Different Approaches to Reduce Salinity in Salt-Affected Soils and Enhancing Salt Stress Tolerance in Plants

Salt stress is one of the most harmful environmental stresses in recent times and represents a significant threat to food security. Soil salinization is caused by spontaneous natural processes of mineral dissolution and human activities such as inappropriate irrigation practices. Natural geological progressions like weathering of rocks, arid climate, and higher evaporation, as well as anthropogenic activities, including the use of brackish water for irrigation, and poor tillage operations, are the foremost causes of soil salinization. Typical characteristics of saline soils are salt stress, high pH, and lack of organic carbon, as well as low availability of nutrients. Disruption of precipitation patterns as well as high average annual temperatures due to climate change additionally negatively affects the process of soil salinization. Productivity and ability to support crop growth are reduced on saline soil. Salinity-induced stress reduces plant growth by modulating the antioxidative system and nutrient orchestration. The aim of this work is to show that the mentioned problems can be alleviated in several ways such as the addition of biochar, exogenous application of several elicitors, seed priming, etc. Research has shown that the addition of biochar can significantly improve the recovery of saline soil. The addition of biochar has no significant effect on soil pH, while the cation exchange capacity of the soil increased by 17%, and the electrical conductivity of the saturated paste extract decreased by 13.2% (depends on the initial salinity and the type of biochar raw material). Moreover, biochar enriched with silicon increases the resistance of bananas to salt stress. In addition, exogenous application of several elicitors helps plants to alleviate stress by inducing stress-related physicochemical and molecular changes (selenium, sulfur, silicon, salicylic acid). Finally, seed priming showed positive effects on metabolomics, proteomics and growth of plants subjected to abiotic stress. Priming usually involves immersing the seed in a solution for a period of time to induce physiological and metabolic progression prior to germination.

Early ABA-stimulated maintenance of Cl^(−) homeostasis by mepiquat chloride priming confers salt tolerance in cotton seeds

Mepiquat chloride(MC)priming alleviates the effects of salt stress during seed germination in cotton(Gossypium hirsutum L.),but the mechanisms underlying its effects are unknown.We found that MC priming increases salt tolerance,as evidenced by marked increases in seed vigor and germination rates,and alleviated salt toxicity by reducing Cl^(−)accumulation in germinating seeds.Consistently,electrophysiological experiments revealed that the seeds with MC priming displayed superior Cl^(−)exclusion ability in the root apex.These beneficial effects of MC priming were abolished by the abscisic acid(ABA)-synthesis blocker fluridone under salt stress.MC priming induced an early response to acclimatization and stress,as indicated by rapidly increasing ABA content during initial exposure to salt stress.Transcriptome analyses revealed that MC priming induced an array of differentially expressed genes(DEGs)in germinating seeds.The most noticeable changes in germinating seeds were MC priming-induced increases in the expression of DEGs encoding components of ABA biosynthesis,ABA catabolism,and ABA signaling pathways under salt stress.MC priming also increased the expression of some DEGs encoding Cl^(−)ion transporters(e.g.CCC,SLAC1/SLAH1/SLAH3,CLC,and ALMT9)in germinating seeds.These results indicate that MC priming-induced ABA contributes to Cl^(−)homeostasis in tissues and acts as a positive regulator of salt tolerance via regulation of Cl^(−)transporters(particularly CCC and SLAC1/SLAH1/SLAH3).Taken together,these findings shed light on the molecular mechanism underlying MC-mediated tolerance to salt stress during seed germination.

Seed Priming Improves Enzymatic and Biochemical Performances of Rice During Seed Germination under Low and High Temperatures

As an abiotic stress,adverse germination temperatures cause serious disruptions in physiological and biochemical processes involved in seed germination.Using a factorial experiment,we examined the effects of different seed priming treatments on enzymatic and biochemical performances of rice seed germination under different temperatures.Each of the rice genotypes(Hashemi,Sadry-domsefid,IRON-70-7053-7 and NORIN-22)was primed with hydro-hardening,KCl,CaCl2 and ascorbic acid(AsA)and without a priming agent as a control at low(15℃),optimum(25℃)and high(35℃)germination temperatures.The results showed that the enzymatic and biochemical performances of all the rice genotypes were affected by the seed priming agents,especially under the low germination temperature.At 15℃,seed priming with AsA was found to be the best agent for the activities of amylase,α-amylase,catalase(CAT),peroxidase(POX),ascorbate peroxidase(APOX)and superoxide dismutase(SOD)as well as the content of soluble sugars in the NORIN-22 genotype,and for protease activity and soluble protein content in the IRON-70-7053-7 genotype.SOD at the low germination temperature and CAT,POX and protease at the optimum and high germination temperatures were the most important enzymes in occurrence of germination potential in terms of seedling length,vigor index,normal seedling rate and germination rate.Under the priming agents,the highest changes in normal seedling rate were observed at the low and optimum germination temperatures by AsA priming in the Hashemi and NORIN-22 genotypes,and at the high germination temperature under KCl priming in the Hashemi genotype.

