Physiology and Molecular Biology of Stress ... - KHAM PHA MOI

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CHAPTER 3
SALT STRESS
ZORA DAJIC
Faculty of Agriculture, University of Belgrade,
Nemanjina 6, 11080 Belgrade, Serbia and Monte Negro
(e-mail: zorad@eunet.yu)
Key words: Compartmentation, glycophytes, halophytes, ion homeostasis, salinity,
salt tolerance, sodium, succulence
1. INTRODUCTION
Saline water occupies 71% of the Earth area. It is thought that even a quarter of the
whole pedosphere is affected by salts (Glenn and O’Leary, 1985), amounting to 950 x 10 6
ha (Flowers and Yeo, 1995), while 23 % of the 1.5 x 10 9 ha cultivated land is considered
as saline (Rhoades and Loveday, 1990). Furthermore, about a half of all the existing
irrigation systems of the world (3 x 10 8 ha) are under the influence of secondary salinization,
alkalization and waterlogging, and about 10 x 10 6 ha of irrigated land are abandoned
each year because of the unfavorable effects of secondary salinization and
alkalization (Szabolcs, 1987). Such unfavorable soils of low fertility are generally unsuitable
for agricultural production, causing unacceptable yield reduction, and in some
cases, being far from any reasonable utilization. Because of the increased need for food
production and increasing distribution of soils affected by salinity, research on plant
responses to salinity has rapidly expanded in recent decades.
Studies of plant tolerance to salt stress cover many aspects of the influences
of salinity on plant behavior, including alterations at the morphological, physiological
and molecular levels. Recently, investigations are focusing more on: biotechnology,
transgenic plants, improvement of breeding and screening methodologies and modification
of the genetic structure of existing crops aiming at enhanced adaptation to
salinity conditions.
The alterations in physiological traits caused by salt stress have been frequently
reviewed during the past decades (Waisel, 1972; Flowers et al., 1977; Greenway
and Munns, 1980; Munns et al., 1983; Ungar; 1991, Munns, 2002). However, the progress
of research methodologies and techniques has created a platform for better understanding
of molecular aspects (Yeo, 1998; Hasegawa et al., 2000; Tester and Davenport,
K.V. Madhava Rao, A.S. Raghavendra and K. Janardhan Reddy (eds.),
Physiology and Molecular Biology of Stress Tolerance in Plants, 41–99.
© 2006 Springer. Printed in the Netherlands.
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