ECOTOXICOLOGY
AND
ENVIRONMENTAL
Selenium Tolerance,
SAFETY
21,47-56
(199
1)
Salt Tolerance, and Selenium Accumulation in Tall Fescue Lines
LIN Wu AND ZHANG-ZHI HUANG Departmen/
c~f‘Environmen~al
Horticulture, Received
Universily March
o~‘(hl~fiwh.
Duvis.
Cal$mia
95616
20. 1990
High levels of soil salinity and Se concentration are coexisting problems in the San Joaquin Valley, California. Tall fescue is a potentially useful crop plant for land management in soils containing elevated concentrations of Se and salinity. Information regarding its physiological mechanism and genetic variation of Se accumulation in this species is scant. Thirteen tall fescue (Festucu arundinacea Schreb.) lines were examined for Se and salt tolerances and Se accumulation in nutrient solution culture. Genetic variation of both Se and salt tolerances was detected among six American cultivars and seven worldwide tall fescue lines. Selenium tolerance and salt tolerance are independent of each other and are negatively correlated with tissue Se and salt concentrations. These relationships suggest that an exclusion mechanism is responsible for the tolerance. This diversity of Se and salt tolerance and Se accumulation among the tall fescue lines is important for the application of this species for land management. o 1991 Academic FWSS IIIC.
INTRODUCTION Selenium was at one time considered a highly toxic, carcinogenic element used primarily for industrial purposes (Nelson et al., 1943; Volgarey and Tscherkes, 1967: Schrauzer et al., 1977). This perception changed in 1957 when Se was found to prevent dietary hepatic necrosis in rats (Schwarz and Flotz, 1957). Since then, considerable attention has been given to selenium deficiency in livestock (Muth, 1963) and Se uptake by forage plants (Carter et al., 1968; Gissel-Nielson and Bisbjerg, 1970; Davies and Watkinson, 1969; Peterson and Butler, 1966). Selenium is not known to be a required nutrient element for plant growth. Plants may contain concentrations from below detectable limits to several thousand milligrams Se per kilogram dry weight depending upon the plant species, the soil, and soil parent material (Peterson and Butler, 1966). Extensive information regarding Se toxicity to animals resulting from ingestion of plants containing from five to several thousand milligrams Se per kilogram dry weight has been reported (Rosenfield and Beath, 1964) but very little information is available regarding Se toxicity to plants (Mahendra and Narendra, 1979; Smith and Watkinson, 1984; Wu et al., 1988). The discovery of high levels of Se in soil and water samples from the San Joaquin Valley, California, and responsibility of Se for the deformity and death of wildlife at the Kesterson National Wildlife Refuge (Marshall, 1985; Presser and Barnes, 1984) have renewed interest in the bioaccumulation and chemistry of this element. Selenium is a naturally occurring nonmetallic trace element which is similar to sulfur in chemical behavior (Lakin, 1973). It has four oxidation states: Selenide (-2) exists in highly insoluble metal selenide, organic selenides, and hydrogen selenide. a gas that readily decomposes in the presence of oxygen to form elemental selenium. Elemental Se (0) is virtually insoluble in water and seems to be an unreactive form of 41
0147-6513/91
$3.00
Copyright Cl 1991 by Academic Press. Inc. All rights of reproduction in any form rexwed.
