Journal of Cereal Research Volume 14 (Spl 1): 17-41

face=”italic”> et al.,6.4.1. SO
2
 induced drought priming in wheat
Another prevalent cause restricting plant growth and 
production is drought stress. Sulphur dioxide (SO
2
) has 
been shown to boost plants by protecting them from 
stressful conditions (Corpas and Palma 2020). The impact 
of SO
2
on the molecular mechanisms and physiological 
functions of wheat plants at early developmental and 
growth phases to drought stress was investigated (Li et al., 
2021). Under abiotic stresses e.g., drought, pre-treatment 
of wheat seedlings with 10 mg/m3 SO
2
improved the 
chances of survival and relative water content (RWC), 
showing that pre-disposition to an adequate dose of
SO
2
might improve plant tolerance towards drought. A recent 
study found that pre-treatment of foxtail millet seedlings 
with SO
2
protected these plants against drought stress 
damage (Han et al., 2019).
For a long time, SO
2
was considered to be a prevalent air 
contaminant with deleterious impacts on the crop (Liu et 
al., 2017). SO
2
toxicity is primarily caused by oxidative 
stress, which is regulated by an increase in ROS production, 
comparable to drought stress. Low concentrations of SO
2
were shown to stimulate transcriptome reprogramming 
in grape berries, which is linked to oxidative signaling, 
indicating that SO
2
indeed has a physiologically 
metabolic role under defensive processes(Xue and Yi 2018). 
These reactions were linked to the increased proline build-
up produced by SO
2
pre-treatment in drought-stricken 
wheat seedlings. Whilst, in drought-treated wheat seedlings, 
SO
2 
pre-treatment elevated the functions of superoxide 
dismutase (SOD) and peroxidase (POD) (Corpas and 
Palma 2020). However, these treatments had significantly 
lowered the concentration of hydrogen peroxide (H
2
O
2
) 
and malondialdehyde (MDA), implying that mitigate 
drought-induced oxidative injury can be mitigated 
through SO
2
by bolstering antioxidant processes and 
pathways in wheat plants (Li et al., 2021). Gene expression 
analyses of transcription factor NAC, MYB, and ERF in 
wheat after SO
2
pre-treatment lowered the expression 
of TaNAC69. Whereas the expression of TaERF1 and 
TaMYB30 altered a little and remained at elevated amounts 
in wheat seedlings in drought stress tolerance (Baillo et al., 
2019) (Table 1). Interestingly, SO
2
pre-treatment caused a 
crucial enhancement in hydrogen sulfide (H
2
S) build-up 
upon exposing juvenile wheat plants to desiccation (Ausma 
and De Kok 2019). The activities of antioxidant enzymes 

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Abiotic stress tolerance in wheat
31
and TF genes expression were reduced when H2S was 
scrounged by spraying Hypotaurine (HT), whereas the 
concentration of H
2
O
2
and MDA enhanced to the level 
of drought treatment solely, implying a central role in 
the regulation of SO2-induced H
2
S in plant tolerance to 
drought stress (Corpas and Palma 2020). Overall, this 
research found that SO
2
increased drought endurance 
in wheat seedlings via H
2
S signaling, indicating a novel 
method for culminating drought tolerance in wheat crops 
(Li et al., 2021).
Table 1. Physiological Alterations upon pretreatment of wheat plants with chemicals to develop drought 
tolerance
Abiotic 
Stress
Pretreatment 
of wheat 
seedlings
Metabolic 
Alterations
Stress Response Genes
Physiological 
Alterations
References
Up-
Regulation
Down-
Regulation
Drought 
Stress
SO
2