Mepiquat chloride priming confers the ability of cotton seed to tolerate salt by promoting ABA-operated GABA signaling control of the ascorbate–glutathione cycle

Background Ensuring that seeds germinate and emerge normally is a prerequisite for cotton production,esp.in areas with salinized soil.Priming with mepiquat chloride(MC)can promote seed germination and root growth under salt stress,but its mechanism has not been fully elucidated.In this study,physiological and biochemical experiments revealed that MC-priming promotes the tolerance of cotton seeds to salt stress by increasing the ability of antioxidant enzymes related to the ascorbate-glutathione(AsA-GSH)cycle to scavenge reactive oxygen species(ROS).Results Results revealed that treatment with inhibitors of abscisic acid(ABA)and γ-aminobutyric acid(GABA)biosynthesis reduced the positive effects of MC-priming.Similarly,MC-priming increased the contents of ABA and GABA under salt stress by stimulating the expression levels of GhNCED2 and GhGAD4 and the activity of calmodulin-binding(CML)glutamate decarboxylase(GAD).Further analysis showed that an inhibitor of ABA synthesis reduced the positive impacts of MC-priming on the content of GABA under salt stress,but the content of ABA was not affected by the GABA synthesis inhibitor.Furthermore,a multi-omics analysis revealed that MC-priming increased the abundance and phosphorylation levels of the proteins related to ABA signaling,CML,and Ca^(2+)channels/transporters in the MC-primed treatments,which resulted in increased oscillations in Ca^(2+)in the MC-primed cotton seeds under salt stress.Conclusion In summary,these results demonstrate that MC-mediated ABA signaling operates upstream of the GABA synthesis generated by GAD by activating the oscillations of Ca^(2+)and then enhancing activity of the AsA-GSH cycle,which ensures that cotton seeds are tolerant to salt stress.

Effect of seed priming with different concentrations of potassium nitrate on the pattern of seed imbibition and germination of rice(Oryza sativa L.)

Low germination and vigor of rice seed associated with dry-seed broadcasting are common problems encountered by rice growers.The objectives of this study were to evaluate the role of potassium nitrate（KNO3）on the pattern of seed imbibition and to determine the effect of seed priming with KNO3 on the germination percentage,speed and uniformity of germination in rice seed.Experiment 1 compared the patterns of seed imbibition of six concentrations of KNO3（0,0.25,0.50,1.00,1.50,and 2.00%）in two rice cultivars-KDML105 and RD15.The results showed that soaking rice seed in KNO3 at higher concentrations could delay the imbibition time.The higher concentrations of KNO3 delayed the imbibition time of rice seed and took a longer time to reach the end of phases 1 and 2 compared to the lower concentrations.The patterns of seed imbibition using distilled water of both rice cultivars（KDML105 and RD15）were quite similar,but with different concentrations of KNO3,the imbibition time taken to reach the end of phases 1 and 2 was slightly postponed in KDML105 suggesting that different rice cultivars may need different imbibition times for soaking seed in the priming process.Experiment 2 evaluated the effects of seed priming with 1.0 and 2.0%KNO3 at different imbibition times.It was found that priming with 1.0%KNO3 showed better seed germination than priming with 2.0%KNO3 and seed priming with 1.0%KNO3 at the imbibition time of early phase 2（or 28 h for KDML105）improved seed germination and increased both the speed and uniformity of seed germination.The results of this study show promise for the use of priming with 1.0%KNO3 soaked until early phase 2 of seed imbibition for improving the seed germination and vigor of rice in dry seed broadcasting.

