Keywords
Heat stress · Temperature stress · Crop productivity · Heat tolerance
3.1
Introduction
By the year 2050, the world population grows exponentially and will exceed nine
billion resulting in more food demand, despite the reduction of soil fertility and less
availability of productive land, water, and other variable factors incidental to climate
change (Mickelbart et al. 2015; Govindaraj et al. 2018). In recent years climate
change and its variability are emerging as major challenges for the world and its
efficacy on crop yield is highly diverse (Deryng et al. 2014). One of the major
changes seen in the decade is an increase in the intensity of heat stress (HS), which is
one of the inimical stresses that are rising constantly. The rise in temperature makes
alternation in crops growing periods and the distribution and thus cause serious
threat to crop production and productivity worldwide (Smith 1996; Hall 2001; Stone
2001; Porter 2005; Lesk et al. 2016). The global air temperature is reported to be
increasing at the rate of 0.18
C per decade (IPCC 2014), which will lead to an
increase the temperature as 1.5–4.5
C (IPCC 2012) higher than the current level by
2100 (Hansen et al. 2012).
The rise in temperature even by a single degree beyond a certain threshold level
for a period sufficient to induce irreversible damage to plant growth and development is referred to as HS (Hall 2001; Wahid et al. 2007; Hasanuzzaman et al. 2013).
The direct effect of HS can be seen at the protein level where its aggregation and
denaturation increases the cell membrane fluidity, while indirectly it affects through
enzymes inactivation in chloroplasts and mitochondria cell organelle, either
inhibiting synthesis or degradation of protein and loss of cell membrane integrity
(Smertenko et al. 1997; Howarth 2005). All these alterations result in catastrophic
collapse of cellular organization leads to cell injury and death within a few minutes
(Schoffl et al. 1999). The occurrence of high temperature (HT) is common during
anthesis and grain filling stages in many cereals crops and in maize especially during
the flowering and grain filling period (Giaveno and Ferrero 2003; Barnabas et al.
2008) and wheat crops (Rahman et al. 2009) which ultimately affect the production
and productivity (Wahid et al. 2007; Hansen et al. 2012).
Wheat and maize are the most widely grown cereal crops grown across the world.
Wheat is grown about 30% of the world’s cereal area in temperate environments, and
also as winter season crop in many tropical cropping system areas with over
220 million ha cultivated worldwide, therefore it is known as the “King of cereals”
Ramdas et al. (2019). It shares about 20% of the total dietary calories and proteins
around the globe (Lobell and Gourdji 2012; Shiferaw et al. 2013). Whereas, Maize is
known as the “Queen of cereals” and is the second most widely cultivated crop after
wheat, which is grown over a range of agroclimatic zones around the world (FICCI
2014). Maize is not only an important food source for the human diet but also a basic
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R. Gajghate et al.
Heat stress · Temperature stress · Crop productivity · Heat tolerance
3.1
Introduction
By the year 2050, the world population grows exponentially and will exceed nine
billion resulting in more food demand, despite the reduction of soil fertility and less
availability of productive land, water, and other variable factors incidental to climate
change (Mickelbart et al. 2015; Govindaraj et al. 2018). In recent years climate
change and its variability are emerging as major challenges for the world and its
efficacy on crop yield is highly diverse (Deryng et al. 2014). One of the major
changes seen in the decade is an increase in the intensity of heat stress (HS), which is
one of the inimical stresses that are rising constantly. The rise in temperature makes
alternation in crops growing periods and the distribution and thus cause serious
threat to crop production and productivity worldwide (Smith 1996; Hall 2001; Stone
2001; Porter 2005; Lesk et al. 2016). The global air temperature is reported to be
increasing at the rate of 0.18
C per decade (IPCC 2014), which will lead to an
increase the temperature as 1.5–4.5
C (IPCC 2012) higher than the current level by
2100 (Hansen et al. 2012).
The rise in temperature even by a single degree beyond a certain threshold level
for a period sufficient to induce irreversible damage to plant growth and development is referred to as HS (Hall 2001; Wahid et al. 2007; Hasanuzzaman et al. 2013).
The direct effect of HS can be seen at the protein level where its aggregation and
denaturation increases the cell membrane fluidity, while indirectly it affects through
enzymes inactivation in chloroplasts and mitochondria cell organelle, either
inhibiting synthesis or degradation of protein and loss of cell membrane integrity
(Smertenko et al. 1997; Howarth 2005). All these alterations result in catastrophic
collapse of cellular organization leads to cell injury and death within a few minutes
(Schoffl et al. 1999). The occurrence of high temperature (HT) is common during
anthesis and grain filling stages in many cereals crops and in maize especially during
the flowering and grain filling period (Giaveno and Ferrero 2003; Barnabas et al.
2008) and wheat crops (Rahman et al. 2009) which ultimately affect the production
and productivity (Wahid et al. 2007; Hansen et al. 2012).
Wheat and maize are the most widely grown cereal crops grown across the world.
Wheat is grown about 30% of the world’s cereal area in temperate environments, and
also as winter season crop in many tropical cropping system areas with over
220 million ha cultivated worldwide, therefore it is known as the “King of cereals”
Ramdas et al. (2019). It shares about 20% of the total dietary calories and proteins
around the globe (Lobell and Gourdji 2012; Shiferaw et al. 2013). Whereas, Maize is
known as the “Queen of cereals” and is the second most widely cultivated crop after
wheat, which is grown over a range of agroclimatic zones around the world (FICCI
2014). Maize is not only an important food source for the human diet but also a basic
52
R. Gajghate et al.