48
WU
AND
HUANG
Se in aquatic systems (U.S. Environmental Protection Agency, 1979). Selenite (+4) salts are moderately soluble in acidic water and selenite seems to be the predominant form of Se in most freshwater environments (Brooks, 1984). Selenate (+6) is the most abundant form of dissolved Se in alkaline systems, such as the water in the San Luis Drain service area, and is the most stable soluble form of Se readily available to plants under alkaline conditions. In addition, the soil and water Se concentrations of the San Joaquin Valley are found highly correlated with soil and groundwater salinity, and the distribution of Se is related to movement of soluble salts to the agricultural drainage (Deverel et al., 1984). Salinity and Se are coexisting problems in this region. Therefore, in recent studies in Se accumulation of crop plants, in view of potential animal health problems and/or land and water quality improvement, both Se and salinity effects are considered (Mikkelsen et al., 1988a, b; Wu et al., 1988). Tall fescue is a potentially useful crop plant for land management in soils containing elevated concentrations of Se and salinity. It is a perennial grass used for forage and turf purposes, and it has an extensive, deep root system and high transpiration rate. Land planted with such a grass may have a reduced water table level and drainage problems. As a result of repeated harvesting of the grass much of the Se may be removed from the soil. The plant materials may be used as a supplement for livestock feeds defficient in Se. However, information regarding its physiological mechanism and genetic variation of Se accumulation and Se tolerance is scant. This report presents evidence of genotypical variation of Se and salt accumulation in six American tall fescue cultivars and seven worldwide lines and the function of the genotypical difference in determining the tissue Se concentration and effectiveness of bioaccumulation of Se. MATERIALS
AND
METHODS
Six commercially available tall fescue (Festuca arundinacea Schreb.) cultivars, Alta, Fawn, Kentucky 3 1, Mustang, Olympic, and Rebel, supplied by Jacklin Seed, Inc., and seven worldwide germplasm lines, Australia (No. 150 156) Chile (No. 427 127) Italy (No. 237559), Israel (No. 200339), South Africa (No. 774975), and Soviet Union (No. 2833 14), supplied by USDA Regional Plant Introduction Center Pullman, WA, were used for the Se and salt tolerance studies. Selenium
Tolerance and Se Accumulation
A preliminary test for tolerance of Se was conducted to determine an appropriate Se concentration for the experiments. A range of Se concentrations including control (no addition of Se), 0.5, 1.0, 1.5, 2.0, and 2.5 mg liter-’ Se as selenate (NazSe04) was added to a one-fourth concentration, modified Hoagland, nutrient solution (Epstein, 1972). Twenty seeds of Olympic cultivar were sown on an g-cm-diameter fiberglass sheet and a stretched nylon mesh supported by a styrofoam frame. The whole apparatus floated in a 2-liter plastic container of nutrient solution. Each treatment was repeated three times. The containers were placed on a greenhouse bench and completely randomized and kept in a temperature-controlled greenhouse at 2 1“C during the day and 18°C at night with an average natural sunlight of 320 pmol photon m-* set-‘. The nutrient solutions were aerated with compressed air and replaced every 4 days. At the end of the fifth week, the plants were harvested, and the root and shoot dry weights were measured.
Se AND
SALT
TOLERANCE
AND
Se ACCUMULATION
49
The growth response to Se stress is presented as tolerance ratios, which are the percentage of growth in nutrient solution containing Se to that without Se. The advantage of using a tolerance ratio rather than an absolute growth value for comparative measures of response to Se stress is that it avoids a possible error generated by intrinsic growth differences between varieties. The tolerance ratios represented by dry weight were used for data presentation throughout this report. The preliminary test using Olympic cultivar revealed that 2 mg liter-’ Se produced about 45% growth inhibition relative to the control treatment. This Se concentration was chosen for the Se tolerance and accumulation studies. All of the 6 American varieties and the 7 worldwide tall fescue lines were used for this experiment. Twenty seeds were sown in 2-liter containers. Seventy-eight containers including 13 tall fescue lines, two levels of Se treatments (control and 2 mg liter-’ Se), and three replications were completely randomized on a greenhouse bench. The nutrient solution culture and greenhouse conditions were identical to the conditions used for the preliminary Se tolerance test. After 3 weeks of growth, the plants were thinned to 10 plants per container for an additional 2 weeks of growth under identical conditions. The plants were harvested at the end of the fifth week. The root and shoot