a1_We investigated the influence of salinity (0, 25, 50, or 75 mM NaCl) on gas exchange and physiological characteristics of nine citrus rootstocks (Cleopatra mandarin, Carrizo citrange, Macrophylla, Iranian mandarin Bakraii, Rangpur lime, Rough lemon, Sour orange, Swingle citrumelo, and Trifoliate orange) in a greenhouse experiment. Total plant dry mass, total chlorophyll (Chl) content, and gas-exchange variables, such as net photosynthetic rate (PN), stomatal conductance (g s), intercellular CO2 concentration, were negatively affected by salinity. In addition, ion concentrations of Cl- and Na+ increased by salinity treatments. Salinity also increased Mg2+ content in roots and reduced Ca2+ and Mg2+ concentrations in leaves. The K+ concentration in leaves was enhanced at low salinity (25 mM NaCl), whereas it decreased with increasing salinity stress. Salinity caused a decline in K+ contents in roots., a2_The rootstocks showed major differences in the extent of Cl- and Na+ accumulation in leaves and in their ability to maintain the internal concentrations of essential nutrients in response to different salinity. Therefore, in addition to inhibitory effects of high concentrations of Cl- and Na+, an imbalance of essential nutrients may also contribute to the reduction in gas exchange under saline conditions. Higher tolerance of rootstocks to salinity could be associated with the reduction of Cl- and Na+ uptake and transport to leaves, ability to keep higher Chl, gs, PN, and better maintenance of nutrient uptake even under high salinity. We found that Sour orange and Cleopatra mandarin were the rootstocks most tolerant to salinity of all nine studied. In addition, Trifoliate orange, Carrizo citrange, and Swingle citrumelo were the rootstocks most sensitive to salt stress followed by the Rough lemon and Macrophylla that showed a low-to-moderate tolerance, and Rangpur lime and Bakraii, with a moderate-to-high tolerance to high salinity., D. Khoshbakht, A.A. Ramin, B. Baninasab., and Obsahuje bibliografii
We investigated the effects of supplementary KNO3 and NaCl on one-year-old, potted Valencia orange (Citrus sinensis) scions grafted on Iranian mandarin Bakraii [Citrus reticulate × Citrus limetta] (Valencia/Bakraii) and Carrizo citrange [C. sinensis × Poncirus trifoliata] (Valencia/Carrizo) rootstocks. After watering plants for 60 days with 50 mM NaCl, the lowest reduction in dry mass, stomatal conductance, and chlorophyll (Chl) content was found in Valencia/Bakraii. Bakraii accumulated more Cl- and Na+ in roots and transferred less to Valencia leaves compared with Carrizo rootstock. Moreover, higher net photosynthetic rate was found in Valencia/Bakraii than those on Carrizo rootstock. NaCl caused a decrease in the maximal efficiency of PSII photochemistry (Fv/Fm) and effective quantum yield (ΦPSII) but elevated coefficient of nonphotochemical quenching. Salinity reduced Ca2+, Mg2+, and total N contents, and increased Na+/K+ ratio in leaves and roots of both grafting combinations. Salinity increased K+ and proline content in leaves and decreased K+ concentrations in roots of both grafting combinations. In salinized plants, nitrate supplementation (10 mM KNO3) reduced leaf abscission, Cl-, Na+, Na+/K+, and Ca2+ concentrations in leaves and roots of both combinations. K+ and N concentrations and proline increased in leaves of the nitrate-supplemented salinized plants. Supplementary nitrate increased leaf number and area, stem elongation, Chl content, Fv/Fm, and ΦPSII and stimulated photosynthetic activity. Thus, nitrate ameliorated the deleterious effects of NaCl stress and stimulated the plant metabolism and growth. It can be used as a vital treatment under such condition., D. Khoshbakht, A. Ghorbani, B. Baninasab, L. A. Naseri, M. Mirzaei., and Obsahuje bibliografii
