Changes in growth,photosynthetic capacity and ionic relations in spring wheat (<Emphasis Type=Italic>Triticum aestivum</Emphasis> L.) due to pre-sowing seed treatment with polyamines

The influence of pre-sowing seed treatment with polyamines (2.5 mM putrescine, 5.0 mM spermidine and 2.5 mM spermine) on growth, photosynthetic capacity, and ion accumulation in two spring wheat (Triticum aestivum L.) cultivars MH-97 (intolerant) and Inqlab-91 (tolerant) was examined. The primed seeds of each treatment and non-primed seeds were sown in a field containing 15 dS m⁻¹ NaCl. Although all three polyamines were effective in improving shoot growth and grain yield in both cultivars under saline conditions, the effect of spermine was very pronounced particularly in improving grain yield. Different priming agents did not affect the net CO₂ assimilation rate and transpiration rate of either cultivar. However, pre-treatment with spermidine increased stomatal conductance (g_s) in the tolerant cultivar, whereas with spermine stomatal conductance decreased in the intolerant cultivar under salt stress. Priming agents had different effects on the accumulation of different ions in wheat plant tissues. When spermidine and distilled water were used as priming agents, they were effective in reducing shoot [Na⁺] in the tolerant and intolerant cultivars, respectively under saline conditions. Although all priming agents caused an increase in shoot [K⁺], distilled water was more effective in improving shoot [K⁺] in both cultivars under salt stress. Pre-treatment with spermidine was very effective in reducing shoot [Cl⁻] under saline conditions particularly in the tolerant cultivar. However, the pattern of accumulation of different ions in roots due to different seed priming treatments was not consistent in either cultivar except that root Na⁺ decreased due to priming with spermine and spermidine in the intolerant and tolerant cultivars under saline conditions. In conclusion, although all three priming agents, spermine, spermidine and putrescine, were effective in alleviating the adverse effect of salt stress on wheat plants, their effects on altering the concentration of different ions and growth were different in the two cultivars differing in salt tolerance.     

A preliminary study on the effects of E-Z Mixin® and EquiPlus® extenders supplemented with Edible Bird’s Nest on the quality of chilled Arabian stallion semen

The aim of this study was to evaluate the effects of adding different concentrations of edible bird’s nest (EBN) which is secreted by swiftlet birds (Aerodramus fuciphagus), into EquiPlus® and E-Z Mixin® extenders on the quality of chilled Arabian stallion semen at various storage times (0, 24 and 48 h). Ten ejaculates were collected from five stallions, and diluted using the two extenders containing 0% (control), 0.12%, 0.24% and 0.24% of EBN + seminal plasma (SP). All the diluted semen samples were then cooled and stored at 5 °C, and examined at 0, 24 and 48 h. Sperm kinetic parameters were assessed using computer assisted sperm analysis (CASA) and viability were assessed using Hoechst33342/PI stain. In both extenders, total motility (TM) and progressive motility (PM) were significantly higher at 0.12% and 0.24% compared to 0.24% + SP at 24 and 48 h. At 0.12%, E-Z mixin® treated semen had significantly higher TM and PM than EquiPlus^® at 24 and 48 h. At 0.12% and 0.24%, average path velocity (VAP), straight-line velocity (VSL) and curvilinear velocity (VCL) were significantly higher in E-Z mixin® treated semen compared to EquiPlus^® at 24 and 48 h. Comparisons between the two extender types at different concentrations of EBN showed no significant difference in lateral head amplitude (ALH), linearity (LIN), straightness (STR), beat cross frequency (BCF) and viability, irrespective of the storage time. The percentage of viable was significantly higher in E-Z mixin® than EquiPlus® at 0 and 48 h in control and 0.12%. Supplementation of the E-Z mixin^® extender with 0.12% and 0.24% EBN concentrations in the absence of SP provided better CASA parameters such as TM, PM, VAP, VSL, and VCL at 24 and 48 h storage time. In conclusion, the results of this study indicated that chilled semen from Arabian stallion that was extended using E-Z mixin® and supplemented with 0.12% and 0.24% EBN concentrations performed better and yielded superior results in sperm kinetic parameters and % viable compared to EquiPlus® at 24 and 48 h storage time.     