dry weights were measured, and Se tolerance ratios were calculated. For tissue Se concentration measurement, plants were separated into root and shoot tissues and dried at 60°C for 72 hr. Five milliliters of concentrated HN03 and 2.5 ml of concentrated HC104 were added to 50 mg of dried, ground plant material in a 75 ml volumetric digestion tube digested overnight at room temperature. Further tissue digestion and Se oxidation to Se (IV) were conducted at 150 to 210°C on a heating block (Scientific Instruments, Inc., Pleasantville, NY). Selenium was determined using hydride generation flame atomic absorption spectroscopy (Perkin-Elmer) with a heated quartz cell utilizing argon as the carrier gas. Salt Tolerance Test In this report, salt tolerance is expressed as NaCl tolerance. Solution-culture methods used for the Se tolerance studies were used also for the present study. One-fourth concentration, modified Hoagland nutrient solution (Epstein, 1972) was the control treatment. The solution with 0.1 M NaCl was used for the salt treatment. Cultural solutions were changed every 4 days. Cultural conditions were identical to those described before for the Se tolerance test. Salt tolerance ratios were measured using the shoot dry weight. For measurements of plant tissue Na and Cl concentration, shoot and root tissues were ground into powder and extracted with 0.1 M HNOJ at room temperature for 24 hr and filtered with Whatman No. 1 paper. Sodium content was determined using an atomic absorption spectrophotometer. Chloride was measured with an automatic titrator (Buchler Instruments, Fort Lee, NJ). Analysis of variance and Duncan’s new multiple range test were performed for tolerance ratio, dry weight, and tissue Se and tissue salt concentrations. Values of tolerance ratios were log transformed before statistic analysis. Correlation analysis was performed to test the correlations between the shoot dry weight tolerance and the root dry weight tolerance, the tissue Se concentration and the Se tolerance ratio, the selenium tolerance and the salt tolerance, and the tissue Na concentration and the salt tolerance. Broad-sense heritability estimates were calculated for Se tolerance and salt tolerance
50
WU
AND
HUANG
on a variety basis from the analysis of variance using the component method described by Gardner ( 1963).
of variance
RESULTS
Selenium Tolerance and Se Accumulation The preliminary Se tolerance test showed (Fig. 1) that 0.5 mg liter-’ Se did not affect the growth of tall fescue. If the Se concentration in the culture solution was increased up to 2 mg liter-‘, Se tolerance ratios measured by shoot and root dry weight were reduced to about 50%. In 2.5 mg liter -’ Se the tolerance ratios were further reduced to 30%. Two milligrams Se liter-’ concentration was chosen for the following Se tolerance and Se accumulation studies. The Se tolerance ratios of shoot dry weight (Table 1) indicate that among the six American commercial cultivars, Kentucky-31 had the lowest tolerance ratio (25%). The rest of the five lines had tolerance ratios ranging from 34 to 45% and were not significantly different from one another. Among the seven world tall fescue lines, the Soviet Union line had a tolerance ratio of 45%, being the most tolerant, and the Israel line had a tolerance ratio of 28%, being the least tolerant. The tolerance ratios of the remaining six lines ranged from 43 to 3 1%. Selenium tolerance ratios represented by the root dry weight are correlated positively with the shoot dry weight tolerance ratios (Fig. 2). Shoot tissue Se concentrations of the 6 American commercial cultivars ranged from 650 to 755 mg kg-’ dry weight. Among the 7 world lines, the tissue Se concentrations 120r
201 0.5
0 Se
FIG. 1. Selenium
1.0
concentration
1.5
2.0 (mg
L-’
2.5 1
tolerance ratios represented by shoot (0) or root (0) dry weight of Olympic tall fescue grown in nutrient culture solution supplemented with different concentrations of Se as sodium selenate. Vertical bars indicate standard errors of the means.
51
Se AND SALT TOLERANCE AND Se ACCUMULATION TABLE 1 SH~~TDRYWEIGHTPRODUCTION,S~TOLERANCERATIO,ANDS~ACCUMULATION OF 13-TALLFESCUELINESAFTER 5 WEEKSGROWTHINSOLUTIONCULTURE SUPPLEMENTEDWITH 2 mg LITER-' Se
Variety American commercial cultivars Alta Fawn Ky-3 1 Mustang Olympic Rebel World lines Australia Chile Israel Italy Japan South Africa Soviet Union
Dry weight of 10 plants (mg)
Tolerance ratio W)
Tissue selenium concentration (ms kg-‘)
abc ab f bcde bed bcde
2982 at 3212 a 1450 b 2007 b 2188 b 1943 b
42 45 25 36 45 34
1042 et 1421 cde 936 e 1106 e 1482 cde 932 3 1071 e
33 cdef 43 abc 28 ef 37 bed 39 bed 31 def 54 a
706 649 767 755 733 714
de ef cde de de de
929 b 927 b 1191 a 925 a 843 bed 906 bc 521 f
Total Se accumulation (Pi%)
2138 a 2092 a 1114cde 1518 b 1607 b 1388 bd 970 def 1306 bed 1106 cde 1018 de 1258 bcde 845 ef 560 f
t Means separatedby Duncan’s new multiple rangetest, P = 1%.
