Effects of drought stress on the photosynthetic physiological parameters of Populus 3 euramericana ‘‘Neva'

Populus 9 euramericana ‘‘Neva' is the main poplar species in China, where drought stress is becoming extremely urgent. We carried out this research to study the effects of drought stress on the photosynthesis of Populus 9 euramericana ‘‘Neva'. Drought stress was induced by 58–62%(light), 48–52%(moderate), and 38–42%(severe) relative soil moisture content(RSMC). The effects of drought stress on photosynthetic rate, chlorophyll fluorescence parameters, and other related physiological parameters were investigated during treatment. Net photosynthetic rate(PN), and stomatal conductance decreased significantly and intercellular CO_2 concentration initially increased and then declined, whereas the stomatal limitation factors showed opposite trends in the light under moderate drought stress. Photosystem II(PSII) maximum photochemical efficiency, actual photochemical efficiency,and photochemical quenching decreased gradually under drought stress, whereas nonphotochemical quenching initially increased and then declined. Superoxide dismutase,peroxidase, and catalase activities initially increased and then decreased as RSMC was reduced, whereas malondialdehyde(MDA) content and relative electric conductivity(REC) increased gradually. These results suggest that stomatal factors accounted for the decline in PNunder light and moderate drought stress, whereas leaf PNdecreased mainly due to non-stomatal factors under severe drought stress. PSII was damaged; thus, photosynthetic electron transfer was restricted, indicating that heat dissipation is important for the light protection mechanism of plants.Antioxidant enzymes increased at the beginning of treatment, and the increased MDA and REC led to cell membrane damage. These results suggest that poplar seedlings stabilized their photosynthetic apparatus by reducing the light trapping ability under light and moderate drought stress conditions. This helped dissipate heat and enhance antioxidant enzyme activity. Stomatal factors accounted for the decline in P_N, whereas damage to PSII and antioxidant enzymes under severe drought stress suggested that the decline in P_N was caused by non-stomatal restrictive factors.     

Spartina alterniflora invasion affects methane emissions in the Yangtze River estuary

Journal of Soils and Sediments - Wetlands are the largest natural sources of atmospheric methane (CH4) and are often susceptible to plant invasion and hydrological fluctuations. However, the effect...     

内蒙古东部湿地植被演替的初步研究

湿地植被是湿地生态系统的基本组分,其演替过程受地表水分、水深浅、水流速度、流向、微地形等诸多因素的影响,伴随着这些因素影响所引起的微生境的变化,湿地植被的类型也发生着相应的变化和迁移,从而沿河湖岸形成一定的梯度变化规律,呈现出一定的空间分布序列,而这一序列恰恰在某种程度上反映出了一些湿地类型的湿地植被的演替过程。因此,本文试图以内蒙古东部区湿地植被现状和类型的调查结果为例描述其湿地植被在不同因素作用下的演替序列。     

基质固相分散-高效液相色谱法测定小麦籽粒中吡虫啉和啶虫脒残留

建立了以C18键合硅胶作为固相分散剂,高效液相色谱法同时测定小麦籽粒中吡虫啉和啶虫脒残留的分析方法。C18键合硅胶与样品一起研磨均匀制成基质固相分散柱,用乙腈淋洗,浓缩后用高效液相色谱检测。结果表明:吡虫啉在0.05~0.8 mg/L、啶虫脒在0.1~1.0 mg/L的范围内线性良好,相关系数分别为0.999 6、0.999 7。在0.05、0.1、0.5 mg/kg水平时,吡虫啉和啶虫脒的添加回收率分别在88.5%~98.4%和93.2%~98.9%之间,相对标准偏差分别在2.0%~3.8%和3.6%~9.8%之间,仪器最低检出量分别为0.1 ng和0.4 ng,方法最小检出浓度分别为0.04 mg/kg 和 0.1 mg/kg。该方法简便、快速、溶剂消耗少,满足农药残留分析的要求。     

日本花柏心材和边材精油的组分

芳香植物日本花柏天然耐久,富含精油。日本花柏心材和边材的精油组分气相色谱-质谱分析结果表明其心材与边材精油组分均主要由醇类和萜烯类化合物组成;心材精油主要挥发性组分为δ-杜松醇(40.64%)和β-荜澄茄油烯(12.67%);边材精油主要挥发性组分为α-杜松醇(29.98%)和α-依兰油烯(10.18%)。日本花柏心材和边材精油的挥发性组分不同,日本花柏心材精油中最高含量的δ-杜松醇为木材抗白蚁活性成分,萜烯类化合物具有化感作用。日本花柏心材精油在环境友好型农药开发上具有潜在价值。     

