Salinity and salt composition effects on seed germination and root length of four sugar beet cultivars

Salinization is one of the most important factors affecting agricultural land in the world. Salinization occurs naturally in arid and semiarid regions where evaporation is higher than rainfall. Sugar beet yield declines with an increase in salinity, but the sensitivity to salts varies with salt composition in water and sugar beet growth stage. The aim of this study was to determine the effect of water salinity levels and salt composition on germination and seedling root length of four sugar beet cultivars (PP22, IC2, PP36, and 7233). The experiments were undertaken with irrigation water with two salt compositions (NaCl alone and mixture of MgSO₄ + NaCl + Na₂SO₄ + CaCl₂) in three replicates. Thirteen salinity levels with electrical conductivity (EC) of the irrigation water ranging from 0 to 30 dS/m were applied to each cultivar in both experiments. Seed germination percentage and seedling root length growth were determined in 13 days. Statistical analysis revealed that germination and root length were significantly affected by salt composition, cultivars and salinity levels. Regardless of salt composition, seed germination and seedling root length were significantly affected by the irrigation water with EC up to 8 dS/m and 4 dS/m, respectively. Except for cultivar PP22, the adverse effect of salinity of the irrigation water on seed germination and seedling root length was higher for NaCl alone than for the salt mixture, which refers to lower salt stress in field conditions with natural salt composition. Presented at the International Conference on Bioclimatology and Natural Hazards, Poľana nad Detvou, Slovakia, 17–20 September 2007.     

盐胁迫下赤霉素对黄瓜种子萌发及幼苗生长的影响

研究外源GA₃对盐胁迫下黄瓜种子萌发和幼苗生长的影响。结果表明,添加不同质量浓度GA₃的各处理,其发芽率、发芽势和发芽指数均显著高于NaCl胁迫处理,其中以100 mg/L GA₃处理的发芽势、发芽率和发芽指数最高,幼苗的叶面积、根长、根冠比也最大,同时叶片中叶绿素含量最高,幼苗叶片的光合速率(P_n)、气孔导度(G_s)、胞间CO₂摩尔分数(C_i)及蒸腾速率(T_r)等均达到最大;而当赤霉素的质量浓度为50 mg/L时,叶片中的POD活性为2 005 U/(g·min）,达最大值。     

Hoary cress (Cardaria draba (L.) Desv.) seed germination ecology,longevity and seedling emergence

The effects of gibberellic acid (GA₃), potassium nitrate (KNO₃), prechilling, temperature, salt stress and osmotic potential on seed germination and sowing depth on seedling emergence and burial depth on seed viability of hoary cress (Cardaria draba (L.) Desv.), were studied in a series of laboratory, glasshouse and outdoor experiments. The optimal temperature for hoary cress seed germination was 20°C, both in light/dark and darkness regimes. Seed germination of hoary cress at 400 ppm concentration of GA₃ in a light/dark regime was maximal. Potassium nitrate concentrations increased the percentage of germination in comparison with the control treatment. Increasing the duration of dry prechilling to 30 and 45 days promoted the seed germination of hoary cress. Germination of hoary cress markedly decreased as salt and drought stress increased. Seed germination of hoary cress occurred at a range of pH from 3 to 11. Seedling emergence significantly decreased as planting depth increased. Total seed viability decreased with increasing burial depth. The maximum increase in mortality occurred in seeds that were buried at 5‐cm depth.     

Effect of GA3 on the Phytotoxicity of Aldicarb and Carbofuran on Seedling Growth in Capsicum frutescens var. California Wonder and Rate of Root Knot Nematode Infestation

