Interactive effects of plant growth-promoting rhizobacteria and drought stress on the growth and yield of shallot (Allium ascalonicum L.) cultivated in saline soil

Improving drought tolerance in pre-sprouted sugarcane through inoculation with plant growth-promoting bacteria: assessment of biochemical activity, nutrient uptake, and physiological performance

Pre-sprouted sugarcane seedlings are increasingly used to ensure uniform crop establishment; however, their performance is highly constrained by water deficit under climate change scenarios. This research evaluated whether a consortium of Bacillus licheniformis (FMCH001) and Bacillus subtilis (FMCH002) could mitigate drought stress by improving root development, soil microbial activity, and plant nutritional and physiological responses under different water regimes. The experiment was conducted in a randomized block design using a 4 × 2 factorial scheme, with four water regimes (20, 40, 60, and 80% of field capacity) and two inoculation treatments (with and without bacteria), with four replicates. Bacillus inoculation alleviated the adverse effects of water deficit, particularly under severe water restriction (20, 40, and 60% of field capacity), by increasing root length, surface area, volume, and diameter. Inoculated treatments showed higher arylsulfatase, β-glucosidase, acid phosphatase, and urease activities, indicating enhanced soil microbial functioning. These responses were associated with increased leaf concentrations of N, P, K, Ca, Fe, and Zn. Furthermore, inoculated plants exhibited improved photosynthetic performance, including higher PSII efficiency, electron transport rate, net CO 2 assimilation, water use efficiency, and carboxylation efficiency, contributing to better establishment and development throughout the sugarcane growth cycle. Inoculation with Bacillus subtilis and Bacillus licheniformis mitigated the effects of water deficit in pre-sprouted sugarcane seedlings by promoting root development, enhancing soil microbial activity, and increasing nutrient acquisition, thereby improving plant mineral nutrition and photosynthetic performance.

Physiological and molecular responses of lentil to plant growth-promoting rhizobacteria (PGPR) inoculation and targeted foliar application of melatonin and spermidine under dryland drought stress

Growth and physiological responses of potato plantlets (Solanum tuberosum L. cv. Cipanas) to NaCl-induced salinity stress under in vitro conditions

Potato (Solanum tuberosum L. cv. Cipanas) is a high-yielding cultivar; however, its cultivation is often limited by salinity stress in marginal lands, which adversely affects plant growth and development. This study aimed to evaluate the effects of different NaCl concentrations on the growth and physiological responses of in vitro-grown potato plantlets and to determine the maximum salinity level that could be tolerated. The experiment consisted of five NaCl concentrations (0, 0.25, 0.50, 0.75, and 1.00%) arranged in a completely randomized design. Quantitative data were analyzed using one-way analysis of variance (ANOVA), followed by Tukey's honestly significant difference (HSD) test at the 5% significance level. Increasing NaCl concentrations significantly reduced plantlet height, leaf number, and stomatal index, and induced progressive changes in plantlet color from green to yellowish-green and brownish-green. Potato plantlets remained tolerant to NaCl concentrations of 0.25% based on plantlet height and leaf number, whereas tolerance up to 0.50% was observed for plantlet color and stomatal index, with no significant differences compared with the control. These findings indicate that S. tuberosum L. cv. Cipanas exhibits moderate tolerance to NaCl-induced salinity under in vitro conditions.

Salicylic Acid Improves Morpho-Physiological Traits and Biomass of Kale under Drought Stress

Drought stress in agricultural land disrupts the physiological processes, growth, and yield of kale (Brassica oleracea L. var. acephala). This study evaluated the physiological responses, growth, and yield of kale treated with salicylic acid, a potential strategy to enhance plant tolerance to drought stress, in a greenhouse at the Department of Agriculture, Universitas Diponegoro, Semarang. A 4 × 4 factorial experiment was arranged in a Completely Randomized Design (CRD) with three replications. The first factor was drought level (100%, 80%, 60%, and 40% field capacity). The second factor was salicylic acid (SA) concentration 0, 0.75, 1.5, and 2.25 mM). The results indicated that physiological responses (chlorophyll a, chlorophyll b, total chlorophyll, relative water content, and electrolyte leakage) remained largely stable under moderate drought stress (60% FC), whereas plant growth parameters (plant height, leaf number, and leaf area) were reduced by 14.5–20.7% compared with the control (100% FC). At 40% FC, both physiological and growth responses were more severely affected; electrolyte leakage increased markedly, and plant height, leaf area, and dry biomass weight decreased by 24.4%, 47.2%, and 60.5%, respectively, compared with the control (P < 0.05). The best treatment was the application of 1.5 mM salicylic acid, which increased the relative water content by 4.13% and decreased the electrolyte leakage by 34.70% compared to untreated plants (P < 0.05). This concentration was likely more effective due to optimal stomatal regulation, increased antioxidant enzyme activity, and maintained membrane integrity, indicating that 1.5 mM SA has potential as a biostimulant to improve kale water status and membrane stability. However, field validation across locations and seasons is needed before recommending it for dryland farming.

