Interactive Effects of High Boron and NaCl Stresses on Subcellular Localization of Chloride and Boron in Wheat Leaves

Salinity and boron (B) toxicity often occur simultaneously and may have interactive effects on plant responses. This study aims at further investigating long‐term effects of salinity, B toxicity and their combination on wheat plants. Plants grown in hydroponics were treated with 2.5 μm H₃BO₃ (control), 75 mm NaCl, 200 μm H₃BO₃ or 75 mm NaCl + 200 μm H₃BO₃ and were analysed on a subcellular level 6 weeks after germination. Shoot fresh and dry weight (DW), water content, transpiration rate and osmolality were reduced, while Na⁺ and Cl^? concentrations increased under salinity stress. However, Cl^? was reduced in all compartments by an additional application of B toxicity. At adequate B supply, NaCl increased apoplastic and symplastic soluble B concentrations, whereas the total B content remained unchanged. At high B level, however, soluble and total B was reduced by additional salt stress. Despite this antagonistic effect of a combined salt and B toxicity stress on Cl^? and B concentrations, an additive effect was observed regarding shoot fresh weight reduction. Our results confirm an alleviating effect of the combined stresses on toxic ion concentrations, which did not prevent additive growth reductions.     

Exogenous calcium alleviates the impact of cadmium-induced oxidative stress in Lens culinaris medic. Seedlings through modulation of antioxidant enzyme activities

The effect of calcium (Ca) on lentil (Lens culinaris Medic.) seedlings exposed to cadmium (Cd) stress was studied by investigating plant growth and antioxidant enzyme activities. Plants were grown for 14 days in full-strength Hoagland nutrient media supplemented with Cd concentrations of 0, 10, 20, and 40 μM, and on corresponding medium supplied with 5 mM Ca(NO₃)₂ prior to Cd addition. Increasing Cd led to accumulation of metal and reduced the fresh weight of the shoots more strongly than that of the roots. Cd concentrations of 20 and 40 μM were selected to study its toxic effect on seedlings. Activities of superoxide dismutase, ascorbate peroxidase, catalase, dehydroascorbate reductase, and glutathione reductase decreased at much higher magnitude in the shoots than those observed in the roots under Cd exposure. Failure of antioxidant defense in scavenging of reactive oxygen species was evidenced by abnormal rise in H₂O₂, resulting in enhancement of lipid peroxidation and membrane electrolyte leakage as the marks of Cd-induced oxidative stress in lentil seedlings. Ca priming in the media significantly reduced the Cd accumulation and considerably alleviated the adverse impact of Cd treatment by modulating the antioxidant enzyme activity. Mitigation of Cd-induced stress by Ca application was strongly suggested by declining levels of H₂O₂ and consequent lowering of oxidative damage of membrane. Consequently, this enhanced fresh mass of plant parts as the sign of Ca-mediated normal growth in Cd-treated lentil seedlings.     

Salicylic acid acts as potent enhancer of growth,photosynthesis and artemisinin production in <Emphasis Type="Italic">Artemisia annua</Emphasis> L.

Plant secondary metabolites constitute the most important class of natural products with diverse and valuable chemical properties and biological activities. Artemisinin, isolated from Artemisia annua L., is potentially a drug that could be effective against multidrug-resistant strains of the malarial parasite, Plasmodium. Salicylic acid (SA) acts as a potential plant growth regulator and plays an important role in regulating a number of plant physiological and biochemical processes. The present study was conducted to assess the alterations in plant growth, photosynthetic capacity, enzyme activities, and content and yield of artemisinin in Artemisia annua L. in response to foliar application of SA. Four levels of SA (0.00, 0.25, 0.50, and 1.00 mM SA) were applied on the aboveground plant parts. Plant height and dry weight were altered significantly as the level of SA increased. Besides, application of SA positively improved chlorophyll and carotenoid contents. Furthermore, significant enhancement in net photosynthetic rate (31.7%) and the activity of nitrate reductase (17.2%) and carbonic anhydrase (10.9%) was noticed as the level of SA was increased from 0.00 to 1.00 mM SA. Most importantly, the content and yield of artemisinin was positively regulated by the SA. In comparison to no SA application (control), SA at 1.00 mM increased the content and yield of artemisinin by 25.8 and 50.0%, respectively.     