The present investigation dealt with the effect of the two granular systemic nematicides aldicarb and carbofuran, individually and in combination with 100 mg · 1^-1 GA₃, on plant growth and root knot formation in C. frutescens var. California Wonder. Both nematicides and GA₃ were applied as a seed-dip treatment. GA₃ increased seed germination and seedling growth. All concentrations (2 to 20 g a.i. · 1^-1) of aldicarb and carbofuran, when applied independently, reduced seed germination and length of epicotyl and hypocotyl. However, application of these nematicides in combination with 100 mg · 1^-1 GA₃ showed antagonistic behaviour. All the treated seedlings were inoculated with 1000 nematode larvae of Meloidogyne incognita. Vegetative parameters of the plant were studied 15 days after transplantation. A combination of GA₃ (100 mg · 1^-1) with different concentrations of nematicides showed a synergistic effect on treated plants. Root knot index in plants treated with nematicides was found to be reduced with increasing concentrations of both nematicides. Maximum reduction in root knot index was observed at highest dose (20 g a.i. · 1^-1) of both nematicides, when applied in combination with 100 mg · 1^-1 GA₃. Proteolytic activities were decreased in plants treated with both aldicarb and carbofuran. Supplementation of the nematicides with GA₃ resulted in an increase in enzyme activities of the treated plants. Toxic residues increased with increasing concentration of both nematicides, whereas it was reduced at highest concentration of both nematicides when applied in combination with GA₃.     

Effects of seed priming with ascorbic acid to mitigate salinity stress on three wheat (Triticum aestivum L.) cultivars.

In this study, the effect of seed priming using ascorbic acid (ASA) on three commercial wheat cultivars i.e., Punjab-2011, Faisalabad-2008, and Ujala-2016 under salinity stress in both homogenous and heterogeneous environments has been investigated. It revealed that different levels of salinity have significantly reduced the growth attributes like percent germination, germination index, radical & plumule length, seed vigor index (In-vitro), seedling length, fresh & dry weight, and total chlorophyll content (In-vivo) with subsequent treatments. Salinity stress was induced by using NaCl in three different concentrations (100, 150, and 200 mM). Seeds of the three cultivars primed with 50, 100, and 150 mg/L ascorbic-acids have not only improved percent germination but also considerably reduced germination time and increased germination index (GI) indicating the potential for tolerating saline conditions. Seedling growth (seedling length, Fresh weight, and dry weight) of seeds primed with 50, 100, and 150 mg/L (ASA) was significantly higher than other non-primed seeds under the prevailing saline conditions. Hormonal priming with different concentrations of ascorbic acid was effective, nevertheless, the best results were obtained with 100 and 150 mg/L (ASA) concentrations. We concluded that the delay in germination and seedling growth was mainly due to excessive Na⁺ accumulation in the seeds of wheat cultivars. On the other hand, seed priming with various concentrations of ascorbic acid has proved to be effective in inducing salt tolerance in terms of germination parameters, seedling characteristics, and chlorophyll retention in the three local commercial wheat cultivars.     

Effect of salinity on seed germination,seedling growth,and physiological characteristics of Perilla frutescens

Abstract

Salt stress is one of the major environmental factors limiting crop growth and yield. To understand the effect of salt stress on plant growth, we investigated the response of three perilla varieties (Suyin 1, Ziye 7, and Ziye 10) to NaC1 exposure at concentrations of 0, 50, 100, 150, 200, and 250 mM in terms of seed germination, seedling growth, root activity, contents of soluble sugar, proline, and malondialdehyde (MDA), and peroxidase (POD) enzyme activity. Germination characteristics, such as the percentage of seed germination, tended to decrease with increasing NaC1 concentrations. After three weeks of salt stress, the three varieties exhibited different salt tolerance in terms of seed germination, seedling growth, and physiological changes: seedling growth was inhibited to various degrees, seedling vigor and root activities decreased, and MDA, proline, and soluble sugar contents increased with increasing NaCl concentrations. POD enzyme activity, a protective mechanism against salt stress, increased at low NaC1 concentrations in Suyin1 (0–150 mM) and Ziye 7 (0–100 mM), and then decreased at higher NaCl concentrations. In Ziye 10, on the other hand, POD activity dropped significantly with increasing NaCl concentrations. These results suggest that among the three varieties Suyin 1 is more salt tolerant than Ziye 7 and Ziye 10, and that Ziye 10 is the most sensitive to salt stress.     

