Climate change is causing soil salinization, resulting in crop losses throughout the world. The ability of plants to tolerate salt stress is determined by multiple biochemical and molecular pathways. Here we discuss physiological, biochemical, and cellular modulations in plants in response to salt stress. Knowledge of these modulations can assist in assessing salt tolerance potential and the mechanisms underlying salinity tolerance in plants. Salinity-induced cellular damage is highly correlated with generation of reactive oxygen species, ionic imbalance, osmotic damage, and reduced relative water content. Accelerated antioxidant activities and osmotic adjustment by the formation of organic and inorganic osmolytes are significant and effective salinity tolerance mechanisms for crop plants. In addition, polyamines improve salt tolerance by regulating various physiological mechanisms, including rhizogenesis, somatic embryogenesis, maintenance of cell pH, and ionic homeostasis. This research project focuses on three strategies to augment salinity tolerance capacity in agricultural crops: salinity-induced alterations in signaling pathways; signaling of phytohormones, ion channels, and biosensors; and expression of ion transporter genes in crop plants (especially in comparison to halophytes).

Drought stress not only effect the population and activities of microorganisms inhabiting the rhizosphere but also various physiological and biochemical process in plants that is, photosynthesis, respiration, translocation, uptake of ions, carbohydrates, and nutrient metabolism. Plant growth promoting rhizobacteria (PGPR) and their exopolysaccharides (EPS) showed profound effects on plant growth and drought tolerance. Reactions of bacteria to drought stress at various organizational levels are different which depends on intensity of stress, duration, species, and growth stage. PGPR could be effectively utilized in developing strategies to facilitate water conservation strategies of plants. They have the ability to improve plant growth directly by enhancing level of phytohormones, siderophore, biofilm, and exopolysaccharides production and by increasing the nutrient availability in the rhizosphere or indirectly by protecting plants from pathogen attack. EPS producing bacteria are capable to maintain higher soil moisture content and growth of plants even under severe dried sandy soils. The evidence of survival of rhizobacteria under low moisture content obtained from the fact of rhizobacterial occurrence in the soil of desert and effective nodule formation in desert soil. Beside this, EPS produced by PGPR form rhizosheath around the roots and thus protect the plant roots from desiccation for a longer period of time. Important role exhibited by exopolysaccharides includes, protection from desiccation, microbial aggregation, plant-microbe interaction, surface attachment, bioremediation and its use by many industries for stabilizing, thickening, coagulating, gelling, suspending and for film forming. Plants inoculated with EPS-producing bacteria showed higher accumulation of proline, sugars, and free amino acids under water deficit stress. Biofilms formed by the PGPR around the roots are made up of bacterial populations or bacterial communities that encased inside the polymeric extracellular matrix formed by bacteria itself, they adhered to the external surfaces that contain sufficient moisture. It is concluded that the application of PGPR in combination with their EPS is a promising measure to combat drought stress thus, increasing global food security.

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The present study was aimed to isolate and characterize plant growth promoting rhizobacteria (PGPR) from the rhizosphere of rainfed area (Karak) in Pakistan. The influence of isolated rhizobacteria, in association with salicylic acid (SA), physiological attributes, drought tolerance potential, and phytoremediation in drought-stressed sunflower exposed was investigated. The isolated bacteria were named P1 and P2 and characterized on the basis of colony morphology and biochemical traits. Both PGPR P1 and P2 were identified on the basis of 16S-rRNA gene sequencing as Planomicrobium chinense strain P1 (Accession No. MF616408) and Bacillus cereus strain P2 (Accession No. MF616406). The fresh cultures (24 h old) of isolates were used to soak the seeds pre-sowing. SA was foliar applied at three-leaf-stage. Likewise, the 30-days-old seedlings (three leaf stage) were exposed to drought stress. Drought stress was imposed to 30-days-old plants (three-leaf stage) by withholding water supply for the next 15 days until the soil water content reached 10%. The PGPR and/or SA treatment resulted in significant accumulation of Cd (84%), Pb (66%), and Ni (65%) in the rhizosphere. PGPR also induced accumulation of Cd and Ni in plant shoot. Combined treatment of PGPR and SA increased the Cu (21%), Co (11%), and Zn (8%) accumulation but decreased (12%) the Fe accumulation as compared to coinoculation of PGPR P1 and P2. Inoculation of plants with PGPR significantly increased shoot length (60%), root length (68%), root fresh (61%), and dry (63%) biomass under water stress. The inoculated plants had increased chlorophyll (67%), carotenoid (70%), leaf protein (64%), sugar (64%), and phenolic (62%) contents while lower leaf proline (62%) content, malondialdehyde (MDA) (64%), and antioxidant enzymes (67%) which suggest their role in drought tolerance. It is concluded that integrative use of PGPR in combination with SA found to be an efficacious strategy to improve the phytoremediation of heavy metals and plant growth under stressed conditions particularly under water-deficient conditions.

