As natural plant growth stimulators, amino acids are widely used to improve the yield and quality of crops. Several studies have illustrated the effects of different amino acids on lettuce plant parts. However, the effects of applying single amino acids on root growth remain elusive. The objective of this study was to evaluate the effect of root application of L-methionine on the growth of lettuce. In this study, two successive experiments on butterhead lettuce were conducted under hydroponic conditions. Three amino acids, L-methionine (20 mg/L), L-glycine (210 mg/L), and L-tryptophan (220 mg/L), were applied separately. L-methionine significantly increased the growth performance by 23.60%, whereas growth using L-tryptophan and L-glycine decreased by 98.78% and 27.45%, respectively. Considering the results of the first experiment, a second experiment was established with different concentrations of L-methionine (2200 mg/L, 220 mg/L, 22 mg/L, 2.2 mg/L, 0.2 mg/L, and 0.02 mg/L). The plants were allowed to grow for four weeks. Leaf width, plant area, leaf area, chlorophyll contents, etc., were evaluated. The results show that plant growth significantly improved by applying L-methionine at the lowest concentrations of 0.2 mg/L and 0.02 mg/L, which can, therefore, improve hydroponic production of lettuce and, accordingly, human nutrition.

Excessive application of fertilizers has become a major issue in croplands of intensive agricultural systems in China, resulting in severe non-point source pollution; thus, reduction in the use of chemical fertilizers has received significant attention. Improving the nutrient storage capacity of soils or substrates is an effective approach for solving this problem. Humic acids (HA) are excellent soil conditioners. Thus, in the present study, their ability to improve the physico-chemical properties of three substrates with different textures was evaluated. HA treatments included 1% HA root application in three different types of substrates, including pure sand, pure cocopeat, and a mixture of sand:cocopeat (1:1, v/v) and their relative controls. We examined the morphological parameters of cucumber seedlings as well as pH buffering capacity (pHBC), total organic carbon (TOC), organic matter (OM), cation exchange capacity (CEC), and nutrient storage capacity of the three substrates. The results show that HA application improved the morphological parameters of cucumber seedlings (plant height, stem diameter, and biomass) in pure cocopeat and cocopeat-sand mixture treatments. On the contrary, HA addition had harmful effects on the cucumber seedlings cultivated in sand due to the low pHBC of sand. The seedlings cultivated in pure cocopeat showed the best morphological parameter performances among the seedlings grown in the three substrates. Furthermore, pHBC, TOC, OM, and CEC were enhanced by HA application. Incorporation of HA improved ammonium (NH₄⁺) and potassium (K⁺) storage capacity while decreasing phosphorus (P) storage. Pure cocopeat had the highest pHBC, TOC, OM, CEC, and nutrient storage capacity among the three substrates. In conclusion, mixing 1% HA into substrates promoted cucumber growth, improved substrate properties, and enhanced fertilizer use efficiency. Pure cocopeat is a suitable substrate for cucumber cultivation, and mixing cocopeat with sand amends the substrate properties and consequently improves plant growth.

Cucumber, a widely cultivated vegetable, is mostly grown under greenhouse conditions. In recent years, the overuse of inorganic fertilizers for higher yield attainment adversely has affected human health and the environment. Therefore, a greenhouse experiment was designed to evaluate the effects of different nutrient sources (poultry manure (PM) and mineral fertilizer (MF)) on productivity-enhancing parameters of cucumber via univariate and multivariate analyses. Amounts of PM and MF (NPK15:15:15) were added to coco-peat per cubic meter by weight/volume (w/v) ratios as follows: T₁ (control), 60 kg PM; T₂, 30 kg PM + 3 kg MF; T₃, 30 kg PM + 5 kg MF, and T₄, 30 kg PM + 7 kg MF. The univariate analysis performed on the collected data illustrated the significant enhancement in growth and productivity for the integrated use of PM and MF. Multivariate analyses (correlation, clustering, and Principal Component Analysis) validated the results of univariate analysis by differentiating treatments into two groups. The three treatments obtained a distinguished group from T₁ (Control) and did not show significant differences among each other, with a maximum yield increase by T₂ (74.6%). According to these results, T₂ could improve cucumber productivity under greenhouse conditions. It can be taken as recommendations for better quality and yield enhancement in future improvement programs and cucumber-related farming communities.

Tomato flower abscission is a critical agronomic problem directly affecting yield. It often occurs in greenhouses in winter, with the weak light or hazy weather leading to insufficient photosynthates. The importance of carbohydrate availability in flower retention has been illustrated, while relatively little is understood concerning the mechanism of carbohydrate regulation on flower abscission. In the present study, we analyzed the responding pattern of nonstructural carbohydrates (NSC, including total soluble sugars and starch) and the potential sugar signal pathway involved in abscission regulation in tomato flowers under shading condition, and their correlations with flower abscission rate and abscission-related hormones. The results showed that, when plants suffer from short-term photosynthesis deficiency, starch degradation in flower organs acts as a self-protection mechanism, providing a carbon source for flower growth and temporarily alleviating the impact on flower development. Trehalose 6-phosphate (T6P) and sucrose non-fermenting-like kinase (SnRK1) signaling seems to be involved in adapting the metabolism to sugar starvation stress through regulating starch remobilization and crosstalk with IAA, ABA, and ethylene in flowers. However, a continuous limitation of assimilating supply imposed starch depletion in flowers, which caused flower abscission.

