寒温带兴安落叶松林土壤温室气体通量的时间变异

采用静态箱/气相色谱(GC)法,对寒温带兴安落叶松林区6-9月生长季土壤CO2、CH4和N2O通量进行原位测定,研究了土壤温室气体通量的季节和昼夜变化及其与环境因子的关系.结果表明:在生长季,兴安落叶松林土壤为大气CH4的汇,吸收通量为22.3～107.8 μg CH4-C·m-2·h-1,6-9月月均甲烷吸收通量为(34.0±7.1)、(71.4±9.4)、(86.3±7.9)和(40.7-±6.2) μg·m-2·h-1;不同季节土壤CH4昼夜通量的变化规律相同,一天中均在10:00达到最大吸收高峰.土壤CO2日通量呈明显的双峰曲线,月均CO2通量大小顺序为7月＞8月＞6月＞9月.土壤N2O通量变异较大,在-9.1 ～31.7μg·m-2·h-1之间.土壤温度和湿度是影响CO2和CH4通量的重要因子,N2O通量主要受温度的影响.在兴安落叶松林区,10:00左右观测获得的温室气体地-气交换通量,经矫正后可以代表当日气体通量.     

Methane emission associated with anatomical and morphophysiological characteristics of rice (Oryza sativa) plant

Plant-mediated transport is the primary route of methane (CH(4)) emission from the reduced paddy field to the aboveground atmosphere. Experiments were conducted at North Bank Plain Agro-climatic Zone of Assam, India, during monsoon rice-growing season (July to December 2006) to elucidate the influences of anatomical and morphophysiological characteristics of rice (Oryza sativa L.) cultivars on methane emission from submerged agroecosystem. Ten rice cultivars were grown in light-textured loamy soil under rainfed uniform field condition. Among the 10 cultivars, 5 were traditional rice genotypes commonly grown in the agroclimatic zone and the other 5 were improved high-yielding varieties. Wide variation in CH(4) flux was recorded among the rice cultivars, which may be regulated by the difference in anatomical and morphophysiological characteristics of rice plant. Microscopic analysis of stem portion showed that high- and medium-CH(4)-emitting cultivars recorded higher size of the medullary cavity. Leaf area and transpirational rates were also found to be higher in high-CH(4)-emitting varieties. Scanning electron microscopic analysis revealed higher stomatal frequencies in high-methane-emitting cultivars. Data presented in this study suggest that variation in anatomical and morphophysiological characteristics among different rice genotypes may influence CH(4) emission from paddy fields.     

鄱阳湖秋季水-气界面CH4排放通量的区域差异及影响因素

有限的观测点以及空间的异质性已经成为准确估算湖泊水-气界面CH4通量的挑战。鄱阳湖是我国最大的淡水湖,为了解秋季湖区水-气界面的CH4排放通量,2010年10月利用密闭静态箱-气象色谱法对星子、都昌、南矶山和吴城4个湖区水-气界面CH4排放通量及气象、底泥、水体等因素进行了测定。研究表明,都昌湖区CH4排放通量平均值为0.26mg·m-2·h-1,显著高于星子(0.15mg·m-2·h-1)、吴城(0.13mg·m-2·h-1)和南矶山(0.10mg·m-2·h-1)湖区。鄱阳湖水-气界面秋季CH4排放通量平均为0.17mg·m-2·h-1,变异系数为58.6%。相关分析表明,风速显著影响CH4排放通量(P<0.01)。在排除风速>5m·s-1的数据后,底泥有机碳以及水体铵态氮含量与CH4排放通量显著相关,而水体DOC含量与CH4排放通量呈显著负相关(P<0.05)。对鄱阳湖CH4排放量的精确估算,依赖于较广区域和较长时间的观测。     

