Physiological responses to saline irrigation in two summer mungbean vigna radiata (l ) wilczek genotypes

P H Y S I O L O G I C A L RE S P O N S E S T O S A L I N E
I R R I G A T I O N I N T W O S UM M E R M U N G B E A N
[ V I G N A R A D I A T A ( L . ) W I L C Z E K ] G E N O T YP E S
By

DUONG HOANG SON
(2010BS100D)
Thesis submitted to the Chaudhary Charan Singh
Haryana Agricultural University in partial fulfillment
of the requirements for the degree of

Doctor of Philosophy
In
Plant Physiology

DEPARTMENT OF BOTANY AND PLANT PHYSIOLOGY
COLLEGE OF BASIC SCIENCES AND HUMANITIES
CCS HARYANA AGRICULTURAL UNIVERSITY
HISAR – 125 004

2013


CERTIFICATE–I
This is to certify that this thesis entitled, “Physiological responses to saline
irrigation in two summer mungbean [Vigna radiata (L.) Wilczek] genotypes” submitted
for the degree of Doctor of Philosophy in the subject of Plant Physiology to the CCS
Haryana Agricultural University, Hisar, is a bonafide research work carried out by Mr.
Duong Hoang Son under my supervision and guidance and that no part of this thesis has
been submitted for any other degree.
The assistance and help received during the course of investigation have been fully

acknowledged.

(Dr. Neeraj Kumar)
Major Advisor
Scientist of Plant Physiology
Department of Botany and Plant Physiology
College of Basic Sciences and Humanities
CCS Haryana Agricultural University
Hisar-125 004 (Haryana) India


CERTIFICATE–II
This is to certify that this thesis entitled “Physiological responses to saline
irrigation in two summer mungbean [Vigna radiata (L.) Wilczek] genotypes”, submitted
by Mr. Duong Hoang Son to the CCS Haryana Agricultural University, Hisar, in partial
fulfillment of the requirement for the degree of Doctor of Philosophy in the subject of Plant
Physiology, has been approved by the Student’s Advisory Committee, after an oral
examination on the same, in collaboration with an external examiner.

MAJOR ADVISOR

HEAD OF THE DEPARTMENT

DEAN, POST-GRADUATE STUDIES

EXTERNAL EXAMINER


ACKNOWLEDGEMENTS

All above, I want to express my deep sense of indebtedness to my
family, especially my parent, my wife Quynh Mai and my sons Nhat Ha and
Nhat Minh for their love, understanding and great companion.
I have no words to express my deep sense of gratitude and
indebtedness to my advisor, Dr. Neeraj Kumar, Scientist, Department of
Botany and Plant Physiology, for his great kindness, constant
encouragement and precious time to me in all aspects from the first day I
came to India as well as during my study and investigation.
I owe deep and fervent thanks to Dr. A.S. Nadwal, Additional
Director Research - Directorate of Researh, who spent a lot of time reading
and discussing my thesis.
It gives me immense pleasure to record my sincere gratitude towards
the learned members of my advisory committee: Dr. S.K. Sharma, Sr.
Scientist (Soil Science), Dr. Ramesh Hasija, Sr. Scientist (Statistic) and Dr.
Satish Kumar, Associate Dean PGS, for their intellectual enlightenment,
sympathetic interest and pertinent suggestions throughout the pursuit of
this study. This study could not be completed without their kind help and
support.
It is my profound privilege to express my heartiest thanks to Dr.
(Mrs.) Sunita Sheokand, Sr. Scientist, Dr. K.D. Sharma, Scientist, Dr. Rajiv
Angrish, Sr. Scientist and Dr. H.R. Dhingra, Professor of the Department of
Botany and Plant Physiology for their timely help and willing cooperation.
Distinctive words of thanks are due to Dr. (Mrs.) Rupa Dhawan,
former Head, Dr. J.K. Sandooja, Head, Department of Botany and Plant
Physiology, for providing the necessary facilities and cordial help whenever
required.
I am thanking to all my friends for their help during my study,
cheerful company and the research fellows and seniors especially Dr. Anita
Kumari and Dr. Gunjan Geera for her guidance in the analysis of
antioxidant enzymes, protein profile and informative discussions during the

writing-up of this thesis, and Mr. Suraj Bhan and Mr. Raghubir Signh for
technical assistance.
I am thankful to Dr. Le Van Banh, Director, and Dr. Cao Van
Phung, Head of Soil Science department, CuuLong Delta Rice Research
Institute, Vietnam, for providing me opportunity to study in India
Financial help provided by Vietnam International Education
Development (VIED), Ministry of Education and Training (MOET) in the
form of 322 project fellowship is duly acknowledged.
(Duong Hoang Son)
Date:
Hisar


ABBREVIATIONS
APS

-

Ammonium per sulphate

APX

-

Ascorbate peroxidase

AsA

-

Ascorbate

ATP

-

Adenosine tri phosphate

CAT

-

Catalase

CD

-

Critical difference

CRD

-

Complete randomized design

CSI

-

Chlorophyll stability index

DAT

-

Days after treatment

DMSO

-

Dimethyl sulphoxide

DW

-

Dry weight

EDTA

-

Ethylene diamine tetra acetic acid

FW

-

Fresh weight

G

-

Genotype

G×V

-

Genotype × variety

GR

-

Glutathione reductase

GPX

-

Glutathione peroxidase

GST

-

Glutathione S-transferase

RWC

-

Relative water content

MPa

-

Mega Pascal

MW

-

Molecular weight

NPQ

-

Non-photo chemical quenching

OD

-

Optical density

PS1

-

Photosystem I

PSII

-

Photosystem II

POX

-

Peroxidase

PVP

-

Polyvinyl pyrolidone

ROS

-

Reactive oxygen species

SDS-PAGE

-

Sodium dodecyl sulphate- Polyacrylamide gel electrophoresis

SOD

-

Superoxide dismutase

TTC

-

2,3,5- triphenyl tetrazolium chloride

w

-

Water potential

s

-

Osmotic potential


CONTENTS
CHAPTERS

TITLE

PAGE(S)

1

INTRODUCTION

1-4

2

REVIEW OF LITERATURE

5-19

3

MATERIAL AND METHODS

20-36

4

RESULTS

37-72

5

DISCUSSION

73-83

6

SUMMARY AND CONCLUSIONS

84-86

BIBLIOGRAPHY

i-xiii


LIST OF TABLES
S.
No.

Title

Page
No.

1

Changes in water potential (-MPa) in leaf of mungbean genotypes under
saline irrigation.

39

2

Changes in osmotic potential (-MPa) in leaf of mungbean genotypes under
saline irrigation.