应用组织染色法研究硼胁迫对西瓜叶片的生理伤害

为了研究硼胁迫对西瓜叶片的生理伤害,笔者以籽瓜、‘黑美人’西瓜和野生西瓜为材料,设4 个硼浓度,应用组织染色法观察3 种类型西瓜O2 · ?、H2O2积累量、POD活性及死亡细胞数量。结果表明：3种类型西瓜叶片的O2 ·?和H2O2积累量在硼胁迫下均显著提高,POD活性上升,死亡细胞数量明显增加,且高硼胁迫的西瓜O2 ·?、H2O2积累量和死亡细胞数量都大于缺硼胁迫,野生西瓜活性氧清除能力强于其他2 种类型西瓜。硼胁迫导致西瓜叶片的活性氧大量积累,抗氧化酶活性增强,细胞大量非正常死亡,高硼胁迫的生理伤害大于缺硼胁迫。野生西瓜在胁迫下的抗逆性最强。组织染色法准确、直观,可应用于西瓜等植物的逆境生理研究。     

硼胁迫对不同类型西瓜活性氧代谢与抗氧化系统的影响

【目的】为了研究硼对不同类型西瓜活性氧代谢与抗氧化系统的影响。【方法】以籽瓜、“黑美人”西瓜和野生西瓜为材料,设0.00,0.05,0.20,0.60 mmol/L 四个硼浓度,测定三种类型西瓜O2.?、H2O2和MDA含量及SOD、POD和CAT活性。【结果】结果表明：三种类型西瓜的O2和H2O2产生速率在硼胁迫下均显著提高,且高硼胁迫的西瓜O2.?和H2O2产生速率都大于缺硼胁迫,并导致MDA的积累。硼胁迫使三种类型西瓜的POD活性上升,CAT活性下降。籽瓜和“黑美人”的SOD活性下降,野生西瓜SOD活性上升。【结论】硼胁迫引起西瓜的活性氧爆发,并启动了西瓜的抗氧化系统,但仍然无法完全抵御硼胁迫带来的活性氧伤害,野生西瓜对硼胁迫的抗逆最强。     

硼素胁迫对甜菜叶片结构及性能的影响

研究硼素水平对甜菜叶片硼素状况和叶片结构及性能的影响,阐明硼素对甜菜叶片性能的影响机制,为甜菜生产实践硼肥施用提供理论依据。以甜菜单粒种HI0099为试验材料,在水培条件下,设置十分缺乏(T1,0.05 mg/L)、缺乏(T2,0.5 mg/L)、正常(T3,2.0 mg/L)及过量毒害(T4,30.0 mg/L)4个硼营养浓度,对甜菜叶片硼含量及其光合性能进行测定,分析甜菜叶片硼含量及光合性能变化规律。结果表明：甜菜叶片的硼含量随着施硼量的增加而增加;在硼胁迫下,叶绿素含量、净光合速率和蒸腾速率均有下降的趋势。胞间CO2浓度在硼素缺乏时呈先降低后升高的趋势,在毒害时则呈现升高趋势。硼素胁迫均增加了栅栏组织、海绵组织及叶片厚度,硼毒害处理降低了上表皮和下表皮厚度。综合分析表明,硼素胁迫改变了叶片硼素水平和叶片结构,在一定程度上降低了叶片的光合性能。因此,在甜菜生产中合理施用硼肥来改善叶片结构及光合性能具有重要实践意义。     

高硼胁迫对观赏凤梨植株生长和元素含量的影响

以观赏凤梨为试材,研究了高硼胁迫对植株生长、叶绿素含量、可溶性糖和淀粉含量、元素含量的影响。结果表明,与不施硼相比,施硼抑制了观赏凤梨地上部和根系的生长,随硼浓度增加,抑制程度增加;施硼引起植株中下部叶片叶尖发黄焦枯坏死,叶片叶绿素含量降低;施硼引起叶片和根系可溶性糖和淀粉含量下降;施硼提高了根系N、P、Fe、Mn、Zn含量,但降低了叶片这些元素含量,引起叶片和根系Cu含量的下降。表明,观赏凤梨对硼过量的反应非常敏感,栽培基质或灌溉水中含硼不利于观赏凤梨植株生长。     

