Triticeae Genomics and Genetics, 2025, Vol.16, No.3, 110-119 http://cropscipublisher.com/index.php/tgg 111 2 Drought Stress inTriticeae: Agricultural Relevance and Impact 2.1 Physiological consequences of drought onTriticeae (wheat, barley, rye) What happens when plants lack water? In wheat crops, the most obvious manifestation is the closure of stomata and the reduction of water content, which directly affects the efficiency of photosynthesis. Like wheat, when drought occurs, its stomatal conductance and leaf water content will decrease significantly, while substances related to stress response such as malondialdehyde and proline will increase (Qiao et al., 2024). Not only that, but their leaves and roots also grow more slowly. However, not all genotypes respond in the same way. Some drought-tolerant types, such as wild species or local varieties, tend to grow deeper or wider roots, which can absorb more water (Ullah et al., 2017). Of course, these "smart" response mechanisms are not always capable of withstanding prolonged drought. For instance, when stomata close, although it can reduce water loss, it also limits photosynthesis and affects the final yield (Hussein et al., 2022). Different varieties and different genetic backgrounds also have varying "tolerance" to drought. 2.2 Economic and food security implications in drought-prone regions When it comes to the impact of drought, the decline in output is just the tip of the iceberg. The situation is even more serious in those arid or semi-arid regions that are already short of water (Begna et al., 2021). According to some studies, drought can reduce wheat production by more than half, while those droughts that are not particularly extreme but last for a long time are more likely to cause cumulative losses (Figure 1) (Wan et al., 2022). These losses are not just a matter of figures in the granary. They directly affect the wallets of farmers and even the food and clothing problems of the population who rely on these staple grains for survival (Fadiji et al., 2022). Moreover, climate change has made droughts increasingly difficult to predict, making it impossible to prevent them. To address these issues, technical means can be used to find solutions, but there are also many places to spend money-especially when adaptive measures need to be invested, the cost pressure rises significantly. Figure 1 The effect of drought type (TD: Terminal drought stress; CD: Continuous drought stress), N application level [Low N (0-100 kg/ha); Medium N (100-200 kg/ha); High N (>200 kg/ha)], soil type, wheat type, mean annual precipitation, and mean annual temperature on the lnRRs of (A) GY: grain yield and (B) GPY: grain protein yield. The sample size of each variable is noted beside each bar. The effect of drought is significant if the ±95% confidence intervals of effect size do not overlap zero (Adopted firom Wan et al., 2022)
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