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Introduction: The escalating threat of drought poses a significant challenge to sustainable food production and human health, as water scarcity adversely impacts various aspects of plant physiology. Maize, a cornerstone in staple cereal crops, faces the formidable challenge of drought stress that triggers a series of transformative responses in the plant. Methods: The present study was carried out in two sets of experiments. In first experiment, drought stress was applied after maintaining growth for 45 days and then irrigation was skipped, and plant samples were collected at 1st, 3rd and 6th day of drought interval for evaluation of changes in plant growth, water relation (relative water content) and antioxidants activity by inoculating indigenously isolated drought tolerant biofilm producing rhizobacterial isolates (Bacillus subtilis SRJ4, Curtobacterium citreum MJ1). In the second experiment, glycine betaine was applied as osmoregulator in addition to drought tolerant PGPR to perceive modulation in photosynthetic pigments (Chlorophyll a and b) and plant growth under varying moisture stress levels (100, 75 and 50% FC). Results and discussion: Results of the study revealed upsurge in root and shoot length, fresh and dry biomass of root and shoot besides increasing chlorophyll contents in water stressed inoculated plants compared to uninoculated plants. Glycine betaine application resulted in an additional boost to plant growth and photosynthetic pigments, when applied in combination with bacterial inoculants. However, both bacterial inoculants behaved differently under drought stress as evident from their biochemical and physiological attributes. Isolate SRJ4 proved to be superior for its potential to express antioxidant activity, leaf water potential and relative water contents and drought responsive gene expression while isolate MJ1 showed exclusive increase in root dry biomass and plant P contents. Though it is quite difficult to isolate the bacterial isolates having both plant growth promoting traits and drought tolerance together yet, such biological resources could be an exceptional option to be applied for improving crop productivity and sustainable agriculture under abiotic stresses. By exploring the combined application of PGPR and glycine betaine, the study seeks to provide insights into potential strategies for developing sustainable agricultural practices aimed at improving crop resilience under challenging environmental conditions. [ABSTRACT FROM AUTHOR]

Potassium (K) deficiency is becoming a major productivity constraint in semi-arid agriculture. It is an essential mineral nutrient that has key role in various plant physiological and biochemical functions. Balanced nutrient application always tends to ensure better plant growth and development. Therefore, in the present study, efficacy of different K fertilizers for mediating maize plant growth and productivity in the presence and absence of KSB inoculant was assessed. A potassium solubilizing rhizobacterial strain, Klebsiella oxytoca KSB-17, was used in a 5 × 2 factorial pot experiment involving maize plant. The treatments comprised of control, waste mica (WM), K chemical fertilizer (KCF), WM-enriched compost (WMEC) and KCFenriched compost (KCFEC). Compared to control treatment, KCF fertilization increased all plant physiological parameters both in presence and absence of KSB inoculation. From the results obtained, KCFEC followed by CF alone with KSB, demonstrated the most pronounced effect with significant increase in plant height (50%), shoot biomass (59%), root biomass (73%), root length (92%), plant K uptake (154%), grain starch (16%), protein (31%), oil content (22%) as well as photosynthetic rate (104%), transpiration rate (30%) and water use efficiency (54%) compared to control. Potassium solubilizing bacteria (KSB) prompted down-regulation of plant antioxidant enzyme activities against all K fertilizer treatments. Compared to control treatment, catalase (CAT) activity decreased significantly on application of KCF as well as with KCFEC in the presence of KSB inoculation. Regardless of KSB inoculation, plant growth, physiological, antioxidant and K nutritional traits showed slight improvement with either of WM fertilizers compared to control. Our findings concluded that K enriched compost with efficient KSB inoculant can be used to enhance maize growth and productivity in semi-arid agroecosystems. [ABSTRACT FROM AUTHOR]

