Pitaya (Hylocereus polyrhizus L.) is highly tolerant to drought stress. Elucidating the response mechanism of pitaya to drought will substantially contribute to improving crop drought tolerance. In the present study, the physiological and proteomic responses of the pitaya cultivar ‘Zihonglong’ were compared between control seedlings and seedlings exposed to drought stress (−4.9 MPa) induced by polyethylene glycol for 7 days. Drought stress obviously enhanced osmolyte accumulation, lipid peroxidation, and antioxidant enzyme activities. Proteomic data revealed drought stress activated several pathways in pitaya, including carbohydrate and energy metabolism at two drought stress treatment time-points (6 h and 3 days). Other metabolic pathways, including those related to aspartate, glutamate, glutathione, and secondary metabolites, were induced more at 3 days than at 6 h, whereas photosynthesis and arginine metabolism were induced exclusively at 6 h. Overall, protein expression changes were consistent with the physiological responses, although there were some differences in the timing. The increases in soluble sugar contents mainly resulted from the degradation and transformation of insoluble carbohydrates. Differentially accumulated proteins in amino acid metabolism may be important for the conversion and accumulation of amino acids. GSH and AsA metabolism and secondary metabolism may play important roles in pitaya as enzymatic and nonenzymatic antioxidant systems. The enhanced carbohydrate and energy metabolism may provide the energy necessary for initiating the above metabolic pathways. The current study provided the first proteome profile of this species exposed to drought stress, and may clarify the mechanisms underlying the considerable tolerance of pitaya to drought stress.

Nitrogen (N) forms include ammonium [NH₄⁺-N], nitrate [NO₃⁻-N], and urea [CO(NH₂)₂]. Urea is the most common nitrogen fertilizer in agriculture due to its inexpensive price and high N content. Although the reciprocal influence between NO₃⁻-N and NH₄⁺-N is well known, CO(NH₂)₂ interactions with these inorganic N forms have been poorly studied. We studied the effects of different nitrogen forms with equal nitrogen on dry matter, yield, enzyme activity, and gene expression levels in cucumber. NO₃⁻-N treatment with equal CO(NH₂)₂ promoted nitrate reduction, urea utilization, and the GS/GOGAT cycle but reduced the nitrate content. UR-2, NR-2, NR-3, NiR, GOGAT-1-1, and GS-4 were upregulated in response to these changes. NH₄⁺-N treatment with equal CO(NH₂)₂ promoted nitrogen metabolism and relieved the ammonia toxicity of pure NH₄⁺-N treatment. UR-2, GOGAT-2-2, and GS-4 were upregulated, and GDH-3 was downregulated in response to these changes. Treatment with both NO₃⁻-N with added equal CO(NH₂)₂ and NH₄⁺-N with added equal CO(NH₂)₂ enhanced the activities of GOGAT, GS, and UR and the amino acid pathway of urea metabolism; manifested higher glutamate, protein, chlorophyll, and nitrogen contents; and improved dry matter weight. A greater proportion of dry matter was distributed to the fruit, generating significantly higher yields. Therefore, the addition of urea to ammonium or nitrate promoted N metabolism and N utilization in cucumber plants, especially treatments with 50% NO₃⁻-N + 50% CO(NH₂)₂, as the recommended nitrogen form in this study.

Purpose of the study: To explore the effects of adding different bacterial agents before fermentation on the Agricultural Jiaosu derived from waste from Chinese cabbage.Material and methods: This study used the waste from Chinese cabbage as the raw material and added Lactobacillus, Acetobacter, Yeast, and Bacillus subtilis respectively for fermentation treatment. Systematic research was conducted on the effects of different bacterial agents on the nutritional elements, microbial diversity, organic acid content of Agricultural Jiaosu, as well as their impacts on the growth and yield of Chinese cabbage.Results: The results showed that there were significant differences in the above aspects among the treatments with different bacterial agents. In terms of nutritional elements, the treatment group with Lactobacillus addition had the highest total carbon, total nitrogen, and total phosphorus contents; the treatment group with Acetobacter addition had the highest total potassium and carbon-nitrogen ratio. Microbial diversity analysis revealed that the relative abundance of Bacteroides was higher in the Lactobacillus treatment group; Arcobacter and Vishniacozyma were relatively more abundant in the Acetobacter and Bacillus subtilis treatment groups; and the relative abundance of Lysinibacillus was higher in the Yeast treatment group. Organic acid content analysis indicated that the benzoic acid content was higher in the Lactobacillus treatment group; the benzenepropanoic acid, azelaic acid, and pyroglutamic acid contents were higher in the Acetobacter treatment group; the succinic acid content was the highest in the Yeast treatment group; and the glutaric acid content was the highest in the Bacillus subtilis treatment group. Moreover, the effects of the Yeast and Acetobacter treatment groups on promoting the growth of Chinese cabbage were more significant.Conclusion and future prospective: In conclusion, Agricultural Jiaosu is rich in abundant nutritional elements, diverse microbial communities, and various organic acids, and has a significant fertilizer effect on Chinese cabbage production. Adding different bacterial agents before fermentation leads to differences in the composition and function of the finished Agricultural Jiaosu products. Therefore, appropriate bacterial agents can be selected for fermentation according to specific application goals to optimize the performance and application effect of Agricultural Jiaosu.