Silicon decreases chloride transport in rice (Oryza sativa L.) in saline conditions

Silicon can alleviate salt damage to plants, although the mechanism(s) still remains to be elucidated. In this paper, we report the effect of silicon on chloride transport in rice (Oryza sativa L.) seedlings in saline conditions. In the absence of salinity, silicon enhanced the growth of shoots, but not roots in three cultivars (cv. GR4, IR36, and CSR10). Salinity reduced the growth of both shoots and roots in all three genotypes. In saline conditions, addition of silicon to the culture solution again improved the growth of shoots, but not of roots. Under these saline conditions, the concentrations of chloride in the shoot were markedly decreased by adding silicon and the ratio of K⁺/Cl⁻ was significantly increased, while the concentration of chloride in the roots was unchanged. The decrease in chloride concentration in the shoot was correlated with the decrease in transpirational bypass flow in rice, as shown by the transport of the apoplastic tracer trisodium-8-hydroxy-1,3,6-pyrenetrisulphonic acid (PTS). Addition of silicon increased the net photosynthetic rate, stomata conductance, and transpiration of salt-stressed plants in cv. IR36, indicating that the reduction of chloride (and sodium) uptake by silicon was not through a reduction in transpiration rate. Silicon addition also increased the instantaneous water use efficiency of salt-stressed plants, while it did not change the relative growth rate of shoots. The results suggest that silicon addition decreased transpirational bypass flow in the roots, and therefore decreased the transport of chloride to the shoot.     

Clonal variation of tea [Camellia sinensis (L.) O. Kuntze] in countering water deficiency

Various clones of tea [Camellia sinensis (L.) O. Kuntze] such as TTL-1, TTL-2, TTL-4, TTL-5, TTL-6, UPASI-2 and UPASI-3 planted in the field were subjected to soil moisture stress conditions by withholding irrigation. A control set of the same clones were maintained by watering regularly. The soil water content of the irrigated and non irrigated plants was monitored through the soil moisture status. The extent of effect of drought on tea plants were monitored through various physiological parameters such as shoot weight, leaf water potential, chlorophyll and carotenoid content, chlorophyll fluorescence (Fv/Fm), net photosynthetic rate, transpiration rate, stomatal conductance and biochemical parameters such as extent of proline accumulation and free radical generation. These parameters were studied on the 30 d of non irrigation and on the 5 d during recovery from drought. The plants recovered when re-irrigated after 30 d of non-irrigation, which suggests that permanent wilting did not occur due to non-irrigation up to 30 d. On the 30 d of non-irrigation the clones TTL-1, TTL-6 and UPASI-2 showed lesser reduction of shoot weight, leaf water potential, chlorophyll fluorescence, photosynthetic rate, transpiration rate and stomatal conductance and increased proline and lesser lipid peroxidation as compared to the other clones. From these results it can be concluded that the clones TTL-1, TTL-6 and UPASI-2 are comparatively more drought tolerant than the clones TTL-2, TTL-4, TTL-5 and UPASI-3.     

Use of plant growth-promoting bacteria to enhance salinity stress in soybean (Glycine max L.) plants

The effects of three rhizobacterial isolates namely Pseudomonas fluorescens (M1), Pseudomonas putida (M2) and Bacillus subtilis (M3) were examined to enhance growth and chemical components such as chlorophyll and proline of three cultivars of soybean (Glycine max L.) under two levels of salinity stress (S1 = 200 mM and S2 = 400 mM of NaCl salt). Several morphological and physiological parameters were investigated. The highest mean values of final germination percent (FGP) were registered in cultivar Crawford (95%) followed by Giza111 cultivar (93%) in the presence of P. fluorescens, while, FGP of Clark was 85%. Mean germination time was decreased by the application of P. fluorescens or P. putida in both salt stressed and unstressed traits. All growth parameters were significantly decreased by salinity treatments, particularly at S2. A significant increase in stem length and shoot fresh weight was recorded in plants treated with P. fluorescens. This enhancing trend was followed by the application of P. putida then B. subtilis. Chlorophyll contents and plant soluble proteins were decreased, while proline content was increased as compared with control treatment. Results showed that the salt tolerant cultivar, Crawford, may have a better tolerance strategy against oxidative damages by increasing antioxidant enzymes activities under high salinity stress. These results suggest that salt induced oxidative stress in soybean is generally counteracted by enzymatic defense systems stimulated under harsh conditions. Our results showed that inoculation with plant growth-promoting rhizobacterial (PGPR) alleviated the harmful effects of salinity stress on soybean cultivars. The diversity in the phylogenetic relationship and in the level of genetic among cultivars was assessed by SDS-PAGE and RAPD markers. Among the polymorphism bands, only few were found to be useful as positive or negative markers associated with salt stress. The maximum number of bands (17) was recorded in Crawford, while the minimum number of bands (11) was recorded in Clark. Therefore, the ISSR can be used to identify alleles associated with the salt stress in soybean germplasm.     