Effects of salinity and heat-shock on wheat seedling growth and content of carbohydrates,proteins and amino acids

The effects of salinity (0, 50, 100, 150, and 200 mM NaCl) and heat-shock (42°C) and their interactions on germination, seedling growth, and some relevant metabolic changes of two cultivars (cv. Giza 155 and cv. Stork) of wheat (Triticum vulgaris L.) were studied. Germination studies indicate that plants tolerated salinity up to 100 mM NaCl. The lengths of roots and shoots and their water content, as well as fresh and dry matter yield of cv. Giza 155 seedlings remained more or less unchanged up to 100 mM NaCl and of cv. Stork up to 50 mM NaCl. Salinity induced progressive increase in soluble carbohydrates, soluble proteins and proline in cv. Giza 155 and in soluble proteins, proline and other free amino acids in cv. Stork. However, under the higher salinity levels, in cv. Giza 155 increase in soluble carbohydrates was accompanied by lose in other free amino acids, whereas in cv. Stork an opposite effect was obtained. Heat-shock treatment (42°C for 24 h) induced a significant decrease in the final germination percentage, the shoot and root lengths, fresh matter yield and the water content. The dry matter yield of the two cultivars was considerably increased as compared with the corresponding treatments with NaCl only. Heat-shock treatment resulted in a significant increase, in the amount of soluble carbohydrates and proline in salt treated seedlings of both cultivars. The pattern of changes in amino acids was opposite to that of soluble proteins, indicating that the increase in soluble proteins was at the expense of other amino acids in cv. Giza 155 andvice versa in cv. Stork.     

The combined effects of gibberellic acid and salinity on some antioxidant enzyme activities,plant growth parameters and nutritional status in maize plants

The combined effects of salt stress and gibberellic acid (GA₃) on plant growth and nutritional status of maize (Zea mays L. cv., DK 647 F1) were studied in a pot experiment. Treatments were (1) control (C): nutrient solution alone, (2) salt stress (S): 100 mM NaCl, (3) S + GA1: 100 mM NaCl and 50 ppm GA₃ and (4) S + GA2: 100 mM NaCl and 100 ppm GA₃. Salt stress (S) was found to reduce the total dry matter, chlorophyll content, relative water content (RWC), but to increase proline accumulation, superoxide dismutase (SOD; EC 1.15.1.1), peroxidase (POD; EC 1.11.1.7) and polyphenol oxidase (PPO; 1.10.3.1) enzyme activities and electrolyte leakage. GA₃ treatments overcame to variable extents the adverse effects of NaCl stress on the above physiological parameters. GA₃ treatments reduced the activities of enzyme in the salt-stressed plants. Salt stress reduced some macro and micronutrient concentrations but exogenous application of GA₃ increased these to levels of control treatment. Foliar application of GA₃ counteracted some of the adverse effects of NaCl salinity with the accumulation of proline which maintained membrane permeability and increased macro and micronutrient levels.     

Ethylene antagonizes the inhibition of germination in Arabidopsis induced by salinity by modulating the concentration of hydrogen peroxide

The capacity of plants to achieve successful germination and early seedling establishment under high salinity is crucial for tolerance of plants to salt. The gaseous hormone ethylene has been implicated in modulating salt tolerance, but the detailed role of how ethylene modulates the response of early seedling establishment to salt is unclear. To better understand the role of the ethylene signal transduction pathway during germination and seedling establishment, an ethylene insensitive mutation (ein2-5) and an ethylene sensitive mutation (ctr1-1) of Arabidopsis were analyzed under saline conditions and compared with the wild type plant (Col-0) as control. High salinity (>100?mM NaCl) inhibited and delayed germination. These effects were more severe in the ethylene insensitive mutants (ein2-5) and less severe in the constitutive ethylene sensitive plants (ctr1-1) compared with Col-0 plants. Addition of the ethylene precursor 1-aminocyclopropane-1-carboxylic acid (ACC) or inhibitors of ethylene action implied that ethylene was essential for early seedling establishment under normal and saline conditions. Salt stress increased the endogenous concentration of hydrogen peroxide (H₂O₂) in germinating seeds and ACC reduced its concentration. Our results suggest that ethylene promotes germination under salinity by modulating the endogenous concentration of H₂O₂ in germinating seeds. These findings demonstrate that ethylene is involved in regulating germination as an initiator of the process rather than consequence, and that ethylene promotes germination by modulating the endogenous concentration of H₂O₂ in germinating seeds under salinity.     

