Oxygen enrichment with magnesium peroxide for minimizing hypoxic stress of flooded corn

Flooding/waterlogging is a major factor responsible for hypoxic stress in agriculture. The aim of this study was to develop an effective oxygen buffer with magnesium peroxide (MgO₂) to generate hydrogen peroxide (H₂O₂) and release bioavailable oxygen. MgO₂ provided a relatively stable level (approx. 300 µM) of bioavailable oxygen. The oxygen‐buffer system is adjustable and controllable by adding Mg²⁺ or EDTA to the aqueous system. Regular H₂O₂ was also able to provide bioavailable oxygen but the system was poorly buffered with respect to oxygen release. The accessibility of plants to bioavailable oxygen was indicated by the activity of alcohol dehydrogenase (ADHase, EC 1.1.1.1), an anaerobically induced enzyme of flooded plants. The application of MgO₂ to flooded soil reduced ADHase activity in corn‐root tips by 91.3%. This application of MgO₂ presents a novel pathway to significantly (P < 5%) minimize adverse impacts of hypoxia on flooded corn seedlings. This finding may have broad implications for addressing hypoxicity problems in crop science and technology.     

Excess Nickel Modulates Oxidative Stress Responsive Enzymes in Groundnut

Groundnut plants exposed to excess nickel (Ni) produced visual symptoms of toxicity that intensified with increasing level and duration of metal supply. Decreased concentrations of pigments along with a marked increase in the activities of anti-oxidative enzymes such as superoxide dismutase, ascorbate peroxidase, and peroxidase suggest strong induction of oxidative stress due to excess Ni. The decreased activity of catalase may suggest interference of excess nickel in iron metabolism of plants. The appearance of metal specific toxicity is a likely result of damage predominantly due to enhanced generation of reactive oxygen species (ROS) at higher (300–400 μM) nickel supply. The threshold of toxicity (10% growth reduction) and toxicity (33% growth reduction) values of Ni in groundnut were 26 and 72 μg g^?1 in leaves, 17 and 94 μg g^?1 in stem and 45 and 240 μg g^?1 in roots respectively.     

褪黑素对缓解植物逆境胁迫作用的研究进展

褪黑素（N-乙酰-5-甲氧基色胺）是一种自然产生的吲哚胺类激素,在动物松果体合成与分泌,是一种为人熟知的作用于动物昼夜节律调节的激素。近些年,研究发现褪黑素也广泛存在于高等植物体内,对植物的各种生理活动起重要作用,尤其是可以缓解各种逆境环境对植物的损伤。经查找资料发现,国内外关于褪黑素对植物的作用的研究还不足,本文根据近几年的研究成果对褪黑素增强植物的抗逆性作用进行综述,并且对褪黑素未来的研究方向进行展望。     

水分和铅双重胁迫对紫穗槐苗木叶片抗氧化酶活性的影响

为了探讨在水分和铅双重胁迫条件下,紫穗槐(Amorpha fruticosa L.)苗木叶片抗氧化酶活性的变化,采用旱棚盆栽试验,研究了不同水分胁迫处理(土壤相对含水量分别为田间持水量的100%,80%,60%和40%)和铅胁迫处理(土壤中铅含量分别为0,1 000,2 000,4 000和6 000mg/kg)及其双重作用对紫穗槐苗木叶片的超氧化物歧化酶(SOD)、过氧化物酶(POD)和过氧化氢酶(CAT)活性的影响。结果表明,在单一的铅胁迫处理下,随着胁迫的加剧,紫穗槐苗木叶片的SOD和CAT活性呈先升高后降低的趋势,POD活性一直呈升高趋势;在单一的水分胁迫处理下,随着胁迫的加剧,SOD和POD活性呈先升高后降低的趋势,CAT活性呈先降低后升高的趋势;水分和铅双重胁迫对SOD和POD活性有显著的激活作用,对低铅含量(≤2 000mg/kg)处理的CAT活性有激活作用;适度的双重胁迫(铅含量≤2 000mg/kg,土壤相对含水量≥40%)有利于提高紫穗槐苗木对水分和铅双重胁迫的耐受性。     

Soil enzyme activities during the 2011 Texas record drought/heat wave and implications to biogeochemical cycling and organic matter dynamics

