硫肥对春油菜幼苗生理指标和土壤酶活性的影响

该研究以春油菜幼苗为材料,采用土壤盆栽试验,设7个不同施硫(0、35、70、105、140、175、210mg·kg^-1)处理,通过测定春油菜幼苗的株高、植株鲜重、叶绿素含量、MDA含量、SOD、POD、CAT活性、土壤全氮含量、pH、蔗糖酶、过氧化氢酶和脲酶活性指标,分析不同施硫量对春油菜幼苗生理生化指标和土壤相关酶活性的影响。结果表明:在春油菜苗期施用硫肥对幼苗的农艺性状、生理生化指标和土壤酶活性均产生了一定影响。施硫量在35~105mg·kg^-1范围时,对植株鲜重有明显的促进作用;施硫量在70~105mg·kg^-1范围时,类胡萝卜素含量达到最高;施硫量在70~105mg·kg^-1范围时,叶片中POD和CAT的活性明显升高,而MDA含量明显下降;经相关分析,MDA含量与POD活性呈极显著负相关(r=-0.92,P<0.01),与CAT活性呈显著负相关(r=-0.72,P<0.05),说明叶片MDA含量受POD和CAT活性变化的影响;施硫量高于105mg·kg^-1时,土壤脲酶和蔗糖酶活性受到抑制;施硫量高于140mg·kg^-1时,土壤过氧化氢酶活性受到抑制;随着施硫量的增加,土壤pH值和叶片SOD活性逐渐下降;经相关性分析,土壤脲酶活性和全氮含量间呈极显著正相关(r=1,P<0.01),表明土壤全氮含量受土壤脲酶活性变化的影响。由此可知,在低硫(35~105mg·kg^-1)条件下对春油菜幼苗生理生化指标及土壤酶活性具有一定的促进作用,而在高硫(>105mg·kg^-1)条件下则产生抑制。     

The Earthworm Eisenia fetida Can Help Desalinate a Coastal Saline Soil in Tianjin,North China

A laboratory microcosm experiment was conducted to determine whether the earthworm Eisenia fetida could survive in a saline soil from a field site in North China, and an experiment using response surface methodology was conducted at that field site to quantify the effects of E. fetida and green waste compost (GWC) on the salt content of the soil. The microcosm results showed that E. fetida survived in GWC-amended saline soil and increased the contents of humic acid, available N, and available P in the GWC-amended soil. The data from the field experiment were described by the following second-order model:y^ =-1.76+0.091x1+0.48x2-0.00083x1x2-0.00078x12-0.022x22, where y is the decrease in soil salinity (g of salt per kg of dry soil) relative to the untreated control, x ₁ is the number of E. fetida added per m², and x ₂ is the quantity of GWC added in kg per m². The model predicted that the total salt content of the saline soil would decrease by > 2 g kg^-1 (p<0.05) when 29–90 individuals m^-2 of E. fetida and 6.1–15.0 kg m^-2 of GWC were applied. We conclude that the use of E. fetida for soil desalination is promising and warrants additional investigation.     

Reactive Oxygen Species and Relative Enzyme Activities in the Development of Aerial Roots of Chinese Banyan (Ficus microcarpa)

Although previous research has indicated that reactive oxygen species (ROS) regulate cell extension and tissue ontogenesis, the functions of ROS in aerial roots have not been previously studied. This research evaluated ROS production and dissipation in aerial roots of Chinese banyan (Ficus microcarpa). Aerial root segments (4 cm long) were cut from trees and divided into developmental zones 1, 2, and 3 (0–5, 5–15, and 15–25 mm from root tip, respectively). According to histochemical and biochemical determinations, production of the superoxide radical (O ₂ ^·– ), hydrogen peroxide (H₂O₂), and the hydroxyl radical (^·OH) decreased from zone 1 to zone 3. The detected ROS increased with the application of exogenous stimulators of ROS generation and decreased with the application of exogenous inhibitors of ROS generation. Based on protein content, superoxide dismutase (SOD) activity increased but peroxidase (POD) and catalase (CAT) activities decreased from zone 1 to zone 3, whereas based on root segment fresh weight, SOD and CAT activities did not differ among the zones but POD activity decreased from zone 1 to 3. We conclude that ROS are generated mainly in the rapidly developing zones of aerial roots and suggest that NADPH oxidase, POD, and SOD control ROS generation. POD activity and the hydroxyl cycle seem particularly important in ROS generation in aerial roots.     