不同培养条件对草菇菌丝体生物量的影响

为给草菇液体菌种的工业化生产提供具体的参考配方,明确草菇液体菌种生产过程中各种环境条件要求,在液体培养条件下,研究了不同培养基配方、培养温度、摇瓶装液量、接种量、pH及培养时间对草菇V37菌丝体生物量的影响。结果表明,草菇液体培养基适宜的配方是配方B,适宜的摇瓶装液量在80 mL,适宜的接种量在10%,适宜的pH 6~9,适宜的培养温度在30~32℃之间,适宜的培养时间是6~8天。     

六个强筋小麦品种不同出粉点面粉和面片的色泽及其褐变特点

为研究不同出粉点面粉面条色泽品质的差异,测定了6个强筋小麦品种通过布勒实验磨制粉获得的不同出粉点面粉的品质特性与面片色泽及褐变情况。结果表明,3道心磨和3道皮磨的面粉和面片色泽的L^*值均随出粉点后移呈下降趋势,而a^*值和b^*值则呈上升趋势;在面片放置过程中,3道心磨和3道皮磨面粉所加工面片色泽亮度的下降值、偏红度的上升值和偏黄度的上升值均随出粉点后移呈加速趋势。面片色泽与蛋白质含量、灰分含量和面粉L^*值关系密切。鲜面片放置24 h后色泽亮度的下降值与面粉粗蛋白质含量和灰分含量均呈极显著正相关,相关系数分别为0.444和0.758,而与面粉L^*值呈极显著负相关,相关系数为-0.681;色泽偏红度的上升值与面粉灰分和破损淀粉含量均呈极显著正相关,相关系数分别为0.834和0.760;色泽偏黄度的上升值与所有指标的相关均不显著。3心粉的色泽差,其所加工的面片色泽也较差,且色泽不稳定,在面片放置过程中色泽的亮度、偏红度和偏黄度保持性最差,褐变程度严重;1心粉的色泽好,其所加工的面色泽好,并在面片放置过程中,色泽的亮度和偏红度保持性较好,而色泽的偏黄度不如1皮粉和2皮粉的稳定。     

不同覆盖材料土壤水温效应与作物增产效应分析

在位于山西省阳曲县河村的“国家‘十一五’支撑计划农业综合节水研究示范基地”,采用大田试验对不同材料（普膜、降解地膜、秸秆、液膜）覆盖下的土壤水分和温度动态变化以及玉米生长和产量效应、WUE进行了研究,并分析了不同覆盖材料的经济效益。结果表明：供试降解膜和普膜覆盖均具有显著的增温效果和一定的保水作用,秸秆覆盖同时具有显著的降温作用和保水作用,而供试液膜只具有一定的增温效应,无保水作用,不同覆盖材料的增温或降温效应主要表现在玉米生育前期。供试降解膜和普膜覆盖均显著促进了玉米生长发育,玉米产量和WUE以降解膜覆盖最高,普膜覆盖次之,但经济效益以普膜覆盖最好,降解膜覆盖次之。供试液膜对玉米生长也具有一定促进作用,玉米产量、WUE和经济效益也均略好于CK,但差异均不显著。而秸秆覆盖影响了玉米生长发育,产量、WUE和经济效益均显著低于CK。由以上结果可见,在试验区域低温干旱并存的条件下,有效的覆盖材料应同时具备增温作用和保水作用,而且增温作用较保水作用更为重要。因此,秸秆不适合作为低温干旱并存区域的覆盖材料,供试液膜因其效果欠佳也不适宜推广应用,而普膜覆盖的推广应用可获得最大的经济效益,但考虑到普膜的环境污染成本,供试降解膜也具有良好的推广应用价值。     

中早熟番茄新品种“黄山1号”的选育及 抗青枯病鉴定

番茄青枯病是一个世界性的严重病害,已成为番茄生产上的重要障碍.种植抗病品种是防治植物病害最经济有效的方法,但番茄在抗青枯病品种培育中存在着抗病性与品质和产量相矛盾的问题.对此,该研究采用杂交和回交相结合,并自回交后代参与病理程序的选育方法,获得了具有较高的田间抗病性"黄山1号"番茄新品种.人工接种表明,黄山1号的平均发病率为5.5%,极显著低于对照感病品种强丰的平均发病率(94.6%),且产量和生食风味均优于丰产亲本"强丰".     

中国三大区域农业经济结构的现状及其未来走向

2003年中国农业经济结构的现状是:GDP为117251.9亿元（当年价）,一、二、三产业之比14.6:52.2:33.2;农林牧渔业产值为16997.2亿元（1990年不变价）,农、林、牧、渔业产值之比48.6:5.0:33.8:12.6;作物总播种面积为152414.9千hm2,粮作、经作、其他面积之比65.2:16.2:18.6。根据三大区域农业经济结构的现状及其水资源禀赋条件的差异,分析了结构调整的近期走向:在2010年前后,东、中、西部GDP年增长率将分别为8.2%、7.1%、6.8%;农林牧渔业产值年增长率分别为4.6%、4.3%、5.7%;作物总播种面积年增长率极小。