Effects of salt,alkali and salt–alkali mixed stresses on seed germination of the halophyte Salsola ferganica (Chenopodiaceae)

Salsola ferganica L. (Chenopodianceae) is an annual halophytic species. Experiments were carried out in laboratory to determine the effects of temperature, perianths and various types of salinity on seed germination and germination recovery. Seeds were germinated at 6 levels of temperature with perianths, plus perianths and removed perianths in complete darkness for 9 days. The germination responses of the seeds without perianths at 25 °C were determined over a wide range of NaCl, NaHCO₃ or NaCl–NaHCO₃ mixed stress for 13 days. Perianths seriously affected germination as a barrier for seed germination and the optimal temperature was at 25 °C. Highest germination percentage was obtained under control and seed germination was progressively inhibited with the increase of salinity concentration. The negative effect of NaHCO₃ at the same concentration on germination was stronger than that of NaCl and NaCl–NaHCO₃ mixed. When substrate salinity was removed, seeds exposed to a high NaCl concentration (400–800 mM), NaHCO₃ (50–200 mM) and NaCl–NaHCO₃ mixed (100–400 mM) germinated well. Final germination of Salsola ferganica seeds was significantly affected by types of salt at the low salinity (?200 mM) and with increased salinity it was influenced mainly by salinity concentration for various proportion of salt–alkali mixed stress.     

Potentiality of Different Seed Priming Agents to Mitigate Cold Stress of Winter Rice Seedling

Seed priming has proved to be an effective pre-germination seed invigoration technique for different crops to improve seed and seedling performance under different abiotic stresses. In Bangladesh, winter rice is very often exposed to cold waves just after sowing in the nursery bed resulting in poor seed germination and seedling emergence, yellowish and thin seedlings production, and a very low survival rate. Seed priming may mitigate the cold stress during seed germination and seedling emergence and helps in the quality seedling production of winter rice. To evaluate the efficacy of different seed priming techniques in increasing seedling emergence, growth, vigor and survivability of winter rice cultivars under cold stress, a pot experiment was conducted at the Department of Agronomy, Bangladesh Agricultural University during December 2018 to January 2019. The experiment comprised two factors, (A) Winter rice variety namely, i) BRRI dhan29 and ii) BRRI dhan36; (B) Seed priming agent namely i) Control (no priming), ii) 20000 ppm NaCl, iii) 30000 ppm NaCl, iv) 20000 ppm KCl, v) 30000 ppm KCl, vi) 20000 ppm CaCl₂, vii) 30000 ppm CaCl₂, viii) 50 ppm CuSO₄, ix) 75 ppm CuSO₄, x) 10000 ppm ZnSO₄, xi) 15000 ppm ZnSO₄, xii) 2 ppm Na₂MoO₄, xiii) 3 ppm Na₂MoO₄, xiv) 100 ppm PEG (Polyethylene glycol 4000) and xv) 150 ppm PEG. Seeds were sown on two different dates viz., 1st December and 1st January so that seedlings are exposed to cold stress at different stages. The experiment was laid out in a completely randomized design (CRD) with three replications. Results indicated that (in most of the cases) seed priming has a positive impact on seedling emergence rate (%), root length, shoot length, root shoot ratio, root dry weight, shoot dry weight, seedling dry weight and survival rate (%). Among the priming agents, KCl and CaCl₂ performed best; while priming with NaCl and PEG showed no advantages over no priming for both the sowing dates. In general, BRRI dhan36 performed better than BRRI dhan29 in terms of seedling growth because of its higher tolerance to cold stress. But, both the varieties performed similarly in terms of emergence rate and survival rate. Thus, priming is an effective tool to increase seed germination, better seedling growth, and higher seedling survivability of winter rice under cold stress, and KCl (20000 ppm) or CaCl₂ (20000 ppm) can be considered as a viable priming agent.     

Alleviation of salt stress by plant growth regulators and IAA producing bacteria in wheat

The action of phytohormone producing bacteria and plant growth regulators on germination and seedling growth of wheat under saline conditions were studied. Seed dormancy enforced by salinity (100 mM NaCl) was substantially alleviated and the germination was promoted by gibberellin, auxin, zeatin, and ethephon from 54 to 97%. The IAA producing bacterial strains Pseudomonas aureantiaca TSAU22, Pseudomonas extremorientalis TSAU6 and Pseudomonas extremorientalis TSAU20 significantly increased seedling root growth up to 25% in non-salinated conditions and up to 52% at 100 mM NaCl, compared to control plants. It is concluded that growth regulators considerably alleviated salinity-induced dormancy of wheat seeds. The facts mentioned above make it possible to recommend root colonizing bacteria that produce phytohormone to alleviate salt stress of wheat grown under conditions of soil salinity.     

