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Biology and Physiology of Saline Plants
David N. Sen* and Pawan K. Kasera
University of Jodhpur, Jodhpur, India
Sher Mohammed
Government Lohia (PG) College, Churu, India
563I. INTRODUCTION
Worldwide agricultural production is greatly affected by a number of environmental hazards, major
among which is salinity associated with aridity. Saline lands are not only distributed in desert and
semidesert regions but also frequently occur in fertile alluvial plains, river, valleys, and coastal regions,
close to densely populated areas and irrigation systems. These soils cover an area of about 1 billion ha on
our planet earth, out of which 75 million ha lie in Southwest Asia. Iran tops the latter group with nearly
27 million ha, followed by India (23.8 Mha), Pakistan (10.5 Mha), Iraq (6.7 Mha), Afghanistan (3 Mha),
and Turkey (2.5 Mha) [1]. It is therefore important to examine saline ecophysiology in terms of the envi-
ronment and adaptability of plant species found therein.
The interactions between salinity and soil water and climatic conditions change the plant’s ability to
tolerate salinity. A basic understanding of the interaction between salinity and environment is necessary
for an accurate assessment of salt tolerance. In addition to precipitation, temperature and atmospheric hu-
midity can markedly influence salt tolerance [2].
An excess of salts in the soil inhibits plant growth in various ways. When rain failure is prolonged,
it affects vegetation by reducing the level of the water table and increasing salinity by capillary move-
ment. Temperature is one of the most critical factors of the environment that exerts a pronounced effect
on all the physiological activities by controlling the rate of chemical reactions.
Salinity and aridity are the two oldest enemies of agriculture. The salinity stress problem arises when
semiarid or arid lands are subjected to cultivation because saline soils, excessive use of chemical fertiliz-
ers, and excessive irrigation have turned hundreds of hectares of cultivated fertile lands into saline lands
[3]. It is believed that about 10% of the total surface area of the world is salt affected [4]. About 15% of
the arid and semiarid lands are affected by salts, and one third of all agricultural lands are also becoming
saline [5]. The rapidly growing demand for increased food, fiber, and fuel in the presence of rapidly de-
clining availability of agricultural land due to increased soil salinity makes it imperative that crop pro-
duction under saline conditions be significantly increased. It is believed that halophytes have potential
value for agriculture and could be grown in these degraded lands.
The most serious problem of the arid/inland saline areas is the scarcity of water. In hot deserts, most
of the rainfall occurs during the summer, which leads to a high rate of evapotranspiration. During that
time, the effective utilization of water by plants is also high. In fact, only a small group of higher plants,
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