Influence of Seed Priming on Performance and Water Productivity of Direct Seeded Rice in Alternating Wetting and Drying

Direct seeded rice is promising alternative to traditional transplanting, but requires appropriate crop and water management to maintain yield performance and achieve high water productivity. Present study evaluated the effect of seed priming and irrigation on crop establishment, tillering, agronomic traits, paddy yield, grain quality and water productivity of direct seeded rice in alternate wetting and drying （DSR-AWD） in comparison with direct seeded rice at field capacity （DSR- FC）. Seed priming treatments were osmo-priming with KCI （2.2%）, CaCI2 （2.2%） and moringa leaf extracts （MLE, 3.3%） including hydro-priming as control. Among the treatments, seed osmo-primed with MLE emerged earlier and had higher final emergence, followed by osmo-priming with CaCI2. Tillering emergence rate and number of tillers per plant were the highest for seed priming with CaCI2 in DSR- AWD. Total productive and non-productive tillers, panicle length, biological and grain yields, harvest index were highest for seed priming with MLE or CaCI2 in DSR-AWD. Similarly, grain quality, estimated in terms of normal grains, abortive and chalky grains, was also the highest in DSR-AWD with MLE osmo-priming. Benefit cost ratio and water productivity was also the highest in DSR-AWD for seed priming with MLE. In conclusion, seed priming with MLE or CaCI2 can be successfully employed to improve the direct seeded rice performance when practiced with alternate wetting and drying irrigation.

Exogenous Hydrogen Sulfide Enhanced Antioxidant Capacity, Amylase Activities and Salt Tolerance of Cucumber Hypocotyls and Radicles

In the present experiment, effects of sodium hydrosulfide （NariS）, a H2S donor, on the oxidative damage, antioxidant capacity and the growth of cucumber hypocotyls and radicles were studied under 100 mmol L^-1 NaCl stress. NaCl treatment significantly induced accumulation of H2O2 and thiobarbituric acid-reactive substances （TBARS） in cucumber hypocotyls and radicles, and application of NariS dramatically reduced the accumulation of H/O2 and lipid peroxidation. However, the alleviating effects greatly depended on the concentrations of NariS, and 400 ~tmol L-1 NariS treatment showed the most significant effects. Corresponding to the change of lipid peroxidation, higher activities of antioxidant enzymes as well as the antioxidant capacity indicated as DPPH scavenging ac＇tivity, chelating activity of ferrous ions and hydroxyl radical （.OH） scavenging activity were induced by Naris treatment under NaCI stress, especially by 400 Ixmol L-I Naris treatment. With the alleviating lipid peroxidation, the amylase activities in cotyledons were increased, and the length of cucumber hypocotyls and radicles were significantly promoted by NariS treatment under NaCI stress. Unlike the effects of NariS, pretreatment with other sodium salts including Na2S, NazSO4, NaHSO4, Na2SO3, NaHSO3 and NaAc did not show significant effects on the growth of cucumber hypocotyls and radicles. These salts do not release H2S. Based on above results, it can be concluded that the effects of NariS in the experiment depended on the H2S rather than other compounds derived from NariS, and the alleviating effects might related with its function in modulating antioxidant capacity and amylase activities.

Arsenic Accumulation in Rice:Sources,Human Health Impact and Probable Mitigation Approaches

The human body loading with arsenic(As)through rice consumption is a global health concern.There is a crucial need to limit As build-up in rice,either by remediating As accumulation in soils or reducing As levels in irrigation water.Several conventional approaches have been utilized to alleviate the As accumulation in rice.However,except for some irrigation practices,those approaches success and the adoption rate are not remarkable.This review presents human health risks posed due to consumption of As contaminated rice,evaluates different biomarkers for tracing As loading in the human body,and discusses the latest advancement in As reducing technologies emphasizing the application of seed priming,nanotechnology,and biochar application for limiting As loading in rice grains.We also evaluate different irrigation techniques to reduce As accumulation in rice.Altering water management regimes significantly reduces grain As accumulation.Bio-and nano-priming of rice seeds improve germination and minimize As translocation in rice tissues by protecting cell membrane,building pool around seed coat,methylation and volatilization,or quenching harmful effects of reactive oxygen species.Nanoparticle application in the form of nano-adsorbents or nano-fertilizers facilitates nano-remediation of As through the formation of Fe plaque or sorption or oxidation process.Incorporating biochar in the rice fields significantly reduces As through immobilization,physical adsorption,or surface complexation.In conclusion,As content in cooked rice depends on irrigation source and raw rice As level.

