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.     

Aspirin priming circumvents the salinity-induced effects on wheat emergence and seedling growth by regulating starch metabolism and antioxidant enzyme activities

Though seed priming has been emerged as an effective and pragmatic approach, efforts are being made to discover and optimize the new priming agents which are cheaper and easily accessible to the farmers. Here, we established two independent experiments, to ascertain the role of aspirin priming in salinity tolerance of wheat. In the first experiment, various concentrations of aspirin (125, 250, 375, and 500 ppm) were examined for emergence and seedling growth of wheat. A non-primed control, hydropriming, and hydrogen peroxide priming treatments were also maintained for comparison. Among the different treatments, seeds primed with 125 and 250 ppm aspirin depicted better emergence, vigorous seedling growth, and higher starch metabolism. Therefore, these treatments were further used in the second experiment under salinity stress (10 dS m^?1). Salinity stress caused delayed and erratic emergence hampered the shoot and root growth, chlorophyll contents, and enhanced the lipid peroxidation and phenolics content in wheat seedlings. However, wheat seed priming particularly with aspirin effectively alleviated the negative effects of salinity on most of the observed parameters. Aspirin priming also significantly enhanced the activities of antioxidant enzymes (catalase, peroxidase, and superoxide dismutase), and reduced oxidative stress in wheat seedlings. Vigorous growth and greater salinity tolerance of wheat seedlings derived from aspirin primed seeds were related with better starch metabolism, strong antioxidative defense system, and lower lipid peroxidation.     

Differences in physiological and biochemical characteristics in response to single and combined drought and salinity stresses between wheat genotypes differing in salt tolerance

The combined drought and salinity stresses pose a serious challenge for crop production, but the physiological mechanisms behind the stresses responses in wheat remains poorly understood. Greenhouse pot experiment was performed to study differences in genotype response to the single and combined (D + S) stresses of drought (4% soil moisture, D) and salinity (100 mM NaCl, S) using two wheat genotypes: Jimai22 (salt tolerant) and Yangmai20 (salt‐sensitive). Results showed that salinity, drought and/or D + S severely reduces plant growth, biomass and net photosynthetic rate, with a greater effect observed in Yangmai20 than Jimai22. A notable improvement in water use efficiency (WUE) by 239, 77 and 103% under drought, salinity and D + S, respectively, was observed in Jimai22. Moreover, Jimai22 recorded higher root K⁺ concentration in drought and salinity stressed condition and shoot K⁺ under salinity alone than that of Yangmai20. Jimai22 showed lower increase in malondialdehyde (MDA) accumulation, but higher activities of superoxide dismutase (SOD, EC 1.15.1.1) and guaicol peroxidase (POD, EC 1.11.1.7), under single and combined stresses, and catalase (CAT, EC 1.11.1.6) and ascorbate peroxidase (APX, EC 1.11.1.11) under single stress. Our results suggest that high tolerance of Jimai22 in both drought and D + S stresses is closely associated with larger root length, higher Fv/Fm and less MDA contents and improved capacity of SOD and POD. Moreover, under drought Jimai22 tolerance is firmly related to higher root K⁺ concentration level and low level of Na⁺, high‐net photosynthetic rate and WUE as well as increased CAT and APX activities to scavenge reactive oxygen species.     