Na+ Retention in the Root is a Key Adaptive Mechanism to Low and High Salinity in the Glycophyte,Talinum paniculatum (Jacq.) Gaertn. (Portulacaceae)

Talinum paniculatum is an important leafy vegetable and medicinal plant, used in many parts of South America, Africa and Asia. Its adaptation to abiotic stress has received little attention and therefore worthy of interest, especially as environmental conditions are rendering arable lands increasingly unfavourable for agriculture. Therefore, this study was undertaken to examine the influence of salt stress on the vegetative growth of the plant by subjecting seedlings to 0, 25, 50, 100, 200 and 300 mm NaCl stress for 10 days. The dry weight, ion concentrations, relative water content, oxidative damage, proline, osmotic potential and some antioxidants were determined. The plants were found to retain Na⁺ mainly in the root, with less affected leaf K⁺ concentration, and consequently very low shoot Na⁺/K⁺ ratios (<0.2) under all the stress treatments. The proline content significantly increased under the 100–300 mm treatments (18‐ to 244‐fold), with a corresponding significant reduction in osmotic potential and hence high osmotic adjustment. The antioxidant enzyme activities and non‐enzyme antioxidants showed significant increase only under the highest salinity. Taken together, these results suggest that shoot Na⁺ exclusion is characteristic of this plant and is mainly responsible for its adaptation to low salinity.     

硼胁迫对不同基因型西瓜部分生理指标的影响

为了研究硼胁迫对不同基因型西瓜细胞壁、细胞膜以及碳氮代谢的影响,以籽瓜、‘黑美人’西瓜和野生西瓜为材料,设4个硼浓度,测定3种类型西瓜细胞膜透性、游离脯氨酸、可溶性糖、可溶性蛋白含量及PAL和PPO活性。结果表明：3种类型西瓜在硼胁迫下的PPO活性上升,细胞膜透性与游离脯氨酸含量上升,可溶性糖和可溶性蛋白含量有所减少。PAL活性在缺硼胁迫时下降,在高硼胁迫时应激上升。硼胁迫破坏了3种类型西瓜细胞壁结构,产生醌等大量次生产物损伤细胞膜,使细胞膜透性增强,细胞内离子浓度失衡脱水。进而阻碍了细胞正常功能运转,间接削弱西瓜碳代谢系统与氮代谢系统,减少了可溶性糖与可溶性蛋白质等代谢产物的生成。     

硼素对甜菜植株全硼影响的研究

研究不同硼供应水平下甜菜植株硼营养吸收规律,为甜菜生产实践硼肥施用提供理论依据。以甜菜单粒种HI0099为试验材料,在水培条件下,设置十分缺乏（T1,0.05mg/L）、缺乏（T2,0.5mg/L）、正常（T3,2.0mg/L）及过量毒害（T4,30.0mg/L）4个硼营养浓度,利用甲亚胺比色法对甜菜植株全硼含量进行测定,分析甜菜全硼含量变化与不同供硼营养之间的关系。结果表明：不同硼素营养处理后各时期同一部位硼含量均表现为硼素毒害处理＞硼素正常处理＞硼素缺乏处理＞硼素十分缺乏处理;同一处理不同部位硼含量趋势表现相同,均为成熟叶片＞幼叶片＞成熟叶柄＞幼叶柄＞根。综合分析说明,植株硼含量受硼营养水平影响显著,随着硼供应的增加而增加,且成熟叶片需硼量最大,对硼供应水平最敏感,因此甜菜生产中根外追肥为简单有效补充硼营养的一种方法。     

Oxidative damage in forage rape (Brassica napus L.) seeds following heat stress during seed development

A short period (240°C hr; Tb = 25°C) of heat stress (30°C day/25°C night) during forage rape (Brassica napus L.) seed development or at seed physiological maturity can reduce seed vigour, but the extent of oxidative damage associated with this short heat stress was not known. Heat-stressed seeds were assessed for malondialdehyde (MDA) content, hydrogen peroxide (H₂O₂) accumulation, antioxidant enzyme activity, adenylate energy charge and seed ultrastructural integrity, and compared with that of non-heat-stressed seeds. Heat stress increased both MDA content and H₂O₂ accumulation by 35%–50%, reduced antioxidant enzyme activity by between 12% and 67%, and significantly reduced adenosine energy charge. Transmission electron microscope images showed clear evidence of seed deterioration in heat-stressed seeds, including ruptures in cell wall and plasma membranes, fused lipid bodies and damaged mitochondria. Heat stress at physiological maturity caused more oxidative damage than the same heat stress during seed development. Seed vigour decreased as H₂O₂ accumulation increased and antioxidant enzyme activity decreased, but no direct relationship between lipid peroxidation and seed vigour was established. The extent of damage resulting from even shorter periods of heat stress (<240°C hr) before or at seed physiological maturity requires investigation.     