The effects of dopamine on antioxidant enzymes activities and reactive oxygen species levels in soybean roots

In the current work, we investigated the effects of dopamine, an neurotransmitter found in several plant species on antioxidant enzyme activities and ROS in soybean (Glycine max L. Merrill) roots. The effects of dopamine on SOD, CAT and POD activities, as well as H₂O₂, O₂^•−, melanin contents and lipid peroxidation were evaluated. Three-day-old seedlings were cultivated in half-strength Hoagland nutrient solution (pH 6.0), without or with 0.1 to 1.0 mM dopamine, in a growth chamber (25°C, 12 h photoperiod, irradiance of 280 μmol m⁻² s⁻¹) for 24 h. Significant increases in melanin content were observed. The levels of ROS and lipid peroxidation decreased at all concentrations of dopamine tested. The SOD activity increased significantly under the action of dopamine, while CT activity was inhibited and POD activity was unaffected. The results suggest a close relationship between a possible antioxidant activity of dopamine and melanin and activation of SOD, reducing the levels of ROS and damage on membranes of soybean roots.     

Antioxidative response of metal-accumulator and non-accumulator plants under cadmium stress

The present study aims to elucidate the role of antioxidative enzyme in the adaptive responses of metal-accumulators (Thlaspi caerulescens and Brassica juncea) and non-accumulator plant (Nicotiana tabacum) to Cadmium stress. When seedlings of plants were grown in hydroponic condition for a period of 4 days in the presence of 200 or 400 μM CdCl₂, photosynthetic rate, transpiration rate and stomatal conductance in metal-accumulators decreased more slowly than that in tobacco. MDA content and electrolyte leakage increased with elevated Cd concentration and exposure time in all plant species, while the oxidative damage in tobacco was more serious than that in metal-accumulators. The activities of SOD and CAT in metal-accumulators were significantly higher than that in tobacco under normal condition, whereas there was no significant difference in the activity of POD between Indian mustard and tobacco. The activities of antioxidative enzymes increased rapidly in metal-accumulators in response to the Cd treatments, especially SOD and CAT. In tobacco, CAT activity declined rapidly by exposure to the Cd treatment, though the activity of SOD and POD was enhanced, indicating that the antioxidative enzymes in tobacco could not fully scavenge ROS generated by Cd toxicity. These results collectively indicate that the enzymatic antioxidation capacity is one of the important mechanisms responsible for metal tolerance in metal-accumulator plant species.     

Combined effects of hypoxia and excess Mn2+ on oxidative stress and antioxidant enzymes in tomato seedlings

Effects of high level of Mn²⁺ on the changes in ROS generation, root cell viability, antioxidant enzyme activities, and related gene expression in tomato (Solanum lycopersicum L., cv. Zhongza 9) seedlings were studied under normoxic and hypoxia conditions. Mn²⁺ concentrations, ranged between 10 and 200 ??M, led to significantly higher activities of superoxide dismutase (SOD), peroxidase (POD), ascorbate peroxidase (APOD), glutathione reductase (GR), and also ascorbic acid (AsA) content in leaves and roots, improved root cell viability, and decreased O ₂ ^·? accumulation compared with the higher Mn²⁺ level under hypoxia stress, which indicated that low Mn²⁺ could eliminate the active oxygen and protect the membrane lipid from the hypoxia hurt. When the concentration of Mn²⁺ reached 400?C600 ??M under hypoxia stress, the activities of SOD, POD, APOD, and GR and AsA content were decreased remarkably. In contrast, the MDA content was increased at the higher Mn²⁺ concentration. A number of antioxidant-related genes showed high expression at the lower level of Mn²⁺. The expression levels of SOD, POD, CAT, APOD, and GR genes were 7.95, 5.27, 3.18, 5.54, and 8.81 times compared to control, respectively. These results illustrated that the appropriate amount of Mn²⁺ could alleviate the detrimental effects of hypoxia stress, but reversely, the high level of Mn²⁺ just aggravated the existing damage to the tomato seedlings.     

