Physiological and Biochemical Mechanisms of Salinity Tolerance in Carex morrowii Boott

Carex species are widely used in many parts of the world and contain a large number of ecologically diverse species.Among the Carex species,some of them are known to be glycophytes,while others are halophytes.Carex morrowii Boott(Cyperaceae)is resistant to trample through their root structure and has an essential ornamental value in the landscape with their leaves.However,no information was found about the level of salinity tolerance/sensitivity of the Carex morrowii among these species.In the present study,changes in trace element contents(Na,K,Ca,Cu,Mn,Mg,Ni,Fe,P,Zn,and N)and their transport from roots to leaves,osmotic regulation,alterations in chlorophyll and carotenoid contents,nitrogen assimilation(nitrate reductase activity;NRA)and total soluble protein content in both roots and leaves of Carex morrowii under different salinity concentrations(50 mM,100 mM,200 mM and 300 mM NaCl)were examined in detail.Our study provides the first detailed data concerning the responses of leaves and roots and the determination of the level of salinity tolerance/sensitivity of the Carex morrowii.The K+/Na+ratio was preserved up to 200 mM NaCl,and accordingly,the element uptake and transport ratios showed that they could control moderate NaCl levels.Ca homeostasis that is maintained even in 200 mM NaCl concentration can be effective in maintaining the structural integrity and selective permeability of the cell membranes,while 300 mM NaCl concentration caused decreased photosynthetic pigments,and deterioration in element content and compartmentation.Moreover,these data suggest that plant parts of Carex morrowii respond differently against varied levels of salinity stress.Although the decrease in NR activity at 200 mM and 300 mM NaCl concentrations in the leaves,NR activity was maintained in the roots.Consequently,Carex morrowii is moderately tolerant to salinity and the carotenoid content and osmotic regulation of Carex morrowii appears to be instrumental in its survival at different salinity levels.Especially the roots of Carex morrowii have a remarkable role in salinity tolerance.

Improved drought tolerance in Festuca ovina L.using plant growth promoting bacteria

Numerous ecological factors influence a plant’s ability to live and grow,in which dryness is a substantial constraint on plant growth in arid and semi-arid areas.In response to a specific environmental stress,plants can use the most effective bacteria to support and facilitate their growth and development.Today,plant growth promoting rhizobacteria(PGPR)is widely used to reduce drought stress on plant growth.In this study,the effects of drought on Festuca ovina L.germination,growth,and nutrient absorption were investigated using PGPR in a factorial test with a completely random design under four water regimes.Soil water content was kept at 100%FC(field capacity),70%FC(FC),50%FC,and 30%FC.The treatments were inoculated with Azotobacter vinelandii,Pantoea agglomerans+Pseudomonas putida,and a mixture of bio-fertilizers.Results showed that the effects of drought stress were significantly reduced(P<0.05)when A.vinelandii and P.agglomerans+P.putida were used separately,however,the combined treatment of bio-fertilizers had a greater influence on seed germination than the single application.P.agglomerans+P.putida under 30%FC condition resulted in higher increases in stem,root length,and plant dry biomass.The highest uptake of nutrients was observed for the combined treatment of bio-fertilizers under 30%FC condition.Therefore,the use of A.vinelandii and P.agglomerans+P.putida,applied separately or combined,increased tolerance to drought stress in F.ovina by increased germination indices,dry weight,stem length,and root length.Because of the beneficial effects of PGPR on the growth characteristics of plants under drought conditions and the reduction of negative effects of drought stress,inoculating F.ovina seeds with Azotobacter and Pseudomonas is recommended to improve their growth and development characteristics under drought conditions.PGPR,as an affordable and environmentally friendly method,can improve the production of forage in water-stress rangelands.