Response of Antioxidant Enzymes,Phytochelatins and Glutathione Production Towards Cd and Zn Stresses in Cajanus cajan (L.) Millsp. Genotypes Colonized by Arbuscular Mycorrhizal Fungi

Most metal polluted natural environments are contaminated with multiple metals, and arbuscular mycorrhizal (AM) fungi are among the extracellular strategies to avoid metal toxicity. To understand the interaction between Cd, Zn and AM fungi Glomus mosseae, two genotypes (Sel 85N and P792) of pigeonpea (Cajanus cajan L. Millsp.), differing in their metal tolerance, were chosen for study. Results revealed that root dry weights were more severely affected than shoot dry weights as both the metals were accumulated in roots than in the aerial parts. Mycorrhization promoted biomass yields by decreasing metal content in plant tissues. Exposure to the metals resulted in oxidative burst (high H₂O₂, malondialdehyde contents and electrolyte leakage), which was accompanied by decreased membrane stability. However, increase in the level of total non‐protein thiols (TNP‐SH) and the activity of antioxidant enzymes like superoxide dismutase (SOD), catalase (CAT), peroxidase (POD) and glutathione reductase (GR) suggested that all these parameters were synergistic in combating heavy‐metal‐induced oxidative stress. Zn supplementation proved to be inhibitory for Cd‐induced oxidative stress. AM fungi alleviated oxidative stress through enhanced production of TNP‐SH as well as through upregulation of antioxidant enzymes. Sel 85N exhibited lesser oxidative damage and more efficient defence mechanism than P792.     

Cadmium Enhances Generation of Hydrogen Peroxide and Amplifies Activities of Catalase, Peroxidases and Superoxide Dismutase in Maize

Maize (Zea mays L. cv. 777) plants grown in hydroponic culture were treated with 50 μm CdSO₄. Growth and metabolic parameters indicative of oxidative stress and antioxidant responses were studied in leaves of plants treated with Cd. Apart from increasing lipid peroxidation and H₂O₂ accumulation, supply of Cd suppressed growth, fresh and dry mass of plants and decreased the concentrations of chloroplastic pigments. The activities of catalase (CAT; EC 1.11.1.6), peroxidase (POD; EC 1.11.1.7), ascorbate peroxidase (APX; EC 1.11.1.11) and superoxide dismutase (SOD; EC 1.15.1.1) were increased in plants supplied 50 μm Cd. Localization of activities of isoforms of these enzymes (POD, APX and SOD) on native gels also revealed increase in the intensities of pre‐existing bands. Stimulated activities of CAT, POD, APX and SOD in maize plants supplied excess Cd do not appear to have relieved plants from excessive generation of reactive oxygen species (ROS). It is, therefore, concluded that supply of 50 μm Cd induces oxidative stress by increasing production of ROS despite increased antioxidant protection in maize plants.     