40

3

Changes in osmotic potential (-MPa) in root of mungbean genotypes under
saline irrigation.

41

4

Changes in relative water content (RWC %) in leaf of mungbean genotypes
under saline irrigation.

41

5

Changes in relative water content (RWC %) in root of mungbean genotypes
under saline irrigation.

42

6

Changes in relative stress injury (RSI %) in leaf of mungbean genotypes
under saline irrigation.

43

7

Changes in relative stress injury (RSI %) in root of mungbean genotypes
under saline irrigation.

44

8

Changes in Na+/K+ ratio in leaf of mungbean genotypes under saline
irrigation.

50

9

Changes in Na+/K+ ratio in root of mungbean genotypes under saline
irrigation.

50

10

Changes in chloride (Cl-) content (mg g-1 DW) in leaf of mungbean
genotypes under saline irrigation.

51

11

Changes in chloride (Cl-) content (mg g-1 DW) in root of mungbean
genotypes under saline irrigation.

52

12

Changes in sulphate (SO42-) content (mg g-1 DW) in leaf of mungbean
genotypes under saline irrigation.

53

13

Changes in sulphate (SO42-) content (mg g-1 DW) in root of mungbean
genotypes under saline irrigation.

53

14

Changes in in vitro pollen germination (%) and pollen tuber growth (µm) in
two mungbean genotypes under saline irrigation.

69

15

Changes in yield and yield attributes in two mungbean genotypes under
saline irrigation.

71

16

Changes in ECe of soil under saline irrigation.

72


LIST OF FIGURES
S. No.

Title

1

Changes in plant height (cm) in mungbean genotypes under saline

irrigation.

37

2

Changes in dry matter (g plant-1) content in leaf of mungbean genotypes
under saline irrigation.

38

3

Changes in dry matter (g plant-1) content in root of mungbean genotypes
under saline irrigation.

38

4

Changes in lipid peroxidation (MDA) content (nmoles g-1 DW) in leaf of
mungbean genotypes under saline irrigation.

45

5

Changes in lipid peroxidation (MDA) content (nmoles g-1 DW) in root of
mungbean genotypes under saline irrigation.

45

6

Changes in chlorophyll ‘a’ content (mg g-1 DW) in leaf of mungbean
genotypes under saline irrigation.

46

7

Changes in chlorophyll ‘b’ content (mg g-1 DW) in leaf of mungbean
genotypes under saline irrigation.

47

8

Changes in total chlorophyll content (mg g-1 DW) in leaf of mungbean
genotypes under saline irrigation.

47

9

Changes in chlorophyll stability index (%) in leaf of mungbean genotypes
under saline irrigation.

48

10

Changes in quantum yield (Fv/Fm) in leaf of mungbean genotypes under
saline irrigation.

48

11

Changes in hydrogen peroxides (H2O2) content (moles g-1 DW x 10-4) in
leaf of mungbean genotypes under saline irrigation.

54

12

Changes in hydrogen peroxides (H2O2) content (moles g-1 DW x 10-4) in
root of mungbean genotypes under saline irrigation.

55

13

Changes in proline content (mg g-1 DW) in leaf of mungbean genotypes
under saline irrigation.

55

14

Changes in proline content (mg g-1 DW) in root of mungbean genotypes
under saline irrigation.

56

15

Changes in total soluble carbohydrates content (mg g-1 DW) in leaf of
mungbean genotypes under saline irrigation.

57

16

Changes in total soluble carbohydrates content (mg g-1 DW) in root of
mungbean genotypes under saline irrigation.

57

17

Changes in superoxide dismutase (SOD) specific activity (Units mg-1
protein) in leaf of mungbean genotypes under saline irrigation.

58

18

Changes in superoxide dismutase (SOD) specific activity (Units mg-1
protein) in root of mungbean genotypes under saline irrigation.

59

Page
No.


19

Changes in catalase (CAT) specific activity (Units mg-1 protein) in leaves
of mung bean genotypes under saline irrigation.

60

20

Changes in catalase (CAT) specific activity (Units mg-1 protein) in root of
mungbean genotypes under saline irrigation.

60

21

Changes in peroxidase (POX) specific activity (Units mg-1 protein) in leaf
of mungbean genotypes under saline irrigation.

61

22

Changes in peroxidise (POX) specific activity (Units mg-1 protein) in root
of mungbean genotypes under saline irrigation.

61

23

Changes in ascorbate peroxidase (APX) specific activity (Units mg-1
protein) in leaf of mungbean genotypes under saline irrigation.

62

24

Changes in ascorbate peroxidase (APX) specific activity (Units mg-1
protein) in root of mungbean genotypes under saline irrigation.

63

25

Changes in glutathione reductase (GR) specific activity (Units mg-1
protein) in leaf of mungbean genotypes under saline irrigation

63

26

Changes in glutathione reductase (GR) specific activity (Units mg-1
protein) in root of mungbean genotypes under saline irrigation.

64

27

Changes in glutathione S transferase (GST) specific activity (Units mg-1
protein) in leaf of mungbean genotypes under saline irrigation.

65

28

Changes in glutathione S transferase (GST) specific activity (Units mg-1
protein) in root of mungbean genotypes under saline irrigation.

65

29

Changes in glutathione peroxidase (GPX) specific activity (Units mg-1
protein) in leaf of mungbean genotypes under saline irrigation.

66

30

Changes in glutathione peroxidase (GPX) specific activity (Units mg-1
protein) in root of mungbean genotypes under saline irrigation.

66

31

Changes in ascorbate (AsA) content (µmoles g-1 DW) in leaf of mungbean
genotypes under saline irrigation

67

32

Changes in ascorbate (AsA) content (µmoles g-1 DW) in root of mungbean
genotypes under saline irrigation

