Hydrogen sulfide alleviated chromium toxicity in wheat

Effects of H₂S on seed germination under chromium (Cr) stress were investigated in wheat (Triticum aestivum L.). Under Cr stress, the percentage of germination of wheat seeds decreased, but this decrease could be alleviated by pretreatment with NaHS, an H₂S donor, in a dose-dependent manner. Furthermore, NaHS significantly enhanced the activities of amylase, esterase, superoxide dismutase, catalase, ascorbate peroxidase, and guaiacol peroxidase in Cr-stressed germinating seeds, whereas reduced the Cr-induced increase in lipoxygenase activity and over-production of malondialdehyde (MDA) and H₂O₂, and sustained slightly higher content of endogenous H₂S.     

NaHS对NaHCO3胁迫下黑籽南瓜种子萌发及生理特性的影响

以黑籽南瓜(Cucurbita ficifolia)种子为试材, 研究了外施不同浓度的NaHS对NaHCO₃胁迫下种子萌发及生理特性的影响。结果表明, NaHCO₃胁迫显著抑制了黑籽南瓜种子的发芽率、胚轴长和胚根长, 降低了种子萌发过程中的可溶性糖含量, 抑制了α-淀粉酶、β-淀粉酶、SOD及POD活性。而外施不同浓度的NaHS显著促进了NaHCO₃胁迫下黑籽南瓜萌发种子胚轴和胚根的生长, 提高了可溶性糖含量及α-淀粉酶、β-淀粉酶、SOD和POD活性, 降低了MDA含量; 外施其它盐类(Na₂S、Na₂SO4、NaHSO₄和NaHSO₃)及不同pH值(pH5.8–7.8)的Na₂HPO₄-NaH₂PO₄缓冲液对NaHCO₃胁迫下黑籽南瓜种子的萌发则无影响。外施NaHS可有效缓解NaHCO₃胁迫对黑籽南瓜种子萌发的抑制作用, 其缓解效应可能与其释放的H₂S有关。     

油菜素内酯浸种对盐胁迫番茄种子萌发的影响及其生理机制

为揭示油菜素甾醇类化合物提高作物耐盐的效应和机理,研究了10^-11、10^-10、10^-9、10^-8、10^-7、10^-6、10^-5 mol/L 2,4-表油菜素内酯（EBL）浸种处理对0、50、100、150、175 mmol/L NaCl胁迫7 d的番茄种子萌发、生长、溶质积累、抗氧化代谢的影响。结果显示：NaCl浓度越高的盐胁迫下,10^-9 mol/L EBL浸种可体现出越显著的促进番茄种子萌发的效应;在所有处理下,EBL浸种浓度过高,即10^-6、10^-5 mol/L EBL,均表现出对种子萌发的抑制效应。盐胁迫下种子萌发后,一定浓度的EBL浸种可表现出明显的增加种子胚根和下胚轴长,提高萌发种子鲜重和种子活力指数,其中10^-9 mol/L EBL浸种处理促进效果最适;EBL浸种浓度过高,则表现出抑制效应。150 mmol/L NaCl胁迫或非盐胁迫下,10^-9 mol/L EBL浸种均可降低萌发种子体内的O₂^·-、H₂O₂、丙二醛（MDA）和脯氨酸（Pro）含量;盐胁迫下,10^-9 mol/L EBL浸种可显著提高萌发种子可溶性糖（SS）和可溶性蛋白（SP）的含量。150 mmol/L NaCl胁迫或非盐胁迫下,10^-9 mol/L EBL处理可不同程度促进番茄种苗超氧化物歧化酶（SOD）和过氧化物酶（POD）活性的上升。综上所述,盐胁迫下,一定浓度范围内的EBL浸种可明显促进番茄种子萌发或成苗,其中以10^-9 mol/L EBL浸种的效果最好,主要是因为EBL施用可积极促进番茄种子萌发中物质转化,SS和SP等溶质积累增多,增强其渗透调节能力;同时SOD和POD酶活增强,缓解盐胁迫导致番茄种子萌发中的次生氧化胁迫。     