Nitrate nitrogen (NO₃⁻-N) is widely used in the cultivation of the cucumber (Cucumis sativus L.). In fact, in mixed nitrogen forms, partially substituting NO₃⁻-N with NH₄⁺-N can promote the absorption and utilization of nitrogen. However, is this still the case when the cucumber seedling is vulnerable to the suboptimal-temperature stress? It remains unclear as to how the uptake and metabolism of ammonium affect the suboptimal-temperature tolerance in cucumber seedlings. In this study, cucumber seedlings were grown under suboptimal temperatures at five ammonium ratios (0NH₄⁺, 25%NH₄⁺, 50%NH₄⁺, 75%NH₄⁺, 100%NH₄⁺) for 14 days. Firstly, increasing ammonium to 50% promoted the growth and root activity and increased protein and proline contents but decreased MDA content in cucumber seedlings. This indicated that increasing ammonium to 50% enhanced the suboptimal-temperature tolerance of cucumber seedlings. Furthermore, increasing ammonium to 50% up-regulated the expression of the nitrogen uptake-transport genes CsNRT1.3, CsNRT1.5 and CsAMT1.1, which promoted the uptake and transport of nitrogen, as well as the up-regulation of the expression of the glutamate cycle genes CsGOGAT-1-2, CsGOGAT-2-1, CsGOGAT-2-2, CsGS-2 and CsGS-3, which promoted the metabolism of nitrogen. Meanwhile, increased ammonium up-regulated the expression of the PM H⁺-ATP genes CSHA2 and CSHA3 in roots, which maintained nitrogen transport and membranes at a suboptimal temperature. In addition, 13 of 16 genes detected in the study were preferentially expressed in the roots in the increasing ammonium treatments under suboptimal temperatures, which, thus, promoted nitrogen assimilation in roots to the enhance the suboptimal-temperature tolerance of cucumber seedlings.

Tomatoes cultivated in facility agriculture often encounter low-light stress in autumn, winter, and early spring. This study aimed to investigate the effects of supplementary lighting with different spectral compositions dominated by red-blue (RB) light on plant growth, fruit development, and quality formation of early spring facility-grown tomatoes. Six supplementary lighting treatments were set up: red-blue (RB), red-blue + red (RB + R), red-blue + blue (RB + B), red-blue + green (RB + G), red-blue + far-red (RB + FR), and red-blue + ultraviolet A (RB + UVA). The treatment with no supplementary lighting served as the control (CK), and supplementary lighting was provided from 06:00 to 08:30 and from 18:30 to 22:00 daily. The results showed that, compared with CK, supplementary lighting with different spectral compositions significantly promoted plant growth, accelerated fruit ripening, and improved yield and quality (P < 0.05). Compared with the RB treatment, the RB + R treatment significantly increased the number of large fruits and yield per plant by 25.79% and 6.94%, respectively, demonstrating a superior effect on promoting yield formation over other treatments; the RB + B treatment was beneficial for increasing stem diameter and leaf SPAD value, and the contents of vitamin C and soluble protein were significantly higher than those in the RB treatment during the late stage of fruit development (fruit color-breaking stage and mature stage); the RB + G treatment had the highest average fruit weight, which was significantly increased by 8.29% compared with the RB treatment; during the late stage of fruit development, the contents of lycopene, soluble protein, amino acids, and total phenols in the RB + G treatment were significantly higher than those in the RB treatment, and the soluble sugar content and sugar-acid ratio was the highest at the fruit mature stage; the RB + FR treatment significantly increased the contents of soluble protein, soluble sugar, amino acids, and the sugar-acid ratio during the late stage of fruit development, and the fruit color parameters (a^* and b^* values) were significantly higher than those of the RB treatment; the RB + UVA treatment stimulated plant height growth in the short term and significantly increased the contents of soluble protein, soluble sugar, and organic acids during the late stage of fruit development. The results of this study provide a theoretical basis and technical reference for the regulation of the light environment in facility agriculture and the efficient production of facility-grown tomatoes.