Genetic improvement of peanut (Arachis hypogea L.) genotypes by developing short duration hybrids

Peanut, the only cash crop of rainfed areas of Pakistan, is facing immense challenges due to global warming. Climatic factors particularly the temperature fluctuations and rain pattern shift significantly impact the production and yield of peanut and unavailability of resilient varieties exacerbate this impact. To deal with the cropping pattern change and yield losses, due to climate vagaries, a study was conducted to develop early maturing hybrids using line into tester mating design. The F₁ hybrids from the parental lines were produced in the year 2018 using Line × Tester mating design and then grown in the field in the year 2019 for further evaluation. The hybrids were evaluated based on the early maturity and yield-related attributes in comparison with the parental lines. Based on the general combining ability estimate, line V-3 (Golden), was found as best parent with highly significant values for plant height, days to peg formation, days to maturity, number of pegs per plant, number of pods per plants, number of seeds per plant, 100 pod weight 100 seed weight. Similarly, tester V-7 (PI 635006 01 SD) showed highly significant results of GCA for days to germination, day to 50% flowering, plant height, days to peg formation, days to maturity, number of pegs per plant, number of pods per plants, number of seeds per plant, 100 kernel weight, shelling percentage. All the combinations were evaluated for specific combining ability and significant results were observed for V-3 × V-4 (Golden × PI 619175 01 SD) and V-1 × V-6 (BARI-2000 × PI 564846 01 SD) by developing or maturity and yield-related attributes. The hybrid combinations V-3 × V-5 (Golden × PI 635006 01 SD) followed by V-3 × V-6 showed highly significant results for mid parent heterosis and better parent heterosis for days to 50% flowering, plant height, days to peg formation, number of pegs, days to maturity, number of mature seeds per plant, shelling ratio, 100 pod weight and 100 kernel weight. These parents and hybrid combinations with early maturity genes and high yield attributes can further be used for the development of short duration variety.     

Operationally defined species characterization and bioaccessibility evaluation of cobalt,copper and selenium in Cape gooseberry (Physalis Peruviana L.) by SEC-ICP MS

Physalis peruviana could attract great interest because of its nutritional and industrial properties. It is an excellent source of vitamins, minerals, essential fatty acids and carotenoids. Physalis Peruviana is also known to have a positive impact on human health. Unfortunately, still little is known about trace elements present in Physalis Peruviana and their forms available for the human body. Thus, the aim of this study was to estimate bioaccessibility and characterization of species of cobalt, copper and selenium in Physalis Peruviana fruits.Total and extractable contents of elements were determined by mass spectrometer with inductively coupled plasma (ICP MS). In order to separate the different types of metal complexes Physalis peruviana fruits were treated with the following solvents: Tris–HCl (pH 7.4), sodium dodecyl sulfate (SDS) (pH 7.4) and ammonium acetate (pH 5.5). The best efficiency of extraction of: cobalt was obtained for ammonium acetate (56%) and Tris–HCl (60%); for copper was obtained for SDS (66%), for selenium the best extraction efficiency was obtained after extraction with SDS (48%).To obtain information about bioaccessibility of investigated elements, enzymatic extraction based on in vitro simulation of gastric (pepsin) and intestinal (pancreatin) digestion was performed. For copper and selenium the simulation of gastric digestion leads to the extraction yield above 90%, while both steps of digestion method were necessary to obtain satisfactory extraction yield in the case of cobalt.Size exclusion chromatography (SEC) coupled to on-line ICP MS detection was used to investigate collected metal species. The main fraction of metal compounds was found in the 17 kDa region. Cobalt and copper create complexes mostly with compounds extracted by means of ammonium acetate and SDS, respectively. Cobalt, copper and selenium were found to be highly bioaccessible from Physalis Peruviana. Investigation of available standards of cobalt and selenium allows confirming the presence of vitamin B₁₂ and probably selenomethionine in the fraction bioaccessible by human body (obtained during enzymatic extraction). It should be noted that the presence of small seleno-compounds in Cape gooseberry was performed for the first time.The results show that the combination of SEC and ICP MS could provide a simple method for separating of soluble element species.     