Inducing salt tolerance in maize (Zea mays L.) through seed priming with chloride salts: Growth and ion transport at early growth stages

The study was conducted to determine whether salt tolerance could be induced in maize at germination stage by soaking of seeds for 8 h in distilled water or in 200 meq·L⁻¹ of NaCl, KCl, CaCl₂·2H₂O. Both primed and un-primed seeds were subjected for 14 days to 0, 100 or 200 mol·m⁻³ NaCl under controlled conditions. Although all priming agents were effective in alleviating adverse effects of salt stress on maize at germination stage, CaCl₂·2H₂O proved to be more effective since the seeds primed with this salt had significantly higher final germination, rate of germination and fresh and dry weights of plumules and radicles than those treated with other salts or distilled water. Concentration of Na⁺, K⁺ and Ca²⁺ increased significantly in all parts of germinating seeds of maize seeds primed with NaCl, KCl, or CaCl₂·2H₂O, respectively. In addition, seeds primed with CaCl₂·2H₂O were the highest in Cl⁻ accumulation in all parts of the germinating seeds, followed by seeds treated with NaCl and KCl. Most of the Ca²⁺ was retained in seeds and mesocotyl, because of which, transport of this ion to plumules and radicles was low.     

Salt tolerance of two differently drought-tolerant wheat genotypes during germination and early seedling growth

Summary Osmotic and specific ion effect are the most frequently mentioned mechanisms by which saline substrates reduce plant growth. However, the relative importance of osmotic and specific ion effect on plant growth seems to vary depending on the drought and/or salt tolerance of the plant under study. We studied the effects of several single salts of Na⁺ and Ca²⁺−NaCl, NaNO₃, Na₂SO₄, NaHCO₃, Na₂CO₃, and Ca(NO₃)₂—on the germination and root and coleoptile growth of two wheat (Triticum aestivum L.) cultivars, TAM W-101 and Sturdy, the former being more drought tolerant than the latter. The concentrations used were: 0, 0.02, 0.04, 0.08, 0.16, and 0.32 mol L⁻¹. Significant two- and three-way interactions were observed between cultivar, kind of salt, and salt concentration for germination, growth of coleoptile and root, and root/coleoptile ratio. Salts differed significantly (P<0.001) in their effect on seed germination, coleoptile and root growth of both cultivars. Germination of TAM W-101 seeds was consistently more tolerant than that of Sturdy to NaCl, CaCl₂, Ca(NO₃)₂, and NaHCO₃ salts at concentrations of 0.02, 0.04, 0.08, 0.16 mol L⁻¹. The osmotic potential, at which the germination of wheat seeds was reduced to 50% of that of the control, was different depending on the kind of salt used in the germination medium. NaCl at low concentrations (0.02 and 0.04 mol L⁻¹) stimulated the germination of both wheat cultivars. At concentrations of 0.02 to 0.16 mol L⁻¹, Ca²⁺ salts (CaCl₂ and Ca(NO₃)₂) were consistently more inhibitory than the respective Na⁺ salts (NaCl and NaNO₃) for germination of Sturdy. This did not consistently hold true for TAM W-101. Among the Na⁺ salts, NaCl was the least toxic and NaHCO₃ and Na₂CO₃ were the most toxic for seed germination. Root and coleoptile (in both wheat cultivars) differed in their response to salts. This differential response of coleoptile and root to each salt resulted in seedlings with a wide range of root/coleoptile ratios. For example, the root/coleoptile ratio of cultivar TAM W-101 changed from 2.09 (in the control) to 3.77, 3.19, 2.8, 2.44, 1.31, 0.32, and 0.0 when subjected to 0.08 mol L⁻¹ of Na₂SO₄, NaCl, CaCl₂, NaNO₃, Ca(NO₃)₂, NaHCO₃, and Na₂CO₃, respectively. Na₂CO₃ at 0.08 mol L⁻¹ inhibited root growth to such an extent that germinated wheat seeds contained coleoptile but no roots. The data indicate that, apart from the clear and more toxic effects of NaHCO₃ and Na₂CO₃ and lesser toxic effect of NaCl on germination and seedling growth, any toxicity-ranking of other salts done at a given concentration and for a given tissue growth may not hold true for other salt concentrations, other tissues and/or other cultivars. The more drought-tolerant TAM W-101, when compared to the less drought tolerant Sturdy, showed higher tolerance (at most concentrations) to NaCl, CaCl₂, Ca(NO₃)₂ and NaHCO₃ during its seed germination and to Na₂SO₄ and CaCl₂ for its root growth. This supports other reports that some drought-tolerant wheat cultivars are more tolerant to NaCl. In contrast, the coleoptile growth of drought-sensitive Sturdy was noticeably more tolerant to NaNO₃, Ca(NO₃)₂ and NaHCO₃ than that of drought-tolerant TAM W-101. Based on the above and the different root/coleoptile ratios observed in the presence of various salts, it is concluded that in these wheat cultivars: a) coleoptile and root tissues are differently sensitive to various salts, and b) at the germination stage, tolerance to certain salts is higher in the more drought-tolerant cultivar.     