温度对干旱、盐胁迫下两种黄芪属种子萌发和幼苗生长的影响

为探讨温度对干旱、盐胁迫下黄芪属种子萌发和幼苗生长特性的影响,以黄芪属蒙古黄芪和扁茎黄芪2种种子为研究对象,纯净水处理为对照组,NaCl、PEG处理为实验组,设置4个渗透势水平(0、-0.1、-0.3、-0.5 MPa),置于5种不同的温度(10、15、20、25、30 ℃)下,每日观察并记录两种种子萌发和幼苗生长情况。结果表明：旱盐胁迫下蒙古黄芪和扁茎黄芪种子萌发最适宜的温度分别为25和20 ℃左右;蒙古黄芪耐高温不耐低温,而扁茎黄芪恰恰相反;但25和20 ℃均适宜两种幼苗生长,包括胚根、胚轴和子叶的生长。蒙古黄芪各处理组(除未发芽的种子)的平均发芽时间都比扁茎黄芪长;NaCl胁迫程度的增加使得两种种子的最终发芽率降低,但蒙古黄芪的耐盐性高于扁茎黄芪;随着PEG胁迫程度的增加,二者的发芽均受到抑制,甚至会出现完全不萌发,但扁茎黄芪的耐旱性高于蒙古黄芪;在相同的渗透势时,尤其是-0.5 MPa,PEG比NaCl对两种种子的影响大;交互胁迫作用下,随着渗透势的增加两种幼苗的鲜重、干重以及胚根、胚轴、子叶的长和宽变化较大;利用Design Expert软件预测发现：温度25 ℃、NaCl渗透势为-0.1 MPa,温度24 ℃、PEG渗透势为-0.04 MPa的处理是蒙古黄芪种子萌发和幼苗生长达到最优化的组合;而扁茎黄芪最优化的组合则为23 ℃下NaCl渗透势为-0.07 MPa的处理,20 ℃下PEG渗透势为-0.13 MPa的处理。     

Combined effect of salicylic acid and potassium mitigates drought stress through the modulation of physio-biochemical attributes and key antioxidants in wheat

Improving physio-biochemical traits in wheat under drought stress conditions has received more research attention in recent years for better adaptability and higher yield. In this study, we explored the potential bio-physiological mechanisms underlying improved plant growth and water use efficiency in wheat following soil application of potassium (0 and 100 kg ha^?1) and seed primed salicylic acid (SA) (150 mg per L) and SA foliar application (100 mg per L) under drought stresses (100%, 60% and 30% FC). Two years' average data revealed that inducing drought stress resulted in a decrease in plant pigments content, growth traits, and plant water status however, the influence was substantially reduced with the combined application of K and SA under drought stress conditions. The SA foliar spray in combination with K had increased chlorophyll a (174% and 83%), chl b (130% and 192%), chl a + b (156% and 120), carotenoid (22% and 11%), proline contents (24% and 29%) leaf relative water content (24% and 29%) while reduced leaf WSD (17% and 20%), WRC (6% and 7%), and WUC (23% and 28%) under mild and severe drought stresses, respectively. The increase in grain yield by 41% and 37% with enhanced water use efficiency was obtained with combined foliar SA and K under mild and severe drought stress, respectively indicating its vital role in overcoming the deleterious effects of drought via regulation of osmotic and metabolic processes and stabilizes cell components. RDA analysis revealed that the studied traits were completely discriminated under severe stress than mild or no drought stress. A positive and significant association was found between plant pigments with seed yield whereas a negative and significant correlation existed between water leaf traits and plant pigments. It was concluded that both foliar SA and seed primed SA with K fertilization combat the adverse effects of drought and improved plant water status as well as growth and bio-physiological traits of wheat under drought stress conditions.     

普甜玉米种子萌发期糖代谢和水解酶活性动态变化

种子萌发是一个较复杂的生理生化过程,是种子贮藏物质在酶的作用下经过一系列反应生成蔗糖、葡萄糖、果糖等各种糖类化合物,为种子萌发提供碳源和能量。该研究利用两个不同来源、籽粒营养成分具有差异的普甜玉米种子动态分析了种子萌发期蔗糖、果糖和葡萄糖代谢及关键水解酶活性的变化。结果表明:在种子萌发过程中,E22和T26两个普甜玉米种子的物质动员量、物质利用率、蔗糖、葡萄糖和果糖含量均存在遗传差异,其中淀粉含量较高的T26种子具有较突出的物质利用率,表明淀粉是影响普通甜玉米种子萌发的关键因子;在种子萌发4~8 d、6~10 d时,E22分别具有较高的蔗糖和葡萄糖含量,而T26是在萌发10 d时具有较高的果糖含量。随着种子发芽进程,蔗糖合成酶活性、淀粉酶活性都呈逐渐上升的趋势,但淀粉酶活性变幅较明显;进一步关联分析8个种子萌发物质利用性状间关系,结果表明种子萌发期间,种子物质动员量主要受淀粉酶活性影响,而种子物质利用率则主要受糖含量多少制约。因此,提高甜玉米种子萌发期物质利用率对其种子发芽和幼苗生长,增强其与杂草生长的竞争力,提高甜玉米产量均具有重要意义。     