甜菜保护酶系统对硼胁迫响应及其与内源激素相关性研究

研究不同硼素供应水平下, 硼对甜菜保护酶系统的影响规律以及保护酶系统与内源激素相关性, 丰富甜菜生理学理论。以甜菜单粒种 ‘HI0099’ 为试验材料, 在水培条件下, 设置 4个硼营养浓度, 对甜菜叶片保护酶系统以及内源激素含量进行测定。结果表明： 4种不同硼素处理的甜菜, 叶片中丙二醛(MDA)含量均随着生育进程有减少趋势, 而脯氨酸含量均呈增加趋势; 硼素胁迫处理时, 叶片 MDA含量以及脯氨酸含量增加。不同硼素处理下, 甜菜叶片超氧化物歧化酶(SOD)活性、 过氧化物酶(POD)活性表现为随生育进程逐渐升高趋势; 同一日期, 不同硼浓度表现为缺乏或者毒害胁迫下 SOD活性有升高的趋势, 并且随着甜菜生长, 硼胁迫情况下 SOD活性处理间差异有变小趋势; 在硼胁迫条件下, SOD活性与 ZT含量呈显著负相关(P＜0.05), 与 GA₃呈极显著负相关(P＜0.01)。不同日期各硼素营养处理间过氧化氢酶(CAT)活性变化规律一致, 呈现先降低后升高的趋势。综合分析说明, 硼素胁迫引起膜脂过氧化, 甜菜叶片通过提高保护酶活性来防御硼毒害, 但其防御功能是有限的, 随着生育进程, 甜菜对硼胁迫防御功能达到临界值, 保护酶活性变化不再显著, 且甜菜植株在硼素胁迫下的生长发育受保护酶系统及内源激素间共同调控。     

Genetics of tolerance to high concentrations of boron in Brassica rapa

The inheritance of tolerance to high concentrations of boron in Brassica rapa was studied in F₂ and F₃ segregating populations. The F₁ hybrids were produced from genotypes contrasting in their reaction to boron. The F₁ hybrids responded similarly to the tolerant parent indicating that boron tolerance was dominant trait. Segregation patterns for boron tolerance in F₂ populations and F₃ derived families were established by the measurements of primary root length and tissue boron concentrations. The segregation ratios were explained in terms of two major genes interacting in a dominant epistatic manner to govern tolerance. Evaluation of selected tolerant and susceptible F₃ families indicated that tolerant families produced significantly longer primary roots as compared to susceptible families.     

Exploring the Role of Calcium to Improve Chilling Tolerance in Hybrid Maize

Abiotic stresses, including chilling, impede the plant growth and development mainly by oxidative damage. In this study, seed priming with CaCl₂ was employed to reduce the damage caused by chilling stress in hybrid maize. Maize hybrid (Hycorn 8288) seeds were soaked in 50, 100 and 150 mg l⁻¹ (ppm) aerated solution of CaCl₂ for 24 h and dried. Treated and untreated seeds were sown at 27 °C (optimal temperature) and 15 °C (chilling stress) under controlled conditions. Seed priming with CaCl₂ significantly reduced the chilling damage and improved the germination rate, root and shoot length, and seedling fresh and dry weights. Activities of antioxidants, including catalase, superoxide dismutase and ascorbate peroxidase, were also improved. Soluble sugars and α-amylase concentrations determined as general metabolic indicators of stress were also increased by seed priming with CaCl₂. Priming also improved the performance of maize at optimal temperature. Maintenance of tissue water contents, reduction in membrane leakage and increase in antioxidant activities, and carbohydrate metabolism seemed to induce chilling tolerance by CaCl₂. Seed priming with 100 mg l⁻¹ CaCl₂ was the optimal concentration in improving the performance of hybrid maize both under optimal and stress conditions.     

Morphological,physiological and biochemical aspects of osmopriming-induced drought tolerance in lentil

Lentil (Lens culinaris Medik.) is an important grain legume crop, mostly grown in semi-arid environments and often faces intermittent drought spells during different growth stages, which severely hamper its yield. This study, comprising of three separate experiments, was conducted to evaluate the potential of seed priming with CaCl₂ in improving drought tolerance in lentil. In the first experiment, lentil seeds were hydroprimed (water) or osmoprimed with 0.5 and 1% CaCl₂; while non-primed seeds were taken as control. In the second and third experiments, lentil seeds were subjected to pre-optimized osmopriming (1% CaCl₂) and hydropriming followed by surface drying or re-drying of primed seeds to original weight. The first two experiments were conducted in petri plates, while, in experiment 3, seeds were planted in plastic pots containing peat moss, maintained at 75% water holding capacity (WHC; well-watered) or 50% WHC (water deficit). Hydropriming and osmopriming improved seed germination, seedling growth, biomass production, chlorophyll intensity, sugar accumulation and reduced the oxidative stress in lentil under water deficit. However, osmopriming (1% CaCl₂) was more effective than the hydropriming in improving the lentil growth, biomass production, Ca accumulation and sugar metabolism under both well-watered and water deficit conditions. Seed surface drying, after priming, was more beneficial in improving the lentil performance, under both well-watered and water deficit conditions, than re-drying to original weight. Osmopriming (1% CaCl₂) increased the seeding dry weight (67%), SPAD value (140%), leaf Ca concentration (56%), α-amylase activity (55%), total soluble sugars (48%) and reduced malanodialdehyde content (35.9%) and total antioxidant activity (29.2%) than un-primed seeds under water deficit. In conclusion, osmopriming improved the lentil performance under optimal and water deficit conditions through early and synchronized emergence, better sugar and Ca accumulation which reduced the oxidative damage and resulted in better seedling growth and biomass production.     

