Global warming causes heat and drought stress in plants, which affects crop production. In addition to osmotic stress and protein inactivation, reactive oxygen species (ROS) overaccumulation under heat and drought stress is a secondary stress that further impairs plant performance. Chloroplasts, mitochondria, peroxisomes, and apoplasts are the main ROS generation sites in heat- and drought-stressed plants. In this review, we summarize ROS generation and scavenging in heat- and drought-stressed plants and highlight the potential applications of plant nanobiotechnology for enhancing plant tolerance to these stresses.

The root system is the only vital organ for plants to connect with soil moisture and nutrients and obtain feedback information. This research aimed to explore the response of different spike type winter wheat varieties to plant and row spacing configurations. Multi-spike and large-spike winter wheat varieties were used as materials. By setting different plant row configurations and planting densities, the spatial and temporal distribution of root length density, root diameter, root dry weight density, and the main control factors of root growth and development of winter wheat during the whole growth period were studied. The results showed that the root system was the most widely distributed and the root diameter was the largest in the 0–40 cm soil depth, with an average root system diameter of more than 0.5 mm. The root length density and root diameter peaked at the heading stage, decreased at the maturity stage, and the root dry weight density peaked at the jointing stage. The jointing stage and heading stage are the most vigorous periods of root growth in winter wheat, when the center of gravity of root growth in winter wheat is gradually moving down. Therefore, the rapid growth and elongation time of a root system can be effectively prolonged at the jointing stage and heading stage, and the root growth rate can be improved. Promoting root thickening can effectively meet the needs for water and nutrients, for the formation and filling of aboveground plants and grains, in the later stage, which is conducive to the formation of aboveground dry matter production and final yield. The root distribution was greatest in the 0–60 cm soil depth, accounting for 95.13–97.84% of the total root length. After the heading stage occurs, the upper roots begin to decline in large quantities. Thus, the jointing stage and heading stage require fertilization and other farmland management operations to increase root nutrients for the ground parts and dry matter accumulation to provide sufficient nutrients so that the number of effective panicles, grain weight, and the number of spike grains coordinate to achieve the highest grain yield. Results showed that the highest yield can be achieved with the planting pattern X2M1. A comprehensive analysis showed that the genetic characteristics of winter wheat varieties were different, and there were some differences in the correlation between wheat yield and root system at the different growth stages. The correlation between the root parameters and yield of multi-spike winter wheat during the overwintering-jointing stage was obvious. For large-spike type winter wheat in the jointing stage, the yield correlation is most obvious.

Primary mechanism through which nanomaterials enhance plant photosynthesis.

Nitrogen fertilizer setback and planting density both affect wheat yield. However, the differences in winter wheat yield and its components, canopy structure, and microenvironment caused by N fertilizer setback at different planting densities are not clear. A two-year field experiment was conducted to investigate the most suitable planting density and N fertilizer setback combinations for winter wheat. Three planting densities of 3.3, 2.36, and 1.77 million plants·hm⁻², and two basal fertilizer/nodulation and fertilizer/spike fertilizer ratios of 6:4:0 and 4:3:3, respectively, were used in the experiment. The results of the two-year experiment showed that, under the same planting density, the yields of wheat with nitrogen fertilizer setback increased by 8.2%, 2.7%, and 2.8%, respectively; the total leaf area of the upper trifoliate leaves increased by 10.7–17.4%; and the leaf area index (LAI) increased by 5.4% and 5.3%, respectively. The results showed that the yield, the effective number of spikes, leaf area index, and vertical light interception of wheat at a density of 3.30 million plants·hm⁻² were higher than those of the other treatments. In both years of the experiment, the planting density of 3.30 million plants·hm⁻² with nitrogen fertilizer setback (basal fertilizer/nodulation fertilizer/spike fertilizer = 4:3:3) was the best. Therefore, a nitrogen application of 240 kg·hm⁻² and a planting density of 3.30 million hm⁻² with nitrogen fertilizer setback was found to be the best combination.

Soybean, an important cash crop, is often affected by soil salinity, which is one of the important types of abiotic stress that affects its growth. Poly (acrylic) acid coated Mn₃O₄ (PMO) has been reported to play a vital role in defending against a variety of abiotic stresses in plants. To date, the effects of PMOs on soybean have not been reported; this study explored the mechanism of PMO-enhanced soybean germination under salt stress. In this experiment, 100 mg/L PMO was used as an immersion agent with a salt treatment of 150 mM NaCl. The results showed that when compared with the PMO treatment, salt stress significantly decreased the germination rate, fresh weight, carbohydrate content, and antioxidant enzyme activity of soybean and significantly increased the contents of reactive oxygen species, malondialdehyde, and osmoregulatory substances. However, PMO treatment enhanced the antioxidant defense system and significantly reduced the malondialdehyde content of soybean. Moreover, the activities of H⁺-ATPase and Ca²⁺-ATPase were significantly higher in treated soybean than in the control, and the content of ATP was also higher in treated soybean than in the control. Generally, PMO regulates the homeostasis of reactive oxygen species and reduces ATP consumption, thereby improving the ability of soybeans to germinate under salt stress. This study provides new insights into how nanomaterials improve plant salt tolerance.

To study the optimal plant row configuration of the multiple cropping of soybeans that are suitable for planting in southern Xinjiang, a field experiment using soybean variety SN35 was carried out employing different plant row designs. Three row spacing treatments of 15 cm (H1), 30 cm (H2), and 45 cm (H3) and three density treatments of 52.56 million (M1), 55 million (M2), and 60 million (M3) plants per hectare were set up in this experiment to explore the effects of different plant row spacing configurations on agronomic traits, photosynthetic characteristics, dry matter accumulation, and the soybean yield of the multiple cropping of soybeans. The results showed that the soybeans’ plant height, diameter, main stem node number, leaf shape index, leaf area index (LAI), leaf area duration (LAD), and pod dry matter distribution ratio increased gradually with the growth process. In contrast, the stem dry matter distribution ratio decreased gradually, and the leaf dry matter distribution ratio first increased and then decreased. The plant height of the soybeans treated with H2M3 was the highest, reaching 67.38 cm. The number of primary stem nodes of the soybeans treated with H1M3 was the highest, reaching 12.7 nodes. The stem diameter of the soybeans treated with H1M1 was the highest, reaching 0.64 cm. The leaf shape index of the soybeans treated with H3M1 was the highest, reaching 2.72. Intercellular CO₂ concentration closely affects the final yield; the correlation coefficients with the pod number per plant, seed number per plant, and yield reached 0.75, 0.78, and 0.87, respectively. The theoretical maximum hundred-grain weights under the H1M1 and H2M1 treatments were higher, reaching 20.33 g and 17.98 g, respectively. The H3M3 treatment had the most significant one-hundred-grain weight, reaching 21.27 g. The soybean yield of each density treatment was M3 > M1 > M2. With the increase in row spacing, the average pod number per plant, grain number per plant, grain weight per plant, and yield of soybeans decreased gradually, and the hundred-grain weight increased gradually. The yield of the density treatment with 60 million plants per hectare under 15 cm row spacing was the highest, reaching 6155.8 kg·hm⁻², followed by the density treatment with 60 million plants per hectare under 30 cm row spacing, reaching 5850.6 kg·hm⁻².