Polyunsaturated Aldehydes from Large Phytoplankton of the Atlantic Ocean Surface (42°N to 33°S)

Polyunsaturated aldehydes (PUAs) are organic compounds mainly produced by diatoms, after cell wounding. These compounds are increasingly reported as teratogenic for species of grazers and deleterious for phytoplanktonic species, but there is still scarce information regarding concentration ranges and the composition of PUAs in the open ocean. In this study, we analyzed the spatial distribution and the type of aldehydes produced by the large-sized (>10 μm) phytoplankton in the Atlantic Ocean surface. Analyses were conducted on PUAs released after mechanical disruption of the phytoplankton cells, referred to here as potential PUAs (pPUAs). Results show the ubiquitous presence of pPUA in the open ocean, including upwelling areas, as well as oligotrophic gyres. Total pPUA concentrations ranged from zero to 4.18 pmol from cells in 1 L. Identified PUAs were heptadienal, octadienal and decadienal, with heptadienal being the most common (79% of total stations). PUA amount and composition across the Atlantic Ocean was mainly related to the nitrogen:phosphorus ratio, suggesting nutrient-driven mechanisms of PUA production. Extending the range of trophic conditions considered by adding data reported for productive coastal waters, we found a pattern of PUA variation in relation to trophic status.     

The Effect of Dissolved Polyunsaturated Aldehydes on Microzooplankton Growth Rates in the Chesapeake Bay and Atlantic Coastal Waters

Allelopathy is wide spread among marine phytoplankton, including diatoms, which can produce cytotoxic secondary metabolites such as polyunsaturated aldehydes (PUA). Most studies on diatom-produced PUA have been dedicated to their inhibitory effects on reproduction and development of marine invertebrates. However, little information exists on their impact on key herbivores in the ocean, microzooplankton. This study examined the effects of dissolved 2E,4E-octadienal and 2E,4E-heptadienal on the growth rates of natural ciliate and dinoflagellate populations in the Chesapeake Bay and the coastal Atlantic waters. The overall effect of PUA on microzooplankton growth was negative, especially at the higher concentrations, but there were pronounced differences in response among common planktonic species. For example, the growth of Codonella sp., Leegaardiella sol, Prorodon sp., and Gyrodinium spirale was impaired at 2 nM, whereas Strombidium conicum, Cyclotrichium gigas, and Gymnodinium sp. were not affected even at 20 nM. These results indicate that PUA can induce changes in microzooplankton dynamics and species composition.     

Quantification of dissolved and particulate polyunsaturated aldehydes in the Adriatic sea

Polyunsaturated aldehydes (PUA) are supposed to play critical roles in chemically-mediated plankton interactions. Laboratory studies suggest that they act as mediators of chemical defense and chemical communication. PUA are oxylipins containing an α,β,γ,δ-unsaturated aldehyde structure element and are mainly found in diatoms. We present here a detailed surface mapping of PUA during a spring bloom of the diatom Skeletonema marinoi in the Adriatic Sea. We monitored dissolved PUA, as well as particulate PUA, which are produced by phytoplankton after cell disintegration. Our survey revealed a patchy distribution of PUA and shows that at most stations S. marinoi is the major contributor to the overall PUA. Our data also suggest that lysis of a diatom bloom can contribute significantly to the dissolved PUA concentrations and that other producers, which are smaller in cell size compared to diatoms, have to be taken into account as well if the total PUA content of marine samples is considered. The analyses of samples collected in deeper water suggests that diatom contribution to PUA decreases with depth, while smaller-sized unidentified organisms take place as dominant contributors to the PUA concentrations.     

Biosynthesis of Polyunsaturated Fatty Acids in Marine Invertebrates: Recent Advances in Molecular Mechanisms

Virtually all polyunsaturated fatty acids (PUFA) originate from primary producers but can be modified by bioconversions as they pass up the food chain in a process termed trophic upgrading. Therefore, although the main primary producers of PUFA in the marine environment are microalgae, higher trophic levels have metabolic pathways that can produce novel and unique PUFA. However, little is known about the pathways of PUFA biosynthesis and metabolism in the levels between primary producers and fish that are largely filled by invertebrates. It has become increasingly apparent that, in addition to trophic upgrading, de novo synthesis of PUFA is possible in some lower animals. The unequivocal identification of PUFA biosynthetic pathways in many invertebrates is complicated by the presence of other organisms within them. These organisms include bacteria and algae with PUFA biosynthesis pathways, and range from intestinal flora to symbiotic relationships that can involve PUFA translocation to host organisms. This emphasizes the importance of studying biosynthetic pathways at a molecular level, and the continual expansion of genomic resources and advances in molecular analysis is facilitating this. The present paper highlights recent research into the molecular and biochemical mechanisms of PUFA biosynthesis in marine invertebrates, particularly focusing on cephalopod molluscs.     

