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Comparison of inorganic solute accumulation in shoots,radicles and cotyledons of Vicia cracca during theseedling stage under NaCl stressYing Wang a , Jiyun Yang b , Shicheng Jiang b , Yu Tian b , Haixia Sun a , Minling Wang a ,Guangdi Li a & Daowei Zhou aa Northeast Institute of Geography and Agroecology, Chinese Academy of Sciences ,Changchun , Chinab Key Laboratory of Vegetation Ecology of Ministry of Education, Institute of GrasslandScience, Northeast Normal University , Changchun , ChinaPublished online: 15 Feb 2012.

To cite this article: Ying Wang , Jiyun Yang , Shicheng Jiang , Yu Tian , Haixia Sun , Minling Wang , Guangdi Li & Daowei Zhou(2012) Comparison of inorganic solute accumulation in shoots, radicles and cotyledons of Vicia cracca during the seedlingstage under NaCl stress, Soil Science and Plant Nutrition, 58:1, 24-31, DOI: 10.1080/00380768.2011.647606

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Soil Science and Plant Nutrition (2012), 58, 24—31 http://dx.doi.org/10.1080/00380768.2011.647606

ORIGINAL ARTICLE

Comparison of inorganic solute accumulation in shoots, radiclesand cotyledons of Vicia cracca during the seedling stage underNaCl stress

Ying WANG1, Jiyun YANG2, Shicheng JIANG2, Yu TIAN2, Haixia SUN1,Minling WANG1, Guangdi LI1 and Daowei ZHOU1

1Northeast Institute of Geography and Agroecology, Chinese Academy of Sciences, Changchun, China and 2Key Laboratory of

Vegetation Ecology of Ministry of Education, Institute of Grassland Science, Northeast Normal University, Changchun, China

Abstract

In the present study, differences in inorganic solute accumulation in shoots, radicles and cotyledons during the

seedling stage of Vicia cracca Linn were evaluated in response to a range of sodium chloride (NaCl)

concentrations. Seeds were sown in Petri dishes, germinated and grown with NaCl treatment for 10 days in a

growth chamber, with a temperature of 20�C and a 12 h light/dark cycle. Results showed that percentage

germination, germination rate, fresh weight and dry weight, and relative water content decreased as the NaCl

concentration increased in shoots, radicles and cotyledons. There were no significant differences in dry

weight/fresh weight ratios in shoots and radicles among treatments. However, the dry weight/fresh weight

ratio in cotyledons was significantly higher at 200 mM NaCl compared to treatments with lower NaCl

concentrations. Sodiumþ and Cl� concentrations in shoots and radicles increased as the NaCl concentration

increased. Sodiumþ and Cl� concentrations in shoots and radicles were much higher than those in cotyledons.

Similar trends were found for Kþ, Ca2þ, Mg2þ, H2PO�4 . By contrast, SO2�4 concentrations were lower in

shoots and radicles than in cotyledons, while NO�3 concentrations were similar in shoots, radicles and

cotyledons. In particular, Kþ efflux was observed in shoots, radicles and cotyledons when no salt stress was

imposed. In summary, increased NaCl concentration had adverse effects on germination and post-

germination growth. Inorganic ion accumulation in shoots and radicles was high, which might function in

osmotic adjustment in those plant organs. By contrast, inorganic ion accumulation did not occur in

cotyledons, suggesting that in cotyledons osmotic adjustment might not function the same way as in shoots

and radicles, because cotyledons function mainly as storage for carbohydrates or inorganic ions.

Key words: organ types, salinity, osmotic adjustment, solutes, Vicia cracca.

INTRODUCTION

Soil salinity is a major abiotic stress influencing plant

growth and productivity worldwide. About 7% of the

world’s total land area experiences soil salinity problems

(Musyimi 2005). High salt (NaCl) concentrations result in

ionic imbalance and hyperosmotic stress in plants (Zhu

2001), a significant concern due to its potential to

decrease agricultural production, especially in arid and

semiarid regions of the world (Pesarraki 1999). In these

regions, salinity is one of the limiting factors for plant

growth (Sanchez et al. 1998; Shannon et al. 1994). High

salinity disrupts homeostasis in water potential and ion

distribution (Zhu 2001). There is also evidence that salt

tolerance is a complex physiological trait affecting the

entire life history of a plant (Flowers 2004). Halophytes

are tolerant to salinity partly because they can uptake

water by maintaining a high osmotic potential through

accumulation of inorganic and organic solutes (Bradley

and Morris 1991; Martınez-Ballesta et al. 2004). On the

other hand, saline tolerance in glycophytes is associated

Correspondence: Daowei ZHOU, 3195 Weishan Road,Changchun 130012, P. R. China. Tel: þ860431-85542206.Fax: þ860431-85542206. Email: zhoudaowei@neigae.ac.cnReceived 31 December 2010.Accepted for publication 4 December 2011.

