Environmental and Experimental Botany 55 (2006) 195–200

Seed reserve utilization and seedling growth of wheat as affectedby drought and salinity

A. Soltania, M. Gholipoorb,∗, E. Zeinalia

a Department of Agronomy and Plant Breeding, Gorgan University of Agricultural Sciences, P.O. Box 386, Gorgan, Iranb Department of Agronomy and Plant Breeding, Shahrood University of Technology, P.O. Box 36155-316, Shahrood, Iran

Accepted 27 October 2004

Abstract

In germination stage, decreased wheat (Triticum aestivum L.) seedling growth (mg per seedling) as affected by drought andsalinity stresses is a well-known phenomenon. The heterotrophic seedling growth can be defined as a product of two components:(1) the weight of mobilized seed reserve (WMSR; mg per seed), and (2) the conversion efficiency of utilized seed reserve toseedling tissue (mg seedling dry weight (SLDW) per mg utilized seed reserve). The first component can be further divided into(1) initial seed weight (mg per seed), and (2) the fraction of seed reserve, which is mobilized (mg mobilized seed reserve per mginitial seed weight). The objective of this study was the identification of the sensitive seedling growth component(s) in responseto drought and salinity stresses. Two experiments were separately conducted using various osmotic pressures (OP) inducedby polyethylene glycol (PEG; 0–1.8 MPa, with interval of 0.2) in experiment 1 and by NaCl (0, 0.4, 0.8, 1.2 and 1.6 MPa) inexperiment 2. Two wheat cultivars were used in each experiment. In both experiments, seedling growth, fraction of seed reserve

ught andowth is theprovement

en,

77;90

h re-fail-

utilization and weight of mobilized seed reserve decreased with increasing drought and salt intensity. However, drosalinity stresses had no effect on the conversion efficiency. It was concluded that the sensitive component of seedling grweight of mobilized seed reserve. Thus, appropriate efforts such as plant breeding programs should be focused on imof seed reserve mobilization in order to obtain increased seedling growth under drought and salinity stresses.© 2004 Elsevier B.V. All rights reserved.

Keywords: Drought; Salinity; Seed reserve; Seedling; Wheat

1. Introduction

Drought and salinity are widespread problemsaround the world. Seed germination and seedling

∗ Corresponding author. Tel.: +98 273 3350570;fax: +98 273 3350570.

E-mail address: manouchehrg@excite.com (M. Gholipoor).

growth of wheat (Triticum aestivum L.), like othercrops, were negatively affected by drought (Davidsonand Chevalier, 1987; Kiem and Krostad, 1981; Ow1972; Passioura, 1988) and salinity stresses (Ashrafand McNeily, 1988; El-Sharkawi and Salml, 19Francois et al., 1986; Hampson and Simpson, 19).Poor germination and decreased seedling growtsult in poor establishment and occasionally crop

0098-8472/$ – see front matter © 2004 Elsevier B.V. All rights reserved.doi:10.1016/j.envexpbot.2004.10.012

196 A. Soltani et al. / Environmental and Experimental Botany 55 (2006) 195–200

ure. Poor establishing in turn causes (Soltani andGaleshi, 2002): (1) decreased crop’s competitivenesswith weeds (Lemerle et al., 1996 cited inRebetzkeand Richards, 1999); (2) lower shading of the soil sur-face and subsequently higher loss of soil water throughevaporation and hence, lower availability of water forcrop; (3) lower light interception and yield potential;(4) lower growth in early season when vapor pressuredeficit is low and as a result diminished CO2 fixationper unit transpirational water loss (Condon et al., 1993;Tanner and Sinclair, 1983). Any effect that droughtmight have should be most considerable under salt-stressed conditions, because salinity can affect germi-nation and seedling growth either by creating an os-motic pressure (OP) that prevents water uptake or bytoxic effects of sodium and chloride ions on the germi-nating seed (Bewley and Black, 1982).