Seed Priming Improves Agronomic Trait Performance under Flooding and Non-flooding Conditions in Rice with QTL SUB1

Farmers in South East Asia are adopting rice crop establishment methods from transplanting to direct wet or dry seeding as it requires less labour and time and comparatively less energy than transplanting. In contrast to irrigated condition, in rainfed lowland, direct seeding is a common practice. Early flooding controls weeds but decreases seedling establishment in direct seeded rice. Anaerobic germination is an important trait to counteract damages caused by early flooding. Management options which can help in crop establishment and improve crop growth under flooding might remove the constraints related to direct seeding. The investigation was carried out with two near isogenic lines Swarna and Swarna- Sub1. Swarna-Subl is tolerant to submergence whereas Swarna is susceptible. Seed priming was done with water and 2% Jamun （Syzygium cumini） leaf extract, and it improved seedling establishment under flooding. Acceleration of growth occurred due to seed pretreatment, which resulted longer seedling and greater accumulation of biomass. Seed priming greatly hastened the activities of total amylase and alcohol dehydrogenase in Swarna-Subl than in Swarna. Swarna-Subl outperformed Swarna when the plants were cultivated under flooding. Weed biomass decreased significantly under flooding compared to non-flooding conditions. Seed priming had positive effects on yield and yield attributing parameters both under non-flooding and early flooding conditions.

Seed Priming with Beta-Amino Butyric Acid Improves Abiotic Stress Tolerance in Rice Seedlings

We studied the influence of seed priming with beta-amino butyric acid（BABA） on the growth, physiological and biochemical parameters of seedlings with varied abiotic stress tolerance, which were raised and grown under unstressed and stressed（NaCl/PEG-6000） conditions. Under stressed conditions, the growth of rice seedlings was less when compared to control plants. After BABA priming, the seedling growth increased both under unstressed and stressed conditions as compared to the respective controls. BABA priming of rice seeds caused increase in the photosynthetic pigment content of the leaves, modified the chlorophyll a fluorescence related parameters and also enhanced the photosystem activities of seedlings when compared to their respective non-primed controls. BABA priming also caused increased mitochondrial activities of the rice seedlings. Moreover, BABA priming significantly reduced malondialdehyde content in the seedlings and also resulted in accumulation of proline especially in the NaCl tolerant variety Vyttila 6. BABA seed priming also enhanced the activity of nitrate reductase enzyme and activities of antioxidant enzymes like guaiacol peroxidase and superoxide dismutase. The presence of BABA was detected by high performance thin layer chromatography analysis in the rice seeds whereas in the seedlings it was not detected. Thus, it can be inferred that the seed priming effect of BABA mainly occurred within the seeds, which was further carried to the seedlings. It is concluded that BABA priming of seeds improved the drought and salinity stress tolerance of all the three rice varieties and it was significantly evident in the drought tolerant variety Vaisakh and NaCl tolerant variety Vyttila 6, when compared to the stress sensitive variety Neeraja.

The Effect of Priming on Seed Performance of Chickpea （Cicer arietinum L.） under Drought Stress

In order to investigate the effect of priming on Chickpea seed performance under drought stress, a study was carried out at the Seed Research Laboratory of Razi University, Kermanshah, Iran. The experiment was a factorial with three factors arranged in a completely randomized design with four replications. The first factor was seed priming （control （untreated）, HB-101 （Completely organic herbal extracts, derived from the bark of dark cones）, KNO3 and distilled water）, the second was drought stress levels （0.0, -0.3, -0.6, -0.9, -1.2 MPa） and the third was chickpea cultivars （Arman and Azar）. Results indicated that for both cultivars germination percentage （GP）, mean germination rate （MGR）, radicle length （RL）, plumule length （PL） and seedling dry weight （SDW） were reduced when drought stress level were increased from 0 to -!.2 Mpa, although, the cultivars showed different responses to the increased drought stress level. For all of the traits under study, the best results due to the priming treatments were obtained at the drought stress levels higher than -0.6 or -0.9 MPa. So that, at the -1.2 MPa of drought stress level, GP, MGR, and SDW were increased 53.75, 0.49, and 13.85, respectively by HB -101 when compared with control. However, seeds primed with HB-101 showed better performance than those primed with distilled water and KNO3. In general, this study revealed that seed priming especially with HB-101 improved chickpea seed performance under drought stress condition. However, the improvements were more obvious at the higher levels of drought stress.

Chitosan Seed Priming Improves the Yield and the Root System of Faba Bean(Vicia faba L.)Short Title:Chitosan Impact on Yield of Faba Bean

Faba bean is an important legume crop with food and feed applications.Since 2015,the culture of faba bean has decreased in France.Poor yield caused by climate change is proposed as one of the main reasons.Chitosan is a promising biopolymer with empirically proved impact on germination and disease tolerance of faba bean.However,the impact of chitosan seed priming on germination and yield of this plant is not experimentally studied.We followed chitosan primed faba bean seeds,from sowing until maturation,using germination,fruit and grain parameters.We observed that chitosan seed priming ameliorated several yield related traits.Germination rate,length of radicle and seedling,radicle dry matter,number of pods/plants,number of grains/pods were increased in chitosan primed faba beans.Total grain mass/plant increased up to 47%in treated plants.The probable underlying mechanisms,namely,root enhancement nitrogen metabolism,and elicitation of immune system are discussed.We conclude that,chitosan seed priming with compatible commercial preparations could be a potential solution to recompensate the loss of yield under variable climate conditions.