Seed germination and in vitro propagation of Maytenus canariensis through regeneration of adventitious shoots from axillary and apical buds

Seed germination and micropropagation protocols of the medicinal species Maytenus canariensis (Loes.) G. Kunkel & Sunding were optimized. In vitro seed germination occurred (86 to 94.7 %) only after treatment of the seeds with H₂SO₄, followed by surface sterilization and culture on solid nutrient medium without any growth regulators. Micropropagation failed when explants were taken from mature trees, and browning of the nutrient medium frequently occurred despite testing many growth media. Nonetheless, adventitious shoot regeneration was achieved employing axillary or apical buds taken from 2–2.5 months old plantlets obtained after in vitro germination of seeds, following culture on nutrient media supplemented with benzylaminopurine, kinetin and naphthalenacetic acid (NAA), attaining up to 3.9 shoots per explant, after 4–6 months. Root induction was best on a medium containing 4.0 mg dm⁻³ NAA, achieving a 100 % induction. After hardening of rooted plants, survival after transfer to soil was 71.43 %.     

Water-soluble phenolic compounds in the coat control germination and peroxidase reactivation in <Emphasis Type="Italic">Triticum aestivum</Emphasis> seeds

In this work, we investigated the inhibitory effects of water-soluble phenolic compounds (WSPCs) in the coat of after-ripening wheat (Triticum aestivum L.) seeds on the processes of germination and peroxidase reactivation. Wheat bran has a WSPC content of 862.5 μg gallic acid equivalent g⁻¹ dry weight. When seeds were incubated in the water extract of bran, germination, peroxidase reactivation, and coleoptile and radicle growth were suppressed in a WSPC concentration-dependent manner. The inhibitory effects were significantly ameliorated by removing WSPCs from bran extract by treating with 1% insoluble polyvinylpolypyrrolidone. Pretreatment of seeds with 0.1% H₂O₂ reduced the WSPC content in the coat, which was confirmed using Fourier transform infrared microspectroscopy. With H₂O₂ pretreatment, seed germination, peroxidase reactivation, and post-germination seedling growth were significantly stimulated. Application of the known phenolics caffeic acid, feruic acid, or vanillin to the germination medium blocked seed germination and suppressed peroxidase reactivation. The results described here indicate that WSPCs act as endogenous inhibitors in the coat to control germination of Triticum aestivum seeds, and that inhibition of germination is at least partially caused by suppressing peroxidase reactivation.     