亚麻耐渍的生理机制研究初探

通过研究渍涝胁迫下,不同耐渍型亚麻品种的株高、工艺长度、出麻率等农艺性状以及植株丙二醛(MDA)含量、过氧化物酶(POD)活性的变化,初步揭示了亚麻耐渍的生理机制。试验结果表明:1、渍涝影响亚麻的农艺性状,具体表现在株高降低、工艺长度减短、出麻率下降等方面;渍涝胁迫下根部皮层通气组织的发育是衡量亚麻耐渍强弱的重要特性;2、随着渍涝胁迫时间的增加,不同耐渍型品种植株丙二醛(MDA)含量均有不同程度的增加,且非耐渍型品种的增加幅度大于耐渍型品种,说明渍涝胁迫下,耐渍型品种具有很强的抗膜脂过氧化的能力;3、随着渍涝胁迫时间的增加,不同耐渍型品种过氧化物酶(POD)活性都呈先升高后下降的趋势,耐渍型品种的变化大于非耐渍型品种,说明在渍涝胁迫下耐渍型品种体内过氧化物酶清除活性氧的能力高于非耐渍型品种。     

亚麻耐渍的生理机制研究初探

通过研究渍涝胁迫下,不同耐渍型亚麻品种的株高、工艺长度、出麻率等农艺性状以及植株丙二醛（MDA）含量、过氧化物酶（POD）活性的变化,初步揭示了亚麻耐渍的生理机制.试验结果表明：1、渍涝影响亚麻的农艺性状,具体表现在株高降低、工艺长度减短、出麻率下降等方面;渍涝胁迫下根部皮层通气组织的发育是衡量亚麻耐渍强弱的重要特性;2、随着渍涝胁迫时间的增加,不同耐溃型品种植株丙二醛（MDA）含量均有不同程度的增加,且非耐渍型品种的增加幅度大于耐渍型品种,说明渍涝胁迫下,耐渍型品种具有很强的抗膜脂过氧化的能力;3、随着渍涝胁迫时间的增加,不同耐渍型品种过氧化物酶（POD）活性都呈先升高后下降的趋势,耐渍型品种的变化大于非耐渍型品种,说明在渍涝胁迫下耐渍型品种体内过氧化物酶清除活性氧的能力高于非耐渍型品种.     

外源褪黑素对盐胁迫下金盏菊幼苗生长、光合及生理特性的影响

为探讨褪黑素（melatonine,MT）对盐胁迫下金盏菊幼苗生理机制的影响,采用盆栽砂培法研究不同浓度外源褪黑素（0、50、100、200 μmol/L MT）对不同程度盐胁迫（0、100、200 mmol/L NaCl）下金盏菊幼苗生长、光合作用及生理特性的影响。结果表明,100、200 mmol/L NaCl胁迫严重限制了金盏菊幼苗的生长,叶绿素含量、光化学荧光效率及光合作用强度降低,MDA、H₂O₂含量升高加剧了脂质过氧化程度,诱导POD酶活性升高的氧化应激反应及脯氨酸含量增加。经外源褪黑素处理能有效缓解盐胁迫对金盏菊幼苗的伤害,其中100 μmol/L MT处理下株高、茎围、地上部和根系干重较对照分别平均提高了17.35%、17.64%、32.14%和19.83%;叶绿素含量和F_v/F_m增幅分别达71.96%和4.13%,光合作用参数P_n、G_s和T_r平均分别提高了88.74%、97.21%和58.88%,而C_i降幅达18.07%;MDA和H₂O₂含量降幅达33.77%和64.29%,POD、CAT酶活性及可溶性蛋白、脯氨酸含量平均分别提高了118.02%、67.29%、55.47%和56.30%。盐胁迫条件下,MT处理能有效提高抗氧化酶活性及降低脂质过氧化水平,促进可溶性蛋白和脯氨酸积累,改善光合荧光特性,最终表现为促进金盏菊幼苗生长。     

Development and Distribution of Root System in Two GrainSorghum Cultivars Originated from Sudan under Drought Stress