Physiological,biochemical and molecular evaluation of mungbean genotypes for agronomical yield under drought and salinity stresses in the presence of humic acid

Drought and salinity are potential threats in arid and semi arid regions. The current study was conducted with objective to optimize the production of different exotic genotypes of mungbean (NM-121-25, Chakwal M-6, DM-3 and PRI-Mung-2018) under drought and salinity stresses using humic acid in field experiments. One year tri-replicate field experiment was performed in RCBD using three factorial arrangement and effects of humic acid (60 kg ha^?1) were evaluated at physiological, biochemical, molecular and agronomical level under individual and integrated applications of drought (no irrigation till 15 days) and salinity (EC 6.4 dSM^?1). Data for physiological parameters (total chlorophyll, photosynthesis rate, stomatal conductance, transpiration rate and membrane damage), antioxidant enzymes (superoxide dismutase, catalase, peroxidase) and proline were collected on weekly basis since after the initiation of drought and salinity stresses. However data for agronomic characteristics (plant height, branches plant^?1, LAI, pods plant^?1, pod length and hundred seed weight) and grain carbohydrate content were collected after harvesting, while sampling for drought (VrDREB2A, VrbZIP17 and VrHsfA6a) and salinity (VrWRKY73, VrUBC1 and VrNHX1) related genes expression study was done after plants attained seedling stage. Under both individual and integrated applications of drought and salinity, all genotypes showed significant (p ≤ 0.05) increase in all traits excluding Cell membrane damage and proline during humic acid application. Likewise, genes expression revealed statistically distinct (p ≤ 0.05) up-regulation under humic acid treatment as compared to no humic acid treatment during both individual and integrated applications of drought and salinity. The genotype PRI-Mung-2018 recorded noteworthy performance during study. Moreover correlation and PCA analysis revealed that ultimate agronomical yield due to humic acid is an outcome of interconnection of physiological and biochemical parameters.     

黄河口不同氮基质碱蓬种子萌发及幼苗生长对盐分及氮输入的响应

2014年4-11月,选择黄河入海口北部滨岸高潮滩的碱蓬湿地为研究对象,基于野外原位氮负荷增强模拟试验(N0,无额外氮输入;N1,低氮输入;N2,中氮输入;N3,高氮输入),获取相应的不同氮基质种子(S0,S1,S2和S3),以研究其发芽率以及幼苗生长状况对不同盐分胁迫和氮浓度交互作用的响应。结果表明,不同氮负荷影响下碱蓬成熟种子中的氮含量整体表现为S2S0S1S3,中氮输入更利于种子中氮养分的累积。盐分和氮交互作用下4种氮基质种子的发芽率总体表现为S2S1S0S3(P0.05),S2在不同盐分胁迫下的发芽率最高,幼苗的生长状况也最好。随着盐分的增加,4种氮基质种子的发芽率及幼苗生长状况均受到一定程度的抑制,但较低的盐分有助于其幼苗长度的增长,且随着氮输入量的增加这种抑制作用可得到一定程度缓解。盐分胁迫、氮浓度和种子类型作为单独因素出现时对碱蓬的发芽率、幼苗长度、鲜重和干重均产生显著影响,除幼苗长度受氮浓度和盐分胁迫交互作用的影响达到显著水平外(P0.05),其他因子交互作用对诸生态指标的影响并不明显。研究发现,不同氮输入处理不仅改变了原生环境碱蓬种子的氮含量,而且也使这些具备不同氮基质的种子对不同盐分胁迫与氮浓度环境具有不同的生态适应对策,中氮输入下的碱蓬种子(S2)无论在萌发率还是在幼苗生长状况上均优于其他氮基质的种子。未来,随着黄河口新生湿地氮养分供给的不断增加,当湿地氮养分达到中氮水平时,将更有利于碱蓬种子的萌发以及幼苗的生长,当氮养分达到更高水平时,碱蓬种子的萌发以及幼苗生长可能会受到一定程度的抑制。     