Hydrogen Sulfide Alleviates Aluminum Toxicity in Germinating Wheat Seedlings

Protective role of hydrogen sulfide (H2S) on seed germination and seedling growth was studied in wheat (Triticum) seeds subjected to aluminum (Al3+) stress. We show that germination and seedling growth of wheat is inhibited by high concentrations of AICI3. At 30 mmol/L AICI3 germination is reduced by about 50% and seedling growth is more dramatically inhibited by this treatment. Pre-incubation of wheat seeds in the H2S donor NaHS alleviates AICI3-induced stress in a dose-dependant manner at an optimal concentration of 0.3 mmol/L. We verified that the role of NaHS in alleviating Al3+ stress could be attributed to H2S/HS- by showing that the level of endogenous H2S increased following NaHS treatment. Furthermore, other sodium salts containing sulfur were ineffective in alleviating Al3+ stress. NaHS pretreatment significantly increased the activities of amylases and esterases and sustained much lower levels of MDA and H2O2 in germinating seeds under Al3+ stress. Moreover, NaHS pretreatment increased the activities of guaiacol peroxidase, ascorbate peroxidase, superoxide dismutase and catalase and decreased that of lipoxygenase. NaHS pretreatment also decreased the uptake of Al3+ in AICI3-treated seed. Taken together these results suggest that H2S could increase antioxidant capability in wheat seeds leading to the alleviation of Al3+ stress.     

干旱胁迫下白刺花种子大小与萌发对策

种子大小与种子萌发及其与环境因子的关系是植物种子萌发对策研究中的重要科学问题之一。采用PEG模拟干旱法研究不同干旱胁迫强度(0,5%,10%,15%,20%)下,白刺花(Sophora davidii)种子萌发进程、种子大小与种子萌发及种子命运的关系。结果表明:不同干旱胁迫下,白刺花种子具有相似的萌发进程,但中度干旱处理(10%PEG)萌发率显著高于零干旱(0%PEG)和重度干旱处理(P0.05),重度干旱处理(20%PEG)种子萌发开始时间晚于零干旱和中度干旱处理;种子大小与种子萌发开始时间的关系表现为零干旱处理下呈极显著负线性关系,中度干旱处理(5%PEG,10%PEG)下无相关关系,重度干旱处理(15%PEG,20%PEG)下呈负二次曲线关系;种子大小对种子命运的影响表现为零干旱处理有利于大、小种子萌发和小种子休眠,中度干旱处理(10%PEG)增加中等种子萌发、大种子休眠和小种子死亡风险,重度干旱处理(15%PEG,20%PEG)增加大种子死亡风险、中等种子和小种子休眠。综合分析表明,白刺花种子大小与萌发行为及种子命运的关系具有较强的环境依赖性,即种子萌发行为表现为顺境下种子越大萌发越快,逆境下小种子和大种子较中等种子萌发更快;种子命运表现为顺境增加种子死亡的风险,中度干扰有利于种子萌发,逆境则有利于种子休眠。     

Exogenous nitric oxide improves seed germination in wheat against mitochondrial oxidative damage induced by high salinity

Effects of exogenous nitric oxide (NO) on starch degradation, oxidation in mitochondria and K⁺/Na⁺ accumulation during seed germination of wheat were investigated under a high salinity level. Seeds of winter wheat (Triticum aestivum L., cv. Huaimai 17) were pre-soaked with 0 mM or 0.1 mM of sodium nitroprusside (SNP, as nitric oxide donor) for 20 h just before germination under 300 mM NaCl. At 300 mM NaCl, exogenous NO increased germination rate and weights of coleoptile and radicle, but decreased seed weight. Exogenous NO also enhanced seed respiration rate and ATP synthesis. In addition, seed starch content decreased while soluble sugar content increased by exogenous NO pre-treatment, which was in accordance with the improved amylase activities in the germinating seeds. Exogenous NO increased the activities of superoxide dismutase (SOD, EC 1.15.1.1) and catalase (CAT, EC 1.11.1.6); whereas decreased the contents of malondialdehyde (MDA) and hydrogen peroxide (H₂O₂), and superoxide anions (O₂^??) release rate in the mitochondria. Exogenous NO also decreased Na⁺ concentration while increased K⁺ concentration in the seeds thereby maintained a balance between K⁺ and Na⁺ during germination under salt stress. It is concluded that exogenous NO treatment on wheat seeds may be a good option to improve seed germination and crop establishment under saline conditions.     