The use of chlorophyll fluorescence in assessment of low temperature hardiness in blackcurrant (Ribes nigrum L.)

The effect of freezing stress on chlorophyll fluorescence was examined in leaves of five genotypes of blackcurrant (Ribes nigrum L.). Minimum fluorescence (F_o), variable fluorescence (F_v) and the time for F_v to decay to half its maximum value (q_1/2) all varied between genotypes. Freezing stress significantly reduced F_o in all genotypes, but the effect of freezing stress on F_v was non-significant. Freezing stress significantly increased q_1/2, but the effect varied significantly between genotypes. The increase in q_1/2 induced by freezing stress was greatest in the cultivar Baldwin and least in the accession Ri-74020-6. The effects of freezing on chlorophyll fluorescence, particularly q_1/2, corresponded to the susceptibility of the genotypes to spring frosts. It is concluded that chlorophyll fluorescence can provide a rapid screening technique for assessing frost hardiness in blackcurrant.     

Spatial distributions and net deposition rates of mineral elements in the elongating wheat (Triticum aestivum L.) leaf under saline soil conditions

Wheat leaf growth is known to be spatially affected by salinity. The altered spatial distribution of leaf growth under saline conditions may be associated with spatial changes in tissue mineral elements. The objective of this study was to evaluate the spatial distributions of mineral elements and their net deposition rates in the elongating and mature zones of leaf 4 of the main stem of spring wheat (Triticum aestivum L. cv. Lona) during its linear growth phase under saline soil conditions. Plants were grown in an illitic-chloritic silty loam with 0 and 120 mM NaCl. Three days after emergence of leaf 4, sampling was begun at 3 and 13 h into the 16-h light period. Spatial distributions of fresh weight (FW), dry weight (DW), and Na⁺, K⁺, Cl⁻, NO⁻ ₃, Ca²⁺, Mg²⁺, total P, and total N in the elongating and mature tissues were determined on a millimeter scale. The patterns of spatial distribution of Na⁺, Cl⁻, K⁺, NO₃ ⁻, and Ca²⁺ in the growing leaves were affected by salinity, while those of Mg²⁺, total P, and total N were not. Sodium, K⁺, Cl⁻, Ca²⁺, Mg²⁺, and total N concentrations (mmol · kg⁻¹ FW) were consistently higher at 120 mM NaCl than at 0 mM NaCl along the leaf axis from the leaf base, whereas NO₃ ⁻ concentration was lower at 120 mM NaCl. Deposition rates of all nutrients were greatest in the elongation zone. The elongation zone was the strongest sink for mineral elements in the leaf tissues. Local net deposition rates of Na⁺, Cl⁻, Ca²⁺, and Mg²⁺ (mmol · kg⁻¹ FW · h⁻¹) in the most actively elongating zone were enhanced by 120 mM NaCl, whereas for NO₃ ⁻ this was depressed. The lower supply of NO⁻ ₃ to growing leaves may be responsible for the inhibition of growth under saline conditions. Higher tissue concentrations of Na⁺ and Cl⁻ may cause ion imbalance but probably did not result in ion toxicity in the growing leaves. Potassium, Ca²⁺, Mg²⁺, total P, and total N are less plausibly responsible for the reduction in leaf growth in this study. Higher tissue K⁺ and Ca²⁺ concentrations at 120 mM NaCl are probably due to the presence of high Ca²⁺ in the soil of this study. Received: 13 March 1997 / Accepted: 9 June 1997     

Chemical role of α-tocopherol in salt stress mitigation by improvement in morpho-physiological attributes of sunflower (Helianthus annuus L.)

