BMC Plant Biology最新文献

Background: Soil salinity severely limits plant growth and agricultural productivity. 5-Aminolevulinic acid (ALA), a precursor in tetrapyrrole biosynthesis, has been reported to alleviate salinity stress and is frequently proposed as a key component by which purple non-sulfur bacteria enhance plant stress tolerance. This study compared the treatments of three Rhodopseudomonas palustris strains (PS3, TPN1, and YSC3) with ALA under salinity stress to understand the importance of ALA production for their potential ability to alleviate salinity stress, using Arabidopsis thaliana, a salt-sensitive model plant in which NaCl concentrations above 30 mM induce growth inhibition and physiological stress responses, making it well suited for assessing salinity tolerance mechanisms.

Results: Both bacterial and ALA treatments increased the photosynthetic efficiency, root growth, relative water content, and oxidative balance of salt-stressed plants. These treatments maintained chlorophyll biosynthetic capacity and modulation of ion transport-related responses, consistent with improved ionic homeostasis under salinity stress. Among the strains, TPN1 performed the best, exhibiting altered expression of antioxidant genes, reduced lipid peroxidation, and decreased electrolyte leakage, which indicates improved membrane integrity. The outcomes were associated with the ability of TPN1 to maintain halotolerance and key plant growth-promoting traits, including the production of extracellular polysaccharides and indole-3-acetic acid, under high salinity. Notably, strains with comparatively lower extracellular ALA outputs conferred benefits comparable to those observed with ALA treatment, suggesting that plant stress mitigation is not solely dependent on ALA concentration.

Conclusions: We identified ALA-producing R. palustris strains, particularly TPN1, that help enhance plant tolerance to salinity through coordinated changes in ion regulation, antioxidant balance, and photosynthetic performance, and demonstrate that ALA production may not be the primary factor contributing to R. palustris' enhancement of plant salt tolerance.

Salinity stress severely limits cucumber (Cucumis sativus L.) productivity by disrupting growth, photosynthesis, and ion homeostasis. This study investigated the potential of foliar-applied allantoin (1 mM) and citrulline (1 mM) to enhance salinity tolerance in hairy cucumber, a salt-sensitive Iranian landrace. A completely randomized design factorial experiment with three replications tested salinity levels (0, 50, 100 mM NaCl) and foliar treatments (control, allantoin, citrulline, and their combination). The results showed that salinity reduced plant height, dry weight, chlorophyll content (SPAD, Fv/Fm), and relative water content (RWC) while increasing electrolyte leakage (EL), oxidative markers (MDA, H₂O₂), and Na⁺ accumulation. Allantoin mitigated these effects by enhancing nitrogen (N) metabolism, improving K⁺/Na⁺ homeostasis, and upregulating osmolyte (proline, sugars) and antioxidant (phenolics, ascorbic acid) accumulation. Citrulline boosted nitric oxide (NO) production, which reduced Na⁺ toxicity, improved stomatal conductance, and activated enzymatic antioxidants (SOD, APX). Their combined application synergistically improved growth (44.24% in yield), photosynthesis (5.12% in Fv/Fm), and RWC (6.45%) while reducing H₂O₂ (61.53%) and oxidative stress (43.74% MDA). Notably, salt-stressed plants treated with both compounds exhibited elevated fruit levels of health-promoting metabolites (cucurbitacin, citrulline). Moreover, allantoin enhanced N assimilation and polyamine-mediated membrane stability, while citrulline-derived NO optimized ion transport and ROS scavenging. These findings highlight the dual role of allantoin (N metabolism) and citrulline (NO signaling) in conferring salt tolerance and propose their combined foliar application as a sustainable strategy for improving cucumber resilience in saline agriculture.

Soil salinity threatens global agriculture by impairing plant growth, crop productivity, and soil health. This study was conducted to assess the impact of salinity on chickpea performance at the vegetative stage and the possible ameliorating role of arbuscular mycorrhizal fungi (AMF) and proline applications. A greenhouse experiment with 30 pots (5 replicates × 6 treatments) subjected half the treatments to 200 mM NaCl, AMF was applied at sowing, and proline was sprayed two weeks post-planting. Total pigments dramatically decreased [49.18%] in salt-stressed chickpea. Biomass, protein and carbohydrate metabolism were also affected. For instance, plant height and total fresh weight (TFW) showed inhibitions of 37.83% and 72.19% as compared to control. Conversely, chickpea under salt stress had an increased accumulation of H₂O₂ (13.12 mg/g DW) and higher electrolyte leakage (54.72%), however, proline or AMF supplementation decreased their levels. Also, the total protein content and antioxidant enzymes were higher in salt-stressed treatments. Under stress, the total carbohydrate contents in chickpea leaves were significantly enhanced by AMF inoculation (23.44%) and proline application (19.43%), when compared to the control. Moreover, salinity led to distortion of chickpea leaf anatomy including a decrease in upper and lower epidermis thickness, vessel numbers, as well as degradation of palisade and spongy parenchyma. Salinity also disrupted ion balance, increasing Na⁺ and decreasing K⁺ (lower K⁺/Na⁺ ratio), which elevated H₂O₂ levels and membrane leakage. These results revealed that AMF as a symbiotic microorganism and proline as a well-known osmoprotectant perform several tasks to alleviate NaCl stress by decreasing Na⁺ uptake, H₂O₂ content and membrane leakage. Subsequently, an enhancement in growth criteria, pigment fraction and carbohydrates was achieved with their applications under NaCl stress. Most obviously their applications maintained the chickpea leaf anatomy. As an innovative approach, we propose that AMF inoculation or proline application can reverse salinity-induced damage, offering a pathway to enhance crop tolerance in salt-affected regions.