云锦杜鹃种子萌发及对干旱胁迫的响应

以不同渗透势的PEG-6000溶液模拟干旱胁迫条件, 研究云锦杜鹃种子的萌发、幼苗生长和累积吸水率对干旱胁迫的响应。结果显示：种子于第14 d开始萌发,萌发期为8 d,总萌发率为45.5%±1.7%。在渗透势为-0.3～-0.6 MPa的溶液中, 种子的累计吸水率在第5 d就超过对照(蒸馏水中), 种子的萌发和幼苗的生长也优于对照, 说明云锦杜鹃种子不适合过于湿润的土壤环境中萌发。但溶液的渗透势≥-0.9 MPa时, 种子的吸水减缓、萌发率下降, 同时幼苗的生长也慢, 而当渗透势≥-1.8 MPa时, 种子不能充分吸涨、萌发, 说明云锦杜鹃种子对干旱胁迫比较敏感。另外, 经PEG溶液浸种2天后移入蒸馏水中,萌发率均有一定程度的提高, 其中经-0.3～-1.5 MPa的PEG溶液浸种后, 萌发率显著高于对照。提示用一定浓度范围的PEG溶液浸种可使休眠种子活化, 提高种子繁育的效率。     

Physiological responses of wheat seedlings to drought and UV-B radiation. Effect of exogenous sodium nitroprusside application

Physiological and biochemical responses of wheat seedlings to drought, UV-B radiation, and combined stress were investigated. Drought, UV-B, and combined stresses retarded seedling growth by 26.5, 29.1, and 55.9%, respectively. One reason for growth retardation may be the oxidative damage indicated by an increase in the H₂O₂ content and lipid peroxidation degree. Furthermore, there was negative correlation between shoot fresh weight and H₂O₂ content, fresh weight and the content of thiobarbituric acid-reacting substances (TBARS), and the positive correlation between H₂O₂ content and TBARS (R ² = 0.9251, 0.9005, and 0.9007, respectively). The activities of superoxide dismutase, guaiacol peroxidase, and ascorbate peroxidase increased under drought, UV-B, and the combination of stresses, while catalase activity decreased under the combined stress as compared to the control. The combination of drought and UV-B caused more severe damage to wheat seedlings than stress factors applied separately. Thus, the combined application of drought and UV-B had more strong adverse effects on wheat seedlings. The addition of 0.2 mM sodium nitroprusside (SNP) enhanced wheat seedling growth under drought, UV-B, and combined stress, likely, due to decreasing the accumulation of H₂O₂ and lipid peroxidation as well as activating the antioxidant enzymes. However, SNP treatment decreased the proline content. Published in Russian in Fiziologiya Rastenii, 2007, Vol. 54, No. 5, pp. 763–769. The text was submitted by the authors in English.     

The pepper late embryogenesis abundant protein CaLEA1 acts in regulating abscisic acid signaling,drought and salt stress response

As sessile organisms, plants are constantly challenged by environmental stresses, including drought and high salinity. Among the various abiotic stresses, osmotic stress is one of the most important factors for growth and significantly reduces crop productivity in agriculture. Here, we report a function of the CaLEA1 protein in the defense responses of plants to osmotic stress. Our analyses showed that the CaLEA1 gene was strongly induced in pepper leaves exposed to drought and increased salinity. Furthermore, we determined that the CaLEA1 protein has a late embryogenesis abundant (LEA)_3 homolog domain highly conserved among other known group 5 LEA proteins and is localized in the processing body. We generated CaLEA1‐silenced peppers and CaLEA1‐overexpressing (OX) transgenic Arabidopsis plants to evaluate their responses to dehydration and high salinity. Virus‐induced gene silencing of CaLEA1 in pepper plants conferred enhanced sensitivity to drought and salt stresses, which was accompanied by high levels of lipid peroxidation in dehydrated and NaCl‐treated leaves. CaLEA1‐OX plants exhibited enhanced sensitivity to abscisic acid (ABA) during seed germination and in the seedling stage; furthermore, these plants were more tolerant to drought and salt stress than the wild‐type plants because of enhanced stomatal closure and increased expression of stress‐responsive genes. Collectively, our data suggest that CaLEA1 positively regulates drought and salinity tolerance through ABA‐mediated cell signaling.     