Gibberellin Metabolism and Transport During Germination and Young Seedling Growth of Pea (<Emphasis Type="Italic">Pisum sativum</Emphasis> L.)

The role of gibberellins (GAs) during germination and early seedling growth is examined by following the metabolism and transport of radiolabeled GAs in cotyledon, shoot, and root tissues of pea (Pisum sativum L.) using an aseptic culture system. Mature pea seeds have significant endogenous GA₂₀ levels that fall during germination and early seedling growth, a period when the seedling develops the capacity to transport GA₂₀ from the cotyledon to the shoot and root of the seedling. Even though cotyledons at 0–2 days after imbibition have appreciable amounts of GA₂₀, the cotyledons retain the ability to metabolize labeled GA₁₉ to GA₂₀ and express significant levels of PsGA20ox2 message (which encodes a GA biosynthesis enzyme, GA 20-oxidase). The large pool of cotyledonary GA₂₀ likely provides substrate for GA₁ synthesis in the cotyledons during germination, as well as for shoots and roots during early seedling growth. The shoots and roots express GA metabolism genes (PsGA3ox genes which encode GA 3-oxidases for synthesis of bioactive GA₁, and PsGA2ox genes which encode GA 2-oxidases for deactivation of GAs to GA₂₉ and GA₈), and they develop the capacity to metabolize GAs as necessary for seedling establishment. Auxins also show an interesting pattern during early seedling growth, with higher levels of 4-chloro-indole-3-acetic acid (4-Cl-IAA) in mature seeds and higher levels of indole-3-acetic acid (IAA) in young root and shoot tissues. This suggests a changing role for auxins during early seedling development.     

Germination stimulation in wild oats (Avena fatua L.) by synthetic strigol analogs and gibberellic acid

At concentrations of 0.01–1 mM, five synthetic multiring analogs of strigol were effective germination stimulants of intact and dehulled wild oat (Avena fatua L.) seeds. The effect was concentration-dependent and equaled or exceeded that produced by equimolar gibberellic acid (GA₃). The most effective strigol analog treatments induced 55–80% germination within 7 days in intact wild oat seeds and resulted in 63–86% germination and normal seedling growth over 14 days. Intact wild oat controls germinated 14% after 14 days. The stimulation of wild oat germination by these synthetic strigol analogs demonstrates that these compounds, initially developed as germination stimulants for the seeds of the parasitic weed, witchweed (Striga asiatica L. Kuntz.), have bioregulatory activity in dormant seeds of monocots, as well as dicots. None of the compounds tested significantly affected the germination of nondormant cultivated oat seeds (Avena sativa L.). The commonly used dispersal agent, Tween 20 (0.1%), was found to inhibit germination of cultivated oats, alone and in the presence of 2% acetone.     

Impact of dormancy regulating chemicals on salinity induced dormancy in Lasiurus scindicus and Panicum turgidum: two desert glycophytic grasses

The indigenous forage grasses Lasiurus scindicus and Panicum turgidum are candidate species for the restoration of degraded desert rangelands. The impact of five dormancy regulating chemicals on overcoming salinity-induced germination inhibition was assessed under the best germination conditions in the two species. Seeds were germinated in a series of NaCl concentrations: 0–200 mM NaCl for P. turgidum, and 0–300 mM NaCl for L. scindicus. Lasiurus scindicus seeds were more tolerant to salinity than those of P. turgidum. Twenty percent of P. turgidum seeds germinated in 100 mM NaCl and none in the higher levels, but 47.5% and 8.8% of L. scindicus seeds germinated in 100 and 200 mM NaCl, respectively. The five studied chemicals (fusicoccin, GA₃, kinetin, nitrate and thiourea) did not succeed in improving germination of non-saline treated seeds of the two species, compared to the control, except thiourea in P. turgidum. The salinity-induced germination inhibition in P. turgidum was completely alleviated by the application of gibberellic acid (GA₃), partially alleviated by the application of fusicoccin, kinetin and thiourea, but not affected by nitrate. In L. scindicus, the germination inhibition was completely alleviated by fusicoccin, GA₃, nitrate and thiourea, but partially alleviated by kinetin. For using the two grass species in restoration of degraded rangelands affected by higher salinity, the results suggest using fusicoccin, GA₃, nitrate and thiourea with L. scindicus and GA₃ with P. turgidum seeds as a preseeding treatment can overcome the problem of reduced germination.     

