Mechanistic Study On The Regulation Of Rice Growth And Disease Resistance By Nano Hydroxyapatite

Calcium and phosphorus are essential nutrients in plant growth,and research has shown that calcium and phosphorus not only promote plant growth by improving photosynthesis,but also have a correlation with improving plant disease resistance.However,the content of available calcium and phosphorus in soil in China is low,and both calcium and phosphorus deficient soils account for about two-thirds of the total area.To address the above issues,the traditional solution is mainly to spray calcium and phosphorus fertilizers and pesticides.However,the utilization efficiency of these two fertilizers is low,and improper application can cause a series of environmental problems.With the continuous development of nanotechnology,nanomaterials（NMs）have shown preliminary good effects in promoting crop growth and controlling crop diseases.Nano hydroxyapatite（nHAP）,as a new type of NMs,has good biocompatibility and bioactivity,and can continuously release Ca²⁺and PO₄^3-.In summary,this article selected rice（Oryza sativa L.）as the test plant and established two systems for nHAP to promote rice growth and control rice diseases by spraying nHAP on the leaves.The intrinsic mechanisms of nHAP to promote crop growth and regulate crop diseases were explored.The main research conclusions are as follows:（1）After spraying different concentrations of nHAP（100-400 mg/L）on the leaves,the optimal application concentration of nHAP for promoting rice growth was determined at 200mg/L by measuring the relevant growth parameters of rice and considering economic costs.Subsequently,techniques such as q RT-PCR,metabolomics,and microbiology were used to reveal the mechanism of nHAP promoting crop growth:a)nHAP promotes crop photosynthesis,the net photosynthetic rate increased by 25.8%;b)nHAP increased the levels of growth hormone IAA by 48.6%and increased the abundance of calcium regulatory and increase the abundance of calcium regulatory and phosphorus transport genes to 1.6 and 3.2 times compared with control,respectively;c)Increase the abundance of beneficial phyllospheric microorganisms（such as Firmicutes and Actinomyces）.In addition,the application of nHAP can also alter the metabolic level of rice leaves.（2）Spraying with different concentrations of nHAP（100-400 mg/L）on the leaves can reduce the degree of rice blast disease inoculation,with the 200 mg/L treatment exhibiting the best performance.Subsequently,the mechanism of nHAP controlling crop diseases was summarized using techniques such as q RT-PCR,metabolomics,and enzyme activity measurement:a)The application of nHAP significantly reduces the content of antioxidant enzymes in infected rice and avoids oxidative stress reactions in rice;b)nHAP can increase the resistance hormone SA by 79.3%,increase the content of JA by 2.5 times,and upregulate the expression of disease related genes,thereby activating the acquisition of resistance in crops;c)nHAP can also increase the content of the specific substance sakurarin that is resistant to rice blast,enhancing the ability of rice to resist rice blast.（3）After measuring the yield and quality indicators of rice,it was found that foliar application of 200 mg/L nHAP not only increased the yield of healthy rice and infected rice by2 times and 50.9%,respectively,but also improved the levels of related nutritional indicators（nutrient element content,soluble protein,and starch）in rice,ultimately improving the nutritional quality of rice.In summary,this study found that nHAP can not only promote rice growth,but also regulate rice disease resistance and inhibit the occurrence of rice blast.Meanwhile,due to its better bioavailability,nHAP has stronger growth promoting and disease resistance effects on rice compared to other salt ion control and traditional pesticide control.Therefore,this study provides theoretical support for the development of nHAP as a new type of nano fertilizer and nano pesticide.