Abiotic stresses, such as drought, salinity, heavy metals, variations in temperature, and ultraviolet (UV) radiation, are antagonistic to plant growth and development, resulting in an overall decrease in plant yield. These stresses have direct effects on the rhizosphere, thus severely affect the root growth, and thereby affecting the overall plant growth, health, and productivity. However, the growth-promoting rhizobacteria that colonize the rhizosphere/endorhizosphere protect the roots from the adverse effects of abiotic stress and facilitate plant growth by various direct and indirect mechanisms. In the rhizosphere, plants are constantly interacting with thousands of these microorganisms, yet it is not very clear when and how these complex root, rhizosphere, and rhizobacteria interactions occur under abiotic stresses. Therefore, the present review attempts to focus on root–rhizosphere and rhizobacterial interactions under stresses, how roots respond to these interactions, and the role of rhizobacteria under these stresses. Further, the review focuses on the underlying mechanisms employed by rhizobacteria for improving root architecture and plant tolerance to abiotic stresses.

Drought-induced damages in crop plants are ranked at top amid all losses instigated by diverse abiotic stresses. Terminal drought (drought at reproductive phase) has emerged as a severe threat to the productivity of wheat crop. Different seed enhancement techniques, genotypes and distribution of crop plants in different spacings have been explored individually to mitigate these losses; however, their interaction has rarely been tested in improving drought resistance in wheat. This study was conducted to evaluate the potential role of different seed enhancement techniques and row spacings in mitigating the adversities of terminal drought in two wheat cultivars during two consecutive growing seasons of 2010-2011 and 2011-2012. Seeds of wheat cultivars Lasani-2008 (medium statured) and Triple Dwarf-1 (dwarf height) soaked in water (hydropriming) or CaCl 2 (osmopriming) were sown in 20-, 25-and 30-cm spaced rows; just before heading, the soil moisture was maintained at 100 % field capacity (well watered) or 50 % field capacity (terminal drought) till maturity. Terminal drought significantly reduced the yield and related traits compared with well-watered crop; however, osmopriming improved the crop performance under terminal drought. Among different row spacings, wheat sown in 20-cm spaced rows performed better during both years of study. Wheat cultivar Lasani-2008 performed better than cultivar Triple Dwarf-1 under both well-watered and stress conditions. Maximum net returns and benefit-cost ratio were recorded from osmoprimed seeds of cultivar Lasani-2008 sown in 20-cm spaced rows under well-watered condition. Nonetheless, osmoprimed seeds of cultivar Lasani-2008 sown in 20-cm spaced rows were better able to produce good yield under terminal drought.

Detailed analysis of Land Use/Land Cover (LULC) using remote sensing data in complex irrigated basins provides complete profile for better water resource management and planning. Using remote sensing data, this study provides detailed land use maps of the Lower Chenab Canal irrigated region of Pakistan from 2005 to 2012 for LULC change detection. Major crop types are demarcated by identifying temporal profiles of NDVI using MODIS 250 m  250 m spatial resolution data. Wheat and rice are found to be major crops in rabi and kharif seasons, respectively. Accuracy assessment of prepared maps is performed using three different techniques: error matrix approach, comparison with ancillary data and with previous study. Producer and user accuracies for each class are calculated along with kappa coefficients (K). The average overall accuracies for rabi and kharif are 82.83% and 78.21%, respectively. Producer and user accuracies for individual class range respectively between 72.5% to 77% and 70.1% to 84.3% for rabi and 76.6% to 90.2% and 72% to 84.7% for kharif. The K values range between 0.66 to 0.77 for rabi with average of 0.73, and from 0.69 to 0.74 with average of 0.71 for kharif. LULC change detection indicates that wheat and rice have less volatility of change in comparison with both rabi and kharif fodders. Transformation between cotton and rice is less common due to their completely different cropping conditions. Results of spatial and temporal LULC distributions and their seasonal variations provide useful insights for establishing realistic LULC scenarios for hydrological studies.