An assessment of Agropyron cristatum tolerance to cadmium contaminated soil

A pot experiment was conducted in a greenhouse to assess the tolerance of Agropyron cristatum plants to cadmium contaminated soils (0, 5, 10, 25, 50, 100, 150, and 200 mg kg^?1) for 100 d. Results indicate that Cd in concentrations of 5–50 mg kg^?1 had no significant impact on growth, relative membrane permeability (RMP), lipid peroxidation measured as malondialdehyde (MDA) content, and chlorophyll (Chl) content relative to the control. Exposure of these plants to high concentrations of Cd (100–200 mg kg^?1) caused a small reduction in growth and Chl content and a slight enhancement of RMP and MDA content compared with the control. In addition, superoxide dismutase (SOD) and peroxidase (POD) activities show an increasing trend with the increase of Cd content in soil. The Cd content in the roots was 4.7–6.1 times higher than that in the shoots under all Cd treatments suggesting that the plant can be classified as a Cd excluder. The translocation factor was low and similar at 25–200 mg kg^?1 Cd treatments. In summary, A. cristatum plants tolerated Cd stress and might have potential for the phytoremediation of Cd contaminated soils.     

Physiological and Biochemical Mechanisms Preventing Cd Toxicity in the New Hyperaccumulator <Emphasis Type="Italic">Abelmoschus manihot</Emphasis>

Abelmoschus manihot, an ornamental plant, was examined for phytoremediation purposes in accordance with the ability to accumulate cadmium and physiological mechanisms of cadmium tolerance. A net photosynthetic rate (A _N) glasshouse experiment for 60 days was conducted to investigate the influence of different cadmium amounts (0–100 mg kg^?1) on the growth, biomass, photosynthetic performance, reactive oxygen species (ROS) production, antioxidative enzyme activities, Cd uptake and accumulation of A. manihot. Exposure to cadmium enhanced plant growth even at 100 mg kg^?1, without showing symptoms of visible damage. The cadmium concentration of shoots (stems or leaves) and roots was more than the critical value of 100 mg kg^?1 and reached 126.17, 185.26 and 210.24 mg kg^?1, respectively. BCF values of A. manihot plants exceeded the reference value 1.0 for all the Cd treatments, and TF values were greater than 1 at 15–60 mg kg^?1 Cd treatment. The results also showed that cadmium concentrations of 60 mg kg^?1 or less induced a significant enhancement in plant net photosynthetic rate (A _N), stomatal conductance (G _s), transpiration rate (T _r), photosynthetic pigments and F _v/F _m. These parameters were slightly decreased at the higher concentration (100 mg kg^?1). The ROS production (O₂ ^?, H₂O₂) and antioxidative response including SOD, CAT and POD were significantly enhanced by increasing cadmium. These results suggest that A. manihot can be considered as a Cd-hyperaccumulator and the hormetic effects may be taken into consideration in remediation of Cd contamination soil.     

Calcium Stimulates the Adaptation of Cultured Liquorice Cells to PEG-Induced Water Stress

Calcium may be involved in plant tolerance to water deficit by regulating antioxidant metabolism or/and water relations. This study was designed to examine whether external Ca²⁺ would stimulate drought tolerance in cultured liquorice cells. Water stress induced by 15% PEG significantly reduced fresh weight and relative water content in liquorice cells, but external Ca²⁺ markedly increased them after stress for 7 days. The activities of catalase (CAT), superoxide dismutase (SOD) declined and activity of peroxidase (POD) slowly increased during water stress imposition. External calcium significantly enhanced SOD and CAT activities, but the effect on POD activity was weak. The effect of external Ca²⁺ on water deficit tolerance in liquorice cells was not due to the osmotic adjustment in culture medium. Under nonstress conditions, external calcium slightly increased the activities of SOD, CAT, and POD. Ca²⁺ signal in liquorice cells may be different under stress and nonstress conditions. Under water stress, Ca²⁺ signal involves in reactive oxygen species transduction pathway and affects the processes participating in regulation of antioxidative enzymes; under nonstress conditions, Ca²⁺ signal coming from external calcium might not participate in ROS signal transduction pathway resulting in antioxidative defense response in liquorice cells. Less malondialdehyde was accumulated after water stress for 7 days in Ca²⁺-treated cells than in untreated cells. It was proposed that external calcium could reduce the damage of water deficit and stimulate tolerance to it in liquorice cells by mitigating oxidative stress.     