� 2012 Japanese Society of Soil Science and Plant Nutrition

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with the capacity to limit uptake and/or transport of saline

ions (mostly sodium [Naþ] and chloride [Cl�]) from the

root zone to aerial parts (Greenway and Munns 1980).

In saline environments, seeds and seedlings are often

exposed to higher salt concentrations relative to older

plants because germination typically occurs at or near the

soil surface (Foolad 1999). Germination and seedling

growth, particularly of young seedlings, are vulnerable to

environmental conditions and growth will be determined

by both macro- and micro-site conditions (Malcolm et al.

2003). Salinity reduces or delays germination and post-

germination growth (Fooland and Lin 1997). The first

physiological disorder, which takes place during germi-

nation, is the reduction in imbibition of water by seeds

due to a low solute potential in the saline growth media

to adapt the salinity condition. In different plant species

it was found that salinity caused accumulation of

inorganic solutes, such as Naþ and Cl�, in seedlings

(Ashraf et al. 2003; de Lacerda et al. 2003; Meloni et al.

2008; Ungar 1996).

Vicia cracca L. (Fabaceae) is native to central Asia and

Europe, and has been naturalized in almost all of North

America. The species is one of the most common fodder

plants in Northern China. V. cracca is a wild high-

quality forage widely grown mostly for hay, green

forage, silage or grain. It is a hypogeal-germinating

legume species. The cotyledons are typical embryonic

leaves and therefore function as carbohydrate storage,

but in some cases the cotyledons remain enclosed in the

seed coat, and function exclusively as a food reserve

(Garwood 1996; Kitajima 1992).

To date, the majority of published works on species or

cultivars under NaCl stress has been completed with

older plants (Guo et al. 2009; Zhang and Mu 2009;

Yang et al. 2008). There is limited information on the

salt tolerance of V. cracca during germination and post-

germination growth. The objective of this study was to

compare the inorganic solute accumulation in shoots,

radicles and cotyledons of V. cracca during the seedling

stage in response to different level of NaCl stress.

MATERILAS AND METHODS

Plant materials, germination and seedlingharvest

Seeds used in this study were harvested from the

Ecological Research Station for Grassland Farming,

Chinese Academy of Sciences, Changling, Jiling, China

(44�330N, 123�310E) and stored at 4�C. Prior to the

experiment, seeds were treated with 98% sulfuric acid

(H2SO4) for 25 min to promote germination. Seeds were

then washed thoroughly with distilled water.

Germination was conducted on 100-seed samples

placed on moist blotter paper in 90 mm Petri dishes.

Petri dishes were placed in a growth cabinet for 10 d at

20�C and a 12 h light/dark cycle daily.

The experiment was arranged in a completely ran-

domized design with four treatments and four replicates.

The treatments were 0, 50, 100 and 200 mM NaCl. At

the start of the experiment, about 10 mL of solution with

the designated concentration of NaCl was added to each

Petri dish, so that about half the volume of each seed was

immersed. Distilled water was used for a treatment with

0 mM NaCl as control. The experiment was repeated

three times.

Germination rate was determined by the radicle

penetrating the seed coat. The number of seeds germi-

nated was counted every day to determine percentage

germination and germination rate. The germination rate

was estimated using a modified Timson index of germi-

nation velocity¼P

G/t, where G is the percentage seed

germination at 1-d intervals and t is the total germination

period (Khan and Ungar 1984). The maximum possible

value of this index is 100.

Growth parameters and relative water content

The seedlings were washed with distilled water on

day 10. Seedlings were dissected into cotyledon, radicle

and shoot (the remaining part). The seed coat was

removed if attached before harvesting.

The relative water contents (RWC) of shoot, radicle

and cotyledon were calculated using the following

equation according to Silveira et al. (2003).

RWC ¼FW�DW

TW�DW� 100

where FW is the fresh weight, TW is the turgid weight

measured after 24 h of saturation in distilled water in

Petri dishes at 4�C in the dark, and DW is the dry weight

measured after drying at 70�C for 48 h to a constant

weight. Fifty replications were used. Few shoots emerged

from the seed coat under the 200 mM NaCl treatment;

therefore only radicles and cotyledons were harvested

and their weights measured. The seed coat was removed

before harvesting.