Hg2+ 与POD 复合处理对小麦萌发及幼苗生长的影响

通过水培实验研究了0、10、20、50、70和100 mg.L-1 Hg2+和65 U.mL-1的过氧化物酶(POD)混合浸种对小麦(Triticum aestivum L.)萌发及幼苗生长过程中的10个形态和生理生化指标的影响。结果表明：施加外源POD可明显提高种子发芽率、植株日均增重和幼苗叶片的可溶性蛋白含量,增加幼苗叶片内源超氧物歧化酶(SOD)和POD的活性,拮抗Hg2+胁迫对种子发芽率、苗高、日均增重及叶片可溶性蛋白含量的不利影响,Hg2+浓度较高时(≥50 mg.L-1),对种子发芽率和日均增重的拮抗作用更明显,并对较低浓度Hg2+(≤20 mg.L-1)胁迫引起的叶片SOD活性的上升和低于100 mg.L-1的Hg2+胁迫引起的叶片 POD活性的上升有进一步的促进作用;然而对幼苗平均最长根长度、侧根数和幼苗叶片叶绿素含量则无明显影响。     

Seed zinc content influences early vegetative growth and zinc uptake in oilseed rape (Brassica napus and Brassica juncea) genotypes on zinc-deficient soil

Low-Zn seed (around 80 ng Zn per seed) and high-Zn seed (around 160 ng Zn per seed) of Zhongyou 821 (a traditional Brassica napus genotype from China found to be Zn-inefficient in our previous experiments), Narendra (Zn-efficient B. napus genotype from Australia) and CSIRO-1 (a Zn-efficient B. juncea genotype from Australia) oilseed rape genotypes were sown in pots containing Zn-deficient siliceous sand fertilized with low Zn supply (0.05 mg Zn kg^–1 soil) or high Zn supply (2.0 mg Zn kg^–1 soil) in a controlled environment. After six weeks, plants derived from the high-Zn seed had better seedling vigour, increased root and shoot growth, more leaf area and chlorophyll concentration in fresh leaf, and higher Zn uptake in shoot compared to those from low-Zn seed at low Zn supply; the impact of high-Zn seed was more marked in Zhongyou 821 compared with CSIRO-1 and Narendra. The influence of high-Zn seed was dissipated at high Zn supply. CSIRO-1 was superior in terms of shoot dry matter production and Zn uptake in shoots at low Zn supply. The results demonstrate that although oilseed rape has very small seeds (about 3 mg per seed weight) compared with wheat (30 mg per seed weight), Zn reserves present in this very small seed still have a strong impact on early vegetative growth as well as on Zn uptake of plants in Zn-deficient soils. The results suggest that sowing high-Zn seed coupled with growing Zn-efficient genotypes may help in sustaining the production of oilseed rape in Zn-deficient soils, and this has implications for improved seed technology.     