were highly variable and ranged from 840 to 1190 fig g-’ dry weight. Root tissue Se concentrations were between 150 to 550 mg kg-’ dry weight, and the root tissue Se concentrations were correlated positively with the shoot tissue Se concentrations (Table 4). Shoot tissue dry weight was negatively correlated with the shoot tissue Se concentration. Analysis of variance (Table 2) indicates that among the 13 tall fescue lines the shoot and root dry weight production, tissue Se concentration, and Se tolerance ratios were significantly different. Broad-sense heritability was calculated for the shoot and root dry weight Se tolerance ratios and had values of 0.67 and 0.65, respectively. These heritability ratios include both additive and nonadditive genetic effects. No significant correlation occurred between Se tolerance and the shoot dry weight production (Table 4). Salt Tolerance
The salt tolerance test (Table 3) with 0.1 M NaCl showed considerable variation of salt tolerance among the world tall fescue lines. Salt tolerance ratios ranged from 19% for the Chilean line to 66% for the American Alta cultivar. Generally, the American cultivars had higher salt tolerance ratios than the world tall fescue lines but are much less variable and ranged from 50 to 60%. Shoot Na concentrations were variable among the world lines. A negative correlation was found (Table 4) between the shoot tissue sodium concentrations and salt tolerance ratios of the 7 world lines. Chloride uptake displayed a pattern similar to sodium uptake, but the chloride concentrations in plants
WU AND HUANG
Y =
- 13.384
Y = 1.4130 R - 0.930
+ 1.2177X 60
10
20
30
40
Shoot tolerance
50
60
70
ratio (%)
10
+ 1.0078X p
AND
ENVIRONMENTAL
Selenium Tolerance,
SAFETY
21,47-56
(199
1)
Salt Tolerance, and Selenium Accumulation in Tall Fescue Lines
LIN Wu AND ZHANG-ZHI HUANG Departmen/
c~f‘Environmen~al
Horticulture, Received
Universily March
o~‘(hl~fiwh.
Duvis.
Cal$mia
95616
20. 1990
High levels of soil salinity and Se concentration are coexisting problems in the San Joaquin Valley, California. Tall fescue is a potentially useful crop plant for land management in soils containing elevated concentrations of Se and salinity. Information regarding its physiological mechanism and genetic variation of Se accumulation in this species is scant. Thirteen tall fescue (Festucu arundinacea Schreb.) lines were examined for Se and salt tolerances and Se accumulation in nutrient solution culture. Genetic variation of both Se and salt tolerances was detected among six American cultivars and seven worldwide tall fescue lines. Selenium tolerance and salt tolerance are independent of each other and are negatively correlated with tissue Se and salt concentrations. These relationships suggest that an exclusion mechanism is responsible for the tolerance. This diversity of Se and salt tolerance and Se accumulation among the tall fescue lines is important for the application of this species for land management. o 1991 Academic FWSS IIIC.
