As one of the world’s principal food crops, rice sustains over half of the global population. With global climate change intensifying, the frequency of extreme high temperatures is increasing, posing significant threats to the growth and development, yield, and quality of rice, thereby jeopardizing global food security. This study reviews the impacts of high temperatures on rice at different developmental stages and summarizes previous research on heat tolerance cultivation techniques for rice. Currently, to enhance heat tolerance in rice, the following strategies were primarily adopted: (1) the exploration of heat-tolerant genetic resources and breeding of heat-tolerant varieties; (2) cooling through canopy temperature management via enhanced transpiration regulated by water management; (3) the scientific application of fertilizers to promote the accumulation of assimilates in rice; (4) the application of exogenous regulators to bolster the antioxidant capacity of rice. The implementation of these strategies not only helps to ensure rice yield and quality but also provides robust support for addressing the challenges that global warming poses to agricultural production.

Lodging is one of the key limiting factors in achieving high wheat yield. The application of plant growth retardants (PGRts) is regarded as an effective practice to prevent lodging. For accurate PGRt selection and the establishment of stable, high-yield production plans, it is essential to make clear the regulation strategies for lodging resistance and yield in PGRts. Field experiments were conducted at two test sites. At the initial jointing stage of wheat, Chlormequat Chloride (CCC) or Uniconazole (S₃₃₀₇) was sprayed. Compared with the control (CK), spraying CCC or S₃₃₀₇ significantly reduced the culm lodging index (CLI) and decreased the lodging rate from 7.1% to 15.6%. CCC was more capable of adjusting plant morphology (reducing plant height and second internode length and increasing stem diameter), while S₃₃₀₇ was more effective in enhancing breaking strength. The contents of GA, IAA, and zeatin nucleoside (ZR) and the activities of lignin-related enzymes (TAL and CAD) were significantly correlated with different stem indicators and CLI. Compared with CK, the yield after spraying CCC or S₃₃₀₇ increased by 6.5% and 6.0%, respectively. CCC mainly enhanced the yield by increasing grain weight per spike and the SPAD value of leaves, while S₃₃₀₇ mainly did so by increasing the number of spikes and the effective leaf area. Moreover, carbon metabolism-related enzymes (Rubisco, SS, and SPS) were significantly positively correlated with the yield. The enzyme activity of CCC was higher at the heading stage, while that of S₃₃₀₇ was higher at the filling stage. Hence, spraying CCC or S₃₃₀₇ can significantly enhance lodging resistance and yield. The optimal PGRts should be selected based on the climate and the growth stage of the wheat.

This study investigated the differences in appearance quality among different soft japonica rice varieties based on grain shape, with a particular focus on the broad-ovate soft japonica rice varieties Nanjing 9108 and Nanjing 5718, as well as the slender soft japonica rice varieties Shangshida 19 and Jiahe 218, all sourced from the Yangtze River Delta. The results showed that the slender soft japonica rice varieties exhibited significantly superior appearance quality compared to the broad-ovate varieties. In the case of superior grains, the chalky grain rate of the broad-ovate soft japonica rice was 4307.79 percent higher than that of the slender varieties, and the degree of chalkiness was 8275.00 percent higher. For inferior grains, the chalky grain rate of the broad-ovate soft japonica rice was 238.34 percent higher than the slender varieties, and the degree of chalkiness was 339.96 percent higher. In contrast to the slender soft japonica rice, the broad-ovate varieties had a lower percentage of high-weight grains and a higher percentage of low-weight grains. Compared to the broad-ovate soft japonica rice, the slender varieties exhibited a faster grain-filling rate and shorter effective grain-filling days. Correlation analysis revealed that chalkiness had a significant negative correlation with grain length and aspect ratio. Simultaneously, chalkiness also showed a positive correlation with the number of effective grain-filling days while demonstrating a negative correlation with both the maximum and average grain-filling rates. The slender soft japonica rice exhibited a lower likelihood of developing chalkiness and higher grain-filling efficiency and developed a favorable grain weight distribution. These distinctive attributes significantly contribute to the superior appearance quality of the slender japonica soft rice.