68

33

Changes in pollen viability in two mungbean genotypes under saline
irrigation

68


CHAPTER-I

INTRODUCTION
Environmental stresses are the most important constraints limiting crop productivity.
Among these salinity either of soil or water is a serious problem for agriculture all over the
world (Majid et al., 2011). Salinity limited the growth and development of plant by altering
their morphological, physiological, biochemical attributes and production in most of the arid

and semi arid regions of the world (Mudgal et al., 2010; Kandil et al., 2012).
There are different causes of the development of soil salinity. The major forms are
viz. (i) natural or primary salinity and (ii) secondary or human-induced salinity. Primary
salinity is occurred due to the long-term natural accumulation of salts in the soil or surface
water. Secondary salinity occurs due to anthropogenic activities that disrupt the hydrologic
balance of the soil between water applied (irrigation or rainfall) and water used by crops
(Geetanjali and Neera, 2008). Salinity created due to high salt concentration in the soil
solution is two-fold. First, many of salt ions are toxic to plant cells and second, high salt
represents a water deficit or osmotic stress. Specific ion toxicity is usually associated with
excessive intake of sodium, chloride or other ions and causes disrupt plant potassium and
calcium nutrition (Zhu, 2007).
The deleterious effect of the saline irrigation on plant involve osmotic stress, ion
toxicity and mineral deficiency (Ashraf and Harris, 2004) and reduction in growth and
alterations in several physiological processes including N2- fixation (Nandwal et al., 2000 a,
b; Kukreja et al., 2005). Water potential and osmotic potential become more negative whereas
turgor pressure increases with increasing salinity (Mudgal et al., 2010). Osmotic adjustment
involves either inorganic ions or low molecules weight organic solutes. These play a crucial
role in higher plants grown under saline conditions. The compatible osmolytes generally
found in higher plants are low molecular weight sugars, organic acids, polyols and nitrogen
containing compounds such as amino acids, amides, proteins and quaternary ammonium
compounds (Dionisio-Sese and Tobita, 1998; Ashraf and Harris, 2004; Mudgal et al., 2010;
Sabina and Mehar, 2011).
Several physiological and biochemical processes like pigment content and
photosynthesis, carbohydrate metabolism, protein synthesis, energy and lipid metabolism are
affected by salinity. Salt stress disturbs intracellular ion homeostasis in plants, which leads to
damage in maintaining cell turgor, enzyme activities, membrane dysfunction, attenuation of
1


metabolic activity and other secondary effects that cause growth inhibition and ultimately lead

to cell death (Hasegawa et al., 2000; Saha et al., 2010; Zhu, 2007).
A common consequence of salt stress is that they result, at some stage of exposure, in
an increased production of reactive oxygen spices (ROS) (Ahmad et al., 2008; Kukerja et al.,
2005). ROS production such as superoxide anion (O-2), hydrogen peroxide (H2O2) and
hydroxyl radicals (OH-) caused oxidative damage (Zhu, 2001; Parida and Das, 2005; Kukreja
et al., 2005). These ROS are highly reactive and in the absence of any protective mechanism
caused cellular damage through oxidation of lipids, proteins and DNA injury (Mohammed,
2007). To control the level of ROS and to protect plant cells have to cope constantly with the
damages produced by the ROS, and as a protective system they have evolved a complex
series of enzymatic [superoxide dismutase (SOD), catalase (CAT) and peroxidases (POX)],
detoxifying lipid peroxidation (LP) products [glutathione S-transferases (GST), phospholipidhydroperoxide glutathione peroxidise (GPX) and ascorbate peroxidase (APX), and nonenzymatic antioxidants [ascorbate (AsA), glutathione (GSH), phenolic compounds and
tocopherols]. In addition, a whole array of enzymes is needed for the regeneration of the
active

forms

of

the

antioxidants

[monodehydroascorbate

reductase

(MDHAR),

dehydroascorbate reductase (DHAR) and glutathione reductase (GR)], which are responsible
for scavenging excessively accumulated ROS in plants under stress conditions (Sairam et al.,

2002; Blokhina et al., 2003; Kukreja et al., 2010; Saha et al., 2010; Hossain et al., 2011).
Salinity interfered with the nodule initiation in cowpea and mungbean and also
caused a reduction in number, weight as well as nitrogen fixing efficiency of nodules
(Balasubramnian and Sinha, 1976). In chickpea, nodules were observed in inoculated plants
grown at 6 dS m-1 but nitrogen fixation was completely inhibited. Findings indicated that
symbiosis is more salt sensitive than both rhizobium and host plant (Mudgal et al., 2010).
Salinity adversely affects both qualitative and quantitative features of male functions,
i.e. number of pollen produced, their viability, germination and tube growth, thereby reducing
the relative male fitness to less than half of the control ovule (Abdulla et al., 1978; Dhingra
and Varghese, 1985, 1986). Ottaviano et al. (1975) demonstrated that decline in male fitness
character may result in reduction in both the number and quality of offspring. Salinization
though did not affect ovule production but the number of pollen deposited on the stigmatic
surface during pollination and formation of pods and healthy seeds decrease substantially with
increase in salinity level (Dhingra and Sharma, 1992).
In arid and semi-arid regions, salinity (both soil and water) is one of the major factors
responsible for deterioration of soil and making it unfit for agriculture (Ashraf and Harris,
2


2004). 20 % of world’s cultivated land and 50 % of all irrigated lands are affected by salinity
(Zhu, 2001). Furthermore, more than half of all ground water is naturally saline particularly in
arid and semi arid regions of the world (Yeo, 1999). In India, salt affected soil is about 6.73
mha (2.96 mha saline and 3.77 mha sodic), whereas in Haryana 49.16 th-ha of land is affected
by salinity (Ali, 2009). Ions containing soil salinity are Na+, Cl-, Ca+ and Mg++. High salinity,
most commonly mediated by NaCl, is one of major abiotic stresses globally (Parida and Das,
2005). The problem of salinity is being further aggravated because of use of poor quality
water for irrigation and poor drainage. In arid and semi-arid regions, insufficient precipitation
results in extensive reliance of irrigation and a considerable proportion of underground water
in most of these regions is of poor quality, however, the productivity of this crop is not
optimal under such conditions.

Mungbean [Vigna radiata (L.) Wilczek] is a short duration (70-80 days), warm
season legume crop of this region. Approximately, an area of 2.5 million ha in world has been
used for its cultivation from which 0.8 million tons of seeds are produced per annum (Ahmad
et al., 2011). India is largest producer and consumer of mungbean and it alone accounts for
about 65% of the world acreage and 54% of the world production of this crop (Singh and
Singh, 2011). Recently, In India mungbean is grown in an area of 3.77 m ha with production
of 1.52 m tones. However, it productivity is only 406 kg ha-1 (AICRP on MULLaRP, 2009).
In Haryana, the approximate values are 21 thousand ha, 5.0 thousand tones and 260 kg ha-1,
respectively. For developing country like India, mungbean is a main protein source for the
vegetarian diet. It is the best in nutritional value, having 62-65% carbohydrate, 25-28%
protein, 3.5-4.5% ash and 1-1.5% fat (Navneet et al., 2011). Mungbean is also characterized
by its ability to improve the physiological, chemical and biological properties of soil. It can
also increase the soil fertility through biological nitrogen fixation from atmosphere. The green
plant and hay are utilized as fodder. So, it may be considered as an inevitable component of
sustainable agricultural (Hussain et al., 2008). Mungbean may also be sown as an inter crop
or as a green manure or cover crop.
In order to overcome these problems, genotypes which are resistant to salinity are to
be identify. Selection and breeding programmed to increase salt tolerance will be more
successful if selection is based directly on the physiological mechanism (s) or character (s)
confirming tolerance (Sairam et al., 2002; Kumar et al., 2008). Despite its great economic
importance little work has been done on genotypic variations for salt tolerance. It would
therefore, be important to identify the morpho-physiological and biochemical traits for
salinity resistance in this crop. Salt tolerant mungbean crop may be an alternative for

3


increasing production in these saline soils. In view of these facts, the present investigation
was planned with the following objectives:
1.