Seed germination comprises of two distinguishedmetabolic processes: (1) enzymatic hydrolysis of seedstorage, and (2) formation of new cell structures(Bewley and Black, 1982; Copeland and McDonald,1985; Mayer and Poljakoff-Mayber, 1989). In wheat,like other monocotyledons, gibberellic acid (GA) af-ter synthesis in the scutellum migrates into the aleu-rone layer. Then, it stimulates the synthesis of hy-drolytic enzymes, such as amylase, ribonuclease, pro-tease, phosphatase and 1,3-glucanase. These enzymesare responsible for the hydrolysis of stored substrates,such as carbohydrates, lipids, proteins and phospho-rous compounds. The hydrolyzed products are utilizedi tion,t ert tion(

phics tita-t woc erve( effi-c sue( at-t po-n ght( ervew o.S eedr oft ght

and salt stresses would be useful for improving sensi-tive component and/or components by appropriate ef-forts.

We have found no published references reportingquantitative responses of the wheat seedling growthcomponents to drought and salinity. Therefore, thepresent study was initiated.

2. Materials and methods

Two experiments were separately conducted at SeedResearch Laboratory of Gorgan University of Agricul-tural Sciences, Gorgan, Iran.

2.1. Drought experiment (experiment 1)

Factorial combinations of 2 cultivars (Tajan and Ba-conara) and 10 drought levels were the treatments of thefirst experiment. The experimental design was a ran-domized complete block design with four replicationsper treatment. Osmotic pressures (drought levels) of 0,0.2, 0.4, 0.6, 0.8, 1.0, 1.2, 1.4, 1.6 and 1.8 MPa were cre-ated using polyethylene glycol (PEG), based on equa-tion supplied byMichel and Kaufman (1983). Seedswere germinated in 9 cm petri dishes with one What-man No. 1 filter papers moistened with the appropri-ate solutions or distilled water for 0 MPa. Twenty-fiveseeds per dish were used for each treatment. Seeds wereincubated in the dark at 20± 0.5◦C in a controlled-t

1),d edwi fors eedda

ngsw d)s f theo em-n ervei dryw ra-t ghtw ntage(

n seedling tissues synthesis. During seed germinahe dry weight of growing seedling is always lowhan that of the mobilized substrates, due to respiraBewley and Black, 1982).

Based on the above explanation, the heterotroeedling growth (mg per seedling) could be quanively described as the product of the following tomponents: (1) the weight of mobilized seed resWMSR; mg per seed), and (2) the conversioniency of mobilized seed reserve to seedling tismg mg−1), i.e. the production of seedling dry mer per unit of usage of seed reserve. The first coment can be further divided into (1) initial seed weimg per seed), and (2) the fraction of seed reshich is mobilized (mg mg−1), i.e. seed depletion ratieedling growth is inhibited through reductions in s

eserve utilization and/or efficiency. Identificationhe relative sensitivity of these components to drou

emperature room.Four replicates of 25 seeds were weighed (W

ried at 104◦C for 24 h and then reweighed (W2). Seater content was calculated as [(W1− W2)/W2]. The

nitial seed dry weight was calculated using the dataeed water content and W1. The value of initial sry weight for Tajan and Baconara was 31.18± 0.30nd 31.43± 0.37 mg per seed, respectively.

After seven days, oven-dried weight of seedlias determined. The weight of utilized (mobilizeeed reserve was calculated as the dry weight original seed minus the dry weight of the seed rant. Conversion efficiency of mobilized seed res

nto plant tissue was estimated by dividing seedlingeight (SLDW) by the utilized seed reserve. The

io of utilized seed reserve to initial seed dry weias considered as seed reserve depletion perce

SRDP).