Mounting labor shortages and rising operational costs are threatening the sustainability of mechanized rice production in Southern China, underscoring the urgent need for innovations that reduce labor inputs during nursery preparation and transplanting. To address these challenges, this study developed an innovative double-blanket seedling tray measuring 120 cm in length—twice that of a conventional tray. Based on this design, experiments were conducted to identify suitable lightweight substrates capable of producing cohesive and structurally stable double-blanket rice seedling mats. Two lightweight substrates—crop straw boards and matrix cotton—were evaluated in comparison to traditional nursery soil. Results demonstrated that, when combined with the nutrient solution “Miao Zhuang Feng”, both lightweight substrates significantly improved seedling quality, transplanting performance, and final yield. Notably, the fresh weight of double-blanket seedlings grown on lightweight substrates was comparable to single-blanket seedlings cultivated in soil while being 47.46% lighter than double-blanket seedlings raised with soil. To optimize double-blanket seedling mat formation and transplanting quality, five seeding densities (300, 360, 420, 480, and 540 g/tray) and four seedling ages (10, 15, 20, and 25 d) were tested using crop straw board as the substrate. The results revealed that optimal combinations varied by condition: 480 and 540 g/tray were suitable for 15-day-old seedlings, 420 g/tray for 20-day-old seedlings, 360 g/tray for 20~25-day-old seedlings, and 300 g/tray for 25-day-old seedlings. Compared with single-blanket seedlings, the double-blanket approach reduced the number of trays required per hectare and the total seedling cultivation and transportation cost by 57.97% and 16.67%. Furthermore, increasing the seeding density from 300 to 360, 420, 480, and 540 g/tray led to additional reductions of 16.31%, 26.24%, 34.75%, and 41.13%, respectively—substantially lowering labor requirements for tray handling and seedling feeding during transplanting.

Objective: This study aims to establish a scientific basis for improving rice quality by investigating the relationship between variations in eating and appearance quality and the starch and protein content in soft and non-soft rice varieties.Methods: Two soft rice varieties, Nanjing 5718 and Nanjing 9108, were compared with two non-soft rice varieties, Huaidao 5 hao and Huajing 5 hao. The study focused on eating and appearance quality, starch and protein content, and how these factors varied between superior and inferior grains within each variety.Results: Compared to non-soft rice, soft rice has some disadvantages in appearance quality, which is characterized by high chalky grain rate and chalkiness degree, and large differences in appearance between superior and inferior grains. This is mainly due to the low proportion of high grain weight grains, low amylose content, abnormal development of starch structure, and large protein bodies with high globulin and glutenin content, which destroys the close accumulation of starch particles, resulting in increased light scattering, increased chalkiness, and reduced transparency. Although the appearance quality of soft rice is not outstanding, its eating quality is extremely excellent, which is embodied in good appearance, high viscosity, good balance, high taste value and low hardness. This superior performance may be due to the high proportion of amylopectin in soft rice, which helps to improve the overall taste. In contrast, the amylose content of non-soft rice is higher, which leads to the increase of rice hardness and the decrease of viscosity. In addition, the gelatinization property of soft rice starch is more favorable, which makes the starch dissolve more in the cooking process, so as to further improve its eating quality.

To investigate the differences in carbon and nitrogen metabolism between superior and inferior grains of southern soft and non-soft japonica rice and their relationships with appearance quality, the metabolic characteristics and appearance quality of superior and inferior grains during the grain-filling stage were compared between the two rice types. The results showed that, compared with non-soft japonica rice, the activities of AGPase and GBSS in superior grains of soft rice were significantly lower, whereas the activities of SSS, SBE, and DBE were significantly higher. The amylose content decreased by 32.68–44.72%, while amylopectin increased by 7.27–10.73%. The limitation in carbon metabolism was more pronounced in inferior grains, and the non-structural carbohydrate content was 9.33–17.33% lower than that in superior grains. In terms of nitrogen metabolism, GS activity decreased whereas GOGAT activity increased in superior grains, resulting in a 6.28–8.38% increase in protein content. The protein content of inferior grains was 1.75–6.44% higher than that of superior grains. In addition, the chalky grain rate and chalkiness degree of superior grains in soft rice were 79.00–481.03% higher than those in non-soft japonica rice, while the increases in inferior grains ranged from 67.51% to 136.31%. Correlation analysis indicated that the chalky grain rate of superior grains was positively correlated with starch content during the early grain-filling stage, whereas the chalkiness degree of inferior grains was positively correlated with protein content. These results suggest that differences in carbon and nitrogen metabolism between grain positions are closely associated with the formation of appearance quality.