Abstract

The difference in rooting pattern between two grain sorghum cultivars differing in drought tolerance was investigated under drought stress. The cultivars, Gadambalia (drought-tolerant) and Tabat (droughtsusceptible), were grown in bottomless wooden or acrylic root boxes to examine root parameters. Gadambalia consistently exhibited higher dry matter production and leaf water potential than Tabat under drought stress in both root boxes. In the experiment with wooden root boxes, under a drought condition, Gadambalia extracted more water from deep soil layers (1.1-1.5 m), which was estimated from the reduction in soil water content, than Tabat. This was because Gadambalia had a significantly higher root length density in these soil layers. The high root length density was due to enhanced lateral root development in Gadambalia. In the other experiment with acrylic root boxes, though total root length in the upper soil layer (0-0.5 m) was declined by limited irrigation in both cultivars, the reduction in Gadambalia was moderate compared with that in Tabat owing to the maintenance of fine root growth. Unlike Tabat, Gadambalia had an ability to produce the nodal roots from higher internodes even under drought, which resulted in the high nodal root length of Gadambalia. The growth angle of nodal roots was significantly correlated with root diameter, and the nodal roots from the higher internodes had large diameters and penetrated into the soil more vertically. These results indicate that the responses of roots (i.e. branching and/or growth of lateral root, and nodal root emergence from higher internodes) to soil dryness could be associated with the drought tolerance of Gadambalia.     

Inventory of Fatty Acid Desaturases in the Pennate Diatom Phaeodactylum tricornutum

The diatom Phaeodactylum is rich in very long chain polyunsaturated fatty acids (PUFAs). Fatty acid (FA) synthesis, elongation, and desaturation have been studied in depth in plants including Arabidopsis, but for secondary endosymbionts the full picture remains unclear. FAs are synthesized up to a chain length of 18 carbons inside chloroplasts, where they can be incorporated into glycerolipids. They are also exported to the ER for phospho- and betaine lipid syntheses. Elongation of FAs up to 22 carbons occurs in the ER. PUFAs can be reimported into plastids to serve as precursors for glycerolipids. In both organelles, FA desaturases are present, introducing double bonds between carbon atoms and giving rise to a variety of molecular species. In addition to the four desaturases characterized in Phaeodactylum (FAD2, FAD6, PtD5, PtD6), we identified eight putative desaturase genes. Combining subcellular localization predictions and comparisons with desaturases from other organisms like Arabidopsis, we propose a scheme at the whole cell level, including features that are likely specific to secondary endosymbionts.     

酸雨胁迫下比久（B9）对东魁杨梅生理特性的影响

通过模拟田间试验,研究比久(B9)对酸雨胁迫下6年生东魁杨梅的生理生化特征影响.结果表明:比久能减少酸雨胁迫时丙二醛(MDA)的积累;提高超氧化物歧化酶(SOD)、过氧化物酶(POD)和过氧化氢酶(CAT)活性,减缓膜脂过氧化程度;缓解酸雨胁迫下东魁杨梅叶绿索和类胡萝卜素的降解速度,促进叶片净光合速率的增加,从而提高叶片中可溶性糖和蛋白质含量以及可溶性糖,蛋白质含量的值.但比久处理需要适当的浓度,浓度过高会产生负效应,比久调控的最佳浓度为2500mg/kg左右.     

4个早稻品种苗期低温胁迫的耐寒性比较

采用人工模拟低温条件,以株两优505、金优268、中嘉早17和株两优819等4个早稻品种为试验材料,研究低温处理期和常温恢复期间4个品种耐寒生理指标的变化。结果表明,株两优505经低温胁迫后各项指标均表现为耐寒特征,且常温恢复期电导率和MDA含量大幅降低,叶绿素和可溶性蛋白含量上升,酶活性增强,表明其幼苗低温胁迫后能恢复正常生长,其耐寒性高于其他3个品种;中嘉早17经低温胁迫后的电导率和MDA含量大幅增加,且在常温恢复期仍维持高水平,表现为冷敏感特征,说明其幼苗低温胁迫后受到严重损伤,其耐寒性差;金优268和株两优819介于两者之间,耐寒性中等。     

