptake systems in sorghum. However, once Mg²⁺ has entered the plant, an impact of salinity is manifested by concentrations of this ion in stems and leaves. Impacts of salt were significant in leaves and could have affected the metabolic performance of the plants. A sharp decline in concentration of magnesium in the growth zone of sorghum leaves was found in plants grown under NaCl (Bernstein et al., 1995) implying that there is a shortage of Mg²⁺ when sorghum was grown under saline conditions. The lack of difference in Mg²⁺ concentration between leaf blades and sheaths agrees with the idea that Mg²⁺ freely flows to all parts of a leaf. The results also demonstrate that Mg²⁺ incorporation into a leaf in the presence of salt was affected by leaf age. As observed with Ca²⁺, salinity may somehow control the movement of Mg²⁺, inhibiting its flow to younger leaves in the phloem, possibly resulting in deficiency and reduced photosynthetic reactions.

In conclusion, salinity inhibited the accumulation of K⁺ and Ca²⁺ in roots and stems. Accumulation of Mg²⁺ in roots was minimally affected. Na⁺ accumulates in roots and stems with increase in salinity up to 150 mM where it reaches saturation level. Obviously, these sorghum varieties use Na⁺ allocation to the leaf sheath as a mechanism, among others, for salt tolerance. This mechanism, does not, however, break down when the sheath is exposed to salt at high concentrations and for a long period of time. The negative effect of NaCl on the allocation of K⁺, Ca²⁺, and Mg²⁺ to the leaf tissues may contribute to their deficiency and the accompanying metabolic perturbations. The altered ion and water relations have a severe impact on the photosynthetic performance of the plant, as shown in the accompanying paper (Netondo et al., 2004).

	ACKNOWLEDGMENTS

 
We express our gratitude to the DAAD for financial support to GWN, to Prof. Dr. E. Steudle for providing research equipment and to Mrs. Barbara Scheitler for assisting in element analysis.

Received for publication December 2, 2002.

	REFERENCES

TOP ABSTRACT INTRODUCTION MATERIALS AND METHODS RESULTS DISCUSSION REFERENCES

 