Soilless cultivation is an important alternative to traditional agriculture and facilitates harvest by allowing for the precise control of plant nutrients to maximize the vegetable production of uniform fruits. Nutrient solution concentration is a critical factor affecting nutrient supply in soilless cultivation. Although some nutrient solution concentrations throughout the growth cycle for tomatoes have been developed, there are limited studies on nutrient solution concentrations at different phenological stages. Hence, we studied the effects of nutrient solution concentrations in different growth stages on the physiology, yield and fruit quality of cherry tomatoes with a previously developed nutrient solution formulation. The whole growth cycle of the tomato was divided into three stages which were irrigated with a nutrient solution with different electrical conductivities (ECs). A total of five treatments were set: CK (EC was 3.0 ms·cm⁻¹ for the 1st–3rd stage), T1 (EC was 1.5 ms·cm⁻¹ for the 1st stage, 3.0 ms·cm⁻¹ for the 2nd–3rd stage), T2 (EC was 1.5 ms·cm⁻¹ for the 1st stage, 3.0 ms·cm⁻¹ for the 2nd stage, 4.5 ms·cm⁻¹ for the 3rd stage ), T3 (EC was 1.5 ms·cm⁻¹ for the 1st–2nd stage, 3.0 ms·cm⁻¹ for the 3rd stage), and T4 (EC was 1.5 ms·cm⁻¹ for the 1st stage, 4.5 ms·cm⁻¹ for the 2nd–3rd stage). The results showed that the tomato plants treated with T2 and T4 had the strongest growth (with the highest plant height and leaf formation) as well as the best leaf photosynthetic performance (the chlorophyll content and the net photosynthetic rate were significantly increased). Additionally, the use of T2 and T4 significantly improved cherry tomato fruit quality as reflected by the significant promotion of total soluble solids by 9.1% and 9.8%, respectively, as well as by the improvement of maturity by 12.9% and 13.7%, respectively. Additionally, the yields for treatments T2 and T4 were increased by 7.3% and 13.4%, respectively, which was mainly due to the increase in single fruit weight. More importantly, nutrient solution EC management improved fertilizer use efficiency: the partial fertilizer productivity of T1, T2, and T4 was increased by 2%, 7% and 14%, respectively, while that of T3 was reduced by 7%. A comprehensive comparison showed that the ranking of the effect on production was T4 > T2 > T1 > CK > T3. Our results suggest that the regulation of EC in different growth stages affects the growth and yield characteristics of cherry tomatoes. This study may provide some references for further research to adjust the concentration of nutrient solutions to improve the utilization rate of fertilizer and fruit quality.

The development of cost-effective and eco-friendly fertilizers is crucial for enhancing iron (Fe) uptake in crops and can help alleviate dietary Fe deficiencies, especially in populations with limited access to meat. This study focused on the application of MgFe-layered double hydroxide nanoparticles (MgFe-LDHs) as a potential solution. We successfully synthesized and characterized MgFe-LDHs and observed that 1–10 mg/L MgFe-LDHs improved cucumber seed germination and water uptake. Notably, the application of 10 mg/L MgFe-LDHs to roots significantly increased the seedling emergence rate and growth under low-temperature stress. The application of 10 mg/L MgFe-LDHs during sowing increased the root length, lateral root number, root fresh weight, aboveground fresh weight, and hypocotyl length under low-temperature stress. A comprehensive analysis integrating plant physiology, nutrition, and transcriptomics suggested that MgFe-LDHs improve cold tolerance by upregulating SA to stimulate CsFAD3 expression, elevating GA₃ levels for enhanced nitrogen metabolism and protein synthesis, and reducing levels of ABA and JA to support seedling emergence rate and growth, along with increasing the expression and activity of peroxidase genes. SEM and FTIR further confirmed the adsorption of MgFe-LDHs onto the root hairs in the mature zone of the root apex. Remarkably, MgFe-LDHs application led to a 46% increase (p < 0.05) in the Fe content within cucumber seedlings, a phenomenon not observed with comparable iron salt solutions, suggesting that the nanocrystalline nature of MgFe-LDHs enhances their absorption efficiency in plants. Additionally, MgFe-LDHs significantly increased the nitrogen (N) content of the seedlings by 12% (p < 0.05), promoting nitrogen fixation in the cucumber seedlings. These results pave the way for the development and use of LDH-based Fe fertilizers. Graphical Abstract