Molecular Plant Breeding 2025, Vol.16, No.4, 250-260 http://genbreedpublisher.com/index.php/mpb 255 7 Physiological and Environmental Factors Affecting Adaptability 7.1 Root development, nutrient uptake, and photosynthetic efficiency The root structure and function of japonica rice directly affect its ability to absorb water and nutrients, and it is the basis for whether it can adapt to different planting methods and environments (Zhu and Shen, 2024). The development of roots is controlled by many hormones, such as auxin, cytokinin and jasmonic acid. If there are many lateral roots, long roots and large root surface area, it will be more conducive to absorption, which can help rice be more drought-resistant and cold-resistant, and the yield will also be higher (Meng et al., 2019; Panda et al., 2021; Muzaffar et al., 2024). Some varieties have strong root activity and high antioxidant capacity. Under low temperature or drought weather, they can still maintain the accumulation and transportation of photosynthetic products, which is very helpful for the later panicle differentiation and grain formation (Jia et al., 2022; Miyoshi et al., 2023). Roots can also absorb amino acids and mineral elements, such as amino acids through proteins like OsLHT1, which will affect the growth and yield of the aboveground parts (Guo et al., 2020; Wang et al., 2022; Manna et al., 2024). If the roots can coexist with beneficial bacteria, such as Piriformospora indica, not only can the roots grow better, but also the efficiency of water and nutrient absorption can be improved, and the resistance to external stress can be enhanced (Figure 2) (Bandyopadhyay et al., 2022; Mani et al., 2023). Figure 2 Hypothetical model for explaining the mechanism of nutrient uptake that promotes higher plant growth and biomass in the presence of endophytic fungus P. indica and plant growth-promoting rhizobacterium A. chroococcum strain W5 (Adopted from Bandyopadhyay et al., 2022) 7.2 Soil temperature, moisture, and transplanting shock Soil temperature and humidity also affect the activity of roots. If the temperature in the root zone is above 29℃, it will be more conducive to the absorption of nutrients by the roots, especially the metabolism of nitrogen, and also beneficial to the growth of the entire rice plant (Vu et al., 2020; Farooq et al., 2021). Conversely, when encountering low temperatures or drought, root activity will decline, pollen vitality will deteriorate, and panicle development will also be affected, ultimately affecting yield (Jia et al., 2022; Miyoshi et al., 2023). When transplanting rice seedlings, root injuries combined with sudden environmental changes can easily lead to “transplanting shock”, which results in a short-term decrease in root absorption capacity and photosynthetic efficiency, affecting the process of rejuvenation. At this time, reasonable arrangement of water and fertilizer, such as intermittent irrigation and reasonable nitrogen application, can slow down the aging of roots, help leaves maintain photosynthesis, and increase rice yield and fertilizer and water utilization rate (Wang et al., 2022; Manna et al., 2024). 7.3 Interaction with diseases, pests, and abiotic stress In addition to absorbing water and nutrients, roots also play a significant role in resisting various stresses. Whether it is high temperature, salt, heavy metals, or pests and diseases, roots will regulate their own structure and enhance
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