Exogenous application of thiamin promotes growth and antioxidative defense system at initial phases of development in salt-stressed plants of two maize cultivars differing in salinity tolerance

The effects of thiamin (Thi) applied as seed soaking or foliar spray on some key physiological parameters were investigated in two differentially salt-responsive maize (Zea mays L.) cultivars, DK 5783 and Apex 836 F1, exposed to saline stress in two different experiments. An initial experiment (germination experiment) was designed to identify appropriate doses of Thi which could lessen the deleterious effects of salt on plants and screen all available maize cultivars for their differential tolerance to salt stress (100 mM NaCl). The seeds of nine maize cultivars were soaked for 24 h in solutions containing six levels of Thi (25, 50, 75, 100, 125 and 150 mg l^?1). Based on the results obtained from the germination experiment, maize cultivar DK 5783 was found to be the most salt tolerant and Apex 836 as the most sensitive cultivar. Also, of six Thi levels used, two levels (100 and 125 mg l^?1) were chosen for subsequent studies. In the second experiment (glasshouse experiment), two maize cultivars, DK 5783 (salt tolerant) and Apex 836 (salt sensitive) were subjected to saline regime (100 mM NaCl) and two levels of Thi (100 and 125 mg l^?1) applied as foliar spray. Salt stress markedly suppressed shoot and root dry mass, total chlorophylls (“a” + “b”), leaf water potential and maximum fluorescence yield (Fv/Fm) in the plants of both maize cultivars, but it increased proline accumulation, leaf osmotic pressure, malondialdehyde (MDA) and hydrogen peroxide (H₂O₂) concentrations, electrolyte leakage (EL) as well as activities of some key antioxidant enzymes, superoxide dismutase (SOD; EC. 1.15.1.1), peroxidase (POD; EC. 1.11.1.7) and catalase (CAT; EC. 1.11.1.6). Salt-induced reduction in plant growth parameters was higher in the salt-sensitive cultivar, Apex 836, which was found to be associated with relatively increased EL, and MDA and H₂O₂ levels, and decreased activities of the key antioxidant enzymes. Application of Thi as seed soaking or foliar spray partly mitigated the deleterious effects of salinity on plants of both maize cultivars. The most promising effect of Thi on alleviation of adverse effects of salt stress on maize plants was found when it was applied as foliar spray at 100 mg l^?1. Thiamin application considerably reduced tissue Na⁺ concentration, but improved those of N, P, Ca²⁺ and K⁺ in the salt-stressed maize plants. Exogenously applied thiamin-induced growth improvement in maize plants was found to be associated with reduced membrane permeability, MDA and H₂O₂ levels, and altered activities of some key antioxidant enzymes such as CAT, SOD and POD as well as increased photosynthetic pigment concentration under saline regime.     

Effects of Soil Salinity and Growth Regulators on Germination and Seedling Metabolism of Wheat

Germination studies were carried out with the wheat varieties NP823, Karchia, Sonora 63, Sonora 64, Mayo 64 and Lerma Rojo in artificially salinized soil maintained at EC_e 2, 8, 12 and 16 mmhos/cm at 25°C. Early seedling growth and metabolism of variety NP 823 was studied in salt solutions alone and with addition of the growth regulators GA₃ and Cycocel (2-chloroethyl trimethylammonium chloride). Soil salinity both depressed and delayed the germination. Among the varieties tested NP 823 and Karchia were relatively less susceptible to salt injury while Lerma Rojo exhibited a maximum susceptibility. Salt supply also brought about a reduction in the early seedling growth, the release of reducing sugar and the amylase activity. The adverse effect on amylase activity was not mediated through the synthesis of enzyme protein but by an inhibition of the enzyme activity. Exogenous supply of GA₃ counteracted the adverse effect of salt on amylase activity and the release of reducing sugar but not on the early seedling growth.     