Diurnal variation in methane efflux at different growth stages of tropical rice

Diurnal variation in CH₄ efflux from continuously flooded fields planted to rice (Oryza sativa L. cv. IR-36) was examined at different crop growth stages using a closed chamber method during the wet season. CH₄ emission showed a distinct diurnal pattern especially at tillering, panicle initiation and maturity stages of a field-grown rice crop, with maximum emission in the early afternoon (12.00 to 15.00) followed by a decline to a minimum around midnight. Among several variables (ambient temperature, flood water temperature, redox potential, soil pH, and root oxidase activity), a significant negative correlation existed between oxidase activity of the root base and diurnal fluctuations in CH₄ efflux at tillering stage. Evidence also suggested that redox status in the rhizosphere region and atmospheric, soil, and water temperatures influenced CH₄ emission from rice fields probably by their contrasting effects on CH₄ production and oxidation.     

稻田生态系统中植硅体的产生与积累——以嘉兴稻田为例

本研究在嘉兴杭嘉湖平原实验基地,以嘉花11、浙粳37、宁81、祥湖301、秀水09五个品种水稻及其0~10cm表层土壤为研究对象,运用微波消解和Walkley-Black的方法,研究了稻田生态系统中植硅体的产生和积累通量,为了解植硅体在稻田生态系统硅和碳生物地球化学循环中的作用提供科学参考。结果表明：（1）植硅体含量在不同品种水稻中嘉花11、宁81和祥湖301高于浙粳37和秀水09,在各器官中鞘>叶>茎>根>穗;（2）水稻植株植硅体产生通量为1269.59 kg hm-2 yr-1,其中地上部分为1203.44 kg-hm-2-yr-1,地下部分为66.15 kg-hm-2-yr-1,在种植50年的稻田0~10cm土壤中的积累通量为40.38 kg hm-2 yr-1;（3）选择嘉花11等高植硅体含量品种进行推广种植,对提高水稻植硅体产生通量及其包裹大气中CO2通量有很大的作用。     

不同耕作措施的温室气体排放日变化及最佳观测时间

在连续6 a耕作模式的基础上,利用静态箱-气相色谱法对常规耕作与免耕条件下小麦生育后期麦田CO2、CH4、N2O通量日变化进行了连续48 h观测,并确定1 d中最佳的观测时间。结果表明,常规耕作与免耕条件下小麦生育后期麦田CO2、CH4、N2O通量具有显著的日变化特征,常规耕作处理和免耕处理土壤表现为CH4的吸收汇、CO2、N2O的排放源。CH4日均吸收通量:常规耕作无秸秆还田处理(AC)>常规耕作秸秆还田处理(PC)>免耕(PZ);CO2日均排放通量:常规耕作秸秆还田处理(PC)>常规耕作无秸秆还田处理(AC)>免耕(PZ);N2O日均排放通量:常规耕作秸秆还田处理(PC)>常规耕作无秸秆还田处理(AC)>免耕(PZ)。相关性分析表明,常规耕作及免耕条件下CO2、CH4、N2O通量日变化与地表温度和5 cm地温呈极显著(P<0.01)或显著(P<0.05)的正相关关系,温度是决定温室气体日变化的主要决定因素。通过矫正系数和回归分析表明,在小麦生育后期(4—6月),CO2的最佳观测时间段在8:00—10:00,CH4为8:00—10:00,N2O为8:00—12:00。     

冬灌田影响水稻生长期甲烷排放量的因素分析

冬灌田是CH4排放量最大的一类稻田。对冬灌田6年（1995-2000年）的测定结果表明,越冬期排干,并种植旱作（小麦或油菜）减少后续水稻生长期CH4排放量,水稻垄作并降低冬季垄沟水位也可有效地减少水稻生长期的CH4排放量。对后3年（1998-2000年）不同处理的测定结果分析表明,冬季土壤水分含量与水稻生长期CH4排放量呈显著正相关,可以预测水稻生长期平均CH4排放量56%的年际和处理变化。如果同时考虑水稻生长期的土壤温度,则可预测78%的变化,控制渗漏池地下水位,调节冬季土壤水分,进一步证明冬季土壤水分对后续水稻生长期CH4排放量的影响。由于水稻生长期土壤温度的冬季土壤水分含量与气候因素密切相关,据此,可以认为,冬季降水和水稻生长期温度变化是导致稻田CH4排放量年际变化的主要因素。     