Determination of inorganic solutes

The cotyledons, shoots and radicles were oven-dried at

105�C for 15 min and then subsequently dried at a

second time at 70�C for 48 h to a constant weight at the

time of harvest. Dry samples (50 mg) were treated with

10 mL deionized water at 100�C for 1 h, the homogenate

was centrifuged at 3000 g for 10 min and filtered, and the

filtrate was used to determine free inorganic ion content.

All soluble contents were expressed in mmol g�1 DW.

Inorganic solute accumulation in Vicia cracca 25

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An atomic absorption spectrophotometer (TAS-990;

Purkinje General, Beijing, China) was used to determine

the Naþ, potassium (Kþ) and calcium (Ca2þ) content.

Anions (Cl�, nitrate [NO�3 ], dihydrogen phosphate

[H2PO�4 ] and sulfate [SO2�4 ]) were determined by ion

chromatography (DX-300 ion chromatographic system;

AS4A-SC ion-exchange column, CDM-II electrical con-

ductivity detector, mobile phase: Na2CO3/NaHCO3¼

1.7/1.8 mmol L�1; DIONEX, Sunnyvale, CA, USA).

Data analysis

Data were analyzed using a one-way Analysis of

Variance (ANOVA) in SPSS statistical software version

12.0 (SPSS Inc, Chicago Illinois, USA). Tests of signif-

icant differences among treatments were analyzed using

the Least Significant Difference (LSD) test at P50.05.

RESULTS

Germination and seedling growth

Percentage germination and germination rate decreased

with increased salt treatment levels (Table 1). Shoot and

radicle FW exhibited similar trends with germination

parameters, while the cotyledon FW presented a signif-

icant reduction at 200 mM NaCl compared to the

control (Table 2). Salinity markedly decreased both

shoot and radicle DW. However, no significant change

was observed among different levels of NaCl stress. The

mean weight was 10.39 mg for cotyledon DW (Table 2).

There were no significant differences in shoot and

radicle DW/FW ratios among treatments. However,

DW/FW ratio of cotyledons increased significantly

under the 200 mM NaCl treatment. Shoot, radicle and

cotyledon RWC reduced significantly under NaCl stress

compared to the control (Table 2).

Inorganic solutes

Cation concentrations in shoots and radicles were similar,

but both higher than those in cotyledons (Fig. 1).

Sodiumþ levels increased significantly in shoots and

radicles as well as significantly increased in cotyledons

as the concentration of NaCl increased. A similar pattern

was found for Kþ concentrations in shoots and radicles,

but cotyledon Kþ concentration increased from 0 to

100 mM NaCl, and then decreased significantly at

200 mM NaCl (Fig. 1b). Calcium2þ concentrations in

seedlings were lower compared to other cation concen-

trations (Fig. 1c). With increasing salinity levels, Ca2þ

concentration in shoots increased significantly.

Calcium2þ concentration in radicles was higher at

200 mM NaCl compared to the control. There was no

significant change in cotyledon Ca2þ concentration with

increased NaCl concentration. Overall, Ca2þ concentra-

tions were higher in shoots and radicles than in cotyle-

dons (Fig. 1c). There were no differences in shoot and

cotyledon magnesium (Mg2þ) concentrations among

treatments (Fig. 1d). Magnesium2þ concentrations in

radicles increased at 50, 100, and 200 mM NaCl

compared with the control plants.

With respect to anion concentrations, the Cl� concen-

trations exhibited similar trends to Naþ in shoots,

radicles and cotyledons (Fig. 2a). There were no signif-

icant differences in cotyledon NO�3 concentrations with

various NaCl concentrations. However, the shoot and

radicle NO�3 concentrations increased significantly at 50

and 100 mM NaCl compared to the control (Fig. 2b).