• Ashraf, M., N. Nazir, and T. McNeilly. 2001. Comparative salt tolerances of amphidiploid and diploid Brassica species. Plant Sci. 160:683–689.[Medline]
• Bernstein, N., W.K. Silk, and A. Läuchli. 1995. Growth and development of sorghum leaves under conditions of NaCl stress. Spatial and temporal aspects of leaf growth inhibition. Planta 191:699–705.
• Boursier, P., J. Lynch, A. Läuchli, and E. Epstein. 1987. Chloride partitioning in leaves of salt stressed sorghum, maize, wheat and barley. Aust. J. Plant Physiol. 14:463–473.
• Boursier, P., and A. Läuchli. 1990. Growth responses and mineral nutrient relations of salt-stressed Sorghum. Crop Sci. 30:1226–1233.[Abstract/Free Full Text]
• Colmer, T.D., T.W.-M. Fan, R.M. Higashi, and A. Läuchli. 1996. Interactive effects of Ca²⁺ and NaCl salinity on the ionic relations and proline accumulation in the primary root tip of Sorghum bicolor. Physiol. Plant. 97:421–424.
• Colmer, T.D., T.W.-M. Fan, R.M. Higashi, and A. Läuchli. 1994. Interaction of Ca²⁺ and NaCl stress on the ion relations and intracellular pH of Sorghum bicolar root tips: In vivo 31P-NMR study. J. Exp. Bot. 45:1037–1044.[Abstract/Free Full Text]
• Cramer, G.R., A. Läuchli, and V.S. Polito. 1985. Displacement of Ca by Na from the plasmalemma of root cells. Plant Physiol. 79:207–211.[Abstract/Free Full Text]
• Cramer, G.R., and A. Läuchli. 1986. Displacement of Ca by Na from the plasmalemma of root cells. J. Exp. Bot. 37:321–330.[Abstract/Free Full Text]
• Erdei, L., and E. Taleisnik. 1993. Changes in water relation parameters under osmotic and salt stress in maize and sorghum. Physiol. Plant. 89:381–387.
• Greenway, H. 1962. Plant responses to saline substrates. II. Chloride, sodium, and potassium uptake and translocation in young plants of Hordeum vulgare during and after a short sodium chloride treatment. Aust. J. Biol. Sci. 15:39–57.
• Greenway, H., and R. Munns. 1980. Mechanisms of salt tolerance in nonhalophytes. Annu. Rev. Plant Physiol. 31:149–190.
• Grieve, C.M., and E.V. Maas. 1988. Differential effects of sodium/calcium ratio on sorghum genotypes. Crop Sci. 28:659–665.[Abstract/Free Full Text]
• Hasegawa, P.M., R.A. Bressan, J.K. Zhu, and H.J. Bohnert. 2000. Plant cellular and molecular responses to high salinity. Annu. Rev. Plant Physiol. Mol. Biol. 51:463–499.[Web of Science]
• Hu, Y., and U. Schmidhalter. 1998. Spatial distribution of inorganic ions and sugars contributing to osmotic adjustment in elongating wheat leaf under saline conditions. Aust. J. Plant Physiol. 25:591–597.
• Jones, M.M., and T.C. Turner. 1978. Osmotic adjustment in leaves of sorghum in response to water deficits. Plant Physiol. 61:122–126.[Abstract/Free Full Text]
• Kingsbury, R.W., E. Epstein, and R.W. Pearcy. 1984. Physiological responses to salinity in selected lines of wheat. Plant Physiol. 74:417–423.[Abstract/Free Full Text]
• Koyro, H.W. 1997. Ultrastructure and physiological changes in root cells of sorghum plants (Sorghum bicolor x Sorghum sudanensis cv. Sweet Sioux) induced by NaCl. J. Exp. Bot. 48:693–706.
• Lang, A.P.G. 1967. Osmotic coefficients and water potentials of sodium chloride solutions from 0-40°C. Aust. J. Chem. 20:2017–2023.
• Maas, E.V., J.A. Poss, and G.J. Hoffman. 1986. Salinity sensitivity on sorghum at three growth stages. Irrig. Sci. 7:1–11.
• McCree, J.K. 1986. Whole-plant carbon balance during osmotic adjustment to drought and salinity stress. Aust. J. Plant Physiol. 13:33–43.[Web of Science]
• Munns, R., and A. Termaat. 1986. Whole-plant responses to salinity. Aust. J. Plant Physiol. 13:143–160.[Web of Science]
• Munns, R. 1993. Physiological processes limiting plant growth in saline soils. Some dogmas and hypotheses. Plant Cell Environ. 16:15–24.
• Munns, R., J. Guo, J.B. Passioura, and G.R. Cramer. 2000. Leaf water status controls day-time but not daily rates of leaf expansion in salt treated barley. Aust. J. Plant Physiol. 27:949–957.[Web of Science]
• Munns, R. 2002. Comparative physiology of salt and water stress. Plant. Cell Environ. 25:239–250.[Medline]
• Nakamura, T., M. Ishitani, P. Harinasut, M. Nomura, T. Takabe, and T. Takabe. 1996. Distribution of glycinebetaine in old and young leaf blades of salt stressed barley plants. Plant Cell Physiol. 37:873–877.[Abstract/Free Full Text]
• Netondo, G.W., J.C. Onyango, and E. Beck. 2004. Sorghum and salinity: II. Gas exchange and chlorophyll fluorescence of sorghum under salt stress. Crop Sci. 44:806–811, this issue.[Abstract/Free Full Text]
• Neumann, P. 1997. Salinity resistance and plant growth revisited. Plant Cell Environ. 20:1193–1198.
• Pardossi, A., F. Malorgio, D. Oriolo, R. Gicci, G. Serra, and F. Tognoni. 1998. Water relations and osmotic adjustment in Apium graveolens during long-term NaCl stress and subsequent relief. Physiol. Plant. 102:369–376.
• Plaut, Z., and E. Federman. 1991. Acclimation of CO₂ assimilation in cotton leaves to water stress and salinity. Plant Physiol. 97:515–522.[Abstract/Free Full Text]
• Renault, S., C. Croser, J.A. Franklin, and J.J. Zwiazek. 2001. Effect of NaCl and Na₂SO₄ on red-osier dogwood (Cornus stolonifera Michx). Plant Soil 233:261–268.
• Richardson, S.G., and K.J. McCree. 1985. Carbon balance and water relations of sorghum exposed to salt and water stress. Plant Physiol. 79:1015–1020.[Abstract/Free Full Text]
• Saneoka, H., S. Ishiguro, and R.E.A. Moghaieb. 2001. Effect of salinity and abscisic acid on accumulation of glycinebetaine and betaine aldehyde dehydrogenase mRNA in sorghum leaves (Sorghum bicolor). J. Plant Physiol. 158:853–859.
• Schachtman, D.P., and R. Munns. 1992. Sodium accumulation in leaves of Triticum species that differ in salt tolerance. Aust. J. Plant Physiol. 19:331–340.
• Shalhevet, J., and T.C. Hsiao. 1986. Salinity and drought. A comparison of their effects on osmotic adjustment, assimilation, transport and growth. Irrig. Sci. 7:249–264.
• Sokal, R.R., and F.J. Rohlf. 1995. Biometry: The principles and practice of statistics in biological research. 3rd ed. W.H. Freeman and Company. New York.
• Turner, N.C., and M.M. Jones. 1980. Turgor maintenance by osmotic adjustment: A review and evaluation. p. 87–103. In N.C. Turner and P.J. Kramer (ed.) Adaptation of plants to water and high temperature stress. Wiley Interscience Press, New York.
• Vanderlip, R. L 1993. How a sorghum plant develops.URL: http://www.oznet.ksu.edu/library/crpsl2/samplers/s3.asp; verified 3 December 2003.
• Weimberg, R.H., H.R. Lerner, and A. Poljakoff-Mayber. 1984. Changes in growth and water soluble solute concentrations in Sorghum bicolor with sodium and potassium salts. Physiol. Plant. 62:472–480.
• Yang, Y.W., R.J. Newton, and F.R. Miller. 1990. Salinity tolerance in sorghum. 1. Whole plant response to sodium chloride in S. bicolor and S. halepense. Crop Sci. 30:775–781.[Abstract/Free Full Text]
• Yeo, A.R. 1998. Molecular biology of salt tolerance in the context of whole-plant physiology. J. Exp. Bot. 49:915–929.[Abstract/Free Full Text]

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