玉渡山水库生长季温室气体排放特征及其影响因素

为了探讨温带水库温室气体排放规律,采用静态箱-色谱分析法,研究了温带地区库龄10年内的北京玉渡山水库生长季3种温室气体CO2、CH4及N2O排放特征,及其影响因子。结果表明:样地类型、测定月份与样地类型交互作用对3种温室气体通量影响极显著,5月消落带CO2通量(664.31mg·m-2·h-1)达到最大,显著高于入库口和浅水区;8月消落带CH4通量(0.87mg·m-2·h-1)及N2O通量(3.05mg·m-2·h-1)最大;8月,切除消落带样地地上植物后,3种温室气体通量均有所降低。CO2通量与地下5cm地温、氧化还原电位和水体总氮显著正相关,与地上生物量和水体pH显著负相关;CH4通量与地表温度、地上生物量、水体pH呈显著相关,与水体总氮和水体铵态氮显著负相关;N2O通量与水体总氮含量显著相关,与水体pH显著负相关。采取平均估值法初步推测,在生长季,水库消落带、入库口及浅水区CO2排放量依次为15960、2160、-70kg·hm-2;CH4排放量依次20.04、-7.05、14.8kg·hm-2;N2O排放量依次83.42、3.79、-1.54kg·hm-2;表明消落带3种温室气体的排放量均较高,为玉渡山水库3种温室气体排放的重点区域。     

采伐干扰对东北温带次生林土壤CH4通量的影响

2007年6月至2009年10月,采用静态箱/气相色谱法测定了不同采伐干扰(皆伐后农作、皆伐后造林、50%强度采伐、25%强度采伐和对照)条件下,东北地区典型次生林的土壤CH₄通量. 结果表明: 研究样地的土壤均为CH₄的吸收汇.采伐干扰降低了土壤的CH₄吸收能力,不同处理样地土壤的CH₄吸收通量大小依次为:对照(-85.03 μg CH₄·m^-2·h^-1)>50%强度采伐(-80.31 μg CH₄·m^-2·h^-1)>25%强度采伐(-70.97 μg CH₄·m^-2·h^-1)>皆伐后农作(-65.57μg CH₄·m^-2·h^-1)>皆伐后造林(-62.02μg CH₄·m^-2·h^-1).各处理样地土壤CH₄吸收通量的季节动态相似,均表现为生长季吸收值较高,冬季较低.采伐干扰后各处理的土壤温度、土壤湿度、土壤硝态氮和铵态氮含量均增加,而土壤CH₄吸收通量与土壤温度呈显著二次相关,与土壤含水量呈线性负相关.次生林采伐后土壤含水量、土壤铵态氮和硝态氮含量的增加是土壤CH₄吸收通量降低的重要控制因子.     

Variation in Biomass Properties among Rice Diverse Cultivars

Biomass properties of rice straws were compared among eight cultivars that formed a mini diverse set. The ethanol productivity from rice straws was evaluated employing a laboratory-scale method based on dilute acid-hydrolysis pretreatment. The results indicated significant variation in biomass properties among the cultivars.     

水稻植株对稻田甲烷排放的影响

稻田CH4排放是稻田土壤中CH4产生、氧化和传输不同过程的净效应,水稻植株强烈影响稻田CH4的产生、氧化和传输过程,是导致稻田CH4排放季节性变化规律的一个重要因素,本文综述了水稻植株对稻田CH4排放过程的不同影响,水稻植株根系分泌物和脱落物作为产甲烷前体促进稻田土壤中CH4的产生,在水稻生长后期,植株根系分泌物和脱落物被认为是稻田土壤甲烷产生的主要基质,是导致这一时期稻田CH4高排放通量的主要原因;水稻植株根系泌氧在根际环境形成一个微氧区域氧化稻田甲烷,整个水稻生长季稻田土壤中产生的CH4大约36％～90％在植株根际环境中被氧化;约80％甚至更多的稻田CH4通过水稻植株的通气组织进入大气圈,植株对稻田CH4的传输具有十分重要的意义。     