Potential of Sagittaria trifolia for Phytoremediation of Diesel

The phytoremediation potential and responses of Sagittaria trifolia to diesel were investigated. In order to elucidate the biochemical and physiological responses of S. trifolia to diesel, the chlorophyll content, root vitality, soluble protein content and antioxidant enzymes activity (peroxidase (POD), catalase (CAT) and antioxidant enzymes superoxide dismutase (SOD)) were determined in the plant tissues after 50 d of diesel treatment. The results showed the presence of S. trifolia significantly improved the removal ratios of diesel, from 21～36% in the control soils to 54～85% in the planted soils. The chlorophyll content, root vitality and soluble protein content all increased at low diesel concentration, then decreased at high diesel concentration. The activities of CAT and POD exhibited peak values at 5 g·kg^?1 diesel treatment and declined at higher diesel concentrations. However, the activity of SOD kept stable at lower diesel concentration (1 and 5 g·kg^?1), and also declined at higher diesel concentration. Collectively, S. trifolia had the ability to tolerate certain amount of diesel, but when the concentration was up to 10 g·kg^?1, the growth of S. trifolia would be restrained. The results also showed that variation of antioxidant enzyme activity was an important response in plants to diesel pollution.     

盐胁迫对盐芥（Thellungiella halophila）生长和抗氧化酶活性的影响

在盐芥抽苔期用不同浓度NaCl进行处理,测定单株生长量、苔茎叶和根系的质膜透性、MDA含量、苔茎叶的超氧阴离子（O^-₂）含量,苔茎叶的超氧化物歧化酶（SOD）、过氧化物酶（POD）、过氧化氢酶（CAT）等的活性。结果表明：低浓度NaCl处理盐芥单株干重增加,高浓度NaCl处理则降低盐芥单株的干重,鲜重有抑制作用;盐处理后盐芥地上部质膜透性逐渐增加,地下部质膜透性、叶片中的丙二醛（MDA）和超氧阴离子（O^-₂）含量先降低后升高。抗氧化酶系统中的超氧化物歧化酶（SOD）活性先升高后降低,过氧化物酶（POD）、过氧化氢酶（CAT）的活性呈上升趋势。表明低浓度的盐处理对盐芥生长有利,活性氧及丙二醛（MDA）含量减少,而高浓度的盐处理后,抗氧化酶不能及时将活性氧类清除,从而导致活性氧及MDA积累,引起质膜伤害,盐芥生长量降低。     

Biological Responses in the Earthworm Eisenia fetida Exposed to Soils near a Typical Lead Acid Battery Plant

There are increasing concerns over the environmental implications involved in battery plant due to the elevated metal concentrations in the surrounding soils. Earthworms are regarded as a model organism for evaluation of terrestrial environmental pollution. The biochemical responses in the earthworms, Eisenia fetida, exposed to polluted soils were investigated. Soil samples at 0, 50, 100, 200, 500 and 1000 m from a battery plant were collected and used to assess the relationship between sampling distance and biochemical responses in E. fetida. Biochemical alterations were carried out on 1, 3, 7 and 14 d of exposure. The metallothionein (MT), malondialdehyde (MDA) and antioxidant enzymes (superoxide dismutase (SOD), catalase (CAT) and peroxidase (POD)) were measured. The results demonstrated that concentrations of heavy metals, especially Pb, decreased sharply with increase in distance, which may be due to the leaching and accumulation of Pb in soil during production processes. The concentrations of MT and MDA increased with exposure (dosage and time), indicating that E. fetida presented dose and time dependence after heavy metal exposure. The activities of SOD and CAT increased after heavy metal induction, while the activity of POD was lower than that of the control group. The SOD, CAT and POD present a cooperative effect for the protection of lipids and enzymes due to the pollution. The soils around the battery plant were polluted with metals giving rise to adverse biological effects.     