Buried seed population in the herbaceous lomas on Loma Ancon in the coastal desert of central Peru

Herbaceous lomas in the Peruvian coastal desert, of South America establish in spring, and its habitat is limited to the southern or southwestern slopes along the coast that are affected by thick fog. The time of appearance, the duration and the thickness of the fog vary greatly from year to year, so the lomas can grow only in habitats with enough water to, sustain seed germination and plant growth. This paper studies the species composition and density of the buried seed population, of the herbaceous lomas of Loma Ancon in order to clarify the mechanisms of the lomas' establishment. The mean number of species with viable seeds was about, 12 spp. m⁻² and that of dead seeds was about 22 spp. m⁻². The dominant species wereSolanum tuberiferum, S. pinnatifidum andNolana humifusa, both in viable and dead seeds. Viable seed density was about 5000–8000 seeds m⁻², which is comparable with the seed densities of other herbaceous communities. Dead seed density was about 15000–27000 seeds m⁻², or nearly three times the viable seed density, because the rate of decomposition was slow in the extremely dry conditions. The net increase of viable seeds by seed production was estimated at about 5000 seeds m⁻² in 1980, and the increase in the number of dead seeds was 2200 seeds m⁻².     

朱唇种子吸水特性及其在干旱胁迫下萌发特性

种子粘液质是植物在长期适应环境过程中形成的,该物质对于种子的扩散、定居、生存力的改善、萌发、幼苗生存乃至抵御有毒化学物质毒害等都具有重要的生态学意义。朱唇为唇形科鼠尾草属多年生草本植物,原产美洲热带地区,现已广泛栽植于世界各地。为了理解朱唇种子表面的粘液物质吸水特性和种子在干旱胁迫下的萌发特性,该研究以朱唇种子为材料,运用光学显微镜和扫描电子显微镜观察以及种子萌发试验的方法,对种子和粘液层的形态结构、粘液质对种子萌发的影响进行了研究。结果表明:朱唇种子为卵形,表面为负网状结构,千粒重为(1.611±0.0084)g,无粘液种子吸水倍数为3,粘液种子吸水倍数为25,粘液层吸水倍数为122。粘液和无粘液种子及粘液层的重量都随吸水时间的延长而增长,但脱水过程要远长于吸水过程。朱唇种子吸水2 h达到饱和,经过36 h可干燥失水恢复原重。不同浓度PEG对朱唇种子的萌发均有影响,发芽势随PEG浓度升高而显著降低。朱唇种子在5%PEG胁迫下发芽率最高达(90.00±8.66)%,20%PEG胁迫下发芽率最低为(76.67±10.41)%,低浓度PEG对朱唇种子萌发有一定促进作用。这说明朱唇种子为速萌型种子,其粘液质在种子吸水过程中起到举足轻重的作用,能保证短时间内有充足的水分供其萌发。     

ROS production and antioxidative system activity in embryonic axes of <Emphasis Type="Italic">Quercus robur</Emphasis> seeds under different desiccation rate conditions