Elevated concentrations of salts in soil and water represent abiotic stresses. It considerably restricts plant productivity. However, the use of alpha-tocopherol (α-toc) as foliar can overcome this problem. It can improve crop productivity grown under salinity stress. Limited literature is documented regarding its optimum foliar application on sunflower. That’s why the need for the time is to optimize α-toc foliar application rates for sunflower cultivated in salt-affected soil. A pot experiment was performed to select a better α-toc foliar application for mitigation of salt stress in different sunflower cultivars FH (572 and 621). There were 2 levels of salts, i.e., control (no salt stress) and sodium chloride (120 mM) and four α-toc foliar application (0, 100, 200, and 300 mg L⁻¹). Results showed that foliar application of 100 mg/L- α-toc triggered the remarkable increase in fresh shoot weight, fresh root weight, shoot, and root lengths under salinity stress in FH-572 and FH-621 over 0 mg/L- α-toc. Foliar application of 200 mg/L- α-toc was most effective for improvement in chlorophyll a, chlorophyll b, total chlorophyll and carotenoids compared to 0 mg/L- α-toc. Furthermore, an increase in A was noted in FH-572 (17%) and FH-621 (22%) with α-toc (300 mg L⁻¹) application under saline condition. In conclusion, the 100 and 200 mg/L- α-toc are the best application rates for the improvement in sunflower FH-572 and FH-621 growth, chlorophyll contents and gas exchange attributes. Further investigations are needed to select a better foliar application rate between 100 and 200 mg/L- α-toc at the field level under the different agro-climatic zone and soil types.     

Efficacy of putrescine and benzyladenine on photosynthesis and productivity in relation to drought tolerance in wheat (Triticum aestivum L.)

An experiment was conducted to find out the efficacy of putrescine and benzyladenine on photosynthesis and productivity in wheat. Seeds of wheat genotype HD 2329 (widely adapted under irrigated condition) were grown in ceramic pots under standard package and practices. Putrescine (0.1 mM) and benzyladenine (0.05 mM) were sprayed on the aerial portion of these plants at the time of anthesis. After spray, half of the plants were subjected to water stress by withholding irrigation. The non stressed plants were irrigated to keep the soil humidity at field capacity. Results showed that drought stress severly reduced the photosynthetic attributes, water status and chlorophyll content which were significantly improved by foliar application of putrescine/benzyladenine. The levels of free proline, amino acids and soluble sugars were higher under water stress conditions which were enhanced further by putrescine/benzyladenine. Memrane injury was also reduced by both the chemicals. Yield and yield attributes reduced under water stress conditions, but putrescine and benzyladenine treated plants exhibited significantly higher values over control. Most of these parameters were found significantly correlated with grain yield. It is suggested that both benyzladenine and putrescine were able to impart drought tolerance in wheat but the response of putrescine was more promising owing to better management of various physio-biochemical processes, particularly under water stress conditions.     

Interactive effects of gibberellic acid (GA3) and salt stress on growth, ion accumulation and photosynthetic capacity of two spring wheat (Triticum aestivum L.) cultivars differing in salt tolerance

A sand culture experiment assessed whether gibberellic acid(GA₃) could alleviate the adverse effects of salt stress on thegrowth, ion accumulation and photosynthetic capacity of two spring wheatcultivars, Barani-83 (salt sensitive) and SARC-I (salt tolerant).Three-week-oldplants of both cultivars were exposed to 0, 100 and 200 molm^–3 NaCl in Hoagland's nutrient solution. Threeweeks after the initiation of salt treatments, half of the plants of eachcultivar were sprayed overall with 100 mg L^–1GA₃ solution. Plants were harvested 3 weeks after theapplication of GA₃. Fresh and dry weights of shoots and roots, plantheight and leaf area were decreased with increasing supply of salt, butgibberellic acid treatment caused a significant ameliorative effect on both thecultivars with respect to these growth attributes. However, GA₃caused no significant change in grain yields but increased grain size in boththe cultivars. Saline growth medium caused a marked increase in theconcentrations of Na⁺ and Cl^– in shoots androots of both the lines. However, with the application of GA₃accumulation of Na⁺ and Cl^– was enhanced inboth shoots and roots of both wheat lines, but more ions accumulated in saltsensitive Barani-83 than in salt tolerant SARC-1. Net CO₂assimilation rate (A) of both wheat lines decreased consistently withincreasingsupply of NaCl, but application of GA₃ alleviated the effect of saltstress on this variable in both the cultivars. However, the ameliorative effectof the hormone was more pronounced in Barani-83 than in SARC-1. Althoughwater-use efficiency (A/E=CO₂assimilation/transpiration) and intrinsic water use efficiency(A/g_s=CO₂ assimilation/stomatalconductance) decreased significantly with increasing salt concentration of thegrowth medium in both the cultivars, GA₃ was more effective inenhancing both the water-use attributes in Barani-83 than in SARC-1. Overall,GA₃ treatment stimulated the vegetative growth of both cultivars ofwheat under salt stress, but it caused a slight reduction in grain yield.GA₃ treatment enhanced the accumulation of Na⁺ andCl^– in both shoots and roots of wheat plants under saltstress.It also caused a significant increase in photosynthetic capacity in both linesat the vegetative stage under both saline and non-saline media.     