Dry land soils from the Indo-Gangetic plains are inherently poor in organic matter content and phosphorus (P). Amendment of these soils with P-enriched compost, together with P solubilizing rhizobacterial (PSR) inoculation has been suggested to improve plant growth and P uptake. We performed 3 × 2 factorial experiment using compost i.e. control, raw saw dust P compost (RPC) and acidified saw dust P compost (APC), and PSR inoculation as factors. The pot study investigated the effects of compost and PSR on maize growth, yield, P nutrition and soil biochemical properties. PSR inoculation with APC enhanced shoot length, cob diameter, grain yield and plant P uptake compared to control. APC amendment, either alone or in combination with PSR, also improved root growth and caused extension of rhizosphere by increasing the root length density of the maize plants. Significant improvement in soil biochemical properties i.e. dehydrogenase (DHA), β-glucosidase (BGA), urease (UA) activity, dissolved organic carbon (DOC), soil organic carbon (SOC) and microbial biomass carbon (MBC) are due to the additive effect of compost amendments. A substantial increase in P availability and associated biochemical attributes reflect the significance of substrate quality, structural stability and optimized pH conditions of added compost that may have enhanced PSR performance, specifically with APC. Moreover, increased carboxylate secretions and PSR abundance in the root zone, lowering of pH and increase in rhizosphere fungal parameters, suggest PSR and APC to be synergetic driving of increased P availability for maize. We conclude that efficiency of P enriched compost could be increased with suitable compost additive in the presence of PSR in dry land soil. [ABSTRACT FROM AUTHOR]

Heavy metal contamination of agricultural soil has become a serious global problem. This study was aimed to evaluate the effects of two chromium (Cr) tolerant plant growth promoting bacteria (PGPB) in combination with salicylic acid (SA) on plant growth, physiological, biochemical responses and heavy metal uptake under Cr contamination. A pot experiment (autoclaved sand as growing medium) was performed using maize ( Zea mays L.) as a test crop under controlled conditions. Cr toxicity significantly reduced plant growth, photosynthetic pigment, carbohydrates metabolism and increased H 2 O 2 , MDA, relative membrane permeability, proline and Cr contents in maize leaves. However, inoculation with selected PGPB ( T2Cr and CrP450 ) and SA application either alone or in combination alleviated the Cr toxicity and promoted plant growth by decreasing Cr accumulation, H 2 O 2 and MDA level in maize. Furthermore, dual PGPB inoculation with SA application also improved plant performance under Cr-toxicity. Results obtained from this study indicate that PGPB inoculation and SA application enhanced Cr tolerance in maize seedlings by decreasing Cr uptake from root to shoot. Additionally, combination of both PGPB and SA also reduced oxidative stress by elevating the activities of enzymatic and non-enzymatic antioxidant, also indicated by improved carbohydrate metabolism in maize plant exposed to Cr contamination. Comparatively, alleviation effects were more pronounced in PGPB inoculated plants than SA applied plants alone. The results suggest that combined use of PGPB and SA application may be exploited for improving production potential of maize in metal (Cr) contaminated soil. [ABSTRACT FROM AUTHOR]

Soil salinity is one of the most pernicious environmental hazards affecting crop growth and productivity in arid and semi-arid climates. In saline soils, the crop plants encounter nutrients deficient conditions mainly due to antagonistic affinity of sodium (Na+) and chloride (Cl−). The accumulation of salts in the rhizosphere restricts plant growth, the severity of which depends on the source and concentration of the salt. Therefore, we hypothesized that sodium containing salts could have toxic effects on maize plants either in a single or in combined form. To evaluate the interactive effect of sodium salts on plant growth, ionic homeostasis, and seed quality attributes, a pot study was performed using maize as a test plant at the research area of the College of Agriculture, University of Sargodha. Selected salts including, NaCl, Na 2 SO 4 and their combination (NaCl + Na 2 SO 4), were applied in equal ratio for different salinity levels (7, 10, 13 and 16 dS m−1) and the untreated control. The results show that all the measured growth, yield, biochemical and quality attributes of maize were negatively affected with increasing concentration of all the salt sources; however, severity of these effects were more intense when NaCl was applied at all salinity levels. It is concluded that all salts (NaCl, Na 2 SO 4 and NaCl + Na 2 SO 4) had negative effects on biochemical, qualitative, growth and yield characteristics of maize plant. Most importantly, NaCl was found to be more harmful compared to Na 2 SO 4 and mixtures of both salts due to the dominance of Na+ and Cl-ions. Among all salinity levels, the more detrimental effects of NaCl occurred at salinity level of 16 dS m−1. [Display omitted] • A pot study was established for evaluation of salinity sources and their formulations at different levels. • Higher salinity increased the Na: K ratio in maize tissues, and caused reduction in yield. • NaCl was more toxic than Na 2 SO 4 for maize and mixture of both at all salinity levels. [ABSTRACT FROM AUTHOR]