The seeds of pedunculate oak (Quercus robur L.) were subjected to slow (S) and rapid (R) desiccation at desiccation rates of 0.16 and 0.39% H₂O per hour, respectively. Till ca. 40% water content (WC) the germination capacity of seeds in the S and R variants was high (ca. 100%). Between 40 and 28% WC, germination capacity declined to 20 and 50% in S and R variants, respectively. The decrease in seed viability was accompanied by a significant increase of electrolyte leakage from embryonic axes (28% for S and 15% for R variants). In the embryonic axes of seeds subjected to slow desiccation, malondialdehyde (MDA) and free fatty acid (FFA) contents were significantly higher than those in R variants, indicating greater membrane damage due to lipid peroxidation. The production of ROS (H₂O₂ and O₂^·−) was significantly higher in S than in R variants. The low molecular weight antioxidants α-tocopherol, ascorbic acid (ASA), and phenolic compounds indicated different reactions in response to desiccation stress. ASA levels decreased during desiccation to a similar degree in both the S and R variants. A significant decrease of total phenols was observed in R variant, which coincided with a significant increase of guaiacol peroxidase (POX) activity. α-Tocopherol content was significantly higher in the embryonic axes of seeds subjected to rapid drying. The activities of the enzymatic scavengers APX and GR had similar runs and were slightly higher in R variant. The activities of POX and SOD were significantly higher in the embryonic axes of seeds subjected to rapid drying. These results show that rapid dehydration of Q. robur seeds leads to the greater mobilization of antioxidant system in embryonic axes, particularly increased levels of α-tocopherol and POX and SOD activities, in the first stages of water loss. This mobilization has a greater impact on maintenance of higher viability of seeds after drying to lower level of WC.     

Canola seed germination and seedling emergence from pre-hydrated and re-dried seeds subjected to salt and water stresses at low temperatures

Low soil temperatures and low water potentials reduce and delay the seed germination of canola (Brassica rapa L., B. napus L.) in western Canada. Germination is also very sensitive to the salinity effects of nitrogen fertiliser placed with the seed, especially when the seed bed is relatively dry. The effects of pre-hydration and re-drying treatment on canola (Brassica rapa L. cv. Tobin) seed germination and seedling emergence at 10°C subjected to either a water or salt stress were determined. Low water potentials, induced by polyethylene glycol (PEG 8000), low soil moisture, or high concentrations of salts, reduced both germination and seedling emergence, and increased the time to 50% germination and emergence of seeds at 10°C. At equal osmotic potentials, Na₂SO₄ was less inhibitory on low temperature germination than either NaCl or PEG, suggesting that the sulphate ion partially alleviated the inhibitory effects of low water potential. Solutions of NaCI produced more abnormal seedlings compared to Na₂SO₄, suggesting that NaCl was more toxic than Na₂SO₄ during seedling development. Pre-hydration and re-drying partially overcame the inhibitory effects of both low water potential and salts on seed germination and seedling emergence at 10°C. The seed treatment increased the germination rate in Petri dishes and seedling emergence from a sandy loam soil. Water potentials or soil water contents required to inhibit 50% germination or emergence at 10°C were lower for treated seeds compared to control seeds. Salt concentrations inhibiting 50% emergence were higher for treated seeds than control seeds. Neither treated nor control seeds produced seedlings which emerged if the soil water content was lower than 9% or when the soil was continuously irrigated with salt solutions of 100 mmol kg^-1 of NaCl or 50 mmol kg^-1 of Na₂SO₄. These results suggest that the pre-hydration and re-drying treatment did not lower the base water potentials at which seedling emergence could occur. Abnormal seedlings were observed in both treated and control seeds, particularly if the soil was watered with NaCl solutions; however, the seed treatment reduced the number of abnormal seedlings.     

外源H2O2对盐胁迫下小白菜种子萌发和幼苗生理特性的影响

以小白菜"甜脆青"为试材,研究不同浓度（5、10、25、50和100 mmol/L）过氧化氢（H₂O₂）浸种处理对100 mmol/L NaCl胁迫下小白菜（Brassica chinensis L.）种子萌发、幼苗生长及生理特性的影响。结果表明：100 mmol/L NaCl胁迫明显抑制小白菜种子的萌发状况和幼苗生长,发芽势、发芽指数、活力指数及幼苗根和芽长度和鲜重均明显降低,根和芽中CAT的活性及K⁺含量明显受到抑制,渗透调节物质、活性氧和MDA含量显著增加。不同浓度H₂O₂浸种处理提高了NaCl胁迫下小白菜种子发芽势、发芽指数和活力指数,促进小白菜根和芽的生长,增强了NaCl胁迫下根和芽中SOD、CAT和APX的活性及K⁺含量,降低O₂^-·产生速率及H₂O₂和MDA含量,进一步促进脯氨酸和可溶性糖含量的增加,降低体内Na⁺含量。其中以10 mmol/L H₂O₂处理缓解盐胁迫效果最好,明显缓解NaCl胁迫对小白菜种子萌发和幼苗生长的抑制。     