To study the morpho-physiological traits and antioxidant defense mechanism in
mungbean under saline conditions.

2.

To study the protein profile (SDS-PAGE) of leaves and roots in mungbean under
saline conditions.

4


CHAPTER-II

REVIEW OF LITERATURE
The sustainability of irrigated agriculture in many arid and semiarid areas of the
world is at risk because of a combination of several interrelated factors, including lack of
fresh water and drainage, the presence of high water tables, and salinization of soil and
groundwater resources (Geetanjali and Neera, 2008). Among them; salinity is a major
abiotic stress in plant agriculture worldwide restricting many plant physiological and
biochemical processes such as photosynthesis, protein synthesis, energy and lipid
metabolisms (Parida and Das, 2005). Seed germination, seedling growth and vigour,
vegetative growth, flowering and fruit set are adversely affected by high salt concentration,
ultimately causing diminished economic yield and also quality of produce (Hasegawa et
al., 2000; Sairam and Tyagi, 2004).
Plants are classified as glycophytes and/or halophytes according to their capacity
to grow on high salt medium. Unfortunately, the major crops are almost universally nonhalophytic. For example, bean yield is inhibited almost entirely at 50 mol m-3 (Sairam and
Tyagi, 2004; Mass and Grieve, 1987). The deleterious effects of salinity on plant growth
are associated with low osmotic potential of soil solution creating water stress in plant.
Secondly, they cause severe ion toxicity. Finally, the interactions of salts with mineral

nutrition may result in nutrient imbalances and deficiencies. The consequence of all these
can ultimately lead to plant death as a result of growth arrest and molecular damage (Zhu,
2001; Jain et al., 2003; Sairam and Tyagi, 2004; Parvaiz and Satyawati, 2008).
Plants develop defense strategies against salt stress based on (i) selective
accumulation or exclusion of ions, (ii) control of ion uptake by roots and transport into
leaves, (iii) compartmentalization of ions at cellular and whole plant levels, (iv) synthesis
of compatible sulutes, (v) change in photosynthetic pathway, (vi) alteration in membrane
structure, (vii) induction of antioxidant enzymes and induction of plant hormone (Parida
and Das, 2005). Legumes are key component of sustainable agriculture and can offer many
economic and environmental benefits because of their input of fixed N 2 improving the
physical and chemical properties of the soil and help to reintroduce agriculture to these
lands (Rolfe and Gresshoff, 1988; Geetanjali and Neera, 2008).
Voluminous literature is available on the effect of salt stress on the physiological
and biochemical aspects of growth and development. Relevant available literature on
salinity has been reviewed as follow:
5


2.1

Growth parameters
Morphological, the most typical symptom of salinity is stunted plant growth.

Suppression of growth occurs in all plant, but their tolerance levels and rates of growth
reduction at lethal concentrations of salt vary widely among different plant species (Parida
and Das, 2005). Salt tolerance is usually assessed as the percent biomass production in
saline versus control conditions over a prolonged period of time (Munns, 2002).
In mungbean plant, genotypes revealed remarkable differences at all the growth
stages for the symptoms. Ionic injury was evident in form of tip burning, chlorosis and
necrotic spot on leaflet of both young and old ages. Results also showed that number and

area of green leaves were more affected by salinity than the total shoot dry weight in
mungbean plants (Wahid et al., 2004). The shoot root ratio of mungbean increase at high
salt levels (Ashraf and Rasul, 1988).
Salt stress by NaCl at 100, 200 and 300 mM cause marked decreases in root and
shoot lengths, number of lateral roots and leaves, total leaf area plant -1, fresh and dry
weight of shoot and roots as well as percentage of water content in mungbean plant
(Sumithra et al., 2006). Effect of NaCl at 100 and 150 mM on mungbean seedling caused
drastic effects on roots compared to shoots. Accompanying reductions in length, number of
root hairs and branches, roots become stout, brittle and brown in color (Saha et al., 2010).
Mohamed and Kramany (2005) studied effect of saline water (2000 and 4000 ppm) for
irrigation on four varieties of mungbean resulted decreased dry weight of leaves and stems
plant-1; leaves area and depression in dry matter accumulation in both ages 35 and 50 days
after treatment. Salt stress was observed more effectively at vegetative, flowering and seed
filling stages rather than seed development stage in mung bean genotypes. Delayed
maturity due to salt stress pushes the plant also be desiccation stress causing shriveled
seeds (Ahmed, 2009).
2.2

Plant water relation
Dissolved solutes in the root zone create a low osmotic potential that lower the soil

water potential. The general water balance of plant is thus affected, because the shoot
needs to have an even lower potential to maintain a “down hill” gradient of water potential
between the soil and leaves (Taiz and Zeiger, 1998). Plants subjected with salt stress
revealed that halophytes accumulate salts whereas glycophytes tend to exclude the salts.
Halophytes have evolved mechanisms to accumulate ions in order to lower cell osmotic
potential. This osmotic adjustment is necessary because the plant have to continue to
extract water from the salty solution to meet transpiration demands of their leaves (Zhu,
2007).

6


2.2.1

Water potential (Ψ w )
Decrease in plant water potential under salt accumulation, must immediately be

offset by decrease in osmotic potential, through increase solute content for turgor potential
to be maintain (Mudgal et al., 2010). However, the water potential (Ψw) increased
markedly due to application of K at both control and salt treatment (Kabir et al., 2004).
Salinity induced reduction in leaf (Ψ w) of number of plant spices like mungbean (Nandwal
et al., 2000 a, b) and pea (Hernandez et al., 1999).
2.2.2

Osmotic potential (Ψ s )
Plants may maintain water uptake from saline soil by a process known as osmotic

adjustment (Sheldon et al., 2004). However, osmotic adjustment might be an adaption for
plants surviving under salt stress conditions but may also reduce growth due to ion
toxicity, ion deficiency and/or other physiological process (Volkmar et al., 1998). Effect of
NaCl and PEG stress on mung bean plant showed that the contribution of inorganic solutes
was high in saline stress and organic solute decreased in both treatments (Saffan, 2008).
Zayed and Zeid (1998) revealed that osmotic potential of mungbean seedlings under water
stress induced by PEG were affected much more than under salinity. The values of Ψ s of
leaves, roots and nodules became more negative with increasing salt stress in mungbean
genotypes i.e. K-851 and a mutant. However, values were more negative in mutant than in
K-851 (Nandwal et al., 2000 a, b).
2.2.3