Influence of exogenous application of glycinebetaine on antioxidative system and growth of salt-stressed soybean seedlings (Glycine max L.)

Glycinebetaine is one of the most competitive compounds which play an important role in salt stress in plants. In this study, the enhanced salt tolerance in soybean (Glycine max L.) by exogenous application of glycinebetaine was evaluated. To improve salt tolerance at the seedling stage, GB was applied in four different concentrations (0, 5, 25 and 50 mM) as a pre-sowing seed treatment. Salinity stress in the form of a final concentration of 150 mM sodium chloride (NaCl) over a 15 day period drastically affected the plants as indicated by increased proline, MDA and Na⁺ content of soybean plants. In contrast, supplementation with 50 mM GB improved growth of soybean plants under NaCl as evidenced by a decrease in proline, MDA and Na⁺ content of soybean plants. Further analysis showed that treatments with GB, resulted in increasing of CAT and SOD activity of soybean seedlings in salt stress. We propose that the role of GB in increasing tolerance to salinity stress in soybean may result from either its antioxidant capacity by direct scavenging of H₂O₂ or its role in activating CAT activity which is mandatory in scavenging H₂O₂.     

Studies of soil moisture stress in barley (Hordeum vulgare L.)

Summary The objective was to find the optimum range of water contents for inducing better growth, physiological efficiency and yield potential of barley plants (Hordeum vulgare L. var. K18). A pot culture experiment was conducted in the Division of Crop Physiology and Biochemistry Kanpur-2. The plants were subjected to various soil moisture stresses,i.e., 0.15, 0.30, 0.45, 0.60 and 0.75 atm tension throughout the crop growth period measured by irrometers.Plants maintained at 0.45 soil moisture tension required 19.07 litre of water and had the best water use efficiency (1765 mg dm/litre of water) which favourably influenced the leaf water balance (85.9%), plant growth as measured by plant height (85.4 cm) and tiller production (35.6) per hill, photosynthetic efficiency (2.185 mg CO₂/g dm/h), grain number (722) and grain yield (33.7 g) per hill while plants irrigated at a tension greater than 0.45 SMT did not develop as well. However, protein and gluten percentage increased gradually with the subsequent increase in soil moisture tension. On the other hand respiration rate (2.090 mg CO₂/g dm/hr) and leaf area (4375 cm²) were recorded to be the highest at 0.60 and 0.30 atm SMT respectively.Thus it is suggested that for reaping high harvest of barley crop, the physiological need of water (19.07 litre) in total of plant life should be made available through scheduled irrigation based on maintenance of plant at 0.45 SMT from seeding to maturity.     

Changes in antioxidant enzymes and some key metabolites in some genetically diverse cultivars of radish (Raphanus sativus L.)

Salt-induced changes in the activities of antioxidant enzymes such as superoxide dismutase (SOD), catalase (CAT), peroxidase (POX), and lipid peroxidation in terms of malondialdehyde (MDA), level of H₂O₂, and some key metabolites such as soluble proteins, free proline and phenolics in the leaves of six radish cultivars (Radish Red Neck, Radish Lal Pari, Radish Mino Japani, Radish 40 Days, Mannu Early and Desi) were investigated. Varying levels of NaCl (0, 80 and 160 mM) applied for 40 days adversely affected the shoot fresh weight, chlorophyll contents and soluble proteins, while increased the levels of proline, and the activities of SOD, POD and CAT. However, leaf H₂O₂ and total phenolic contents were not affected by salt stress. Cultivars Mannu Early, Radish 40 Days and Desi were relatively higher in shoot fresh weight (percent of control) while cvs. Radish Mino Japani and Mannu Early in proline, and cvs. Radish 40 Days and Desi in total soluble proteins at 160 mM of NaCl. However, levels of H₂O₂ and phenolics were higher in cvs. Desi, Radish Lal Pari and Mannu Early and SOD, POD and CAT activities only in Radish Lal Pari and Mannu Early than the other cultivars under saline conditions. Overall, the differential salt tolerance of radish cultivars observed in the present study was not found to be associated with higher antioxidant enzyme activities and other key metabolites analyzed, so these attributes cannot be considered as selection criteria for salt tolerance in radish.     

