Onion plants (Allium cepa L.) react differently to salinity levels according to the regulation of aquaporins

Identification of organic pollutants and heavy metals in natural rubber wastewater and evaluation its phytotoxicity and cytogenotoxicity

The natural rubber industry consumes large volumes of water and annually releases wastewater with rich organic and inorganic loads. This wastewater is allowed for soil irrigation in developing countries. However, the pollutant composition in wastewater and its environmental effects remain unclear. Therefore, we aimed to assess the wastewater's physicochemical parameters, toxic organic pollutants, heavy metals, and phytotoxic and cytogenotoxic. The result revealed that values of comprehensive wastewater parameters were recorded as chemical oxygen demand (187432.1 mg/L), pH (4.23), total nitrogen (1157.1 mg/L), ammonia nitrogen (1113.0 mg/L), total phosphorus (1181.2 mg/L), Zn (593.3 mg/L), Cr (0.6127 mg/L), and Ni (0.2986 mg/L). The organic compounds detected by LC-MS were salbostatin, sirolimus, Gibberellin A34-catabolite, 1-(sn-glycero-3-phospho)-1D-myo-inositol, and methyldiphenylsilane. The toxicity of the identified toxic chemicals and heavy metals was confirmed by onion and mung bean phytotoxicity characterization tests. The wastewater affected the germination of mung bean seeds, reduced or inhibited the growth of onions, and induced various chromosomal aberrations in root apical meristems. Our study shows that the treatment of natural rubber wastewater needs to be improved, and the feasibility of irrigating soil with wastewater needs to be reconsidered.

The differential expressions of aquaporins underline the diverse strategies of cucumber and tomato against salinity and zinc stress

Salinity and excess zinc are two main problems that have limited agriculture in recent years. Aquaporins are crucial in regulating the passage of water and solutes through cells and may be essential for mitigating abiotic stresses. In the present study, the adaptive response to moderate salinity (60 mM NaCl) and excess Zn (1 mM ZnSO4 ) were compared alone and in combination in Cucumis sativus L. and Solanum lycopersicum L. Water relations, gas exchange and the differential expression of all aquaporins were analysed. The results showed that cucumber plants under salinity maintained the internal movement of water through osmotic adjustment and the overexpression of specific PIPs aquaporins, following a "conservation strategy". As tomato has a high tolerance to salinity, the physiological parameters and the expression of most aquaporins remained unchanged. ZnSO4 was shown to be stressful for both plant species. While cucumber upregulated 7 aquaporin isoforms, the expression of aquaporins increased in a generalized manner in tomato. Despite the differences, water relations and transpiration were adjusted in both plants, allowing the RWC in the shoot to be maintained. The aquaporin regulation in cucumber plants facing NaCl+ZnSO4 stress was similar in the two treatments containing NaCl, evidencing the predominance of salt in stress. However, in tomato, the induced expression of specific isoforms to deal with the combined stress differed from independent stresses. The results clarify the key role of aquaporin regulation in facing abiotic stresses and their possible use as markers of tolerance to salinity and heavy metals in plants.

Combined Soil Microorganism Amendments and Foliar Micronutrient Nanofertilization Increased the Production of Allium cepa L. through Aquaporin Gene Regulation

The aim of this study was to investigate the impact of changes in aquaporin expression on the growth of onion (Allium cepa L.) plants when subjected to dual applications of microorganism-based soil amendments and foliar nanoencapsulated mineral nutrients. Multiple physiological parameters related to water, gas exchange, and nutrient content in leaf, root, and bulb tissues were determined. Additionally, the gene expression of aquaporins, specifically PIP1, PIP2 (aquaporin subfamily plasma membrane intrinsic protein), and TIP2 (aquaporin subfamily tonoplast intrinsic protein), was analyzed. The findings revealed that the foliar application of nutrients in a nanoencapsulated form significantly enhanced nutrient penetration, mobilization, and overall plant growth to a greater extent than free-form fertilizers. Amendments with microorganisms alone did not promote growth but influenced the production of secondary metabolites in the bulbs. The combination of microorganisms and nanoencapsulated mineral nutrients demonstrated synergistic effects, increasing dry matter, mineral content, and aquaporin gene expression. This suggests that aquaporins play a pivotal role in the transport of nutrients from leaves to storage organs, resulting in the overexpression of PIP2 aquaporins in bulbs, improved water uptake, and enhanced cell growth. Therefore, the combined treatment with microorganisms and nanoencapsulated mineral nutrients may be an optimal approach for enhancing onion productivity by regulating aquaporins under field conditions.