Relative water content (RWC %)
Responses of two green gram (P. aureus) cultivars differing in salt stress

suggested possible different behaviors of cultivars differing in salt tolerance with respect
to plant fresh and dry weight, water content (Misra and Dwivedi, 2004). Zayed and Zeid
(1998) revealed that salinity stress to decreased the osmotic potential in mung bean
seedlings growth medium induced reduce water content, the reduction was 10% as
compared to control. Water contents of 86-88% should be optimum for mobilization of
reverses from the cotyledons to the embryo axis and the attainment of this level was delay
with increased salinity in mungbean seedling (Promila and Kumar, 2000). Kabir et al.
(2004) reported that salinity decreased relative water content and water retention capacity,
while increased water saturation deficit and water uptake capacity in mungbean plant.
Relative water content in roots and shoots were declined upon salinization in mungbean
plants (Sumithra et al., 2006). Similarly, a significant decrease in RWC of leaves, roots
and nodules was observed at vegetative and flowering stages, when single saline irrigation
was given in mungbean genotypes (Nandwal et al., 2000 a, b).

7


2.3

Membrane injury

2.3.1

Membrane stability
ROSs are generating through oxidative stress and involved in the injury

mechanism due to salt stress. ROS can function to product peroxidants of membrane lipid,

protein and nucleic acid (Katsuhara et al., 2005). Liang et al. (2003) proposed that
accumulation of H2O2 lead to lipid peroxidation, causing membrane damage and leakage
of various micro, macromolecules and electrolytes out of the cell. Cell membrane stability
is technique that has often been used for screening against salinity tolerance in various
crops due to malfunctioning of the cellular membranes by increasing their permeability to
ions and electrolytes (Farooq and Azam, 2006). There are different ionic mechanisms
involved in the perception of the ionic and osmotic components of salt stress (Shabala,
2000).
Increased of electrolyte leakage with increasing of saline stress has been reported
in wheat leaf senescence (Farouk, 2011) and in wheat young leaf (Farooq and Azam,
2006). Similar results has been observed in green gram (Panda, 2001), barley (Li, 2008),
chickpea plants (Kukreja et al., 2006; Sheokand et al., 2008). Dionisio Sese and Tobita
(1998) studied the fourth cultivars of rice Oryza sativa subjected to different level of salt
stress. The amount of electrolyte leakage from the leaves were observed gradual increasing
in all cultivars with increasing salt levels while remain unchanged in salt tolerant rice.
Similar results have been observed in Clitoria ternatea and Lathtrus sativus leaf
(Talukdar, 2011). However, Maia et al. (2010) demonstrated that the tolerant cultivar of
cowpea i.e. Pitiuba, and the susceptible cv. Perola maintained stable electrolyte leakage
similarly in both cultivar. Cavalcanti et al. (2004) reported that leaf membrane damage
was observed increased with long time applied of salt stress.
2.3.2

Lipid peroxidation
An increased production of active and/or reactive oxygen species and an

accumulation of lipid peroxidation products have been associated with a variety of salt
stress (Rodriguez et al., 1999; Katsuhara et al., 2005). Oxidative damage to lipids was
determined as lipid peroxidation by the formation of thiobarbaturic acid reactive
substances (TABRS) in terms of amount of malondialdehyde (MDA) when plant subjected
to salinity (El-baky et al., 2003; Mudgal et al., 2010). Recent investigations have shown

increased MDA content with increasing salinity for Brassica juncea (Verma and Mishra,
2005), Cicer arietinum (Kukreja et al., 2005), Vigna unguiculata (Cavalcanti et al., 2007)
and wheat (Farouk, 2011).

8


The accumulation of MDA was more in the salt susceptible than in the salt tolerant
cultivars in rice (Dionisio-Sese and Tobita, 1998; Vaidayanathan et al., 2003). Changes of
leaf Na + accumulation caused increase TBARS levels in cowpea (Cavalcanti et al., 2004).
Kukreja et al. (2005) reported that increased H2O2 content of root with increasing
salinization might be the cause for increased lipid peroxidation in chickpea. Saha et al.
(2010) observed a higher increased lipid peroxidation in leaves than roots of V. radiata.
2.4

Chlorophyll content
Compositions of the chloroplastic pigments have been reported to be altered under

saline conditions and these changes depend upon the specific nature of ions contributing to
the salinity, plant species and age of the plant (Levitt, 1980). Zaidi and Singh (1995) found
inhibition in the total chlorophyll (Chl), Chl a:b rations with increase in the soil salinity.
The total chlorophyll contents of leaves decrease in general under salt stress
(Hernandez et al., 1999; Yasar et al., 2008). Garg et al. (1996) reported that NaCl at 10 dS
m-1 decreased total chlorophyll in mungbean but did not recorded at 5 dS m-1. Another salt,
Na 2SO4 and NaHCO3 not found any adverse effect on Chl content at 10 dS m-1. It has been
suggested by Asharf and Rasul (1988) that all the Chl contents were reduced significantly
at EC more than 6 dS m-1 in difference mungbean genotypes.
In mungbean seedling, the total Chlorophyll and Chlorophyll a:b and carotenoid
(Car) contents were greatly reduced under salt stress (Zayed and Zeid, 1998; Maity et al.,
2000). Wahid et al. (2004) revealed that the chlorophyll and carotenoid contents were

diminished under salinity in leaflets at young and old mungbean leave ages. Furthermore,
Chl a:b ratio of young leaves of sensitive genotypes increased significantly while the
tolerance ones tended to maintain a fairly values. Increased Chl a:b ratio was positively
related to Na + and Cl-, this revealed an important role of photosynthetic pigment (mainly
Chl b and Car) in the enhance salt tolerance of mungbean genotypes.
2.4.1

Chlorophyll fluorescence
Part of the light energy absorbed by leaf chlorophyll pigments during

photosynthesis is emitted as fluorescence. Chlorophyll fluorescence analysis is a powerful
technique to provide a sensitive indicator of stress condition in plants (Maxwell and
Johnson, 2000). A number of studies utilized chlorophyll fluorescence as parameters to
examine factors limiting photosynthesis of salt effected plant (Maria et al., 2000; Saha et
al., 2010) to compare salt treated and control plants (Song et al., 2001) or to differentiate
between salt tolerant and sensitive genotypes (Suriyan and Chalermpol, 2010).
The Fv/Fm ratio can be used to detect damage to photosymtem II and possible
photo-inhibition (Ahmed et al., 2002). Lee et al. (2004) observed in Paspalum vaginatum
9