Extreme droughts and heat waves due to climate change may have permanent consequences on soil quality and functioning in agroecosystems. During November 2010 to August 2011, the Southern High Plains (SHP) region of Texas, U.S., a large cotton producing area, received only 39.6 mm of precipitation (vs. the historical avg. of 373 mm) and experienced the hottest summer since record keeping began in 1911. Several enzyme activities (EAs) important in biogeochemical cycling were evaluated in two soils (a loam and a sandy loam at 0–10 cm) with a management history of monoculture (continuous cotton) or rotation (cotton and sorghum or millet). Samplings occurred under the most extreme drought and heat conditions (July 2011), after precipitation resulted in a reduction in a drought severity index (March 2012), and 12 months after the initial sampling (July 2012; loam only). Eight out of ten EAs, were significantly higher in July 2011 compared to March 2012 for some combinations of soil type and management history. Among these eight EAs, enzymes key to C (β-glucosidase, β-glucosaminidase) and P cycling (phosphodiesterase, acid and alkaline phosphatases) were significantly higher (19–79%) in July 2011 than in March 2012 for both management histories regardless of the soil type (P > 0.05). When comparing all sampling times, the activities of alkaline phosphatase, aspartase and urease (rotation only) showed this trend: July 2011 > March 2012 > July 2012. Activities of phosphodiesterase, acid phosphatase, α-galactosidase, β-glucosidase and β-glucosaminidase were higher in July 2011 than July 2012 in at least one of the two management histories. Total C was reduced significantly from July 2011 to March 2012 in the rotation for both soils. Only the activities of arylsulfatase (avg. 36%) and asparaginase showed an increase from July 2011 to March 2012 for both soil types, which may indicate they have a different origin/location than the other enzymes. EAs continued to be a fingerprint of the soil management history (i.e., higher EAs in the rotation than in monoculture) during the drought/heat wave. This study provided some of the first evidence of the adverse effects of a natural, extreme drought and heat wave on soil quality in agroecosystems as indicated by EAs involved in biogeochemical cycling.     

Soil fauna across Central European sandstone ravines with temperature inversion: From cool and shady to dry and hot places

Sandstone massifs with their deep ravines or gorges offer the instructive opportunity to study the response of organisms to steep environmental gradients. In 2008–2010, many groups of soil fauna were studied along transects across three ravines in the Bohemian Switzerland National Park (north-western Czech Republic), a part of the Elbe Sandstone Massif. Each transect included five sampling positions: two opposite edges, two opposite mid-slope positions, and the ravine bottom. The ravines had a specific microclimate characterized by temperature inversion. In general, the cooler and more humid ravine bottoms had also less acid soil with lower carbon content but enriched by litter of deciduous trees and herbs. The other transect positions were characterized by spruce (mid-slopes) and pine (edges) stands with mor humus, exposed to drought in the upper parts. The soil animal communities (identified to species level) differed substantially in dependence on their position along the transects. Ravine bottoms hosted a diverse soil fauna, including a rich macrofauna. The thick duff layer of acid soils on the slopes and edges hosted a poorer fauna but supported high densities of important decomposers such as enchytraeids, oribatid mites and microbivorous nematodes. In general, these were higher on the slopes, presumably due to the drought exposure of the edges. Vertical position in the ravine and soil pH were the most important factors explaining community composition. This confirmed that the area's high geomorphological diversity, leading to steep microclimatic gradients and heterogenous soil conditions, is a major cause of its high biodiversity. A shift in community structure in the lower parts of the ravines, observed after the first half of the study period, was possibly caused by summer flash floods. An increased frequency and severity of dry spells and flash floods due to heavy rains, predicted by relevant climate warming scenarios, will probably have an detrimental effect on the ravines'soil fauna.     

Oxidant related biochemical traits are significant indices in triticale grain yield under drought stress condition

Two separate experiments, one as drought stress conditions and the other one as the normal irrigation conditions based on randomized complete block design with three replications were implemented to examine 20 triticale (Triticoseclae wittamack X) genotypes of which 19 genotypes have recently been generated by crossing different parent lines and the other one was Javaniloo, a common cultivar. Based on the results of different statistical techniques and comparing relationships among traits for normal irrigation and stress condition, enzymatic antioxidant could be used as criteria for screening tolerant genotypes of triticale. On the other hand, it is pointed out that superoxide dismutase are the most important criteria to achieve higher tolerant genotypes through indirect selection. Furthermore, hydrogen peroxide and malondialdehyde content having high relationship with rain yield are also the different possible criteria for screening triticale genotypes for water stress conditions in which genotypes with lower content of these traits could be screened.     

