4.2 | Root secretion and soil phosphorus utilization
Phosphorus is one of the essential elements for plants (Arwenyo et al., 2022), and the distribution and transport of soil phosphorus affect plant growth and productivity (Xia et al., 2020, Yadav et al., 2020). S-PT is an enzyme that catalyzes the transfer of phosphate groups from donors to acceptors and is closely related to phosphorus uptake and transport. This study found that under D, T, and N stresses, S. miltiorrhiza up-regulates the activity of root-secreted S-PT, while other stresses down-regulate this activity significantly. In the context of nitrogen stress, synergistic stress of drought or synergistic stress of high-temperature, or synergistic stresses of drought and high-temperature, can significantly down-regulate the activity of root-secreted S-PT (Figure 3-a) (e.g., DN, TN, and DTN stresses). However, under nitrogen and phosphorus stress, synergistic stress of drought or synergistic stress of high-temperature or synergistic stresses of drought and high-temperature synergistic stress can significantly up-regulate the activity of root-secreted S-PT (Figure 3-c) (e.g., DNP, TNP, and DTNP stresses). This also supports the claim that plants respond uniquely to different synergistic stress. It is also suggested that in the absence of microbial participation, most stress environments are not conducive to phosphorus uptake and transport. Most stressful environments that promote phosphorus uptake and transport in plant roots may be directly related to rhizosphere microorganisms (Glaesner et al., 2016).