Swartz ecotypes that with the increase of salinity level (1.1-49.7 dS m-1) initial chlorophyll
fluorescence (Fo) increased while maximum and variable (Fv/Fm) chlorophyll
fluorescence ratio tended to decrease. Applied exogenous of sodium nitropursside (SNP)
increased chlorophyll fluorescence and ultimately protects PS II activity under salt stress
(Uchida et al., 2002).
2.5

Biochemicals

2.4.1

Proline
Accumulation of metabolites that acts as compatible solutes is one of the probable

universal responses of plants to changes in the external osmotic potential. Metabolites with
osmolyte function like simple sugars, sugar alcohols, complex sugar, and other quaternary
amino acid are frequently observed in plant under unfavorable conditions (Jain et al.,
2003; Bartels and Sunkar, 2005; Mudgal et al., 2010; Sabina and Mehar, 2011).
Proline is probably the most wide distributed osmolytes found in plant and many
other organisms, there is strong correlation between increased cellular proline levels and
the capacity to survive the effects of high environmental salinity (Sairam and Tyagi, 2004;
Bartels and Sunkar, 2005; Mudgal et al., 2010). A rapid accumulation of proline under salt
stress has been observed in mungbean crop (Singh et al., 1994). Arora and Saradhi (2002)
studied Vigna radiata were exposed to different concentrations of NaCl in light and dark.
Proline accumulation in the shoots was higher in light than in dark, the increased in proline
content upto 286% as compared to control in light under 200 mM NaCl. Saffan (2008)
observed that the proline content increased in all plants (wheat, barley, mungbean and
kidney bean) under effect of 200 mM NaCl. Similarly, proline content increased with
increasing salt treatments in cowpea, black gram and green gram compared to control.
Accumulation of proline was more in root compared to shoot (Arulbalachandran et al.,
2009). Shabina and Mehar (2011) subjected the seven varieties of mungbean to 50 and 100
mM NaCl stress. Proline content significantly increased in stress plant over control of all
the genotypes. However, the Punt mung exhibited higher adaptive potential under salinity
stress as judged by accumulation of osmoprotectants when compared to other genotypes.
Salt induced increase in proline concentration started shortly after the salt stress
application. In agreement with the above, a better accumulation of proline in leaves, stems,
roots and nodules under salt stress has been observed in various mungbean genotypes
(Nandwal et al., 2000 a, b; Manivannan et al., 2007; Saha et al., 2010).
2.5.2

Total soluble carbohydrate
Information, regarding the role of sugar in adaption of plants to salinity is,

therefore, insufficient to conclude that they are universally associated with salt tolerance.

10


However, potential role for soluble sugar accumulation as an indicator for salt tolerance in
breeding programs for some species (Asharf and Harris, 2004). Several physiological
studies suggest that under stress conditions, carbohydrates accumulated to varying degree
in different plant species (Geetanjali and Neera, 2008). Carbohydrates such as sugars and
starch accumulated under salt stress. Their major functions are osmoprotection, osmotic
adjustment, carbon storage and radical scavenging (Parida et al., 2002; Parida and Das,
2005). Mohammed (2007) reported that there is a highly significant decrease in reducing
sugars and sucrose contents of mungbean plant with increasing salinity levels. Ashraf and
Rasul (1988) reported that, increased salt concentration significantly reduced total
carbohydrate in leaves, stem and roots of mungbean. Arulbalachandran et al. (2009)
revealed that reducing sugar and starch content were increased in both shoot and root with
increasing salt concentrations in cowpea, black gram and green gram as compared to their
respective control. Accumulation of sugar and starch content were more in shoot rather
than root in all three Vigna species.
2.5.3

Hydrogen peroxide (H 2 O 2 )
Salinity stress induced production of H 2O2 and may trigger genetically

programmed cell suicide (Farouk, 2011). H 2O2 is widely generated in many biological
systems and mediates various physiological and biochemical process in plant (Li and Xue,

2010). Salinity induced the generation of H 2O2 (Sairam and Tyagi, 2004). The chief
toxicity of H2O2 are production of hydroxyl radicals and other destructive species such as
lipid peroxides lead to damage vital cellular macromolecules (Vaidyanathan et al., 2003).
Increased in H2O2 production under salinity has been reported in chickpea roots
(Kukreja et al., 2005), tomato leaves (He and Zhu, 2008). A progressive increase in H 2O2
content with increasing the NaCl concentration was observed in Brassica juncea (Verma
and Mishra, 2005). The higher H2O2 content was observed in the salt sensitive as
compared salt tolerant cultivars of Oryza sativa under salt stress (Vaidyanathan et al.,
2003). The H2O2 content increased under NaCl stress in mungbean (Nafees et al., 2010;
Hossain et al., 2011; Neelam, 2013). Saha et al. (2010) revealed that endogenous H2O2
production increased with increasing salt stress in leaves and roots of mungbean. The
maximum H2O2 content was observed in the salt-tolerant cultivars as compared to salt
sensitive cultivars of mungbean under salt stress (Sumithra et al., 2006).
2.6

Antioxidant defence system (ADS)
Reactive oxygen species (ROS) are produced in both unstressed and stressed cells.

Plants have well developed defence systems against ROS, involving both limiting its
formation as well as removal (Alscher et al., 2002). To overcome the effects of salinityinduced oxidative stress, plants make use of a complex antioxidant system, which is
11


composed of low molecular mass antioxidants as well as ROS scavenging enzymes
(Blokhina et al., 2003; Mudgal et al., 2010).
The formation of ROS has been reported to increase under salinity stresses like
osmotic stress in Vigna aconitifolia (Kestwal et al., 2012), Cassia angustifolia seedling
(Agarwal and Pandey, 2004) and rice seedling (Dionisio-Sese and Tobita, 1998). Several
studies have produced evidence roles for ROSs in mungbean plant under salinity.
2.6.1 Superoxide dismutase (SOD)

