Correlation of iron content, spectral forms of chlorophyll and chlorophyll-proteins in iron deficient cucumber (Cucumis sativus)

Leaves and chloroplast suspensions of severely and slightly iron deficient cucumber ( Cucumis sativus L.) plants were characterized by low-temperature fluorescence emission spectroscopy and Deriphat polyacrylamide gel electrophoresis. The emission spectra of the chloroplast suspensions were resolved into Gaussian components and those changes induced by iron deficiency were related to the variations in the chlorophyll-protein pattern. The symptoms described with these methods were also correlated with the iron content of the leaves. It was concluded that the lack of physiologically active iron caused a relative decrease of photosystem I (PSI) and light harvesting complex I (LHCI), together with the long wavelength fluorescence, especially the 740 nm Gaussian component, and. to a much lesser extent, of the photosystem II (PSII) core complexes (relative increase of 685, 695 nm components). However, the relative decrease in the amount of light harvesting complex II (LHCII) was followed by a relative increase in its fluorescence band at 680 nm, showing that energy transfer from LHCII to core complex II (CCII) was partly disturbed. Thus iron deficiency affected the photosynthetic apparatus in a complex way: it decreased the synthesis of chlorophylls (Chls) and influenced the expression and assembly of Chl-binding proteins.     

接枝淀粉载体固定化糖化酶的研究

合成了淀粉接枝丙烯腈及丙烯酰胺的两亲性高分子化合物,并以此为载体,用物理吸附方法固定化了糖化酶。最适偶联条件研究表明：缓冲液的浓度,ｐＨ值及吸附时间和加酶量都对固定化酶活力,比活有一定的影响。在最适固定化条件下,固定化酶的活力为１５００Ｕ／ｇ干胶,蛋白载量为２５ｍｇ／ｇ干胶,比活为６０Ｕ／ｍｇ蛋白,比天然酶的比活（８．０Ｕ／ｍｇ蛋白）提高６倍。最适反应温度比天然酶提高１０℃（天然酶最适反应温度为５０℃）．无底物存在下,固定化酶在５５℃的半衰期为２４ｈ,而天然酶只有１ｈ;有底物存在下,固定化酶在５５℃的半衰期为２２０ｈ,４５℃的操作半衰期由外推法算得为６９天,而且该载体对糖化酶有一定的保护作用,当固定化酶在低于５５℃热处理一段时间后,对酶活力有激活作用,酶活力最大可提高４０％。该载体合成简单,固定化方法简单,步骤少,因而为工业上应用提供了一种新的可能性。     

Insect feeding on cucumber mediated by rhizobacteria-induced plant resistance

Select strains of plant growth-promoting rhizobacteria (PGPR) were evaluated in greenhouse experiments with cucumber for induction of resistance against cucumber beetle (Diabrotica undecimpunctata howardi Barber) feeding and the beetle-transmitted cucurbit wilt disease. When beetles were given a choice between PGPR-treated and nontreated cucumber, their feeding on stems and cotyledons and the severity of wilt symptoms were significantly lower on PGPR-treated plants. HPLC analysis demonstrated that cotyledons from PGPR-treated plants contained significantly lower concentrations of the cucumber beetle feeding stimulant cucurbitacin than nontreated plants. These results suggest that a mechanism for PGPR-induced resistance against cucumber beetle feeding may involve a change in the metabolic pathway for cucurbitacin synthesis.     

Heavy metal accumulation in tissue/organs of a sea cucumber, Holothuria leucospilota

Holothuria leucospilota Brandt, the large black sea cucumber, is a non-selective deposit feeder, and is commonly found in the bottom of shallow waters in Hong Kong, where the sediments are often polluted with heavy metals. This study was designed to test the possibility of heavy metal accumulation by the sea cucumber at two sites in Hong Kong. Atomic absorption spectrophotometer was used to measure Cu and Zn concentrations in various tissue/organs of the animal as well as in the sediments. The result indicated that H. leucospilota accumulated zinc in the longitudinal muscle bands (97.27–98.07 ppm in dry weight) and in the respiratory tree (83.92–89.64 ppm in dry weight). Copper concentrations in these two organs were much lower than that of zinc. After the animals were kept in the aquarium without sediment for40 days, zinc concentration of the longitudinal muscle and respiratory tree decreased by 48% and 39%respectively whereas copper concentration remained unchanged. The concentrations of zinc and copper in the sediment at the two sites differed significantly but the metal level in the animals from the two sites were similar, suggesting that this sea cucumber was not an ideal bioindicator of heavy metal pollution in the sediment. This revised version was published online in August 2006 with corrections to the Cover Date.     

