Relative Water Content Content Research Articles

Application of nitrogen for mitigating the adverse effects of flooding stress in lettuce

Global warming and the subsequent climate change increase the severity and frequency of floods day by day. Therefore, there is a need to develop new strategies to prevent the negative effects of flooding stress and to determine the changes that may occur in the plant under extreme water stress. Thus, in this study, changes in agronomic, physiological, and biochemical properties of lettuce plants exposed to flooding stress under greenhouse conditions were analyzed. In this study, two different irrigation regimes, including full irrigation (I100) and flooding stress (I150) and three different nitrogen doses, including no-nitrogen (N0), 100 kg ha−1 (N10), and 200 kg ha−1 (N20), were applied. The results revealed that while flooding stress caused significant decreases in above-ground fresh and dry weights, membrane damage (MD), contents of carotenoid (CT), proline (PL), and protein (PT), as well as catalase activity (CAT), leaf relative water content (RWC) and peroxidase (POX) content showed significant increases. Increasing nitrogen doses caused the increase in the pigment contents (Cl a, Cl b, and CT) and PL, superoxide dismutase (SOD) of the lettuce. In addition, RWC content and the uptake of Fe and Mn elements increased under flooded conditions. It has been revealed that the application of at least 100 kg of nitrogen fertilizers per hectare to prevent the negative effects of flooding stress in the regions where lettuce cultivation was carried out supported the plant growth both under full irrigation and flooded conditions.

Seasonal changes in some physiological and biochemical responses of six groundcover plants

Landscape groundcover plants are a diverse group of trailing or spreading species that naturally form continuous soil coverage.Ground cover plants that were used in this study consisted of vegetative propagules of: Vinca minor L. ٬Variegatum’, Vinca minor L. ٬Green’, Oxalis brasiliensis G. Lodd, Trifolium repens L., Phyla nodiflora L. and Frankenia thymifolia Desf. The aim of this study was to compare some physiological and biochemical responses of each species used under seasonal changes in Shiraz climatic conditions. Several factors including chlorophyll and relative water content (RWC), electrolyte leakage (EL), proline content, soluble sugars and starch levels and antioxidant enzyme activities of these ground covers were investigated. Results showed that chlorophyll and RWC content were decreased in all ground cover plants during summer time. Furthermore, considerable seasonal variations in antioxidant enzyme activities were detected in all of the studied plants. The highest activity of CAT was obtained in summer, while SOD, POD and APX had their highest activities in autumn and winter seasons. Proline concentration in F. thymifolia was higher than the other species, especially in mid-winter. According to the results of this research, it appears that plants show different mechanisms against natural adverse environmental conditions. It can be concluded that F. thymifolia and P. nodiflora are well-matched with warm season and T. repens and V. minor are well-matched with cool season environmental conditions. Therefore, these plants can be recommended for cultivation in Shiraz green space and the same conditions elsewhere.

Interactive Effect of Fluorescent Pseudomonads Rhizobacteria and Zn on the Growth, Chemical Composition, and Water Relations of Pistachio (Pistacia vera L.) Seedlings under NaCl Stress

ABSTRACTThe role of fluorescent pseudomonads isolates (pf0, pf1, pf2, and pf3) and zinc (Zn) (0 and 5 mg kg−1 soil) interactions in alleviating salinity in pistachio seedlings were investigated. The experiment was conducted following completely randomized design with three replicates. The results revealed that salinity decreased the growth parameters, while application of PGPR (plant growth-promoting rhizobacteria) and Zn increased these parameters. Application of PGPR significantly enhanced phosphorus (P), potassium (K), calcium (Ca), magnesium (Mg), Zn, Ca/sodium (Na), and K/Na contents, while decreased the accumulation of Na and chloride (Cl). Application of PGPR and Zn increased the phenolic compounds, sucrose, membrane stability index (MSI), and relative water content (RWC) but reduced the malondialdehyde (MDA) amount. A positive correlation was observed between Zn concentrations with seedling dry weights, phenolic compounds, MSI, and RWC contents. These results indicated that the combined application of PGPR and Zn could be a simple treatment for growth and establishment of pistachio seedlings under Zn deficiency and soil salinity.