The H2PO�4 concentrations in shoots, radicles and

cotyledons remained unchanged from 0 to 100 mM

Table 2 Fresh weight (FW), Dry weight (DW), DW/FW ratiosand relative water content (RWC) (mean� SE) in cotyledons,shoots and radicles of V. cracca under NaCl stress

Cotyledon Shoot Radicle

FW (mg)0 26.91� 0.72a

y 7.81� 0.40a 4.07� 0.28a

50 25.48� 0.94ab 6.79� 0.22b 3.18� 0.21b

100 26.23� 0.57a 5.25� 0.26c 2.94� 0.15b

200 23.28� 1.21b — 1.47� 0.10c

DW (mg)0 9.95� 0.34a 0.54� 0.04a 0.45� 0.05a

50 10.48� 0.54a 0.50� 0.02a 0.28� 0.02b

100 10.51� 0.21a 0.35� 0.02b 0.26� 0.02bc

200 10.63� 0.73a — 0.15� 0.04c

DW/FW ratios0 0.369� 0.004b 0.069� 0.003a 0.084� 0.006a

50 0.412� 0.017b 0.073� 0.001a 0.087� 0.003a

100 0.402� 0.012b 0.067� 0.002a 0.088� 0.005a

200 0.459� 0.011a — 0.102� 0.004a

RWC (%)0 98.16� 0.38a 96.15� 0.52a 95.54� 0.55a

50 95.19� 0.29b 90.66� 0.56b 92.39� 0.76b

100 90.31� 0.23c 90.83� 0.42b 92.40� 0.70b

200 82.11� 1.37d — 88.24� 1.17c

yWithin a column, means followed by the same letter are not significantly

different at P¼0.05.

Table 1 Percentage germination and germination rate(mean� SE) of V. cracca L. under sodium chloride (NaCl) stress

Percentagegermination (%)

Germinationrate (Number d�1)

0 96� 1.5ay 58� 1.7a

50 86� 0.3b 39� 0.7b

100 85� 0.9b 31� 0.9c

200 20� 1.0c 3� 0.2d

yWithin a column, means followed by the same letter are not significantly

different at P¼0.05.

26 Y. Wang et al.

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NaCl, but slightly and significantly decreased at 200 mM

NaCl in radicles and cotyledons. The H2PO�4 concen-

trations in shoots and radicles were higher than in

cotyledons (Fig. 2c). There were no significant differences

in SO2�4 concentrations in shoots and radicles among all

the NaCl levels. The cotyledon SO2�4 concentration

remained unchanged from 0 to 100 mM NaCl and

decreased significantly at 200 mM NaCl. The SO2�4

concentration was greater in cotyledons than in shoots

and radicles (Fig. 2d). The Kþ/Naþ ratio decreased as salt

stress increased in shoots and cotyledons, but remained

unchanged in radicles from 0 to 100 mM NaCl. The

radicle Kþ/Naþ ratio was significantly lower at 200 mM

NaCl compared to the control (Fig. 3).

DISCUSSION

In saline environments, salt concentrations result in plant

vulnerability to many environmental stresses. Therefore,

adaptation to salinity is crucial for establishment of

species (Koyro and Sayed 2008). Results from the present

study showed that salinity affected seed germination and

post-germination growth. There are several possible

explanations. First, salinity could reduce the ability of

the plant to take up water, leading to slower growth

(Munns et al. 2006). This is the osmotic or water-deficit

effect of salinity. Salt stress exerts effects on water

relationships in both halophytic and glycophytic species

(Yeo and Flowers 1980; Djanaguiraman et al. 2006). In

the present study, RWC in shoot, radicle and cotyledon

followed a similar pattern and decreased with salt

concentrations. In most plants, the solute content of

cells at high salinity is higher than in non-saline

conditions, largely due to accumulation of ions (e.g.

Naþ and Cl�) and organic solutes. During rehydration to

establish turgid weight, the higher solute content in salt-

treated than in untreated shoots, radicles and cotyledons

causes a greater water uptake in the former than the

later. This results in a significantly low RWC with

salinity concentrations (Munns et al. 2006). This result is

consistent with previous studies (Meloni et al. 2008;

Ruffino et al. 2010) although RWC was not a useful

0

0.3

0.6

0.9

1.2N

a+ (

mm

olg–1

DW

)

Cotyledon Shoot Radicle

(a)

a''aa'a

abbb

b''a

c'b

b'b

c''a

d''a ccdc

0

1.2

2.4

3.6

4.8

K+ (

mm

olg–1

DW

)

(b)

bb ac ab bb

a''aa''aa''a

b''a

a'a

a'b

b'a'

0

0.06

0.12

0.18

0.24

NaCl (mM)

Mg2+

(m

mol

g–1D

W)

(d)

abab

ab ab

a'a

a'a a'a

b''a

a''a

a''aa''a

0

0.0003

0.0006

0.0009

0.0012

0 50 100 2000 50 100 200NaCl (mM)

NaCl (mM)0 50 100 2000 50 100 200

NaCl (mM)

Ca2+

(m

mol

g–1

DW

)

(c)

a''a

b''a

a''aa''a

ab

abab

ab

a'a

a'a

b'b

Figure 1 Effects of salt stress on the contents of (a) sodium (Naþ), (b) potassium (Kþ), (c) calcium (Ca2þ) and (d) magnesium (Mg2þ)in shoots, radicles and cotyledons of V. cracca L. Means followed by different letters of a, b and c for cotyledon (a0, b0 and c0 for shootand a0 0, b0 0 and c0 0 for root) are significantly different at P50.05. Means followed by different letters of a, b, and c among the sametreatments are significantly different at P50.05.