A. Soltani et al. / Environmental and Experimental Botany 55 (2006) 195–200 197

2.2. Salinity experiment (experiment 2)

Salinity levels of 0, 0.4, 0.8, 1.2 and 1.6 MPa werecreated using NaCl, according to the Van Hoff formulapresented inSalisbury and Ross (1996). The cultivarswere Tajan and Zagros. In this experiment, each treat-ment was replicated five times and the temperature was23± 0.5◦C. All measurements were similar to droughtexperiment. The calculated initial seed dry weight forTajan and Zagros was 34.8± 0.66 and 43.3± 0.27 mgper seed, respectively.

Data from both experiments were separately ana-lyzed, using the GLM procedure of the Statistical Anal-ysis System (SAS Institute, 1989).

3. Results and discussion

The results indicated that across drought levels, thedifference between cultivars (Tajan and Baconara) wasnot significant for weight of mobilized seed reserve andseed reserve depletion percentage (Table 1; Fig. 1a andb). There was a significant drought× cultivar interac-tion for these traits (Table 1). The difference betweenTajan and Baconara was not significant in drought OPs

Table 1Summary of analysis of variance for weight of mobilized seed reserve(WMSR), seed reserve depletion percentage (SRDP), seed reserveutilization efficiency (SRUE) and seedling dry weight (SLDW) at-tributes in drought and salinity experiments

WMSR SRDP SRUE SLDW

Drought experimentCultivar (C) NS NS NS *Drought (D) ** ** NS **C× D * * NS *

Salinity experimentCultivar (C) ** * NS **Salinity (S) ** ** NS **C× S NS NS NS *

*P < 0.05; **P < 0.01.

less than 1.5 MPa, but at drought stress greater than1.5 MPa, Tajan retained a higher weight of utilized seedreserve and seed reserve depletion percentage (Fig. 1aand b).

The effect of cultivar, drought and their interac-tions was not significant for seed reserve utilizationefficiency (SRUE) (Table 1; Fig. 1c). Effect of culti-var and drought and their interaction was significantfor seedling dry weight (Table 1). Across drought OPs,Tajan had a greater seedling dry weight than Baconara

F ized (m e (b), seedr spring

ig. 1. Effect of PEG-induced drought (MPa) on weight of utileserve utilization efficiency (c) and seedling growth (d) in two

obilized) seed reserve (a), seed reserve depletion percentagwheat cultivars, Tajan (T) and Baconara (B).

198 A. Soltani et al. / Environmental and Experimental Botany 55 (2006) 195–200

Fig. 2. Effect of NaCl-induced salinity (MPa) on weight of utilized (mobilized) seed reserve (a), seed reserve depletion percentage (b), seedreserve utilization efficiency (c) and seedling growth (d) in two spring wheat cultivars, Tajan (T) and Zagros (Z).

(Fig. 1d). While seedling dry weight was declined withdrought in both cultivars, this reduction was greaterfor Baconara at OP more than 1.5 MPa and resulted ingreater difference between the cultivars at OP greaterthan 1.5 MPa. Decline in seedling growth and differentresponse of cultivars to drought were also reported byother researchers (Bhatt and Srinivasa-Rao, 1987; Deand Kar, 1995; Guedira et al., 1997; Day and Intalap,1970; Hegary and Ross, 1976).

Across salinity treatments, the difference betweenTajan and Zagros was significant for weight of mobi-lized seed reserve and seed reserve depletion percent-age (Table 1); Zagros had a greater weight of mobi-lized seed reserve and seed reserve depletion percent-age (Fig. 2a and b). Part of the difference between culti-vars in salinity experiment can be ascribed to their seedsize. Zagros had a greater seed size than Tajan. Salin-ity × cultivar interaction was statistically negligible forweight of mobilized seed reserve and seed reserve de-pletion percentage (Table 1).