Effect of Dates and Methods of Sowing with and without Hydropriming on Growth,Phenology and Yield of Sorghum under Semi Arid Conditions of Eritrea

A study was carried out at the research farm of Hamelmalo Agricultural College during summer 2015 to study the effect of dates and methods of sowing with and without hydro-priming on growth,development and yield of sorghum.The experiment consisted of 2 factors-three dates of sowing viz.D0(Sowing before the onset of first summer rain,June 30),D1(Sowing with the onset of first summer rains,July 7)and D2(Sowing after the onset of summer rains,July 14)and three methods of sowing viz.SP(Direct sowing with hydro seed priming),TR(Transplanting)and DS(Direct sowing without hydro seed priming).The experiment was conducted in split plot design with 4 replications by keeping dates of sowing in the main plots and methods of sowing in the sub plots.The data on growth parameters,crop phenology,yield components and yield were recorded.The data were analysed using GENSTAT software and inferences were drawn by using LSD at 5%level of significance.Sowing methods significantly affected leaf area and leaf area index but sowing dates and their interaction with sowing methods did not show significant difference.Stand count,plant height,phenological parameters,thousand grain weight,grain and biomass yield were significantly affected by the sowing dates and methods but no significant difference in their interaction on all the parameters except in stand count and phenological parameters.Sowing before the onset of first summer rains(D0)resulted in significantly highest grain yield.Among the sowing methods,transplanting resulted in significantly higher grain yield seconded by direct sowing with hydro seed priming.Transplanting is less profitable and practicable as it is more laborious and difficult to apply in larger areas.

Seed priming with chitosan improves maize germination and seedling growth in relation to physiological changes under low temperature stress

Low temperature stress during germination and early seedling growth is an important constraint of global production of maize. The effects of seed priming with 0.25%, 0.50%, and 0.75% （w/v） chitosan solutions at 15 ℃ on the growth and physiological changes were investigated using two maize （Zea rnays L.） inbred lines, HuangC （chilling-tolerant） and Mo17 （chilling-sensitive）. While seed priming with chitosan had no significant effect on germination percentage under low temperature stress, it enhanced germination index, reduced the mean germination time （MGT）, and increased shoot height, root length, and shoot and root dry weights in both maize lines. The decline of malondialdehyde （MDA） content and relative permeability of the plasma membrane and the increase of the concentrations of soluble sugars and proline, peroxidase （POD） activity, and catalase （CAT） activity were detected both in the chilling-sensitive and chilling-tolerant maize seedlings after priming with the three concentrations of chitosan. HuangC was less sensitive to responding to different concentrations of chitosan. Priming with 0.50% chitosan for about 60-64 h seemed to have the best effects. Thus, it suggests that seed priming with chitosan may improve the speed of germination of maize seed and benefit for seedling growth under low temperature stress.

Seed Treatment with Auxins Modulates Growth and Ion Partitioning in Salt-stressed Wheat Plants

Experiments were performed to determine whether seed priming with different concentrations （100, 150, and 200 mg/L） of auxins （indoleacetic acid （IAA）, indolebutyric acid （IBA）, or their precursor tryptophane （Trp）） could alter salinity induced perturbances in salicylic acid and ion concentrations and, hence, growth in wheat （Triticum aestivum L.） cultivars, namely M.H.-97 （salt intolerant） and tnqtab-91 （salt tolerant）. Primed and non-primed seeds were sown in Petri dishes in a growth room, as well as in a field treated with 15 dS/m NaCl salinity. All priming agents, except IBA, increased the final germination percentage in both cultivars. The seedlings of either cultivar raised from Trp-treated seeds had greater dry biomass when under salt stress. In field experiments, Trp priming was much more effective in mediating the increase in grain yield, irrespective of the cultivar, under salt stress. The alleviatory effect of Trp was found to be associated with reduced uptake of Na^＋ in the roots and subsequent translocation to the shoots, as well as increased partitioning of Ca^＋ in the roots of salt-stressed wheat plants. Plants of both cultivars raised from Trp-and IAA-treated seeds accumulated free salicylic acid in their leaves when under salt stress. Overall, the Trp priming-induced improvement in germination and the subsequent growth of wheat plants could be related to ion homeostasis when under salt stress. The possible involvement of salicylic acid in the Trp priming-induced better growth under Conditions of salt stress is discussed.