Inorganic solute accumulation in Vicia cracca 27

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indicator of turgor in salt-treated plants undergoing

osmotic adjustment. In the present study, it was observed

that cotyledon RWC was similar to shoot and radicle

RWC although ionic concentrations were lower in

cotyledons. Generally, plants can reduce water content

as a quick and economical approach to reduce cell water

potential in response to osmotic stress (Lissner et al.1999).

Second, plants are subject to the toxic effects of salt

inside the plant. Inhibition in germination and post-

germination growth can be related to high transport of

Naþ and Cl� to shoot and radicle from the saline growth

media. This is the salt specific or ion-excess effect of

salinity. The excessive accumulation of inorganic ions,

especially Naþ and Cl�, often results in toxicity, which is

the main cause of growth inhibition induced by salinity

(Khan et al. 2000; Yang et al. 2007). In our study, Naþ

and Cl� concentrations in cotyledons, shoots and radi-

cles increased from 0 to 100 mM NaCl (Figs 1 and 2). An

accumulation of high Naþ and Cl� concentrations in

0

0.02

0.04

0.06

NaCl (mM)

SO42–

(mm

olg–1

DW

)

(d)

aa

aaaa

baa'b a''b

a'ba''ba''b

a''ba'b

0

0.2

0.4

0.6

0 50 100 2000 50 100 200

NaCl (mM)

H2P

O4– (m

mol

g–1D

W)

(c)

ab bbab ab

a'a a'aa'a

a''ab''a

a''a a''a

0

1

2

3C

l– (mm

olg–1

DW

)

CotyledomShootRadicle

(a)

abcb ac bbc'b

b'b

a'a

d''a

c''a

b''a

a''a

0

0.002

0.004

0.006

0.008

NO

3 (m

mol

g–1

DW

)–

(b)

b'a

a'aa'a

b''a

a''aa''a a''aaa aa

aaaa

Figure 2 Effects of salt stress on the contents of (a) chlorine (Cl�), (b) nitrate (NO�3 ), (c) dihydrogen phosphate (H2PO�4 ) and(d) sulfate (SO2�

4 ) in shoots, radicles and cotyledons of V. cracca. Means followed by different letters of a, b and c for cotyledon (a0, b0

and c0 for shoot and a0 0, b0 0 and c0 0 for root) are significantly different at P50.05. Means followed by different letters of a, b, and camong the same treatments are significantly different at P50.05.

0

20

40

60

80

0 50 100 200NaCl (mM)

K+/N

a+

Cotyledon Shoot Radicle

aA

bB

a'B

b'A b'AbA bAa''B a''A a''b''A b''A

Figure 3 Effects of salt stress on the Kþ/Naþ ratios in shoots,radicles and cotyledons of V. cracca. Means followed bydifferent letters of a, b and c for cotyledon (a0, b0 and c0 forshoot and a0 0, b0 0 and c0 0 for root) are significantly different atP50.05. Means followed by different letters of A, B, and Camong the same treatments are significantly different atP50.05.

28 Y. Wang et al.

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radicles and shoots may indicate the presence of an

inhibition mechanism for Naþ and Cl� transport to

cotyledons, which may protect or alleviate cotyledon

damage.

In addition, inorganic solute accumulation may func-

tion in osmotic adjustment in shoots and radicles because

increase of the inorganic solutes is one of the factors used

to adjust osmotic potential. Significant entry of Naþ will

result in severe growth reduction or death in sensitive or

glycophytic species, but may benefit halophytes, or lead

to mild toxicity symptoms in salt-tolerant species. The

ability of a plant to adjust high osmotic potential as a

result of excess of Naþ and Cl� in cells is vital for growth

maintenance. In the present study, the Naþ and Cl�

concentrations in shoots and radicles were much higher

than those found in cotyledons and a similar tendency

was observed in the concentration of most important

inorganic solute components. The difference of inorganic

solute accumulation between cotyledons and other

tissues might be due to their different anatomical

structures. Cotyledons function as carbohydrate storage

and contain large amounts of reserve substances (Alche

et al. 2006). During seed development, there are few

vacuoles formed in cotyledons although large vacuoles

compartmentalization takes place accompanied by a

decrease in the reserve substances (Alche et al. 2006). It is

well known that ions acquired in excess of immediate

requirements are mainly accumulated and stored in

vacuoles of mature cells (Karley et al. 2000). Therefore,

cotyledons accumulated relatively smaller amounts of

inorganic solutes, especially Naþ and Cl�, than did

shoots and radicles.

