Metabolomic study on the quality differences and physiological characteristics between rice cultivated in drought and flood conditions

Silicon enhanced phosphorus uptake in rice under dry cultivation through root organic acid secretion and energy distribution in low phosphorus conditions

Dry cultivation of rice (DCR) is one of the important rice cultivation practices aimed at addressing freshwater resource shortages. However, the non-renewable nature of phosphate resources constrains agricultural development. In the context of the contradiction between rice, water, and phosphorus, there is little research on using the silicon phosphorus relationship to improve the phosphorus availability and uptake of DCR. This experiment used field soil and established five fertilization treatments: no phosphorus application, low phosphorus and normal phosphorus (0, 25, 75 kg·ha-1 P2O5) (0P, 25P, 75P), along with two silicon levels (0, 45kg·ha-1 SiO2), resulting in the treatments 0P, 0PSi, 25P, 25PSi, and 75P. The soil phosphorus components and plant phosphorus uptake were analyzed. The results showed that adding silicon to 25P increased the Olsen-P content (14.37%) by increasing Ca8-P (9.04%) and Al-P (19.31%). Additionally, root and leaf phosphorus content increased by 7.6% and 5.8%, respectively, comparable to the levels observed in the 75P treatment. On one hand, adding silicon increases malate (40.48%) and succinate (49.73%) content, enhances acid phosphatase activity, and increases the abundance of Bradyrhizobium, Paenibacillus, and Bacillus, as well as the proportion of Fusarium, forming an "organic acid microbial" activated phosphorus system. On the other hand, the addition of silicon alleviated phosphorus limitations by reducing ATP consumption in roots through a decrease in ATPase and P-ATPase content. This also minimized excessive NSC transport to roots, thereby promoting shoot growth by downregulating SUT1, SWEET11, SUS2, and CIN2. In addition to optimizing root-to-shoot ratio and providing sufficient energy, silicon addition also increases root volume and upregulates OsPT2, OsPT4, and OsPT8, thereby promoting phosphorus uptake. In summary, 25PSi optimizes the root-to-shoot ratio and promotes phosphorus conversion and uptake through organic acid, microbial, and energy pathways. Applying silicon is beneficial for the sustainable and efficient management of phosphorus in DCR.

Adoption of Multi-omics Approaches to Address Drought Stress Tolerance in Rice and Mitigation Strategies for Sustainable Production

Drought is considered one of the major limiting factors for crop production. Drought-affected areas are consistently expanding. As rice stands as a primary grain widely consumed as a staple food by people across the globe, with a particular prominence in Asian countries. Due to its short root structure, thin cuticular wax layer and quick stomatal closure, rice is considered as drought-sensitive crop. The impact of drought on rice amplifies with plant growth and its adverse effects are more pronounced during the reproductive phase, including stages such as blooming, filling and maturity. Every year rice growers are facing a considerable deterioration of yield due to abiotic stresses specially drought. To address this undesirable consequences, multi-omics approaches are successfully being utilized as a mitigation strategy. A thorough, precise and systematic comprehension of the fundamental biological and cellular mechanisms activated by crop plants during stress is achieved through a range of omics technologies, including genomics, transcriptomics, proteomics and metabolomics. The integration of multi omics approaches offers a holistic understanding of cellular dynamics during drought or other stress conditions. These omics-based tools can identify and manipulate drought-tolerant genes. Utilizing omics approaches to stack these genes in rice contributes to the development of a drought resistant plant architecture. This review article aims to compile the latest published strategies on the application of multi omics approaches to accelerate the development of drought-tolerant rice plants.

Silicon Nutrition Improves Lodging Resistance of Rice Under Dry Cultivation

Silicon (Si) has been proven to enhance the stress resistance of rice, but its effect on the lodging resistance of rice under dry cultivation (DCR) is still unclear. The purpose of this experiment is to clarify the appropriate amount of silicon fertilizer for DCR to resist lodging and to elucidate how it coordinates lodging resistance and yield. This experiment used the 'Suigeng 18' cultivar as the material and set six silicon fertilizers (SiO2) with dosages of 0, 15, 30, 45, 60, and 75 kg·ha-1 (Si0, Si1, Si2, Si3, Si4, Si5). Analyze the effects and key indicators of silicon on lodging resistance of DCR from the perspectives of plant weight distribution, stem structure and composition, and root architecture. The results showed that the Si3 treatment had the highest yield and the lowest lodging index (LI). Si3 increases the weight of the upper three leaves and 4-5 internodes, thereby promoting panicle weight and yield. An increase of 13.38% in 2/3PWSI (weight of the 4th-5th stems and upper three leaves/weight of the 1st-3rd stems and lower leaves) can reflect the promoting effect of silicon on stem and leaf development near the panicle. Si3 reduces the GA/IAA value, shortens the length of the second internode, and increases the diameters of the major and minor axes, thereby increasing culm thickness and section modulus (SM), achieving the effect of "short and thick". Si3 also increases the content of silicon and non-structural carbohydrates (NSCs) in the second internode, and increases lignin and cellulose content by upregulating the expression levels of CAD7, PAL, COMT, and CesA4 genes, thereby increasing fullness and flexural strength (M), achieving "short, thick, and strong" and reducing LI. The 38.95% reduction in IFL (second internode length/fullness) reflects the positive effect of silicon on the "short, thick, and strong" stem. In the underground part, adding silicon reduces the CTK/IAA value of roots, and increases root length, root tip number, root surface area, and root weight. The key to coordinating the lodging resistance and yield of DCR with appropriate silicon dosage is to reduce the IFL in the second internode and increase 2/3 PWSI and root growth. The key to DCR and breeding is to focus on the relationship between basal internode length and fullness, as well as stem and leaf growth near the panicle.

Silicon nutrition improves the quality and yield of rice under dry cultivation

BACKGROUND

Dry cultivation of rice is a water-saving, emission reduction and labor-saving rice farming method. However, the development of rice under dry cultivation is hampered by the limitations of dry cultivation on rice yield and rice quality. We hypothesized that additional silicon (Si) would be a measure to address these limitations or challenges.

RESULTS

In the present study, we set up field trials with three treatments: flooded cultivation (W), dry cultivation (D) and dry cultivation plus Si. Yield and quality were reduced under D treatment compared to W treatment. The addition of Si promoted root development, increased plant height and leaf area, increased photosynthetic enzyme activity, net photosynthetic rate and SPAD values, and increased biomass under dry crop conditions. Under the drought conditions, silica up-regulated the expression of AGPSI, SBEI, SBEIIb, SSI and SSII-1 genes and the activities of ADP-glucose pyrophosphorylase (AGPase), soluble starch synthetase (SSS) and starch branching enzyme (SBE) enzymes, which reduced protein, amylose, chalkiness percentage and chalkiness degree, increased brown rice rate, milled rice rate and head milled rice rate, and also improved rice quality. In addition, the increase of AGPase, SSS and SBE enzyme activities promoted the filling rate and the number of spikes was guaranteed, whereas the yield was improved by promoting the seed setting rate and 1000-grain weight.

CONCLUSION

The results of the present study indicate that adding appropriate amounts of Si fertilizer can improve the yield and quality of rice under dry cultivation by regulating source supply capacity and grain starch synthesis. © 2023 Society of Chemical Industry.