锰胁迫和性别竞争交互处理下沙棘雌雄幼苗生理响应特征

沙棘(Hippophae rhamnoides)是重要的雌雄异株人工林防护树种,但对其环境胁迫的性别响应差异研究不足,性别竞争与胁迫因子的交互效应响应特征尚不清楚。为了探讨锰胁迫和性别竞争交互处理下沙棘雌雄植株的生理响应特征和耐受能力,旨在为沙棘修复土壤重金属污染提供实践指导,该文研究了锰胁迫(4 000 mg·kg^-1)和3种不同性别组合模式(雌雄、雌雌、雄雄)处理下沙棘的生理响应,分别测定雌雄沙棘叶片中叶绿素、过氧化物酶(peroxidase,POD)、超氧化物歧化酶(superoxide dismutase,SOD)、丙二醛(malondialdehyde,MDA)、总酚(total phenols, TP)、游离脯氨酸(free proline,Pro)、可溶性糖(soluble sugar,SS)、甜菜碱(glycine betaine, GB)以及锰含量。结果表明:(1)锰胁迫下,在所有竞争组合中,性间竞争的雄株(M/FM)SOD活性最高,而MDA含量与对照相比未有明显升高,表明雄株的抗氧化能力更好,膜氧化损伤程度更小。(2)锰胁迫时M/FM积累了更多的游离脯氨酸,表现出更好的渗透调节能力和耐受能力。(3)交互效应分析显示性别互作和锰胁迫交互处理显著影响了沙棘雌雄叶片的光合色素、抗氧化酶活性和渗透调节能力; 主成分分析显示SOD、POD、MDA、叶绿素b(chlorophyll b, Chlb)、SS、Pro可作为重要的生理响应指示参数。该研究结果对于利用沙棘修复土壤重金属污染可提供一定的参考。     

Exogenous trehalose differentially modulate antioxidant defense system in wheat callus during water deficit and subsequent recovery

To elucidate the resistance mechanism of exogenous trehalose on water deficit further, we investigated the effect of exogenous trehalose (50 mM) in wheat callus during water deficit and subsequent recovery. Enhanced levels of endogenous trehalose were detected in calli exposed to water deficit (W) and trehalose (T) medium, moreover, W plus T treatment showed an additive effect. Water deficit elevated the accumulation of ROS (hydrogen peroxide and formation rate of O ₂ ^.? ) and the endogenous MDA (Malonaldehyde), and resulted in the decrease of cell viability and biomass. Exogenous trehalose (TW) could alleviate the damage induced by water deficit, which was involved in the decrease of MDA and the generation of ROS, and resulted in elevating cell viability and biomass. Additionally, water deficit induced activity of antioxidative enzymes (Peroxidase, POD; Catalase, CAT; Glutathione reductase, GR). Content of AsA (Reduced ascorbate) was also increased by water deficit, while the content of GSH (Glutathione) showed the opposite effect. The combined effect of T and W treatment led to a higher activity of enzymatic antioxidants including SOD (Superoxide dismutase) and GR, and elevated the content of nonenzymatic antioxidants including AsA and GSH, but had a negative effect on enzymatic antioxidants including POD and CAT in comparison to the water deficit treatment alone. During recovery, calli treated by TW showed a greater reduction in ROS resulted in enhancing a higher cell viability and biomass. The scavenging mechanism of ROS by exogenous trehalose is mainly dependent on nonenzymatic antioxidants, especially AsA-GSH cycle, rather than enzymatic mechanisms and trehalose itself.     

Fate and Phytotoxicity of CeO2 Nanoparticles on Lettuce Cultured in the Potting Soil Environment

Cerium oxide nanoparticles (CeO₂ NPs) have been shown to have significant interactions in plants. Previous study reported the specific-species phytotoxicity of CeO₂ NPs by lettuce (Lactuca sativa), but their physiological impacts and vivo biotransformation are not yet well understood, especially in relative realistic environment. Butterhead lettuce were germinated and grown in potting soil for 30 days cultivation with treatments of 0, 50, 100, 1000 mg CeO₂ NPs per kg soil. Results showed that lettuce in 100 mg·kg^-1 treated groups grew significantly faster than others, but significantly increased nitrate content. The lower concentrations treatment had no impact on plant growth, compared with the control. However, the higher concentration treatment significantly deterred plant growth and biomass production. The stress response of lettuce plants, such as Superoxide dismutase (SOD), Peroxidase (POD), Malondialdehyde(MDA) activity was disrupted by 1000 mg·kg^-1 CeO₂ NPs treatment. In addition, the presence of Ce (III) in the roots of butterhead lettuce explained the reason of CeO₂ NPs phytotoxicity. These findings demonstrate CeO₂ NPs modification of nutritional quality, antioxidant defense system, the possible transfer into the food chain and biotransformation in vivo.     