H_2S对干旱胁迫下白三叶幼苗抗氧化防御能力的影响

以‘拉丁诺’白三叶(Trifolium repens cv.‘Ladino’)为试验材料,研究外源H2S处理对PEG6 000(聚乙二醇)模拟干旱胁迫下白三叶叶片相对含水量(RWC)、膜脂过氧化、活性氧成分、抗氧化酶、抗坏血酸-谷胱甘肽循环代谢和非酶抗氧化物质的影响,以揭示H_2S调控白三叶抗旱性的生理机制。结果显示:(1)0.2 mmol/L的外源NaHS(H_2S供体)能显著提高干旱胁迫下白三叶的叶片相对含水量,维持显著较低的电解质渗透率(EL)和丙二醛(MDA)含量。(2)与直接干旱胁迫相比,干旱胁迫下外源添加NaHS处理的白三叶叶片内超氧化物歧化酶(SOD)、过氧化物酶(POD)、过氧化氢酶(CAT)活性显著增强,抗坏血酸-谷胱甘肽循环代谢中关键酶抗坏血酸过氧化物酶(APX)、脱氢抗坏血酸还原酶(DHAR)、单脱水抗坏血酸还原酶(MDHAR)和谷胱甘肽还原酶(GR)活性及其抗氧化中间产物抗坏血酸(AsA)、谷胱甘肽(GSH)含量也显著提高。(3)叶片类黄酮、总酚和原花青素的含量在一定的胁迫时间范围内亦显著增加,并伴随着活性氧成分O_2~(-·)产生速率和H_2O_2水平降低。研究认为,外源H2S能通过促进干旱胁迫下白三叶体内的多重抗氧化防御能力来提高其幼苗的抗旱性。     

Adaptive responses of aglomerular toadfish to dilute sea water

Plasma and urine of toadfish (Opsanus tau) in sea water and 10% sea water were analyzed to assess responses of an aglomerular fish to hypoosmotic challenge. Following transfer to 10% sea water, plasma osmotic pressure decreased slowly from 318 to 241 mmol · kg H₂O⁻¹, over a period of 10–15 days. Urine osmotic pressure decreased in parallel from 299 to 207 mmol · kg H₂O⁻¹, leaving urine/plasma ratios of osmotic pressure essentially unchanged. In contrast, the volume and composition of urine changed rapidly following transfer to 10% sea water. Urine flow rate increased 110% from 3.0 to 6.3 μl · 100g⁻¹ · h⁻¹ and Na⁺ excretion increased 346%, while excretion of Mg²⁻ and SO₄ ²⁻ decreased 81% and 90%, respectively. Excretion rates for Cl⁻ were low in seawater toadfish and decreased further in 10% sea water. An unknown sulfur-containing anion, present in the urine of seawater toadfish, contributed significantly to the composition and ionic balance in urine of toadfish in 10% sea water. These results suggest that the inability to produce strongly dilute urine obliges toadfish to lose salt in order to excrete water, in hypoosmotic media. The decrease in plasma osmotic pressure may be both a strategy to reduce osmotic and ionic gradients in dilute media and a consequence of the kidney's inability to excrete water without salt. Accepted: 22 August 1996     

Protective roles of nitric oxide on germination and antioxidant metabolism in wheat seeds under copper stress