Terminal drought and seed priming improves drought tolerance in wheat

Plants retain the preceding abiotic stress memory that may aid in attainment of tolerance to subsequent stresses. This study was conducted to evaluate the influence of terminal drought memory (drought priming) and seed priming in improving drought tolerance in wheat (Triticum aestivum L.). During first growing season, wheat was planted in field under optimal (well-watered) and drought stress imposed at reproductive stage (BBCH growth stage 49) until maturity (BBCH growth stage 83). Seeds collected from both sources were subjected to hydropriming or osmopriming (with 1.5% CaCl₂ solution); while, dry seed was taken as control. Treated and control seeds, from both sources, were sown in soil filled pots. After the completion of seedling emergence, pots were maintained at 50% water holding capacity (drought) or 100% water holding capacity (well-watered). Drought stress suppressed the plant growth (2–44%), perturbed water relations (1–18%) and reduced yield (192%); however, osmolytes accumulation (3–14%) and malondialdehyde contents (26–29%) were increased under drought. The crop raised from the seeds collected from terminal drought stressed plants had better growth (5–63%), improved osmolyte accumulation (13–45%), and lower lipid peroxidation (3%) than the progeny of well-watered crop. Seed priming significantly improved the crop performance under drought stress as compared to control. However, osmopriming was more effective than hydropriming in this regard as it improved leaf area (9–43%), tissue water status (2–47%), osmolytes accumulation (6–48%) and grain yield (14–79%). In conclusion, terminal drought induced modifications in seed composition and seed priming improved transgenerational drought tolerance through improvement in tissue water status and osmolytes accumulation, and decrease in lipid peroxidation.     

Effect of NaCl and PEG 6000 on germination and seedling growth of rice (ryza sativa L.)

Germination and seedling growth of rice was studied in NaCl and PEG 6000 solutions having osmotic potentials −0.2, −0.4, −0.6 and −0.8 MPa. At isoosmotic concentrations, the NaCl proved more harmful to germination, seedling growth, per cent moisture content of seedling organs as well as mobilization of food matter from seed to the growing seedlings. This fact suggested that in rice, at least in the early stage, a specific ion effect rather than osmotic effect is the prime cause of salt injury. Compared to susceptible cultivar, the tolerant one was less inhibited by salinity.     

镧浸种对盐胁迫下小麦幼苗生长及其生理特征的影响

通过水培方式研究了0、25、50和100 mg/L硝酸镧浸种对盐胁迫条件下小麦品种临抗11和临优2069根系及幼苗生长的影响.结果表明:(1)与对照组相比,盐胁迫处理小麦幼苗植株矮,根系短,叶片叶绿素含量、根系活性吸收面积以及SOD和CAT活性明显降低,叶片MDA与Pro含量水平显著上升;在钠离子浓度相同的情况下,Na2CO3对小麦生长的影响大于NaCl.(2)适当浓度硝酸镧浸种处理增加了盐胁迫下小麦幼苗的株高、总根长、根系活性吸收面积及SOD和CAT活性,且各指标在盐胁迫下增加幅度高于正常水分处理.(3)2个小麦品种对镧处理的敏感程度存在差异,不同小麦品种及不同盐胁迫下最适的镧浸种浓度不同.研究发现,适当浓度镧浸种能有效缓解盐胁迫对小麦幼苗的伤害,具有显著促进小麦根系生长、培育壮苗的作用.     

Seed vigour contributes to yield improvement in dry direct‐seeded rainfed lowland rice

Dry direct‐seeded rice (DSR) cultivation is widely spreading in tropical Asia, but drought and nutrient deficiency stresses often cause crop failure in rainfed lowlands. The objective of this study was to dissect the physio‐morphological characteristics associated with crop establishment and early vigour of DSR under drought and P deficiency conditions in the Philippines. It was found that new drought‐resistant cultivars bred for DSR (Rc348 and Rc192) had faster germination and sprout growth than popular irrigated rice cultivars (Rc222 and Rc10) under soil water deficit due to rapid moisture acquisition by the germinating seeds from drying soils. There was a significant correlation between seed moisture content and the reduction in seed dry weight, and between reduction in seed dry weight and shoot elongation under both control and drought stress treatments at the germination stage. At the seedling stage, the root growth of Rc348 under drought tended to be more vigorous with its higher root‐to‐shoot ratio compared to Rc222 and Rc10. The seedling vigour of Rc348 under P deficiency was also greater than that of Rc222 due to its greater root growth and P uptake. The yields of Rc348 and Rc192 grown under rainfed condition at the target drought‐prone site where a dry spell of 13 days occurred during crop establishment were higher (4.0–4.1 t ha^?1) than the yield of Rc10 (3.0 t ha^?1). These results suggest that quick germination and seedling vigour with quick root anchorage and great nutrient uptake capacity, even with limitations of soil moisture and nutrients, would be important traits for DSR in rainfed lowlands.     