Ammonium nutrition increases photosynthesis rate under water stress at early development stage of rice (Oryza sativa L.)

An hydroponic experiment with a simulated water stress induced by PEG (6000) was conducted in a greenhouse to study the effects of nitrate (NO₃ ⁻), ammonium (NH₄ ⁺) and the mixture of NO₃ ⁻ and NH₄ ⁺, on water stress tolerance of rice seedlings. Rice (Shanyou 63) was grown under non- or simulated water stress condition (10% (w/v) PEG, MW6000) with the 3 different N forms during 4 weeks. Under non-stressed condition no difference was observed among the N treatments. Under simulated water stress, seedlings grown on N-NO₃ ⁻ were stunted. Addition of PEG did not affect rice seedling growth in the treatment of only NH₄ ⁺ supply but slightly inhibited the rice seedling growth in the treatment of mixed supply of NO₃ ⁻ and NH₄ ⁺. Simulated water stress, when only N-NH₄ ⁺ was present, did not affect leaf area and photosynthesis rate, however, both parameters decreased significantly in the NO₃ ⁻ containing solutions. Under water stress, Rubisco content in newly expanded leaves significantly increased in the sole NH₄ ⁺ supplied plants as compared to that in plants of the other two N treatments. Under water stress, the ratio of carboxylation efficiency to Rubisco content was, respectively, decreased by 13 and 23% in NH₄ ⁺ and NO₃ ⁻ treatments, respectively. It is concluded that, water stress influenced the Rubisco activity than stomatal limitation, and this effects could be regulated by N forms. Responsible Editor: Herbert Johannes Kronzucker. Shiwei Guo and Gui Chen contributed equally to this paper.     

Physiological and Biochemical Characteristics and Response Patterns of Salinity Stress Responsive Genes (SSRGs) in Wild Quinoa (<i>Chenopodium quinoa</i> L.)

Cultivating salt-tolerant crops is a feasible way to effectively utilize saline-alkali land and solve the problem of underutilization of saline soils. Quinoa, a protein-comprehensive cereal in the plant kingdom, is an exceptional crop in terms of salt stress tolerance level. It seems an excellent model for the exploration of salt-tolerance mechanisms and cultivation of salt-tolerant germplasms. In this study, the seeds and seedlings of the quinoa cultivar Shelly were treated with different concentrations of NaCl solution. The physiological, biochemical characteristics and agronomic traits were investigated, and the response patterns of three salt stress-responsive genes (SSRGs) in quinoa were determined by real-time PCR. The optimum level of stress tolerance of quinoa cultivar Shelly was found in the range of 250–350 mM concentration of NaCl. Salt stress significantly induced expression of superoxide dismutase (SOD), peroxidase (POD), and particularly betaine aldehyde dehydrogenase (BADH). BADH was discovered to be more sensitive to salt stress and played an important role in the salt stress tolerance of quinoa seedlings, particularly at high NaCl concentrations, as it displayed upregulation until 24 h under 100 mM salt treatment. Moreover, it showed upregulation until 12 h under 250 mM salt stress. Taken together, these results suggest that BADH played an essential role in the salt-tolerance mechanism of quinoa. Based on the expression level and prompt response induced by NaCl, we suggest that the BADH can be considered as a molecular marker for screening salt-tolerant quinoa germplasm at the early stages of crop development. Salt treatment at different plant ontogeny or at different concentrations had a significant impact on quinoa growth. Therefore, an appropriate treatment approach needs to be chosen rationally in the process of screening salt-tolerant quinoa germplasm, which is useful to the utilization of saline soils. Our study provides a fundamental information to deepen knowledge of the salt tolerance mechanism of quinoa for the development of salt-tolerant germplasm in crop breeding programs.     