缺铁对黄瓜叶肉细胞超微结构及某些形态的影响

利用透射电镜,对缺铁黄瓜幼叶肉细胞的超微结构及植株的某些形态学进行了观测,发现缺铁后的幼叶细胞内首先受到影响的细胞器是叶绿体,其次是线料体,细胞核、内质网结构完好。幼苗缺铁２０天后,大部分叶绿体的基料片层和间质片层受到了严重的破坏。少量线粒体出现空泡化倾向,植株在形态学上表现为幼苗长势衰弱,叶色发黄、叶绿素含量下降     

Interspecific interactions between Bemisia tabaci (Hem., Aleyrodidae) and Liriomyza sativae (Dipt., Agromyzidae)

Abstract:  The study examines interspecific interactions between Bemisia tabaci (Hem., Aleyrodidae) and Liriomyza sativae (Dipt., Agromyzidae) feeding on pumpkins and cucumbers. L. sativae density on control pumpkins and cucumbers peaked 3 and 2 weeks after adults were seen, respectively. Compared with controls, L. sativae densities observed for weeks 3–6 and 2–6 in the B. tabaci -pre-infested plants were significantly lower, respectively ( F _2.00 = 22.66, P < 0.01). The survival of L. sativae larvae transplanted to B. tabaci -pre-infested pumpkins and cucumbers was 16.06%, 10.02% and 13.09%, 9.21%, whereas those transplanted to control plants were 52.20%, 36.06% and 48.25%, 28.22% after 5 and 10 days, respectively ( χ ² = 6.9, d.f. = 1, P < 0.01). Pupation rates of L. sativae feeding on control plants were 20.25% and 16.45%, whereas those feeding on the B. tabaci -pre-infested plants only 4.08% and 4.21%, respectively ( χ ² = 7.0, d.f. = 1, P < 0.01). The length and number of mines of L. sativae on the control pumpkins and cucumbers were 54.05%, 54.10% and 89.06%, 76.22% longer or higher than those on B. tabaci -pre-infested plants, respectively. Leaf positions of L. sativae feeding on the plants were also affected by B. tabaci -pre-infested. These results showed that B. tabaci infestations had a significantly negative effect on L. sativae when they were feeding simultaneously on the same host plant.     

Construction of a cucumber genetic linkage map with SRAP markers and location of the genes for lateral branch traits

Using SRAP (sequence-related amplified polymorphism) markers a genetic linkage map of cucumber was constructed with a population consisting of 138 F₂ individuals derived from a cross of the two cucumber lines, S06 and S52. In the survey of parental polymorphisms with 182 primer combinations, 64 polymorphism-revealing primer pairs were screened out, which generated totally 108 polymorphic bands with an average of 1.7 bands per primer pair and at most 6 bands from one primer pair. The constructed molecular linkage map included 92 loci, distributed in seven linkage groups and spanning 1164.2 cM in length with an average genetic distance of 12.6 cM between two neighboring loci. Based on this linkage map, the quantitative trait loci (QTL) for the lateral branch number (lbn) and the lateral branch average length (lbl) in cucumber were identified by QTLMapper1.6. A major QTL lbn1 located between ME11SA4B and ME5EM5 in LG2 could explain 10.63% of the total variation with its positively effecting allele from S06. A major QTL lbl1 located between DC1OD3 and DC1EM14 in LG2 could account for 10.38% of the total variation with its positively effecting allele from S₀₆.     

CsRCA超表达对高温胁迫下黄瓜幼苗光合作用的影响

以CsRCA超表达黄瓜株系T1-7、T1-2和野生型‘08-1’为试材,在三叶一心时用光照培养箱模拟高温环境[40 ℃,光量子通量密度(PFD) 600 μmol·m^-2·s^-1],研究了CsRCA超表达对高温胁迫下黄瓜幼苗光合作用的调控机理.结果表明: CsRCA超表达可显著提高转基因黄瓜幼苗核酮糖-1,5-二磷酸羧化/加氧酶(Rubisco)大、小亚基的mRNA 表达量,Rubisco和Rubisco活化酶(RCA)活性亦显著高于野生型植株.高温胁迫2 h后,超表达和野生型黄瓜幼苗的光合速率(P_n)、以吸收光能为基础的光化学性能指数(PI_ABS)、Rubisco活性和RCA活性及其mRNA表达量均显著降低.经JIP-test分析发现,高温胁迫导致叶绿素荧光快速诱导动力学曲线中K点明显上升, 而捕获的激子将电子传递到电子传递链中Q_A下游的其他电子受体的概率(Ψ_o)和用于电子传递的产额(φ_E0)均显著下降,说明PSⅡ放氧复合体(OEC)和Q_A之后的电子传递链在高温下受到抑制,但是超表达植株的变化幅度要小于野生型植株.可见CsRCA超表达可以通过提高Rubisco、RCA和PSⅡ活性,缓解高温对黄瓜幼苗光合作用的影响,增强其对高温的适应性.     

基于能值代数的湿地生态系统服务评价去重复性计算

在对生态系统服务进行评价时,重复计算一直是困扰学者们的一个难题。目前大部分对湿地生态系统服务价值评估的方法都集中于将服务进行简单的分类后,通过经济学的方法计算和评估湿地生态系统服务的价值。而生态系统服务的产生、传输、消费和再生产其实是一个循环的过程,将其生硬的分类进行评估,势必会对结果的精确度造成影响,如果不能正确地去除湿地生态系统服务价值评价中重复计算的部分,会使评估结果的可信度降低。本文通过建立能值流动流程图,对湿地生态系统服务间"分离、反馈、共产物"这三个基本机制进行整体性的预先分析,将计算结果与未经预先分析的计算结果对比,得到结果误差范围为12%~38%。研究表明,经过对系统的预先分析,可以有效地去除重复性计算所带来的误差,使评价的结果更加精确。