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Biology and Biotechnology of Environmental Stress Tolerance in Plants, Volume 3

a relatively stable and inheritable modification in a gene expression without

attributing changes in the DNA sequence. In 1942, Conrad Hal Waddington

conceived the word “epigenetic.” Epigenetic changes which include Chro­

matin remodeling (DNA and histone modifications) and RNA-mediated

modifications (non-coding RNAs and microRNAs) contribute to gene

expression, proliferation of plant as well as growth patterns under stressful

conditions. When plants face adverse ecological situations, epigenetic stress-

induced gene expression helps them in adaptation. Stress-induced chromatin

marks are meiotically transmitted and can transmit the “memory of stresses”

from parent to offspring plants via transgenerational epigenetic transmission,

suggesting the capacity to respond to a plethora of stresses. This information

in the role of epigenetics in phenotypic plasticity and heritable variation is

vital in understanding how plants can adapt to diverse environmental situ­

ations. Keeping these in the background, this chapter intends to depict the

recent progress in underlying epigenetic processes implicated in the plant’s

reaction against abiotic stress like extreme heat, cold, drought, heavy rain­

fall, salt, hazardous chemicals, and UV radiation. Further, attempts have

been made to illustrate how the epigenetic modifications cross-talks with the

biochemical as well as cellular functions of the plants in adapting to different

abiotic stresses.

12.1 INTRODUCTION

Plants in nature tend to adapt to the diverse environmental cues to which

they are exposed. Some of the environmental conditions may be conducive,

allowing the plant to grow well, but if conditions are hostile, then the plant

will be unable to maintain its growth and normal activities. Stress is defined

as an environment that is inappropriate for plant growth and survival. The

adverse or critical condition that negatively influences or blocks a plant’s

metabolism and growth is known as stress (Lichtenthaler, 1998). There are

numerous environmental challenges which include abiotic stress, i.e., salinity,

drought, heat, freezing, heavy metals and biotic stresses (Kim, 2021; Kong

et al., 2020). During evolution, plants have developed diverse machinery to

face different abiotic stresses throughout their life cycle (Kong et al., 2020;

Sudan et al., 2018). These mechanisms are regulated by the transcription and

translation of stress-induced genes. Since plants are sessile, they are consid­

ered as the most adaptable organisms of nature and can sense a change in

environmental cues thereby initiates gene expression (Luo et al., 2012), has