INTRODUCTION Selenium was at one time considered a highly toxic, carcinogenic element used primarily for industrial purposes (Nelson et al., 1943; Volgarey and Tscherkes, 1967: Schrauzer et al., 1977). This perception changed in 1957 when Se was found to prevent dietary hepatic necrosis in rats (Schwarz and Flotz, 1957). Since then, considerable attention has been given to selenium deficiency in livestock (Muth, 1963) and Se uptake by forage plants (Carter et al., 1968; Gissel-Nielson and Bisbjerg, 1970; Davies and Watkinson, 1969; Peterson and Butler, 1966). Selenium is not known to be a required nutrient element for plant growth. Plants may contain concentrations from below detectable limits to several thousand milligrams Se per kilogram dry weight depending upon the plant species, the soil, and soil parent material (Peterson and Butler, 1966). Extensive information regarding Se toxicity to animals resulting from ingestion of plants containing from five to several thousand milligrams Se per kilogram dry weight has been reported (Rosenfield and Beath, 1964) but very little information is available regarding Se toxicity to plants (Mahendra and Narendra, 1979; Smith and Watkinson, 1984; Wu et al., 1988). The discovery of high levels of Se in soil and water samples from the San Joaquin Valley, California, and responsibility of Se for the deformity and death of wildlife at the Kesterson National Wildlife Refuge (Marshall, 1985; Presser and Barnes, 1984) have renewed interest in the bioaccumulation and chemistry of this element. Selenium is a naturally occurring nonmetallic trace element which is similar to sulfur in chemical behavior (Lakin, 1973). It has four oxidation states: Selenide (-2) exists in highly insoluble metal selenide, organic selenides, and hydrogen selenide. a gas that readily decomposes in the presence of oxygen to form elemental selenium. Elemental Se (0) is virtually insoluble in water and seems to be an unreactive form of 41
0147-6513/91
$3.00
Copyright Cl 1991 by Academic Press. Inc. All rights of reproduction in any form rexwed.
48
WU
AND
HUANG
Se in aquatic systems (U.S. Environmental Protection Agency, 1979). Selenite (+4) salts are moderately soluble in acidic water and selenite seems to be the predominant form of Se in most freshwater environments (Brooks, 1984). Selenate (+6) is the most abundant form of dissolved Se in alkaline systems, such as the water in the San Luis Drain service area, and is the most stable soluble form of Se readily available to plants under alkaline conditions. In addition, the soil and water Se concentrations of the San Joaquin Valley are found highly correlated with soil and groundwater salinity, and the distribution of Se is related to movement of soluble salts to the agricultural drainage (Deverel et al., 1984). Salinity and Se are coexisting problems in this region. Therefore, in recent studies in Se accumulation of crop plants, in view of potential animal health problems and/or land and water quality improvement, both Se and salinity effects are considered (Mikkelsen et al., 1988a, b; Wu et al., 1988). Tall fescue is a potentially useful crop plant for land management in soils containing elevated concentrations of Se and salinity. It is a perennial grass used for forage and turf purposes, and it has an extensive, deep root system and high transpiration rate. Land planted with such a grass may have a reduced water table level and drainage problems. As a result of repeated harvesting of the grass much of the Se may be removed from the soil. The plant materials may be used as a supplement for livestock feeds defficient in Se. However, information regarding its physiological mechanism and genetic variation of Se accumulation and Se tolerance is scant. This report presents evidence of genotypical variation of Se and salt accumulation in six American tall fescue cultivars and seven worldwide lines and the function of the genotypical difference in determining the tissue Se concentration and effectiveness of bioaccumulation of Se. MATERIALS
AND
METHODS
Six commercially available tall fescue (Festuca arundinacea Schreb.) cultivars, Alta, Fawn, Kentucky 3 1, Mustang, Olympic, and Rebel, supplied by Jacklin Seed, Inc., and seven worldwide germplasm lines, Australia (No. 150 156) Chile (No. 427 127) Italy (No. 237559), Israel (No. 200339), South Africa (No. 774975), and Soviet Union (No. 2833 14), supplied by USDA Regional Plant Introduction Center Pullman, WA, were used for the Se and salt tolerance studies. Selenium
Tolerance and Se Accumulation
A preliminary test for tolerance of Se was conducted to determine an appropriate Se concentration for the experiments. A range of Se concentrations including control (no addition of Se), 0.5, 1.0, 1.5, 2.0, and 2.5 mg liter-’ Se as selenate (NazSe04) was added to a one-fourth concentration, modified Hoagland, nutrient solution (Epstein, 1972). Twenty seeds of Olympic cultivar were sown on an g-cm-diameter fiberglass sheet and a stretched nylon mesh supported by a styrofoam frame. The whole apparatus floated in a 2-liter plastic container of nutrient solution. Each treatment was repeated three times. The containers were placed on a greenhouse bench and completely randomized and kept in a temperature-controlled greenhouse at 2 1“C during the day and 18°C at night with an average natural sunlight of 320 pmol photon m-* set-‘. The nutrient solutions were aerated with compressed air and replaced every 4 days. At the end of the fifth week, the plants were harvested, and the root and shoot dry weights were measured.