Influence of saline irrigation on growth,ion accumulation and partitioning,and leaf gas exchange of carrot (Daucus carota L.)

Like those of many horticultural crop species, the growth and leaf gas exchange responses of carrot (Daucus carota L.) to salinity are poorly understood. In this study ion accumulation in root tissues (periderm, xylem and phloem tissues) and in leaves of different ages was assessed for carrot plants grown in the field with a low level of salinity (5.8 mM Na(+) and 7.5 mM Cl(-)) and in a glasshouse with salinity ranging from 1-80 mM. At low levels of salinity (1-7.5 mM), in both the field and glasshouse, carrot leaves accumulated high concentrations of Cl(-) (140-200 mM); these appear to be the result of a high affinity for Cl(-) uptake and a low retention of Cl(-) in the root system. However, Cl(-) uptake is under tight control, with an 80-fold increase in external salinity resulting in only a 1.5-fold change in the Cl(-) concentration of the shoot and no increase in the Cl(-) concentration of the root xylem tissue. In contrast to Cl(-), shoot Na(+) concentrations were comparatively low (30-40 mM) but increased by seven-fold when salinity was increased by 80-fold. Growth over the 56-d treatment period in the glasshouse was insensitive to salinity less than 20 mM, but at higher concentrations the yield of carrot tap roots declined by 7 % for each 10 mM increase in salinity. At low levels of salinity the accumulation of high concentrations of Cl(-) (150 mM) in carrot laminae did not appear to limit leaf gas exchange. However, photosynthesis and stomatal conductance were reduced by 38 and 53 %, respectively, for plants grown at a salinity of 80 mM compared with those grown at 1 mM. Salinity-induced reductions in both p(i) and carbon isotope discrimination (delta) were small (2.5 Pa and 1.4 per thousand, respectively, at 80 mM) indicating that the reduction in photosynthesis was only marginally influenced by CO(2) supply. At a salinity of 80 mM the photosynthetic capacity was reduced, with a 30 % reduction in the CO(2)-saturated rate of photosynthesis (A(max)) and a 40 % reduction in both the apparent rate of RuBP-carboxylase-limited CO(2) fixation (V(cmax)) and the electron transport rate limiting RuBP regeneration (J(max)). This study has shown that carrot growth and leaf gas exchange are insensitive to the high leaf Cl(-) concentrations that occur at low levels (1-7 mM) of salinity. However, growth is limited at salinity levels above 20 mM and leaf gas exchange is limited at salinity levels above 8 mM.     

Role of sedoheptulose-1,7 bisphosphatase in low light tolerance of rice (Oryza sativa L.)

Rice grain yield is drastically reduced under low light especially in kharif (wet) season due to cloudy weather during most part of crop growth. Therefore, 50–60% of yield penalty was observed. To overcome this problem, identification of low light tolerant rice genotypes with a high buffering capacity trait such as photosynthetic rate has to be developed. Sedoheptulose-1,7 bisphosphatase, a light-regulated enzyme, plays pivotal role in the Calvin cycle by regenerating the substrate (RuBP) for RuBisCo and therefore, indirectly regulates the influx of CO₂ for this crucial process. We found a potential role of SBPase expression and activity in low light tolerant and susceptible rice genotypes by analyzing its influence on net photosynthetic rate and biomass. We observed a significant relationship of yield with photosynthesis, SBPase expression and activity especially under low light conditions. Two tolerant and two susceptible rice genotypes were used for the present study. Tolerant genotypes exhibited significant but least reduction compared to susceptible genotypes in the expression and activity of SBPase, which was also manifested in its photosynthetic rate and finally in the grain yield under low light. However, susceptible genotypes showed significant reduction in SBPase activity along with photosynthesis and grain yield suggesting that tracking the expression and activity of SBPase could form a simple and reliable method to identify the low light tolerant rice cultivars. The data were analyzed using the Indostat 7.5, Tukey–Kramer method through Microsoft Excel 2019 and PAST4.0 software. The significant association of SBPase activity with the grain yield, net assimilation rate, electron transfer rate, biomass and grain weight were observed under low light stress. These traits should be considered while selecting and breeding for low light tolerant cultivars. Thus, SBPase plays a major role in the low light tolerance mechanism in rice.Electronic supplementary materialThe online version of this article (10.1007/s12298-020-00905-z) contains supplementary material, which is available to authorized users.