稻秆还田深度对盆栽冬小麦结构和生理特性的影响

为了明确稻秆还田深度影响小麦生长发育的生理机制,采用盆栽试验研究了不同稻秆还田深度对小麦出苗、根系发育、根系结构、旗叶光合特性、旗叶SOD和CAT活性及胚乳细胞中淀粉体的影响。结果表明,(1)稻秆还田深度对小麦出苗率没有显著影响,但影响出苗整齐度;(2)15cm的稻秆还田深度能显著促进小麦根系生长,增加次生根数目,提高根冠比、根系总吸收面积、活性吸收面积及根系TTC还原强度;(3)不同稻秆还田深度对拔节期小麦次生根皮层结构影响不大,但对导管结构影响较大,还田深度越深,导管发育越慢;(4)15cm的稻秆还田深度能显著提高小麦旗叶叶绿素含量和光合速率,在生育后期能延缓旗叶叶绿素的降解速度,增加小麦产量;(5)15cm的稻秆还田深度能提高小麦生育后期旗叶中SOD和CAT的活性,延缓叶片的衰老;(6)15cm的稻秆还田深度能延缓小麦胚乳细胞中淀粉体发育时间。     

Comparison of Root System Development in Two Rice Cultivars During Stress Recovery from Drought and the Plant Traits for Drought Resistance

Summary

A greenhouse experiment was conducted to compare root system development of two upland rice cultivars, IRAT 13 and Senshou, during recovery from drought stress and to identify the plant traits that confer drought resistance. From 62 days after sowing (62 DAS), drought stress was given for 6 d followed by rewatering for 14 d. Root length density (RLD) and root diameter (thickness) were measured at the end of the stress and rewatering periods. Control plants were well-watered throughout the study. Gultivar IRAT 13 had thicker roots and higher relative RLD (ratio of RLD in drought-stressed plants to that in control plants) than under drought stress, and significantly higher root growth recovery after rewatering cultivar Senshou. Related plant traits such as evapotranspiration (ET), leaf and stem dry weights and weight of senescent leaves (dead leaves) in IRAT 13 were significantly more favorable for drought resistance compared to Senshou.     

磷对盐胁迫下玉米幼苗脂质过氧化特性及抗氧化酶活性的影响

采用水培试验,研究不同浓度磷对盐胁迫下玉米幼苗生长、叶片和根系中脂质过氧化特性及其抗氧化酶活性的变化.研究表明,盐胁迫下,增施磷可明显缓解盐胁迫对玉米幼苗生长的抑制,各器官含水量增加,改善植株体内的水分代谢状况.随磷含量增加,玉米幼苗叶片细胞膜透性逐渐降低,叶绿素含量增加,叶片和根系中SOD、CAT和POD活性明显增加...     

Assessment of heat tolerance in potato (Solanum tuberosum ssp.tuberosum) under controlled environmental conditions: the ‘cutting technique’

Summary The ‘cutting technique’ or ‘tuberisation stimulus’ (TS) technique was investigated as a method of identifying heat tolerant clones ofSolanum tuberosum ssp.tuberosum. TS levels were assessed, using leaf cuttings, for 100 experimental clones growing under heat stress in a controlled environment (35/15°C day/night temperatures, 16 h photoperiod). No correlation was found with the tuber yields of these clones when grown in an irrigated trial in Israel. The relationship between TS levels and tuber production was investigated using early and later maturing cultivars grown with and without heat stress. These experiments showed that the cv. Blanka had high TS levels in all environments and high tuber fresh weights when grown under heat stress. However, the correlation between TS levels and tuber fresh weight for all cultivars was weak (r=0.45). The results indicated that this TS technique is unlikely to be an accurate method of screeningtuberosum clones for heat tolerance.     

茶园土壤性状及茶树营养元素吸收、转运机制研究进展

优质安全的茶叶离不开养分条件、环境安全和茶园的土、水、肥的管理。本文在茶园土壤、茶树养分功能和分子营养机制、茶树施肥技术、茶园土壤重金属及茶树累积特点和机制等方面,对近五年来国内外的研究进展进行了综述。在茶园土壤研究方面,除了关注植茶后茶园土壤有机质变化特点外,茶园碳储量在全球碳循环中所起的重要作用也引起了人们的重视,同时分子生物学技术也开始应用于茶园土壤微生物种群数量和演变的研究,并在茶园土壤质量评价、土壤酸化原因以及应用生物质改良酸化茶园土壤等方面取得了一定进展。在茶树养分功能和调控技术方面,对主要营养元素氮、磷、钾等的营养功能及其在茶叶品质成分代谢中的作用和茶树吸收特性等有了更深入的认识,在茶树养分转运子基因克隆、氮营养分子生理机制、抗环境胁迫的分子基础等方面的研究逐渐深入,在机械施肥、水肥一体化、控释肥施用等技术研究方面取得较大进展,施肥的环境效应特别是温室气体排放影响成为近年的研究热点。伴随着对食品安全问题的关注,茶叶产地土壤重金属和稀土等的安全状况、茶树累积特点等方面的研究也取得一定进展。     