不同能源柳无性系对土壤镉污染的抗性研究

运为了比较不同能源柳无性系对土壤镉抗性的差异,采用盆栽方法,设置土壤镉含量5个梯度(0、10、20、40、80 mg·kg^-1),以乡土旱柳为对照,对能柳1、能柳2、能柳E、能柳C的扦插幼苗对土壤镉污染的生理生态反应进行了系统测定,分析了不同无性系的抗性。结果显示,低浓度处理（≤20 mg·kg^-1）促进苗木生长,其中能柳2在10 mg·kg^-1处理下根和单株生物量增幅最大,可达到对照的132.0%和120.0%;随着镉浓度的增加,生长量下降,在最高浓度处理下,能柳C生长量降低最少,根、枝、叶和单株生物量分别为对照的86.1%、85.3%、82.9%、84.9%,旱柳的枝、叶生物量降低最多,为对照（无镉）的43.8%、45.0%,而能柳1的根、单株生物量降低最多,仅为对照的36.1%、44.4%;随着镉浓度的增加,不同能源柳无性系叶片的SOD、POD、CAT活性和根系活力基本呈现先升后降的趋势,其中,CAT活性变化较为平缓;关于SOD活性和根系活力,能柳1、能柳2在20 mg·kg^-1时已显著下降,旱柳在40 mg·kg^-1时显著下降,而能柳E、能柳C在40 mg·kg^-1时才显著下降。采用隶属函数对5个无性系在镉胁迫条件下的生长和酶指标进行综合分析,不同无性系对土壤镉污染的抗性顺序为能柳C>能柳2>能柳1>旱柳>能柳E。不同无性系对镉均有抗性,都可在镉污染区推广种植,栽培中,应根据土壤污染和绿化目标,做出适当选择。     

Biochemical analysis of reactive oxygen species production and antioxidative responses in unripe avocado (Persea americana Mill var Hass) fruits in response to wounding

We analyzed the production of reactive oxygen species (ROS) and of detoxifying enzymes and enzymes of the ascorbate (ASC) acid cycle in avocado fruit (Pesea Americana Mill cv Hass) in response to wounding. The levels of superoxide anion (O₂ ^?), hydroxyl radicals (OH^.) and hydrogen peroxide (H₂O₂) increased at 15 min and 2 and 15 h post-wounding. Peroxidase (POD) activity had increased to high levels 24 h after wounding; in contrast, catalase and superoxide dismutase (SOD) levels hat decreased significantly at 24 h post-treatment. Basic POD was the major POD form induced, and the levels of at least three apoplastic POD isozymes –increased following wounding. Using specific inhibitors, we characterized one MnSOD and two CuZnSOD isozymes. CuZnSOD activities decreased notably 12 h after treatment. The activities of dehydroascorbate reductase and glutathione reductase increased dramatically following the wounding treatment, possibly as a means to compensate for the redox changes due to ROS production.     

Antioxidant Responses of Wheat Seedlings to Exogenous Selenium Supply Under Enhanced Ultraviolet-B

The paper reports the effects of selenium (Se) supply on growth and antioxidant traits of wheat (Triticum aestivum L. cv Han NO.7086) seedlings exposed to enhanced ultraviolet-B (UV-B) stress. Antioxidant responses of seedlings were different depending on the Se concentration. Compared with the control, the lower amount used (0.5 mg Se kg⁻¹ soil) had no significant effect on biomass accumulation. The treatments with 1.0, 2.0, and 3.0 mg Se kg⁻¹ promoted biomass accumulation of wheat seedlings, and the increased amount in biomass was the most at 1.0 mg Se kg⁻¹ treatment. Se treatments with 1.0, 2.0, and 3.0 mg kg⁻¹ also significantly increased activities of peroxidase (POD) and superoxide dismutase (SOD) and reduced the rate of superoxide radical (O₂⁻) production and malondialdehyde (MDA) content of wheat seedlings. In addition, anthocyanins and phenolic compounds content in wheat seedlings evidently increased by the treatments with 1.0 and 2.0 mg Se kg⁻¹. The lower Se treatment had no significant effect on MDA content, although it increased activities of antioxidant enzymes (POD, SOD, and catalase activities) and reduced the rate of O₂⁻ production in wheat seedlings. These results suggest that optimal Se supply is favorable for the growth of wheat seedlings and that optimal Se supply can reduce oxidative stress of seedlings under enhanced UV-B radiation.     

