The role of defensive Phytochemicals promote stress resistance in maize (zea mays L.) accessions

Abstract

Maize (Zea mays L.; 2n=2x=20), a typical C4 plant belonging to the family Poaceae, is substantially contributing to the world’s food and feed demand (Lana et al., 2017). This crop confers improved efficiencies in utilizing water, nutrient, and solar radiation compared to conventional C3 plants, such as rice, wheat, and barley (Ghannoum et al., 2010). In Sri Lanka, maize is commonly grown in the dry and intermediate zones as rain-fed cultivation during the Maha season. Two-thirds of the country's agricultural lands are located in a dry zone extending in the north, north-central, eastern, and southeast parts of the country whereas, Eastern Province has significantly higher maize productivity than other parts (Williams et al., 2018). Owing to this reason, maize cultivation is becoming more popular and large-scale cultivation is undertaken employing hybrid seeds, as such contributing 25 % of the country’s annual maize production (Thadshayini et al., 2020). Since a large extent of maize cultivation depends on rainfall, drought becomes a key limiting factor for its productivity (Barton and Clark, 2014). About a quarter portion of the maize cultivation is affected annually by drought and heatwaves caused to increasing atmospheric temperatures triggered due to the global climate change that has immensely contributed to seasonal variations and weather patterns (Manavalan et al., 2011). The predicted climatic changes is expected to decrease the rainfall by 34 % in 2050 as such raise the atmospheric temperature by 1.6 oC (Thadshayini et al., 2020). This alarming situation might pose a serious threat to Sri Lankan maize production, particularly in the Eastern Province. Plants have a natural tendency and possess defense mechanisms to dilute the effects of rising temperature and water deficit. In this perspective, drought influences the biochemical and physiological metabolic activity of the maize resulting in osmotic stress. Further, it is clear that the plant's responses to drought stress vary significantly depending on plant species and developmental stage, and severity of the interacting stress stimuli (Ahanger et al., 2016). In order to mitigate such adverse situations within the ultracellular environment, maize plants have evolved a well-developed phytochemical defense mechanism modulating a variety of resilience compounds such as proteins, flavonoids, and lignin-like cell wall components to protect the plant tissues (Vaughan et al., 2018). Therefore, the objectives of this report are to elaborate on the types of protective phytochemicals triggered by drought that enables maize plants to withstand stress while allowing plants to maintain substantial biomass and grain yield.