Se AND
SALT
TOLERANCE
AND
Se ACCUMULATION
49
The growth response to Se stress is presented as tolerance ratios, which are the percentage of growth in nutrient solution containing Se to that without Se. The advantage of using a tolerance ratio rather than an absolute growth value for comparative measures of response to Se stress is that it avoids a possible error generated by intrinsic growth differences between varieties. The tolerance ratios represented by dry weight were used for data presentation throughout this report. The preliminary test using Olympic cultivar revealed that 2 mg liter-’ Se produced about 45% growth inhibition relative to the control treatment. This Se concentration was chosen for the Se tolerance and accumulation studies. All of the 6 American varieties and the 7 worldwide tall fescue lines were used for this experiment. Twenty seeds were sown in 2-liter containers. Seventy-eight containers including 13 tall fescue lines, two levels of Se treatments (control and 2 mg liter-’ Se), and three replications were completely randomized on a greenhouse bench. The nutrient solution culture and greenhouse conditions were identical to the conditions used for the preliminary Se tolerance test. After 3 weeks of growth, the plants were thinned to 10 plants per container for an additional 2 weeks of growth under identical conditions. The plants were harvested at the end of the fifth week. The root and shoot dry weights were measured, and Se tolerance ratios were calculated. For tissue Se concentration measurement, plants were separated into root and shoot tissues and dried at 60°C for 72 hr. Five milliliters of concentrated HN03 and 2.5 ml of concentrated HC104 were added to 50 mg of dried, ground plant material in a 75 ml volumetric digestion tube digested overnight at room temperature. Further tissue digestion and Se oxidation to Se (IV) were conducted at 150 to 210°C on a heating block (Scientific Instruments, Inc., Pleasantville, NY). Selenium was determined using hydride generation flame atomic absorption spectroscopy (Perkin-Elmer) with a heated quartz cell utilizing argon as the carrier gas. Salt Tolerance Test In this report, salt tolerance is expressed as NaCl tolerance. Solution-culture methods used for the Se tolerance studies were used also for the present study. One-fourth concentration, modified Hoagland nutrient solution (Epstein, 1972) was the control treatment. The solution with 0.1 M NaCl was used for the salt treatment. Cultural solutions were changed every 4 days. Cultural conditions were identical to those described before for the Se tolerance test. Salt tolerance ratios were measured using the shoot dry weight. For measurements of plant tissue Na and Cl concentration, shoot and root tissues were ground into powder and extracted with 0.1 M HNOJ at room temperature for 24 hr and filtered with Whatman No. 1 paper. Sodium content was determined using an atomic absorption spectrophotometer. Chloride was measured with an automatic titrator (Buchler Instruments, Fort Lee, NJ). Analysis of variance and Duncan’s new multiple range test were performed for tolerance ratio, dry weight, and tissue Se and tissue salt concentrations. Values of tolerance ratios were log transformed before statistic analysis. Correlation analysis was performed to test the correlations between the shoot dry weight tolerance and the root dry weight tolerance, the tissue Se concentration and the Se tolerance ratio, the selenium tolerance and the salt tolerance, and the tissue Na concentration and the salt tolerance. Broad-sense heritability estimates were calculated for Se tolerance and salt tolerance
50
WU
AND
HUANG
on a variety basis from the analysis of variance using the component method described by Gardner ( 1963).