A comparison of nitrate transport in four different rice(Oryza sativa L.) cultivars

As rice can use both nitrate (NO3-) and ammonium (NH4+), we have tested the hypothesis that the shift in the pattern of cultivars grown in Jiangsu Province reflects the ability of the plants to exploit NO3- as a nitrogen (N) source. Four rice cultivars were grown in solution culture for comparison of their growth on NO3- and NH4+ nitrogen sources. All four types of rice,Xian You 63 (XY63), Yang Dao 6 (YD), Nong Keng 57 (NK) and Si You 917 (SY917), grew well and produced similar amounts of shoot biomass with 1 mmol/L NH4+ as the only N source.However, the roots of NK were significantly smaller in comparison with the other cultivars. When supplied with 1 mmol/L NO3-, YD produced the greatest biomass; while NK achieved the lowest growth among the four cultivars. Electrophysiological measurements on root rhizodermal cells showed that the NO3--elicited changes in membrane potential (ΔEm) of these four rice cultivars were significantly different when exposed to low external NO3- (＜1 mmol/L); while they were very similar at high external NO3- (10 mmol/L). The root cell membrane potentials of YD and XY63 were more responsive to low external NO3- than those of NK and SY917. The ΔEm values for YD and XY63 rhizodermal cells were almost the same at both 0.1 mmol/L and 1 mmol/L NO3-;while for the NK and SY917 the values became larger as the external NO3- increased. For YD cultivar, ΔEm was measured over a range of NO3- concentrations and a Michaelis-Menten fit to the data gave a Km value of 0.17 mmol/L. Net NO3- uptake depletion kinetics were also compared and for some cultivars (YD and XY63) a single-phase uptake system with first order kinetics best fitted the data; while other cultivars (ND and SY917) showed a better fit to two uptake systems. These uptake systems had two affinity ranges: one had a similar Km in all the cultivars (0.2 mmol/L); the other much higher affinity system (0.03 mmol/L) was only present in NK and SY917. The expression pattern of twelve different NO3- transporter genes was tested using specific primers, but only OsNRT1.1 and OsNRT2. 1 expression could be detected showing significant differences between the four rice cultivars. The results from both the physiological and molecular experiments do provide some support for the hypothesis that the more popular rice cultivars grown in Jiangsu Province may be better at using NO3- as an N source.     

Influence of rice cultivar on methane emission from paddy fields

Influence of rice cultivars on CH₄ emissions from a paddy field was studied using four Japonica types, two Indica types, and two Japonica/Indica F₁ hybrids. In addition, the suppression of CH₄ emission by interrupting irrigation at the flowering stage was investigated. Patterns of seasonal variation in CH₄ emission rates were similar among the eight cultivars. Two of the Japonica types showed the maximum and minimum CH₄ emissions among the cultivars investigated. Neither the number of tillers, shoot length, shoot weight, and root weight correlated with the CH₄ emission rates at the tillering and reproductive growth stages. Following temporary interruption of irrigation at the flowering stage, CH₄ emission rates decreased drastically and remained at very low levels until the harvesting stage, indicating its great effectiveness for the suppression of CH₄ emission from rice paddies.     

Biochemical defence responses of resistant and susceptible rice genotypes against blast pathogen Magnaporthe oryzae