Gibberellic acid mediated induction of salt tolerance in wheat plants: Growth,ionic partitioning,photosynthesis, yield and hormonal homeostasis

In order to elucidate the GA₃-priming-induced physiochemical changes responsible for induction of salt tolerance in wheat, the primed and non-primed seeds of two spring wheat (Triticum aestivum L.) cultivars, namely, MH-97 (salt intolerant) and Inqlab-91 (salt tolerant) were sown in a field treated with 15 dS m⁻¹ NaCl salinity. Although all the three concentrations (100, 150 and 200 mg L⁻¹) of GA₃ were effective in improving grain yield in both cultivars, the effect of 150 mg L⁻¹ GA₃ was much pronounced particularly in the salt intolerant cultivar when under salt stress. Seed priming with GA₃ altered the pattern of accumulation of different ions between shoots and roots in the adult plants of wheat under saline conditions. Treatment with GA₃ (150 mg L⁻¹) decreased Na⁺ concentrations both in the shoots and roots and increased Ca²⁺ and K⁺ concentrations in the roots of both wheat cultivars. GA₃-priming did not show consistent effect on gaseous exchange characteristics and the concentrations of auxins in the salt stressed plants of both wheat cultivars. However, all concentrations of GA₃ reduced leaf free ABA levels in the salt intolerant, while reverse was true in the salt tolerant cultivar under saline conditions. Priming with GA₃ (150 mg L⁻¹) was very effective in enhancing salicylic acid (SA) concentration in both wheat cultivars when under salt stress. Treatment with GA₃ (100–150 mg L⁻¹) lowered leaf free putrescine (Put) and spermidine (Spd) concentrations in the plants of both wheat cultivars. The decrease in polyamines (Put and Spd) and ABA concentrations in the salt stressed plants of the salt intolerant cultivar treated with GA₃ suggested that these plants might have faced less stress compared with control. Thus, physiologically, GA₃-priming-induced increase in grain yield was attributed to the GA₃-priming-induced modulation of ions uptake and partitioning (within shoots and roots) and hormones homeostasis under saline conditions.     

Effect of calcium on the salinity tolerance of Wimmera ryegrass (Lolium rigidum Gaud., cv. Wimmera) during germination

Summary The modifying effect of calcium (Ca) on the salinity tolerance of Wimmera ryegrass during germination and early seedling growth was studied. Pretreatment of seeds with Ca has no significant effect on germination under NaCl or MgCl₂ salinity. The addition of Ca to the germination medium increased the germination percentage significantly, especially with MgCl₂. Significant increases in seedling shoot and root growth also occurred with Ca addition to the growth medium under MgCl₂ salinity.     

ABA, GA3, and nitrate may control seed germination of Crithmum maritimum (Apiaceae) under saline conditions

Impaired germination is common among halophyte seeds exposed to salt stress, partly resulting from the salt-induced reduction of the growth regulator contents in seeds. Thus, the understanding of hormonal regulation during the germination process is a main key: (i) to overcome the mechanisms by which NaCl-salinity inhibit germination; and (ii) to improve the germination of these species when challenged with NaCl. In the present investigation, the effects of ABA, GA₃, NO⁻₃, and NH⁺₄ on the germination of the oilseed halophyte Crithmum maritimum (Apiaceae) were assessed under NaCl-salinity (up to 200 mM NaCl). Seeds were collected from Tabarka rocky coasts (N-W of Tunisia). The exogenous application of GA₃, nitrate (either as NaNO₃ or KNO₃), and NH₄Cl enhanced germination under NaCl salinity. The beneficial impact of KNO₃ on germination upon seed exposure to NaCl salinity was rather due to NO⁻₃ than to K⁺, since KCl failed to significantly stimulate germination. Under optimal conditions for germination (0 mM NaCl), ABA inhibited germination over time in a dose dependent manner, but KNO₃ completely restored the germination parameters. Under NaCl salinity, the application of fluridone (FLU) an inhibitor of ABA biosynthesis, stimulated substantially seed germination. Taken together, our results point out that NO⁻₃ and GA₃ mitigate the NaCl-induced reduction of seed germination, and that NO⁻₃ counteracts the inhibitory effect of ABA on germination of C. maritimum. To cite this article: A. Atia et al., C. R. Biologies 332 (2009).