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

rapid changes in environmental circumstances, severe consequences on plant

production are intensifying due to the primary and secondary consequences

of abiotic stressors. To quantify the consequences of a climatic emergency,

as well as environmental changes, the frequency of stress intervals, its influ­

ence on everyday life, and destruction of crop, are used. Plant development

and productivity are greatly influenced by abiotic stressors. In their natural

habitat, plants are regularly subjected to a range of stressors, including water­

logging, rainlessness, high temperature, low temperature, and salt (Ashraf

et al., 2018; Benevenuto et al., 2017). Abiotic factors that cause additional

stress include UV-B, light intensities, floods, gaseous release, as well as

physicochemical variables (Suzuki et al., 2014). The average temperature of

the Earth is anticipated to rise from 2°C to 4.5°C in the 21^st century. As per

IPCC-2014 (http://www.ipcc.ch/), the period amid the 19^th and 21^st centuries

are regarded as the most warming (Pachauri et al., 2014). Floods are caused

by extreme precipitation events, whereas drought stressors are caused by a

lack of rainfall or a complete lack of rainfall over an extended period of time

(Khan et al., 2016).

Rice, wheat, and maize are among the world’s staple cereal crops satis­

fying daily food demand (Tack et al., 2015). It is stated that the decrease in

the grain filling phase as a result of rising temperatures is the primary cause

of crop productivity loss in changing climatic circumstances. As a result,

crop yield maintenance and the development of stress-tolerant crop plants

are key tasks in modern agriculture (Abhinandan et al., 2018). Plant organs

and tissues are harmed by numerous pressures and react consequently. Tran­

scriptional responses to diverse stressors differ in individual root cells or

tissues. Salinity, drought, and chemical effluence induce cellular signals such

as stress-responsive protein production, excess amounts of related solutes,

and higher antioxidant ratios (Dinneny et al., 2008). These are referred to as

fundamental stresses, and they result in secondary stresses such as oxidative

and osmotic stress (Carvalho & Amâncio, 2019).

12.4 BASIC OF EPIGENETICS – EPIGENETIC CHANGES AND

REQUISITE MACHINERY

In plants and animals, epigenetic changes, which involve alteration of

histones, DNA methylation, chromatin restructuring, histone variants, as

well as sRNAs, modification of gene expression are not influenced through

DNA sequence, they are transmitted by mitosis and meiosis. They can