High tolerance of aluminum in the grass species Cynodon aethiopicus

Concentrations of aluminum (Al) were determined in leaves of native terrestrial plants, macrophytes and fruit parts (watermelon and tomato) using inductively coupled plasma mass spectrometry. Al concentrations in water and soil were determined by inductively coupled plasma optical emission spectrometry. Potamogeton thunbergii (macrophyte) and Cynodon aethiopicus (terrestrial grass) had the highest leaf Al concentrations (2 and 1 g kg^?1 dw, respectively). Transfer factors (mg kg^?1 dw plants/mg kg^?1 dw soil) based on total Al concentrations in soil varied from 2 × 10^?3 to 0.05 and from 1.9 to 78 based on mobile Al concentrations determined after sequential extraction. Bioconcentration factors (mg kg^?1 dw plants/mg L^?1 water) varied from 19 to 9.5 × 10³ L kg^?1 dw. Plants can accumulate high concentrations of Al when growing in neutral pH soils and slightly alkaline lakes in the Ethiopian Rift Valley. Controlled experiments showed that C. aethiopicus can accumulate high levels of Al both in root and shoot. Compared to Arabidopsis thaliana, C. aethiopicus was more tolerant to Al exposure as ≥400 μM AlCl₃ was needed to inhibit root growth compared to 200 μM in A. thaliana. After exposing C. aethiopicus and A. thaliana in 800 μM AlCl_3, alkaline comet assay indicates significant DNA (deoxyribonucleic acid) damage in A. thaliana while C. aethiopicus was unaffected. No significant induction of reactive oxygen species (ROS), in terms of leaf H₂O₂ levels, could be observed in C. aethiopicus. C. aethiopicus has mechanisms to suppress both Al-induced ROS and DNA damage, thereby increasing tolerance of the species to high Al concentrations.     

Protective effects of complementary Ca2+ on low-light-induced oxidative damage in tall fescue

Low-light (LL) intensity is a primary abiotic stressor that negatively influences turf grass quality. In the present experiment, we studied the effect of exogenous Ca²⁺ (0, 10, 50, 100, and 200 mM) on the antioxidant system, the accumulation of MDA and proline, the content of photosynthetic pigments in plant leaves in order to investigate whether exogenous Ca²⁺ treatment improves LL tolerance in tall fescue (Festuca arundinacea Schreb.). We have found that LL significantly reduced a number of growth parameters (plant height, leaf width, leaf fresh weight, root fresh weight, leaf dry weight, and root dry weight), chlorophyll (Chl) a and Chl b contents, and carotenoid (Car) levels, while considerably enhancing electrolyte leakage (EL), MDA accumulation, calcium (Ca²⁺) concentration, and generation of reactive oxygen species (ROS), such as hydrogen peroxide (H₂O₂) and superoxide radical (O ₂ ^·? ). Moreover, LL significantly induced the activities of antioxidant enzymes, such as peroxidase (POD) and catalase (CAT), and slightly increased the activity of superoxide dismutase (SOD) in tall fescue leaves. In contrast, POD and SOD activities declined considerably while CAT activity significantly increased in plant roots under LL stress. The application of 50 mM Ca²⁺ significantly improved the aforementioned growth parameters, the content of photosynthetic pigments, and further enhanced the activities of POD, SOD, and CAT, but decreased electrolyte leakage and MDA and H₂O₂ levels in the leaves and roots of tall fescue under LL stress. These results suggest that Ca²⁺ is likely involved in a resistance to LL by regulating antioxidant enzyme action in tall fescue leaves and roots.