The effects of environmental salinity on physiological responses, growth, and survival of the Gulf corvina, C. othonopterus, were evaluated in a 6-week completely randomized design experiment. Corvina (17.2±2.3 g mean initial body weight) were subjected to salinities of 5, 15, 25, and 35 ‰ and fed a commercial feed with protein and lipid contents of 46 and 14 %, respectively. Plasma osmolality increased significantly with salinity, ranging from 335.1±5.3 mOsm/kg in fish maintained at 5 ‰, to 354.8±6.8 mOsm/kg in fish kept in seawater, while a significant inverse relationship was observed between salinity and moisture content of whole fish, ranging from 73.8±0.7 (measured at 5 ‰) to 76.9±1.0 % (measured at 35 ‰). In spite of this, growth indices (final weight, weight gain, specific growth rate, condition factor, survival) were not altered, suggesting that, like other members of the family Sciaenidae, the Gulf corvina is a strong osmoregulator. The isosmotic point for this species was estimated to correspond to a salinity of 9.8 ‰. The present study represents the first set of experimental data on salinity tolerance of C. othonopterus and confirms the euryhalinity of this species., M. Perez-Velazquez, P. Urquidez-Bejarano, M. L. González-Félix, C. Minjarez-Osorio., and Obsahuje bibliografii
Effect of NaCl (electrical conductivity of 0, 5, 10, 15, and 20 dS m-1) on growth, gas exchange, and ion uptake in two Ziziphus species (Z. rotundifolia and Z. nummularia) differing in salt tolerance was studied. At 30 and 45 d after first leaf initiation, the dry mass of shoot and leaves, and rates of net photosynthesis (PN) and transpiration (E) decreased significantly with increasing NaCl concentration whereas membrane injury and accumulation of proline increased. The sodium content was highest in the roots of Z. rotundifolia and in the leaves of Z. nummularia. Potassium content did not differ much in the roots but it was significantly higher in the leaves of Z. rotundifolia at 30 and 45 d of observations. Thus both these species were tolerant to salinity but at high salinity Z. rotundifolia performed better owing to its higher PN and E, restricted translocation of sodium from root to leaves, and larger accumulation of potassium in the leaves. and N. K. Gupta ... [et al.].
a1_To determine how the use of a given rootstock can influence the functioning of the photosynthetic apparatus of the scion under salt stress, the growth, gas exchange, photosystem II (PSII) efficiency, xanthophyll cycle, and chloroplast ultrastructure of nongrafted,
self-grafted, and pumpkin-grafted (hereafter referred to as rootstock-grafted) cucumber (Cucumis sativus L.) plants were investigated at day 15 after being treated with 90 mM NaCl. The reductions in plant growth of the rootstock-grafted plants were lower than those of the nongrafted and self-grafted plants under 90 mM NaCl. The net photosynthetic rate, stomatal conductance, maximal and effective quantum yield of PSII photochemistry, photochemical quenching coefficient, and effective quantum-use efficiency of PSII in the light-adapted state of the nongrafted and self-grafted plants were significantly decreased under 90 mM NaCl. However, these reductions were alleviated when the cucumber plants were grafted onto the pumpkin (Cucurbita moschata Duch.) rootstock. The intercellular CO2 concentrations were significantly increased in the nongrafted and self-grafted plants under 90 mM NaCl, whereas it was decreased in the rootstock-grafted plants. Nonphotochemical quenching (NPQ) and the deepoxidation state of the xanthophyll cycle were significantly increased under 90 mM NaCl, particularly in the rootstockgrafted plants, suggesting the rootstock-grafted plants had higher potential to dissipate excess excitation energy and reduce the probability of photodamage to PSII. Under 90 mM NaCl, the number of grana was reduced, the thylakoids were swollen, and starch granules accumulated in all plants. However, the damage of chloroplast ultrastructure was alleviated in the rootstock-grafted plants., a2_Taken together, the use of C. moschata rootstock alleviated salt stress in cucumber plants by delaying photoinhibition, probably due to a lower incidence of both stomatal and nonstomatal factors limiting photosynthesis., Z. X. Liu ... [et al.]., and Obsahuje bibliografii
The plant growth, net photosynthetic rate (PN), intercellular CO2 concentration (ci), and dry matter production of Ceriops roxburghiana Arn. were significantly increased with increasing salinity from 0 to 400 mM NaCl. At 600 mM NaCl, shoot and root lengths, and dry mass were significantly depressed with respect to control. Absence of diurnal fluctuation of concentrations of organic acids, and the low activity of phosphoenolpyruvate carboxylase and high activity of ribulose-1,5-bisphosphate carboxylase confirmed the operation of C3 pathway in Ceriops even at increasing salinity. and A. Rajesh, R. Arumugam, V. Venkatesalu.