Abstract

Rice blast is the leading fungal disease which is caused by Magnaporthe oryzae that contributes for the significant decline in the rice yield throughout the globe. There is a need for the understanding of biochemical changes in rice plant during blast infection for the development of novel disease control strategies. In the present study, we isolated M. oryzae from the local paddy fields and the fungal isolates (VCF and PON) were identified by ITS-PCR using genomic DNA samples. Further, we inoculated resistant (BR2655 and TUNGA) and susceptible (INTAN and HR12) rice cultivars with PON and VCF isolates. PON isolate showed relatively high virulence compared to VCF and standard MTCC fungal strains. Therefore, we evaluated the effect of PON on the total protein content and plant defence-related key enzymes (peroxidase, polyphenol oxidase, phenylalanine ammonia lyase, β-glucosidase, chitinase and lipoxygenase) activities between 24- and 120-hour post-inoculation (hpi). The results demonstrated the decrease in total protein content in all the inoculated cultivars. In addition, we observed the variation in the activity of peroxidase, polyphenol oxidase, β-glucosidase, chitinase and lipoxygenase at different time points in all the tested rice plants compared to respective controls. However, no significant difference was observed in the phenylalanine ammonia lyase activity relative to its control. Taken together, this study emphasizes on the variation in the activities of plant defence enzymes in different plant cultivars against the tested fungal pathogen and also implementation of defence enzymes as biochemical markers for resistant breeding.     

EFFECTS OF SEEDING DENSITY AND BASIC MANURE ON THE GROWTH OF DRY NURSERY SEEDLINGS IN LATE DOUBLE CROPPING RICE IN SOUTH CHINA

During the period of dry nursery seedling raising of late double cropping indica rice in South China, both chemical fertilizer and farmyard manure did not show obvious effect on the growth of shoot and root in young seedlings at 4-leaf stage (18-day-old seedling), but had significant effects on root growth in old seedlings with 6-7 leaves (27-day-old seedling) at suitable seeding densities (65-125g m~(-2)). There were satistically significant differences (at 0.01 or 0.05 levels)between treatments in root number and rooting ability of root-pruned seedlings.     

CO2倍增对稻田CH4排放的影响

 利用开顶室熏气装置,研究了CO2倍增对稻田CH4排放的影响。发现CO2倍增在分蘖初期、孕穗期、抽穗期、灌浆期和成熟期对稻田CH4排放具有明显的促进作用,分别比对照增加了253％、288％、273％、273％和157％。在分蘖末期至灌浆期有一个高峰,排放通量约为1.91mgCH4·d-1·p-1。这种促进作用可能主要是由于CO2倍增使水稻根系生物量以及根系代谢活性发生变化造成的。     

Tolerance to Zinc Deficiency in Rice Correlates with Zinc Uptake and Translocation

To study variation in zinc efficiency (ZE) among current Chinese rice genotypes, a pot experiment was conducted with 15 aerobic and 8 lowland rice genotypes. Aerobic rice is currently bred by crossing lowland with upland rice genotypes, for growth in an aerobic cultivation system, which is saving water and producing high yields. A Zn deficient clay soil was used in our screening. Zn deficiency resulted in a marked decrease in shoot dry matter production of most genotypes after 28 days of growth. Genotypes were ranked according to their tolerance to Zn deficiency based on ZE, expressed as the ratio of shoot dry weight at Zn deficiency over that at adequate Zn supply. Substantial genotypic variation in ZE (50–98%) was found among both lowland and aerobic genotypes. ZE correlated significantly (P < 0.05) with Zn uptake (R ² = 0.34), Zn translocation from root to shoot (R ² = 0.19) and shoot Zn concentration (R ² = 0.27). The correlation with seed Zn content was insignificant. In stepwise multiple regression analyses, variation in Zn uptake and Zn translocation explained 53% of variation in ZE. Variation in Zn uptake could be explained only for 32% by root surface area. These results indicate that Zn uptake may be an important determinant of ZE and that mechanisms other than root surface area are of major importance in determining Zn uptake by rice.     