Like drought experiment, the effect of all sourcesof variations including cultivar, salinity and their in-teractions was not significant for seed reserve utiliza-tion efficiency, indicating that seed reserve utilizationefficiency was a conservative trait. Although the cul-tivar differences was not significant for seed reserveutilization efficiency in both drought and salinity ex-

periments,Soltani et al. (2001)reported significant cul-tivar differences for this trait in wheat. No significanteffect of salinity on seed reserve utilization efficiency isalso in agreement with findings ofSoltani et al. (2002)in chickpea (Cicer arietinum L.) that seed reserve uti-lization efficiency is decreased only at severe salini-ties, greater than 0.9 MPa for chickpea. As a possiblecomparison, mean seed reserve utilization efficiencyof non-stressed Tajan was greater in drought experi-ment compared to salinity experiment, probably due tohigher temperature in experiment 2.Blum and Sinmena(1994)showed that seed reserve utilization efficiencyof wheat decreased with increase in temperature.

Effect of cultivar, salinity and their interaction wassignificant for seedling dry weight (Table 1). Simi-lar findings have been reported byAshraf and Mc-Neily (1988), El-Sharkawi and Salml (1977), Francoiset al. (1986)and Hampson and Simpson (1990)fornegative effect of salinity on seedling dry weight.As shown inFig. 2d, cultivar difference for this traitwas greater at lower OP and decreased with increas-ing OP. The seedling dry weight was not affected byOP up to 0.5 MPa; even a non-significant and neg-ligible increase in it was found. This increase is inagreement with report ofMozafar and Goodin (1986),who reported an increase in seedling dry weight atlow OP. In this experiment, Zagros (with large seed

A. Soltani et al. / Environmental and Experimental Botany 55 (2006) 195–200 199

size) had greater seedling dry weight than Tajan acrosssalinity stress OPs. There are generally conflicting re-ports on the advantage of large seeds in producingmore vigorous seedling. For example,Shroyer andCox (1984) speculated that seedling dry weight ofsome cultivars may not be affected by seed size differ-ences.Lafond and Backer (1986)pointed out that smallseeds germinate and emerge more rapidly than largeseeds. With purple-flower alfalfa (Medicago sativa)(Beveridge and Wilise, 1959), sainfoin (Onobrychis vi-ciafolia Scop) (Carleton and Cooper, 1972), soybean(Glycine max) (Johnson and Luedders, 1974; Johnsonand Wax, 1978), a significant positive relation betweenseed size and seedling dry weight has not been de-tected. On the other hand, there is more experimentalevidence for positive correlation between seed size andseedling vigor (e.g.Bockous and Shroyer, 1996; Dou-glas et al., 1994; Goydani and Singh, 1971; Grieve andFrancois, 1992; Peterson et al., 1989; Randhawa et al.,1974; Singh, 1970; Spilde, 1989). Based on the resultsof present study, it seems that the inconsistency of thereports may be due to the value of seed reserve deple-tion percentage, but not due to seed reserve utilizationefficiency, so that the dry weight of seedling originatedfrom cultivars with large-sized seed, but low seed re-serve depletion percentage, would be similar to that offrom cultivars with small-sized seed, but higher seedreserve depletion percentage. This recent conclusionshould be confirmed in future studies with larger num-ber of cultivars.

ins alin-i eds ), nos entw .T re-s on-v tis-s owthi andpc rtedt rialsd bar-ls mo-b

tion of genetic variation for seed vigor traits found sig-nificant genetic differences for weight of utilized seedreserve and seed reserve depletion percentage as wellas seed reserve utilization efficiency. This genetic vari-ation can be used in breeding programs that aimed atthe improvement in seed reserve utilization rate. Moredetailed studies should be aimed at the study of activityof enzymes and/or hormones involving in seed reserveutilization rate (seed reserve depletion percentage) asaffected by drought and salinity stresses.

References

Ashraf, M., McNeily, T., 1988. Variability in salt tolerance of ninespring wheat cultivars. J. Agron. Crop Sci. 160, 14–21.

Beveridge, J.L., Wilise, C.P., 1959. Influence of depth of planting,seed size and variety on emergence and seedling vigor in alfalfa.Agron. J. 51, 731–734.

Bewley, J.D., Black, M., 1982. Physiology and Biochemistry ofSeeds in Relation to Germination, vol. 2. Springer-Verlag, Berlin.