A hydroponic, greenhouse experiment was conducted to assess the effects of NaCl on growth, gas-exchange parameters, chlorophyll (Chl) content, and ion distribution in seven sesame (Sesamum indicum L.) genotypes (Ardestan, Varamin, Naz-Takshakhe, Naz-Chandshakhe, Oltan, Yekta, Darab). The plants were grown in 4-L containers and subjected to varying levels of salinity (0, 30, and 60 mM NaCl). After 42 days, salt treatments induced decreases of plant fresh and dry mass, total leaf area, and plant height in all genotypes. Increasing NaCl concentration caused significant, genotypedependent decrease in the net photosynthetic rate, stomatal conductance, Chl content, and maximum quantum efficiency of photosystem II, while it increased the intercellular CO2 concentration. Based on the dry matter accumulation under salinity, the genotypes were categorized in two groups, i.e., salt-tolerant and salt-sensitive. The impact of salt on plant ion concentrations differed significantly among the sesame genotypes and between both two groups. The plant Na+ concentrations were significantly lower in Ardestan, Darab, and Varamin genotypes than those found in the remaining genotypes. The highest plant K+ and Ca2+ concentrations together with the lowest Na+/K+ and Na+/Ca2+ ratios were observed in Ardestan, Varamin, and Darab genotypes. Our results indicated the presence of differences in salt response among seven sesame genotypes. It suggested that growth and photosynthesis could depend on ion concentrations and ratios in sesame., A. H. Bazrafshan, P. Ehsanzadeh., and Obsahuje bibliografii
The Jadro River with total length of 4.3 km and average annual discharge of 7.9 m3 s-1 is a relatively small river on the east coast of the Adriatic Sea, close to Split. Field campaign measurements were made to estimate salt intrusion in the Jadro estuary in July 2012. This measurement confirmed the stratified character of the estuary where fresh water flows in a thin layer over denser sea water. Furthermore, a numerical model was set up for simulating unsteady stratified flow without mixing between the layers. The model is applied for the Jadro River and field measurements are used for calibration. In addition, the steady state of stratification within the estuary is analyzed by a box model which assumes mixing between layers. Results of the numerical and the box models were compared. The flushing time estimated with the box model is approximately 1.5 day for summer steady conditions. Numerical analysis however shows that the residence time is much larger owing to flow unsteadiness.
This paper focuses on the morphology, taxonomy and ecology of the widespread cyanobacteria of the genus Nodularia Mertens ex Bornet & Flahault. In this study the benthic strain of N. sphaerocarpa, isolated from a sand-pit near Olomouc (Czech Republic), is compared with brackish and seawater strains. Changes in morphology and growth parameters (biomass and chlorophyll a) recorded in varying salinity gradients were studied and a 16S rRNA sequencing and AFLP analysis conducted. Morphological and ecophysiological characteristics found were in congruence with molecular data. Three major subgroups of the benthic Nodularia (N. sphaerocarpa, N. moravica and N. harveyana) were found using the polyphasic approach. The results of both the molecular and morphological study clearly separated N. moravica and N. sphaerocarpa, as freshwater species preferring a low salinity and the N. harveyana strains originating from a marine environment preferring a high salinity.
The aim of the current work was to determine whether grafting could improve salinity tolerance of melon and cucumber, and whether possible induction of tolerance to salt stress was associated with the protection of the photosynthetic apparatus. Two greenhouse experiments were carried out to determine gas exchange, mineral composition, growth and yield of melon (Cucumis melo L. cv. Cyrano) and cucumber (Cucumis sativus L. cv. Akito) plants, either ungrafted or grafted onto the Cucurbita hybrid rootstocks (Cucurbita maxima Duch. × Cucurbita moschata Duch.), ‘P360’, and ‘PS1313’, respectively. Plants were grown hydroponically and supplied with two nutrient solutions - a nonsalinized control and a salinized solution which contained 40 mmol L-1 of NaCl. Salinity induced a smaller decrease in leaf area index (LAI), in grafted-compared to ungrafted plants. Similarly, the
PN and gs reduction in NaCl treatment compared to control were significantly lower in grafted plants (34% and 34%, respectively, for melon and 14% and 15.5%, respectively, for cucumber) compared to ungrafted plants (42% and 40%, respectively, for melon and 30% and 21%, respectively, for cucumber). In all grafting combinations, negative correlations were recorded between Na+ and Cl- in the leaf tissue and PN. Grafting reduced concentrations of sodium, but not chloride, in leaves. Under saline conditions a smaller reduction in melon and cucumber shoot biomass dry mass and fruit yield were recorded, with positive correlations between shoot biomass, yield and PN. These results suggest that the use of salt tolerant Cucurbita rootstock can improve melon and cucumber photosynthetic capacity under salt stress and consequently crop performance., Y. Rouphael ... [et al.]., and Obsahuje bibliografii