Characterization of Root Exudates at Different Growth Stages of Ten Rice (Oryza sativa L.) Cultivars

Abstract: Plant root exudates play important roles in the rhizosphere. We tested three media (nutrient solution, deionized water and CaSO₄ solution) for three periods of time (2, 4 and 6 h) for collecting root exudates of soil‐grown rice plants. Nutrient culture solution created complications in the analyses of exudates for total organic C (TOC) by the wet digestion method and of organic acids by HPLC due to the interference by its components. Deionized water excluded such interference in analytical analyses but affected the turgor of root cells; roots of four widely different rice cultivars excreted 20 to 60 % more TOC in deionized water than in 0.01 M CaSO₄. Furthermore, the proportion of carbohydrates in TOC was also enhanced. Calcium sulfate solution maintained the osmotic environment for root cells and did not interfere in analytical procedures. Collection for 2 h avoided under‐estimation of TOC and its components exuded by rice roots, which occurred during prolonged exposure. By placing plants in 0.01 M CaSO₄ for 2 h, root exudates of soil‐grown traditional, tall rice cultivars (Dular, B40 and Intan), high‐yielding dwarf cultivars (IR72, IR52, IR64 and PSBRc 20), new plant type cultivars (IR65598 and IR65600) and a hybrid (Magat) were collected at seedling, panicle initiation, flowering and maturity and characterized for TOC and organic acids. The exudation rates were, in general, lowest at seedling stage, increased until flowering but decreased at maturity. Among organic acids, malic acid showed the highest concentration followed by tartaric, succinic, citric and lactic acids. With advancing plant growth, exudation of organic acids substituted exudation of sugars. Root and shoot biomass were positively correlated with carbon exudation suggesting that it is driven by plant biomass. As root exudates provide substrates for methanogenesis in rice fields, large variations in root exudation by cultivars and at different growth stages could greatly influence CH₄ emissions. Therefore, the use of high‐yielding cultivars with lowest root excretions, for example IR65598 and IR65600, would mediate low exudate‐induced CH₄ production. The screening of exciting rice cultivars and breeding of new cultivars with low exudation rates could offer an important option for mitigation of CH₄ emission from rice agriculture to the atmosphere.     

云南高原粳稻品质特性分析

采用表型主成分及聚类分析法,对76个云南高原粳稻的11个品质性状进行了分析。结果表明,（1）直链淀粉含量的平均值达食用稻品种品质1级标准,糙米率、透明度、碱消值和胶稠度达2级标准,精米率达3级标准,其余品质性状的平均值均在3级以下。品种间变异最小的品质性状是糙米率和碱消值,变异最大的是垩白度,其次是垩白粒率。（2）稻米品质性状间存在复杂的相关关系。（3）在选出的6个影响云南稻米品质的主因子中,精米率、垩白粒率和垩白度因子对稻米品质的累积贡献率为49.6%。（4）76个云南粳稻聚为4类,其中第一类包括52个品种,表明遗传距离近,遗传基础狭窄。在今后的云南粳稻品质育种中,应降低垩白粒率和垩白度,提高精米率和整精米率,同时拓宽遗传基础。     

Evaluating the resistance of six rice cultivars to drought: restriction of deep rooting and the use of raised beds

Soil water deficits reduce rice (Oryza sativa L.) productivity under upland field conditions. In this study, we constructed screening facilities to evaluate the performance of rice cultivars under drought conditions and to assess the roles of deep roots. Two experiments were conducted with six rice cultivars, including drought-tolerant and drought-susceptible cultivars, grown in two root environments: a root-restricted treatment that restricted rooting depth with water-permeable sheets, and a raised bed that reduced water availability in the surface soil by inserting a gravel layer between the topsoil and subsoil layers to interrupt capillary transport of water. In the root-restricted treatment, in which root growth was restricted to the surface 25-cm layer, leaf water potential decreased faster in cultivars with a large canopy during drought stress, and there was little difference in panicle weight among cultivars. With a normal (unrestricted) root environment, the deepest-rooting cultivar (‘IRAT109’) maintained higher leaf water potential during drought, although panicle weight under drought stress was affected by yield potential as well as by deep rooting. Under the intermittent drought stress in the raised bed, deep-rooting cultivars accumulated more nitrogen and produced more biomass, and the difference in panicle weight between deep-rooting drought-tolerant and shallow-rooting drought-susceptible cultivars was magnified by the raised bed compared with the yield differences under drought in a normal root environment. These results demonstrate that the drought screening facilities we developed can help to identify superior cultivars under upland field conditions without time-consuming measurement of deep root systems.