The present study also indicated that shoots and

radicles share a similar salt inclusion strategy to deal with

excessive salinity. In this process, the shoot and radicle

tissues were adapted to accumulate large amounts of

saline ions, always greater than the amounts in cotyle-

dons. Despite direct absorption of solutes from the

growth media by the embryo, the germinated seed

transfers most of its inorganic and organic reserves to

the growing tissues. Thus the mechanism of salt tolerance

is likely to become very complex at this stage compared

with other stages. Voigt et al. (2009) suggested that salt-

induced inhibition of seedling growth is narrowly coor-

dinated with the delay of reserve mobilization and the

accumulation of products of reserve hydrolysis in the

cotyledons.

Potassiumþ is essential to all plant life, and in most

terrestrial plants, Kþ is the major cationic inorganic

nutrient. Salinity tolerance typically relies on limiting

Naþ accumulation and maintaining Kþ concentration in

the cytosol to balance ionic homeostasis (Flowers et al.

1977). Therefore, one of the key elements in salinity

tolerance is the capacity to maintain a high cytosolic

Kþ/Naþ ratio, as stated by Yeo (1998). In our study, the

Kþ/Naþ ratios decreased at 50, 100, and 200 mM NaCl

in all three plant organs. The lower endogenous Kþ

concentration in both shoots and radicles at control may

contribute to Kþ efflux and translocation (Al-Karakia

2001; Maathuis and Amtmann 1999), as Kþ was not

contained in the treatment media. However, Kþ concen-

tration in cotyledons decreased significantly at 200 mM,

compared with 50 and 100 mM, NaCl. This finding was

similar to that found in wheat embryos (Petruzzelli et al.

1991; Cramer et al. 1994). Nassery (1979) and Rehman

et al. (1996) reported that the toxic effect of salts in seeds

is usually caused by a reduction in seed Kþ concentra-

tion. Khan et al. (2000) indicated that decreases in

endogenous Kþ levels induced by high external NaCl

concentrations can be attributed to a transmembrane

competition between Kþ and Naþ fluxes. However, it

seemed in our study that competitive inhibition between

Kþ and Naþ fluxes did not exist because Kþ concentra-

tions in shoots and radicles remained higher than in

cotyledons, which may reflect a lack of transfer of

cytosolic Kþ from shoots and radicles to cotyledons.

Sodiumþ, Cl� and Kþ are important saline ions for

total osmotic adjustment. In the present study, seedlings

maintained a high Kþ concentration in shoots and

radicles to keep a high osmotic potential from 50 to

100 mM NaCl stresses, which would enhance the

salinity tolerance of V. cracca. It is suggested that

supplemental K may increase the Kþ/Naþ ratio and

hence would strengthen the salinity tolerance of crops

or cultivars during germination and post-germination

growth. The ability of species or cultivars to survive

during the germination and early seedling stages is

crucial for future improvement of crop yield. In the

present study, the behavior of Kþ and Naþ was

different from Ca2þ and Mg2þ in the response of

plants to salt stress (Yang. 2007). Magnesium2þ is the

key component of chlorophyll and Ca2þ can maintain

membrane stability, help to form cell walls and take

part in signal transduction. Though Ca2þ and Mg2þ

increased significantly under salt stress as compared to

the control, it can be concluded that their contributions

to osmotic adjustment were small because the concen-

trations of Ca2þ and Mg2þ were very low compared to

those of Kþ and Naþ.

In summary, increased NaCl concentration had

adverse effects on germination and post-germination

growth. Inorganic ion accumulation in shoots and

radicles was high, which might function in osmotic

adjustment in those plant organs. These results were not

seen in the cotyledons, probably because cotyledons

mainly function as storage of carbohydrates and inor-

ganic substances.

Inorganic solute accumulation in Vicia cracca 29

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ACKNOWLEDGMENTS

This work was financed by the National NaturalScience Foundation of China (30970493) and Projectsin the National Science & Technology Pillar Program(2009BADB3B02).

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