Bhatt, R.M., Srinivasa-Rao, N.K., 1987. Seed germination andseedling growth responses of tomato cultivars to imposed wa-ter stress. J. Hort. Sci. 62, 221–225.

Blum, A., Sinmena, B., 1994. Wheat seed endosperm utilization un-der heat stress and its relation to thermo tolerance in the au-totrophic plant. Field Crops Res. 37, 185–191.

Bockous, W.W., Shroyer, J.P., 1996. Effect of seed size on seedlingvigor and forage production of winter wheat. Can. J. Plant Sci.76, 101–105.

Carleton, A.E., Cooper, C.S., 1972. Seed size effects upon seedlingvigor of three forage legumes. Crop Sci. 12, 183–186.

C ence

C shipsy andes.

D gly-eat.

D the

D mung00.

D edinter

E inityil 46,

F . Ef-wth

Overall, our results clearly indicate that declineeedling dry weight in response to drought and sty is a consequence of decline in weight of mobilizeed reserve (seed reserve depletion percentageeed reserve utilization efficiency. This is in agreemith observation ofSoltani et al. (2002)in chickpeahey found that seedling dry weight reduction was ault of reduction in seed reserve mobilization, not cersion efficiency of mobilized reserve to seedlingue. Therefore, sensitive component of seedling grs the weight of mobilized (utilized) seed reservelant breeding efforts or physiological remedies{sayhemical application; for instance, it has been repohat H2O2 increases breakdown of storage mateuring seed germination in legumes, tomato and

ey (seeCopeland and McDonald, 1985, Chapter 4)}hould be focused on improvement of seed reserveilization. Fortunately,Soltani et al. (2001)in evalua-

t

opeland, L.O., McDonald, M.B., 1985. Principles of Seed Sciand Technology. McMillan Publ. Co., New York.

ondon, A.G., Richards, R.A., Farquhar, G.D., 1993. Relationbetween carbon isotope discrimination, water use efficienctranspiration efficiency for dryland wheat. Aust. J. Agric. R44, 1693–1711.

avidson, D.J., Chevalier, P.M., 1987. Influence of polyethylencol induced water deficits on tiller production in spring whCrop Sci. 27, 1185–1187.

ay, A.D., Intalap, S., 1970. Some effects of soil moisture ongrowth of wheat. Agron. J. 62, 27–29.

e, R., Kar, P., 1995. Seed germination and seedling growth ofbean (Vigna radiata) under water stress induced by PEG-60Seed Sci. Technol. 23, 301–308.

ouglas, C.L., Wilkins, D.E., Churchill, D.B., 1994. Tillage, sesize and seed density effects on performance of soft white wwheat. Agron. J. 86, 707–711.

l-Sharkawi, H.H., Salml, F.M., 1977. Effects of drought and salon some growth parameters in wheat and barley. Plant So423–433.

rancois, L.E., Maas, E.V., Donovan, T.J., Youngs, V.L., 1986fects of salinity on grain yield and quality, vegetative gro

200 A. Soltani et al. / Environmental and Experimental Botany 55 (2006) 195–200

and germination of semi dwarf and drum wheat. Agron. J. 78,1053–1058.

Goydani, B.M., Singh, C., 1971. Influence of seed size on growthand yield of wheat. Indian J. Agron. 16, 209–212.

Grieve, C.M., Francois, L.E., 1992. The importance of initial seedsize in wheat plant response to salinity. Plant Soil 147, 197–205.

Guedira, M., Shroyer, J.P., Kirkham, M.B., Paulsen, G.M., 1997.Wheat coleoptile and root growth and seedling survival after de-hydration and rehydration. Agron. J. 89, 822–826.

Hampson, C.R., Simpson, G.M., 1990. Effects of temperature, saltand osmotic pressure on early growth of wheat (Triticum aes-tivum). 1. Germination. Can. J. Bot. 68, 524–528.