of variance
RESULTS
Selenium Tolerance and Se Accumulation The preliminary Se tolerance test showed (Fig. 1) that 0.5 mg liter-’ Se did not affect the growth of tall fescue. If the Se concentration in the culture solution was increased up to 2 mg liter-‘, Se tolerance ratios measured by shoot and root dry weight were reduced to about 50%. In 2.5 mg liter -’ Se the tolerance ratios were further reduced to 30%. Two milligrams Se liter-’ concentration was chosen for the following Se tolerance and Se accumulation studies. The Se tolerance ratios of shoot dry weight (Table 1) indicate that among the six American commercial cultivars, Kentucky-31 had the lowest tolerance ratio (25%). The rest of the five lines had tolerance ratios ranging from 34 to 45% and were not significantly different from one another. Among the seven world tall fescue lines, the Soviet Union line had a tolerance ratio of 45%, being the most tolerant, and the Israel line had a tolerance ratio of 28%, being the least tolerant. The tolerance ratios of the remaining six lines ranged from 43 to 3 1%. Selenium tolerance ratios represented by the root dry weight are correlated positively with the shoot dry weight tolerance ratios (Fig. 2). Shoot tissue Se concentrations of the 6 American commercial cultivars ranged from 650 to 755 mg kg-’ dry weight. Among the 7 world lines, the tissue Se concentrations 120r
201 0.5
0 Se
FIG. 1. Selenium
1.0
concentration
1.5
2.0 (mg
L-’
2.5 1
tolerance ratios represented by shoot (0) or root (0) dry weight of Olympic tall fescue grown in nutrient culture solution supplemented with different concentrations of Se as sodium selenate. Vertical bars indicate standard errors of the means.
51
Se AND SALT TOLERANCE AND Se ACCUMULATION TABLE 1 SH~~TDRYWEIGHTPRODUCTION,S~TOLERANCERATIO,ANDS~ACCUMULATION OF 13-TALLFESCUELINESAFTER 5 WEEKSGROWTHINSOLUTIONCULTURE SUPPLEMENTEDWITH 2 mg LITER-' Se
Variety American commercial cultivars Alta Fawn Ky-3 1 Mustang Olympic Rebel World lines Australia Chile Israel Italy Japan South Africa Soviet Union
Dry weight of 10 plants (mg)
Tolerance ratio W)
Tissue selenium concentration (ms kg-‘)
abc ab f bcde bed bcde
2982 at 3212 a 1450 b 2007 b 2188 b 1943 b
42 45 25 36 45 34
1042 et 1421 cde 936 e 1106 e 1482 cde 932 3 1071 e
33 cdef 43 abc 28 ef 37 bed 39 bed 31 def 54 a
706 649 767 755 733 714
de ef cde de de de
929 b 927 b 1191 a 925 a 843 bed 906 bc 521 f
Total Se accumulation (Pi%)
2138 a 2092 a 1114cde 1518 b 1607 b 1388 bd 970 def 1306 bed 1106 cde 1018 de 1258 bcde 845 ef 560 f
t Means separatedby Duncan’s new multiple rangetest, P = 1%.
were highly variable and ranged from 840 to 1190 fig g-’ dry weight. Root tissue Se concentrations were between 150 to 550 mg kg-’ dry weight, and the root tissue Se concentrations were correlated positively with the shoot tissue Se concentrations (Table 4). Shoot tissue dry weight was negatively correlated with the shoot tissue Se concentration. Analysis of variance (Table 2) indicates that among the 13 tall fescue lines the shoot and root dry weight production, tissue Se concentration, and Se tolerance ratios were significantly different. Broad-sense heritability was calculated for the shoot and root dry weight Se tolerance ratios and had values of 0.67 and 0.65, respectively. These heritability ratios include both additive and nonadditive genetic effects. No significant correlation occurred between Se tolerance and the shoot dry weight production (Table 4). Salt Tolerance
The salt tolerance test (Table 3) with 0.1 M NaCl showed considerable variation of salt tolerance among the world tall fescue lines. Salt tolerance ratios ranged from 19% for the Chilean line to 66% for the American Alta cultivar. Generally, the American cultivars had higher salt tolerance ratios than the world tall fescue lines but are much less variable and ranged from 50 to 60%. Shoot Na concentrations were variable among the world lines. A negative correlation was found (Table 4) between the shoot tissue sodium concentrations and salt tolerance ratios of the 7 world lines. Chloride uptake displayed a pattern similar to sodium uptake, but the chloride concentrations in plants
WU AND HUANG
Y =
- 13.384
Y = 1.4130 R - 0.930
+ 1.2177X 60
10
20
30
40
Shoot tolerance
50
60
70
ratio (%)
10
+ 1.0078X p