Improved Cold and Drought Tolerance of Doubled Haploid Maize Plants Selected for Resistance to Prooxidant tert‐Butyl Hydroperoxide

To improve the abiotic stress tolerance of maize (Zea mays L.), doubled haploid (DH) plants were produced by in vitro selection of microspores exposed to tert‐butyl hydroperoxide (t‐BuOOH) as a powerful prooxidant This study investigated the tolerance of the progenies of t‐BuOOH‐selected DH lines to oxidative stress, cold and drought in controlled environment pot experiments by analyses of photosynthetic electron transport and CO₂ assimilation processes, chlorophyll bleaching and lipid peroxidation of leaves. Our results demonstrated that the t‐BuOOH‐selected DH plants exhibited enhanced tolerance not only to oxidative stress‐induced by t‐BuOOH but also to cold and drought stresses. In addition, they showed elevated activities of antioxidant enzymes such as superoxide dismutase, ascorbate peroxidase, catalase, glutathione reductase and glutathione S‐transferase when compared with the DH lines derived from microspores that were not exposed to t‐BuOOH and to the original hybrid plants. The results suggest that the simultaneous up‐regulation of several antioxidant enzymes may contribute to the oxidative and cold stress tolerance of the t‐BuOOH‐selected DH lines, and that the in vitro microspore selection represents a potential way to improve abiotic stress tolerance in maize.     

喷施水杨酸缓解镉对黑麦草毒害作用的研究

为了研究水杨酸缓解重金属镉对黑麦草的毒害作用,采用盆栽模拟方法测定喷施外源水杨酸后在镉胁迫处理下黑麦草的生理指标的变化情况。研究结果表明：喷施100、200和300 mg/L 3种浓度水杨酸对镉胁迫下黑麦草叶绿素含量没有显著影响,但能够提高黑麦草叶片中重要的渗透调节物质脯氨酸和可溶性糖含量,其中200 mg/L浓度水杨酸对脯氨酸的提高作用显著高于其他浓度;喷施水杨酸也能够显著提高SOD、POD、CAT等多种抗氧化酶的活性,降低电解质渗透率和丙二醛含量,各浓度之间作用程度差异不显著,200和300 mg/L浓度的作用更大一些。上述生理指标的测定说明喷施水杨酸可以缓解镉对黑麦草的毒害作用。     

Physiological response of ‘Larry Ann’ plums to cold storage and 1-MCP treatment

The aim of this work was to study the specific effects of low temperature and 1-MCP treatment on ethylene metabolism and oxidative behaviour in plums (Prunus × salicina cv. Larry Ann). Control fruit were stored at 20 °C or 0 °C and the 1-MCP (625 nL L^?1) treated fruit at 0 °C. Changes in the kinetics of ethylene production upon removal were related to changes in ACC metabolism (ACC and MACC levels), oxidative behaviour (H₂O₂ content) and enzymatic antioxidant potential (SOD, CAT and POX enzymes) during cold storage. Low temperature stress inhibited the synthesis of MACC, which appeared to be the basic process that regulated ACC and ethylene production at ambient temperature. Although 1-MCP treatment inhibited ethylene production and ACC accumulation in the cold, it did not inhibit the accumulation of MACC. Neither cold nor 1-MCP treatment induced oxidative stress. Nevertheless, the 1-MCP treatment significantly impaired the increase in POX activity observed during cold storage. Collectively these results showed the underlying role that ACC metabolism plays in the ripening behaviour of cold-stored plums, confirming previous results. The results also indicate that MACC and malonyl transferase activity are the key regulatory factors that control ripening and possibly some ethylene-related disorders such as chilling injury in cold-stored plums.