Hegary, T.W., Ross, H.A., 1976. Effects of light and water deficiton radicle growth of lettuce seeds under high temperature stress.New Phytol. 82, 49–57.

Johnson, D.R., Luedders, V.D., 1974. Effect of planted seed sizeon germination and yield of soybean (Glycine max (L.) Merr.).Agron. J. 66, 117–121.

Johnson, D.R., Wax, L.M., 1978. Relationships of soybean germina-tion and vigor tests to field performance. Agron. J. 70, 273–278.

Kiem, D.L., Krostad, W.E., 1981. Drought response of winter wheatcultivars grown under field stress conditions. Crop Sci. 21, 11–15.

Lafond, G.P., Backer, R.J., 1986. Effects of temperature, moisturestress, and seed size on germination of nine spring wheat culti-vars. Crop Sci. 26, 563–567.

Mayer, A.M., Poljakoff-Mayber, A., 1989. The Germination ofSeeds, fourth ed. Pergamon Press, Oxford.

Michel, B.E., Kaufman, M.R., 1983. The osmotic pressure ofpolyethylene glycol 6000. Plant Physiol. 51, 914–916.

Mozafar, A., Goodin, J.R., 1986. Salt tolerance of two differentlydrought tolerant wheat genotypes during germination and earlyseedling growth. Plant Soil 96, 303–316.

Owen, P.C.J., 1972. The relation of germination of wheat to waterpotential. J. Exp. Bot. 3, 188–192.

Passioura, J.B., 1988. Root signals control leaf expansion in wheatseedlings growing in drying soil. Aust. J. Plant Physiol. 15,687–693.

Peterson, C.M., Klepper, B., Rickman, R.W., 1989. Seed reserves andseedling development in winter wheat. Agron. J. 81, 245–251.

Randhawa, A.S., Anand, S.C., Jolly, R.S., 1974. Effect of seed-sizeand seed-rate on wheat yield. J. Res. 11, 9–12.

Rebetzke, G.L., Richards, R.A., 1999. Genetic improvement of earlyvigor in wheat. Aust. J. Agric. Res. 50, 291–301.

Salisbury, F.B., Ross, C.W., 1996. Plant Physiology. WadsworthPubl. Co., Belmont, CA.

SAS Institute, 1989. SAS/STAT User’s Guide, Version 6, fourth ed.SAS Institute, Cary, NC.

Shroyer, J.P., Cox, T.S., 1984. Effects of cultivar, environment andtheir interaction on seed quality of hard red winter wheat fromproduction fields. J. Appl. Seed Prod. 2, 24–28.

Singh, B.P., 1970. Influence of seed size and depth of sowing on earlygrowth and yield of dwarf wheat. Madras Agric. J. 57, 449–452.

Soltani, A., Zeinali, E., Galeshi, S., Latifi, N., 2001. Genetic variationfor and interrelationships among seed vigor traits in wheat fromthe Caspian Sea coast of Iran. Seed Sci. Technol. 29, 653–662.

Soltani, A., Galeshi, S., Zeinali, E., Latifi, N., 2002. Germination,seed reserve utilization and seedling growth of chickpea as af-fected by salinity and seed size. Seed Sci. Technol. 30, 51–60.

Soltani, A., Galeshi, S., 2002. Importance of rapid canopy closurefor wheat production in a temperate sub-humid environment: ex-perimentation and simulation. Field Crops Res. 77, 17–30.

Spilde, L.A., 1989. Influence of seed size and test weight on severalagronomic traits of barley and hard red spring wheat. J. Prod.Agric. 2, 169–172.

Tanner, C.B., Sinclair, T.R., 1983. Efficient water use in crop pro-duction: research or re-search. In: Taylor, H.M., Taylor, W.R.,Sinclair, T.R. (Eds.), Limitations to Efficient Water Use in CropProduction. ASA/CSSA/SSSA, Madison, WI, pp. 1–27.