Quantification of the Effect of Environmental Factors on Seed Germination and Seedling Growth of Eruca (Eruca sativa) Using Mathematical Models

Eruca (Eruca sativa; Brassicaceae) is an important industrial crop due to its ability to grow under a wide range of climatic conditions and in poor fertility lands and also for the quality of seed oil and protein. Seed germination (SG) is an important event in plant’s life history which can significantly be influenced by several environmental factors such as temperature (T), water potential (ψ), salinity, pH, and burial depth. Therefore, this study aimed (i) to investigate the effects of these environmental factors on SG behavior of Eruca using several mathematical models, (ii) to determine the cardinal Ts and tolerance threshold value for each trait (i.e., 50% reduction than its maximum value) affected by the environmental factor, and (iii) to quantify the response of Eruca seedling growth to each environmental factor. The results indicated that Eruca SG and seedling growth were significantly influenced by these factors (P < 0.05). The estimated cardinal Ts were 1 °C for the base T, 30 °C for the optimum T, and 40.8 °C for the ceiling T. The salt and drought tolerance threshold values were 257 mM NaCl and − 1.2 MPa for SG and 247 mM NaCl and − 1 MPa for the seedling growth, respectively, suggesting that the seedling growth was more sensitive than SG under both salt and drought stresses in Eruca. In addition, the maximum SG and seedling growth were observed at pH 7 and burial depth 1.9 cm. In general, the models used in this study could describe well the response of Eruca SG under different levels of environmental factors and also their parameters could easily be used in Eruca SG simulation models. This information also could help us to better manage the production of this plant under stressful conditions and/or to determine its geographic range expansion in the world.

     

Germination and seedling growth of carrots under salinity and moisture stress

Poor crop stand is a common problem in saline areas. Germination and seedling emergence may be depressed as a result of impeded aeration, saline or dry conditions. In this study, we examined the effects of salinity and moisture stress and their interactions on seed germination and seedling growth of carrots. Variable soil matric and osmotic potentials were either obtained by equilibrating soil salinized to different degrees on a 0.5 MPa ceramic plate soil moisture extractor or by adding different amounts of salt solutions to the same mass of air-dried soil, based on a previously determined soil moisture release curve, and allowing to equilibrate for 1 week. Germination decreased significantly in the investigated silty soil (Aquic Ustifluvent) at soil moisture potentials higher than −0.01 MPa, whereas osmotic potentials as low as −0.5 MPa did not influence germination. Matric potentials of −0.3 and −0.4 MPa, respectively, resulted in a strong decrease (35–95%) of germination and delayed germination by 2 to 5 days in the silty soil to which different amounts (18 and 36%, respectively) and sizes (0.8–1.2 mm and 1.5–2.2 mm, respectively) of sand particles had been added. No effect of sand and grain diameter was detected. Germination was not affected by comparable osmotic potentials. Seedling growth showed a much higher sensitivity than germination to decreasing matric potentials, but was not affected by osmotic potentials ranging from −0.05 to −0.5 MPa. Optimum shoot growth occurred at matric potentials between −0.025 and −0.1 MPa. Shoot and root growth decreased markedly at matric potentials higher than −0.01 MPa. Fresh weight of shoots decreased gradually at matric potentials lower than −0.2 MPa. Root growth was significantly increased at matric potentials of −0.1 to −0.3 MPa, whereas comparable osmotic potentials did not have equivalent effects. It is concluded that germination and seedling growth are differently affected by comparable matric and osmotic stresses and that water stress exerts a more negative effect than salt stress.     

磺胺对小麦种子萌发和幼苗生长的影响

初步探讨了磺胺对小麦种子萌发与幼苗生长的影响。研究表明,用低浓度（＜6.0mg/L)的磺胺溶液浸泡小麦种子,能显著增加幼苗的根重,根长和根冠比,提高根系活力和叶片叶绿素的含量,降低幼苗的苗高,苗重,但对发芽率影响不大。高浓度（＞10．0mg/L)和安则强烈抑制小麦幼苗根,芽的生长,并导致幼苗形态的不良变化。