SOD originally discovered by McCord and Fridovich (1969) react with superoxide
radicals at almost diffusion-limited rates to produce hydrogen peroxide. In general, plants
contain a mitochondria matrix localized MnSOD and cytosolic Cu/ZnSOD present in the
chloroplast stroma (Geetanjali and Neera, 2008). Comparing the mechanisms of
antioxidant production in salt tolerant and salt sensitive plants, Dionisio-Sese and Tobita
(1998) reported a decline in SOD activity in salt sensitive and increased in tolerant rice
varieties. Similarly, results had been reported in wheat (Mandhania et al., 2006) and cotton
leaves (Meloni et al., 2002). It was suggested that the ratio between superoxide dismutase
and H2O2 scavenging enzyme activities could be used as a working hypothesis for a
biochemical marker for salt tolerance in sorghum (Costa el al., 2005). In contrast, Kukreja
et al. (2006) observed two-fold increase in SOD activity in chickpea roots under shortterm salinization.
SOD activity increased under salt stress was observed in both leaves and roots of
mungbean (Chakrabarti and Mukherji, 2003 a), mungbean seedling (Saha et al., 2010).
Manivannan et al. (2007) reported SOD activity was increased in leaves, stems and roots
with increased the NaCl stress and CaCl2 stress versus control in mungbean plant.
2.6.2 Catalase (CAT)
CAT converts H2O2 to water and molecular oxygen. In plant, CAT is found
predominantly in peroxisomes and glyoxysomes where it functions chiefly to remove the
H2O2 form during the photorespiration (Geetanjali and Neera, 2008) and also during salt
stress and other abiotic stress condition (Willekens et al., 1995). Increase in CAT activity
upon salinization has been observed in Ipomoea pes-capraesweet (Venkateshan and
Chellappan, 1999), sugarbeet (Bor et al., 2003), cowpea (Cavalcanti et al., 2007) and
chickpea (Sheokand et al., 2008). Contrary to the above reports, diminished catalase
activity has been reported in salt stressed plants of Phaselous mungo (Dash and Panda,
2001), Catharanthus roseus (Jaleel et al., 2007) and K. virginica (Guo et al., 2009).
Similarly, a significant decrease in CAT activity was also observed in leaves of both salttolerant and salt-sensitive varieties of pea (Corpus et al., 1993).

12

Changes in CAT activity from mungbeans under salinity stress have been reported
in different tissues by Manivannan et al. (2007), root and shoot by Panda (2001), leaves
and root by Chakrabarti and Mukherji (2003 b), seedling by Hossain et al. (2011). Saha et
al. (2010) revealed that CAT activity increased in roots by 64% but slight decreased in
leaves in mung bean under different salinity levels. Zaffar et al. (2007) showed that CAT
activity increased by 2.4 fold at concentration 200mM at 20 DAS in tolerance mungbean
genotypes. Yasar et al. (2008) observed higher CAT activity in leaves of salt tolerant
genotype than sensitive under 50mM and 100mM NaCl treatment. Shabina and Khan
(2004) reported differential effect on the activity of CAT in different cultivars was
exposed to salinity levels. Sumithra et al. (2006) reported that greater increased (4.7 fold)
in CAT activity of tolerant as compared to control cultivar where as sensitive exhibited
only 2 fold increased at 300 mM salt concentration.
2.6.3 Peroxidase (POX)
POX localized in almost all compartments of the plant cell, it plays role in stability
the level of H2O2. Peroxidases, besides their main function in H 2O2 elimination, can also
catalyse O2 and H2O2 formation by a complex reaction in which NADH is oxidized using
trace amounts of H2O2 (Blokhina et al., 2003). Peroxidases are also involved in
biosynthesis of cell wall lignifications and suberization (Passardi et al., 2004).
Experimental evidence shows that salinity causes increases in POX activity in Cassia
angustifolia (Agarwal and Pandey, 2004), Brassia napus (Dolatabadion et al., 2008) and
chickpea plants (Sheokand et al., 2008). However, decrease in POX activity with increase
in NaCl concentration has been observed in Calamus tenuis (Khan and Patra, 2007) and
wheat (Farouk, 2011).
Chakrabarti and Mukherji (2003 a, b) reported that application of NaCl in mung
bean caused increased peroxidase activity in leaf and root. Zaffar et al. (2007) recorded
POX activity increased 2.4 and 2.8 fold under 200 mM NaCl at 20 and 40 DAS in mung
bean plant, respectively. Arulbalachandran et al. (2009) revealed peroxidase activity was
increased in shoot and root with increasing salt concentrations in cowpea, black gram and
green gram compared to respective control and the POX activity was more in root than in
shoot. However, POX activities were highly significant decreasing in mung bean due to

increasing NaCl concentration observed by Mohammed (2007).
2.6.4 Ascorbate peroxidase (APX)
Ascorbate peroxidase (APX) uses ascorbate as its reducing substrate. It is involved
in scavenging of H2O2 in water and AsA-GSH cycle and utilizes AsA as the electron donor
(Ahmad et al., 2008). APX seems to play a more important role in scavenging ROS than
other antioxidative enzymes since ascorbate, in addition to reacting with H 2O2 may react
13


with superoxide anion (O-2), singlet oxygen (1O2) and hydroxyl radical (OH-) (Shigeoka et
al., 2002). Hernandez et al. (1999) reported rapid increased in APX activity in response to
90 mM and 110 mM NaCl concentrations in Pisum sativum leaves. Sheokand et al. (2008)
also reported an increase in APX activity under salt stress in chickpea.
Salinity induced increase APX activity in both tolerant and sensitive plants were
reported in green bean (Yasar et al., 2008), cowpea (Maia et al., 2010), Pistacia vera
(Abbaspour, 2012). Hernandez et al., 2000 reported that tolerant Pisum sativum response
to long term NaCl treatment increased ascorbate peroxidase 3 fold. However, from NaCl
sensitive plant no changes in the specific activity of APX. Similar observe were report by
Amor et al. (2006) in Cakile maritime. Decreased APX activity has been reported in two
tolerance mutants legume leaves Clitoria ternatea and Lathyrus sativus under salt stress
(Talukdar, 2011). Decreased APX activity in leaves and remain unchanged in root were
recorded by Fusun and Mehmet (2007). Kukreja et al. (2006) reported APX specific
activity increased by 9 and 99% at 2.5 and 10 dS m-1 salinity levels in chickpea roots.
2.6.4 Glutathione S-transferase (GST)
GSTs are a family of multifunctional enzymes that play important roles in
oxidative stress resistance (Joseph and Jini, 2011). These dimeric enzymes catalyze the
conjugation of GSH to avariety of electrophylic, hydropobic, and often toxic substrates,
thereby reducing their toxicity (Hossain and Fujita, 2010). Roxas et al. (2000) study the
effect of NaCl concentration at 100 mM on GST of tobacco. Results revealed that wild
type showed approximately 2.5 fold lower GST activity as compare mutant genotypes.