Growth of the whole root system for a plant crop of sugarcane under rainfed and irrigated environments in Brazil

Sugarcane crops are managed over 8 million hectares in Brazil and future extensions might occur on less favorable lands where irrigation would be necessary to increase and stabilize yields. Root growth was studied by sequential soil coring under rainfed and irrigated conditions for one cultivar widely planted in Brazil. Root length densities (RLD) were measured 34, 49, 125, 179, 241 and 322 days after planting (DAP) down to a depth of 1 m. At the harvest (332 DAP), root intersects (a proxy for RLD) were counted on two vertical trench walls in each water supply regime, down to a depth of 6.0 m. The highest RLD in deep layers (below a depth of 0.6 m) were observed in the rainfed crop from 125 DAP onwards. By contrast, the highest RLD in the upper layers during dry periods were found in the irrigated crop. The maximum depth reached by roots at the harvest was little affected by irrigation: 4.70 m and 4.25 m in the rainfed and irrigated crop, respectively. About 50% of root intersects were observed below the depth of 1 m in the two water supply regimes. This pattern suggested a strong genetic control of root growth in deep soil layers. The total amount of root intersects 332 DAP was 49% higher in the rainfed crop than in the irrigated crop, and root distribution was more homogeneous. Mean root front velocity was about 0.5 cm day⁻¹ the first 4 months after planting and increased thereafter up to the end of the harvest (1.86 cm day⁻¹ and 1.75 cm day⁻¹ on average in the rainfed and the irrigated crops, respectively). Our study pointed out the necessity to take into account the development of sugarcane roots in deep soil layers to improve our understanding of net primary production control by water availability.     

低温逆境下氯化胆碱包衣对玉米种子萌发及幼苗生理生化指标的影响

通过室内砂培试验,研究低温逆境下氯化胆碱包衣玉米种子对其萌发及幼苗生理生化指标的影响。结果表明,低温逆境下氯化胆碱包衣能显著提高种子发芽率、发芽指数和活力指数,并提高种子发芽势;包衣处理明显提高低温逆境下玉米幼苗的苗高、根长、茎粗、根冠比和单株干重,具有良好的壮苗作用;低温逆境下包衣处理的幼苗叶片叶绿素含量和脯氨酸含量均高于对照,丙二醛含量和相对电导率低于对照。     

铝、镉胁迫下不同大麦品种根际的铝、镉形态分析

为明确铝(Al)、镉(Cd)单独及复合胁迫下作物根际毒害元素的化学形态及其生物有效性,采用盆栽试验,以耐铝性不同的两个大麦品种(铝敏感品种浙农大9号和耐铝品种Day ten)为试验材料,利用连续提取法和ICP-AES方法分析了拔节期大麦根际的Al、Cd化学形态及其含量.结果表明,所有处理中大麦植株根际溶出Al均主要以毒性较小的酸溶无机Al和腐殖酸Al存在,根际Cd则主要以残留态形式存在.Al、Cd单独胁迫下大麦根际土壤溶液中各形态Al、Cd的溶出量均显著增加,交换态含量占可提取Al、Cd总量的比例增加.其中浙农大9号根际活性Al、Cd含量的增幅均大于Dayton.与单独Al或Cd处理相比,复合胁迫下根际交换态Al和Cd含量增加,其他形态含量下降或变幅不大.     

外源硫化氢对盐碱胁迫下裸燕麦矿质元素吸收、运输和分配的影响

为了解硫化氢(H₂S)对盐碱胁迫下裸燕麦矿质元素吸收、运输和分配的调控效应,以裸燕麦品种定莜9号为材料,采用盆栽砂培试验,研究抽穗期喷施50μmol·L^-1 H₂S供体硫氢化钠(NaHS)溶液对50mmol·L^-1盐碱混合胁迫下裸燕麦根、茎和叶中29种矿质元素和4种阴离子含量及矿质元素选择性运输、质膜Na⁺/H⁺逆向转运蛋白基因SOS1和液泡膜Na⁺/H⁺逆向转运蛋白基因NHX1表达和植株生物量的影响。结果表明,在裸燕麦根、茎和叶中未检出硒元素和CO₃^2-。盐碱胁迫下,外源H₂S对裸燕麦效应：(1)对根、茎和叶中HCO₃^-、Cl^-和SO₄^2-含量无显著影响,可显著缓解盐碱胁迫下裸燕麦根系和地上部干重的下降。(2)显著降低茎、叶中Na含量,对...