Effects of Solution Applied and Different Encapsulation Method of Plant Growth Promoting Bacteria (PGPB) on the Physiological Response of Sunflower to Drought Stress

: Sunflower ( Helianthus annuus L.) is an important food, oil and bioenergy crop frequently affected by drought stress. Plant growth-promoting bacteria (PGPB) can enhance plant growth and resilience to water deficit. However, their efficiency often diminishes over time under prolonged stress due to reduced bacterial survival. This study investigated whether encapsulated forms of Bacillus subtilis , with and without humic acid supplementation, improves bacterial viability and photosynthetic performance of a drought-sensitive sunflower variety under water deficiency. Seedlings were grown in a greenhouse, with water deficit imposed at 30% field capacity for 29 days. Treatments included solution (B) or encapsulated forms (alginate beads alone (EB) or supplemented with humic acid (HEB)) under well-watered (W) and drought (D) conditions. Encapsulation, particularly with humic acid, increased bacterial viability, mitigating damage to photosynthetic reaction centers as reflected by subsequent morphophysiolog-ical measurements. Under drought, all PGPB treatments enhanced plant height (BD: 15.2%, HEBD: 14.6%, EBD: 6.1% vs. D), above-ground biomass (HEBD and BD significantly higher), Gsw (EBD: 3-fold, HEBD: 10-fold vs. D), Φ PSII (HEBD: 10%, BD: 4% vs. D), ETR (HEBD: 31% vs. D), and ChlF indices like PIABS (BD: 95%, HEBD: 81%, EBD: 53% vs. D). Stable encapsulation without premature release, especially with humic acid, sustained bacterial viability and prolonged benefits by protecting the bacteria against stress, improving root interactions and photosynthetic resilience. These findings demonstrate that encapsulation, particularly with humic acid, optimizes PGPB delivery and sustains physiological benefits under drought, highlighting its strong potential as a strategy for sustainable agriculture in semi-arid regions.

Comparative Efficacy of Seed and Soil Inoculation in Soybean Unveiling the Dominant Role of Soil Microbial Activity in Drought Mitigation

Drought stress severely negatively affects the growth and yield of soybean (Glycine max L.) by causing oxidative damage and suppressing physiological functions. While plant growth-promoting rhizobacteria (PGPR) alleviates these effects, the comparative effectiveness of different inoculation techniques has not been adequately investigated. This study investigated the physiological, biochemical, and soil microbiological responses of drought-stressed soybean (50% field capacity) to two Bradyrhizobium japonicum inoculation methods (conventional seed inoculation (A1) versus direct soil inoculation (A2)). Drought significantly reduced plant biomass, relative water content (RWC), and chlorophyll levels while aggravating markers of oxidative stress (H₂O₂, MDA, and electrolyte leakage). Both inoculation methods reduced drought-induced damage; however, soil inoculation (A2) showed significant superiority. Compared to uninoculated stressed plants, A2 treatment increased fresh and dry weight by 91.7% and 104.3%, respectively, while maximally suppressing lipid peroxidation and preserving cell membrane integrity. Moreover, soil inoculation profoundly increased rhizosphere microbial activity, increasing soil respiration (CO₂) and dehydrogenase activity (DHA) by 110.6% and 86.7%, respectively. In particular, Random Forest machine learning analysis identified soil DHA as the most critical determinant in predicting plant biomass under stress, far outweighing internal oxidative stress indicators. These findings suggest that direct soil inoculation optimizes rhizosphere enzymatic activity and offers a more robust agronomic strategy than seed inoculation for sustainable soybean cultivation in drought-prone regions.