Similarly, in tomato, it has been detected that GST activity increased in leaves and roots of
salt tolerant but unchanged in control tomato cultivars under 100m M NaCl (Mittova et al.,
2003 b). Misra and Gupta (2006) studied wild type and mutant of Canthranthus roseus
subjected to salinity. A higher GST activity was observed in leaf pairs (apical, middle, and
basal) and roots under saline conditions, and most marked in roots. GST increased by 95%
was reported at 10 dS m-1 salinity level in chickpea roots (Kukreja et al., 2005). GST
activity was reported to increase in salinity stress in mungbean (Hossain et al., 2011).
2.6.6 Glutathione peroxidase (GPX)
GPX is ubiquitously occurring enzymes in plant cells that involved in scavenging
of H2O2 and sever to detoxify products of lipid peroxidation formed due to activity of
ROS. GPX decomposes peroxides to water or alcohol while simultaneously oxidizing
glutathione (GSH). GPX competes with catalase for H 2O2 as a substrate and is the major
source of protection against low levels of oxidative stress (Ahmad et al., 2008; Hossain
and Fujita, 2010).

14


GPX activity was reported to decrease upon salinization of rice (Lee et al., 2001).
However, GPX activity was reported increased in leaves of tomato plant grown with 100
mM NaCl (He and Zhu, 2008). GPX expression can be considered as a molecular maker
for oxidative stress in plant. Similarly, GPX activity was also reported to increase in
salinity stress in tomato (Mittova et al., 2003 a, b) and mungbean (Hossain et al., 2011).
2.6.7 Glutathione reductase (GR)
GR catalyses the rate limiting last step of AsA-GSH pathway (Ahmad et al., 2008).
GR catalases the NADPH dependent reaction of disulphide bond of GSSG and is thus
important in providing protection against oxidative damage in plants by maintaining the
reduced form of glutathione (Foyer et al., 1991). GR activity has been reported to increase
in B. juncea seedlings with increase in salinity level (Verma and Mishra, 2005). Similarly,
Abbaspour (2012) reported an increased GR activity with increase in NaCl concentration

in Pistacia vera. Salt tolerance in the leaves of Calamus tenuis has been correlated with
elevated GR activity (Khan and Patra, 2007). Yasar et al. (2008) reported in salt-tolerant
cultivar of green bean GR activity is greater than the salt-sensitive cultivar which indicates
that the tolerant plants exhibit a more active ascorbate-glutathione cycle than the nontolerant cultivar.
The increase in GR activity has also been observed in salt tolerant varieties of rice
(Dionisio-Sese and Tobita, 1998), pea (Hernandez et al., 2000), in Brassica juncea (Verma
and Mishra, 2005) and wheat (Sairam et al., 2002) than their respective sensitive varieties.
Decreased GR activity was observed in leaves but increased in root of maize as compared
to control under salt stress (Neto et al., 2005). Salinity stress enhanced increase GR
activity has been demonstrated in leaves of mungbean (Nafees et al., 2010) and in
mungbean seedling (Hossain et al., 2011). Sumithra et al. (2006) reported that increased
GR activity with increased salt stress levels in mungbean cultivars. Pusa Bold showed over
6.9 fold more GR activity than control at 300 mM NaCl while CO-4 showed only 4.6 fold
under same condition.
2.6.8 Ascorbate (AsA)
AsA is the most abundant antioxidant and serves as a major contributor to the
cellular redox state and protects plants against oxidative damage resulting from aerobic
metabolism and a range of biotic and abiotic stresses (Smirnoff, 2000). It is substrate of
cAPX and the corresponding organellar iso-forms, which are critical components of AsAGSH cycle for H2O2 detoxification (Nakano and Asada, 1981). Salt stress caused a
decreased in total AsA in tomato (He and Zhu, 2008) and wheat (Farouk, 2011).
Hernandez et al. (1999; 2000) reported NaCl concentration at 70 mM decreased AsA in
both NaCl tolerant and NaCl sensitive pea cultivars. The decline in ascorbate content was
15


also observed to be linear with increasing salinity level in chickpea (Kukreja et al., 2006).
The higher ascorbate content was observed in the salt-tolerant cultivars as compared to salt
sensitive cultivars of Oryza sativa under salt stress (Vaidyanathan et al., 2003). Amor et
al. (2006) associated high salt-tolerance in Cakile maritima, a coastal halophyte with high
ascorbate. AsA content was reported to be increased in salinity stress in mungbean

(Hossain et al., 2011). Salinity stress severely increased the ascorbate content in leaf of
Vigna radiata reported by Maia et al. (2010).
2.7 Ionic composition
Detrimental effect of salt may be due the toxicity of specific ion, elevation of
osmotic pressure or the increase in alkalinity which may restrict the availability of water or
influence cellular physiology and metabolic pathway (Mudgal et al., 2010). Salinity of soil
and water is caused by the presence of excessive amounts of salts. Most commonly, high
Na + and Cl- cause the salt stress. High salt (NaCl) uptake competes with the uptake of
other nutrient ions, especially K+, leading to K+ deficiency (Parida and Das, 2005). When
the chloride content in the root zone exceeds a threshold value, it adversely affected the
availability of S to plants. Therefore, sulphur requirement of crops is increased
considerably under Cl- dominated saline conditions (Sharma and Khajanchi, 2009).
In recent year, a lot of studies has been done on mungbean regarding with respect
to ionic composition under saline conditions (Sabina and Khan, 2004; Zaffar et al., 2007;
Sabina and Mehar, 2011). K+ concentration was similar in different plant parts but Na + was
high in shoot and root at pre-flowering and flowering stages of growth of mungbean grown
at various salinity levels (Hafeez et al., 1988). Nandwal et al. (2000 b) revealed that
salinity nutrient solution significantly increased Na +/K+ ratio in the leaves and roots as
well as in nodules. Similar, NaCl induced salinity resulted in sharp increase in Na +, Cl- and
decrease in K+ accumulation in the root, stem and leaf on mungbean seedling (Parveen et
al., 2004). However, Zayed and Zeid (1998) reported that NaCl applied in mungbean
seedling resulted Na + accumulation in shoot while reduction in root, K+ content decreased
in both shoot and root, Ca 2+ content accumulation in shoot but remained unchanged in
root, Cl- accumulation high in root and slightly in shoot and Sulfur content decreased
markedly with increasing the salt concentration.
Increased saline irrigation on mungbean caused increase in Na +, Cl-, SO42- and
decrease in K+, accumulation in leaves (Pooja and Sharma, 2010). Similar, Na +, Clincreased and decreased in K+, Ca 2+ and Mg2+ accumulation with increased salinity levels
in shoot and root (Mohammed, 2007). Wahid et al. (2004) reported that all the mungbean
genotypes displayed the accumulation of Na +, Cl- in leaf as the salt levels progressed. Old
leaflets had greater content both these ions than young ones. While sharp reduction in K +

16