4. Regeneration—In this phase if stress has not been so prolonged and extensive,
regeneration may occur.
1.2
Types of Abiotic Stress
The abiotic stress includes inanimate environmental components as mentioned
above. These abiotic stress factors can occur naturally or may be caused by anthropogenic activities. As plants are sessile and their surrounding environment is everchanging the occurrence of physiological plasticity is essential for their survival
(Gaspar et al. 2002). Plants respond to different types of stresses in different ways as
described in different sections:
1.2.1 Temperature as Stress Factor
Plants respond differently to changes in temperature as for every plant species there
is an optimum range in which it survives best. In a same temperature range one
species may survive and other species may be sensitive as their thermo-sensitive
metabolic processes may get hampered due to changes in temperature leading to
change in cell processes. Plant species which are growing in hot and dry deserts or
high altitudes experience very high temperature during day and low during night.
Plants growing in tropical forests or northern forests grow in altogether different
temperature ranges so when such plants grow in different climatic conditions they
get stressed and are prone to injuries.
1.2.1.1 Low Temperature Stress
Low temperature is considered as one of the major abiotic stress limiting the growth
and development. Plants growing in temperate regions are adapted for low temperature conditions, and based on temperature range plants can survive, i.e., cold tolerant
or get injury and are classified as chilling-sensitive (10–15
C); freezing sensitive
(0
C); and freezing resistant plants (able to survive sub-zero temperature) (Pollock
and Eagles 1988; Hughes and Dunn 1990). When exposed to low temperature,
plants exhibit three types of injuries: desiccation, chilling injury, and freezing injury.
Freezing in plants can be induced either from freeing in soil water or freezing of
water inside the cells or at intracellular level. Some plants develop freezing tolerance
due to formation of antifreeze proteins, which along with some sugars (sucrose)
inhibits crystallization at cellular level. Woody or hardy plants are reported to be
highly resistant to chilling injuries. The common symptoms of chilling injury are
changes in membrane structure, composition, protoplast streaming reduced,
increased/decreased respiration, reduced photosynthesis, production of abnormal
metabolites, reduced plants growth, curling of leaves, necrosis, die back of stems,
abnormal ripening of fruit, decreased N partitioning in young shoots, altered
1 Abiotic Stress in Plants: An Overview
5
regeneration may occur.
1.2
Types of Abiotic Stress
The abiotic stress includes inanimate environmental components as mentioned
above. These abiotic stress factors can occur naturally or may be caused by anthropogenic activities. As plants are sessile and their surrounding environment is everchanging the occurrence of physiological plasticity is essential for their survival
(Gaspar et al. 2002). Plants respond to different types of stresses in different ways as
described in different sections:
1.2.1 Temperature as Stress Factor
Plants respond differently to changes in temperature as for every plant species there
is an optimum range in which it survives best. In a same temperature range one
species may survive and other species may be sensitive as their thermo-sensitive
metabolic processes may get hampered due to changes in temperature leading to
change in cell processes. Plant species which are growing in hot and dry deserts or
high altitudes experience very high temperature during day and low during night.
Plants growing in tropical forests or northern forests grow in altogether different
temperature ranges so when such plants grow in different climatic conditions they
get stressed and are prone to injuries.
1.2.1.1 Low Temperature Stress
Low temperature is considered as one of the major abiotic stress limiting the growth
and development. Plants growing in temperate regions are adapted for low temperature conditions, and based on temperature range plants can survive, i.e., cold tolerant
or get injury and are classified as chilling-sensitive (10–15
C); freezing sensitive
(0
C); and freezing resistant plants (able to survive sub-zero temperature) (Pollock
and Eagles 1988; Hughes and Dunn 1990). When exposed to low temperature,
plants exhibit three types of injuries: desiccation, chilling injury, and freezing injury.
Freezing in plants can be induced either from freeing in soil water or freezing of
water inside the cells or at intracellular level. Some plants develop freezing tolerance
due to formation of antifreeze proteins, which along with some sugars (sucrose)
inhibits crystallization at cellular level. Woody or hardy plants are reported to be
highly resistant to chilling injuries. The common symptoms of chilling injury are
changes in membrane structure, composition, protoplast streaming reduced,
increased/decreased respiration, reduced photosynthesis, production of abnormal
metabolites, reduced plants growth, curling of leaves, necrosis, die back of stems,
abnormal ripening of fruit, decreased N partitioning in young shoots, altered
1 Abiotic Stress in Plants: An Overview
5