Seed priming and soil incorporation with silicon influence growth and yield of maize under water-deficit stress

Silicon (Si) has been known to enhance plant tolerance against biotic and abiotic stresses besides its beneficial effects on plant growth and yield. Two experiments were conducted to evaluate the effect of Si against water-deficit stress in maize (Zea mays) applied through seed priming and soil incorporation methods, and to find out the optimum dose of Si under each method. In the seed priming experiment, seeds were exposed to different Si levels, up to 2 mM l^–1, germinating under three soil moisture regimes (100%, 75% and 50% field capacity-FC). In the soil incorporation study, the treatments included were six Si doses from 0 to 600 kg ha^–1 under the same soil moisture regimes. Grain yield was reduced by 59% and 69% in the seed priming and soil incorporation study, respectively, at 50% FC. Si application was effective irrespective of the application methods with higher cob length, 100-kernel weight and grain yield than the control. Application of Si at 1 mM l^–1 as seed priming and 300 kg ha^–1 as soil incorporation was more effective than other doses and could be recommended as optimum dose for Nakhon Sawan 3 hybrid maize variety under water-deficit stress.     

苜蓿压捆过程中压缩与恢复应力传递规律

探索苜蓿在压捆过程中,由松散状态压缩成草片时在压捆室不同位置的轴向应力变化规律及传递模型。以草片为研究对象,选喂入量为4 kg/次,在草物料压捆试验台上进行了5种截面的压捆试验。每种截面布设2套压力传感装置和3个位移传感器,由基于虚拟仪器的草物料压缩测试系统采集各传感器的信号,记录了每次压缩时草片的压缩与恢复应力和位置、草片的压缩量及回弹量等数据。结果表明苜蓿在不同截面下压缩与恢复应力具有相同的传递规律,但截面尺寸影响草片的最大压缩应力和最小恢复应力的数值且为非线性关系。指出了由松散苜蓿压缩成草片所需要的压缩应力最大,是压捆机设计中的基本参数。揭示了草片最大压缩应力随位移的变化呈指数下降,在压缩室内草片(4~5个草片)的压缩应力较高,在捆草室内草片的压缩应力较低,建议压缩室长度为900~1 000 mm。草片最小恢复应力表现为随位移增加而增加,达到一定位置时随位移的增加而下降。通过回归分析,获得了苜蓿在压捆过程中压缩与恢复应力传递规律和相应的数学模型,其复相关系数均大于0.9091,说明压缩与恢复应力和草片的位置密切相关,模型回归效果较好。试验结果可为草物料压捆机的动力选择和优化设计提供基础数据和理论依据。     

拟南芥DA1-Related Protein 2基因参与调控植物对盐胁迫的响应

土壤盐渍化是目前农业生产面临的主要问题之一,同时种子萌发转绿作为植物幼苗形态建成的基础对盐胁迫最为敏感。本研究以Col-0、Ler野生型拟南芥和osr1短根突变体拟南芥为试验材料,通过图位克隆方法得到调控根生长的DAR2(DA1-Related Protein 2)基因。本研究利用RT-PCR方法,发现生长10 d的Col-0幼苗在200 mmol·L 1氯化钠条件下处理6 h和12 h,DAR2基因受盐胁迫诱导;200 mmol·L 1氯化钠处理后,组织化学染色结果显示,萌发1 d的根尖韧皮部和3 d的叶片pDAR2::GUS的表达上升,进一步表明DAR2基因受到盐胁迫的诱导。统计不同MS培养基[0(CK)、100 mmol·L 1氯化钠、150 mmol·L 1氯化钠、200 mmol·L 1氯化钠、150 mmol·L 1氯化钾、200 mmol·L 1甘露醇]上Col-0和dar2-3的萌发率和转绿率发现:随着氯化钠浓度的逐渐增大,突变体无论萌发还是转绿时间明显比野生型晚。在150 mmol·L 1氯化钾和200 mmol·L 1甘露醇培养条件下,萌发和转绿的时间也比野生型要晚。这些结果表明突变体在萌发和转绿期对盐胁迫的敏感性比野生型明显增强,进一步证明了突变体对盐胁迫的敏感性并不是对离子的特异响应。这些研究结果为深入了解逆境胁迫下植物早期生长发育的可塑性调控机制奠定了基础,同时也为通过生物技术改良作物抗逆性提供了理论依据。