Nitric oxide (NO) is a multifunctional gaseous signal in plant. In the present study, we found that pretreatment with NO could significantly improve wheat seeds germination and alleviate oxidative stress against copper toxicity. With the enhancement of copper stress, the germination percentage of wheat seeds decreased gradually. Pretreatment during wheat seed imbibition with sodium nitroprusside (SNP), an NO donor, could greatly reverse the inhibitory effect of the following copper stress to wheat seeds germination. SNP-pretreated seeds also tended to retain higher amylase activities than that of the control without SNP pretreatment. On the other hand, there was no apparent difference in the activities of esterase in wheat seeds pretreated with or without SNP. Further investigations showed that pretreatment with NO donor dramatically stimulated the activities of superoxide dismutase (SOD, EC 1.15.1.1) and catalase (CAT, EC 1.11.1.6), decreased the activities of lipoxygenases, sustained a lower level of malondialdehyde, and interfered with hydrogen peroxide (H₂O₂) excessive accumulation compared with the control, thereby enhancing the antioxidative capacity in wheat seeds under copper stress. In addition, the seed copper contents were not significant different between those pretreated with SNP and the controls, inferring that protective roles of NO was not responsible for preventing Cu uptake. Kang-Di Hu and Lan-Ying Hu contributed equally to this paper.     

Germination studies on three critically endangered endemic angiosperm species of the Kashmir Himalaya,India

The critically endangered and perennial alpine endemic angiosperms, namely, Aquilegia nivalis, Lagotis cashmeriana and Meconopsis latifolia inhabit such habitats in the Kashmir Himalaya that are characterised by short growing season and heavy snow cover for about 3–4 months during winter season. The seeds of these species under natural conditions experience a long period of pre-chilling during winter prior to their germination in following spring season. Taking cue from such a requirement, present study investigated the effect of chilling and exogenous application of growth hormones, NO₃ ⁻ and NH₄ ⁺ on total percent germination of otherwise deep-dormant seeds of these species, under alternate light/dark and continuous dark light regimes. Prolonged pre-chilling followed by treatment of seeds with different doses of GA₃ had a pronounced stimulatory effect on the total germination percentage in all the three species. In fact, highest germination percentage in A. nivalis was recorded only when pre-chilled seeds were treated with 1.5 mM GA₃ under alternate light/dark conditions. Likewise, germination of pre-chilled seeds of L. cashmeriana with ruptured seed coats was improved when treated with various concentrations of GA₃. Seed germination in M. latifolia was also favourably influenced by treatment of pre-chilled seeds with GA₃ or nitrogen applied either as NO₃ ⁻ or as NH₄ ⁺ under alternate light/dark conditions. Treatment of seeds with kinetin (6-furfuryl-aminopurine) had no significant influence on germination percentage in any of the three species. Thus, prolonged chilling of seeds followed by their treatment with GA₃ under alternate light/dark conditions are the requirements necessary for seed germination in these species.     

Accumulation of inorganic and organic osmolytes and their role in osmotic adjustment in NaCl-stressed vetiver grass seedlings

The accumulation of inorganic and organic osmolytes and their role in osmotic adjustment were investigated in roots and leaves of vetiver grass (Vetiveria zizanioides) seedlings stressed with 100, 200, and 300 mM NaCl for 9 days. The results showed that, although the contents of inorganic (K⁺, Na⁺, Ca²⁺, Mg²⁺, Cl⁻, NO₃⁻, SO₄²⁻ and H₂PO₃⁻)) and organic (soluble sugar, organic acids, and free amino acids) osmolytes all increased with NaCl concentration, the contribution of inorganic ions (mainly Na⁺, K⁺, and Cl⁻) to osmotic adjustment was higher (71.50–80.56% of total) than that of organic solutes (19.43–28.50%). The contribution of inorganic ions increased and that of organic solutes decreased in roots with the enhanced NaCl concentration, whereas the case in leaves was opposite. On the other hand, the osmotic adjustment was only effective for vetiver grass seedlings under moderate saline stress (less than 200 mM NaCl).