Grafting improves tomato yield under low nitrogen conditions by enhancing nitrogen metabolism in plants.

To alleviate the effects of increasingly severe environmental conditions and meet the increasing demand for organic agricultural products, this paper studied tomato grafting under low nitrogen conditions in an effort to enhance yield and improve fruit quality by enhancing nitrogen metabolism. In this study, we screened for two tomato genotypes, a high nitrogen use efficiency genotype ('TMS-150') and a low nitrogen use efficiency genotype ('0301111'), using rootstocks from 25 tomato genotypes and studied the effects of tomato grafting on plant yield, fruit quality, nitrogen content, activities of key nitrogen metabolism enzymes, and nitrogen use efficiency (NUE) under different nitrogen fertilizer conditions. The results showed that the yield of the tomato plants, the activities of key enzymes during nitrogen metabolism, the contents of different forms of nitrogen, and the efficiency of nitrogen use were lower at low nitrogen fertilization levels and higher at higher nitrogen fertilization levels, while the measured indicators were the highest under the N40 nitrogen fertilizer treatment. Grafting tomatoes with high-NUE tomato seedlings as the rootstock resulted in significant increases in the nitrogen content and the activity of key enzymes, enhanced the NUE of tomato plants, increased tomato yield, and improved fruit quality compared to those of the seedlings grafted with low-NUE rootstock. Our results indicate that tomato plants grafted with high-NUE rootstock presented enhanced absorption and utilization of nitrogen and increased plant yield by promoting nitrogen metabolism at different nitrogen levels.

Silicon restrains drought-induced ROS accumulation by promoting energy dissipation in leaves of tomato.

Energy dissipation plays a crucial role in mediating responses to oxidative stress in plants. Although the beneficial effects of silicon on plant resistance to drought stress have been well documented, the potential interactions between energy dissipation and Si in response to drought stress have not been examined. Here, a project was initiated that focused on the relationship between energy dissipation and the functions of Si. In this study, silicon-mediated proteins promoted the consumption of light energy capture and NPQ in chloroplasts. Additionally, we confirmed that the role of silicon-mediated energy dissipation in mitochondria was important for photosynthetic optimization. The energy dissipation in mitochondria was improved, which further optimized the energy dissipation in chloroplasts via Si-mediated alternative oxidase and the malate/oxaloacetate shuttle. ROS accumulation decreased because of the silicon-mediated energy dissipation.

Silicon-mediated changes in radial hydraulic conductivity and cell wall stability are involved in silicon-induced drought resistance in tomato.

Plants frequently experience drought stress. It is well known that silicon (Si) facilitates recovery from drought stress by improving drought resistance in plants. However, the effects of Si on the roots associated with the drought resistance in plants remain elusive. In this study, tomato (cv. 'Jinpeng 1#') was adopted to study the silicon-mediated drought avoidance and drought tolerance. The results showed that exogenous Si evidently influenced the drought-induced changes of the related indicators. Roots added with Si were more adaptable to drought stress. Silicon was involved in improving hydraulic conductivity in radial direction, which enhanced water uptake of tomato roots. Si also maintained solute accumulation at a high level, such as proline, soluble sugar, and soluble protein, and the osmotic adjustment ability of root was improved. So silicon promoted the drought avoidance by improving water absorption and water situation in tomato root. In addition, silicon enhanced antioxidant activities, including SOD activity and CAT activity, and reduced O2¯ production rate, H2O2 content, and malondialdehyde content, which contributed to alleviate harmful effects of drought and mitigate drought-induced cell wall rupture. Therefore, via induction of antioxidant activities, detoxification of the ROS, and maintenance of cell wall stability in tomato roots, silicon contributed to the drought tolerance. Though the silicon-mediated drought avoidance and drought tolerance can maintain physiological activities of tomato at relatively lower water potential, the maximal duration at which Si induced drought resistance was 3 or 5 days. When drought stress was for too long time, which exceeded the self-regulation of the tomato, mitigative effects of Si were weakened.