水分胁迫对荔枝叶片氮和核酸代谢的影响及其与抗旱性的关系

水分胁迫下,荔枝叶片蛋白酶活性和Ｐｒｏ含量增加,ＰＤＨ活性与可溶性蛋白质含量下降,抗旱性强的品种蛋白酶活性增加的幅度蛋白质含量下降的幅度小于抗旱性弱的品种,而ＰＤＨ活性下降的幅度和Ｐｒｏ含量上升的幅度均大于抗旱性弱的品种。水分胁迫引起荔枝叶片核酸,ＤＮＡ和ＲＮＡ含量下降,ＤＮＡ含量下降的幅度小于ＲＮＡ含量下降的幅度;ＤＮａｓｅ和ＲＮａｓｅ活性上升,ＤＮａｓｅ活性上升的幅度小于ＲＮａｓｅ活性上升的幅     

水分胁迫对荔枝叶片氮和核酸代谢的影响及其与抗旱性的关系

水分胁迫下,荔枝叶片蛋白酶活性和Ｐｒｏ 含量增加,ＰＤＨ 活性和可溶性蛋白质含量下降;抗旱性强的品种蛋白酶活性增加的幅度和蛋白质含量下降的幅度小于抗旱性弱的品种, 而ＰＤＨ 活性下降的幅度和Ｐｒｏ 含量上升的幅度均大于抗旱性弱的品种。水分胁迫引起荔枝叶片核酸、ＤＮＡ 和ＲＮＡ 含量下降,ＤＮＡ 含量下降的幅度小于ＲＮＡ 含量下降的幅度;ＤＮａｓｅ 和ＲＮａｓｅ 活性上升,ＤＮａｓｅ 活性上升的幅度小于ＲＮａｓｅ 活性上升的幅度。抗旱性强的品种核酸、ＤＮＡ 和ＲＮＡ 含量下降的幅度以及ＤＮａｓｅ 和ＲＮａｓｅ 活性上升的幅度均小于抗旱性弱的品种。     

硅对盐胁迫下西葫芦幼苗水分代谢及光合特性的影响

【目的】探究外源硅对盐胁迫下西葫芦幼苗水分代谢及光合作用的保护机制,可为西葫芦抗盐栽培提供理论参考。【方法】以西葫芦品种‘寒绿7042’为试材,通过水培试验,共设置对照、硅处理(0.3 mmol/L Na₂SiO₃·9H₂O)、盐胁迫(150 mmol/L NaCl)、盐胁迫+硅等4个处理,处理10 d后测定幼苗的根系形态和活力,叶片含水量、水势、光合气体交换参数、叶绿素含量、叶绿素荧光参数及根系质膜水通道蛋白基因的表达等指标。【结果】盐胁迫显著抑制了西葫芦幼苗根系的生长,降低了根系活力、叶片含水量、叶片水势和蒸腾作用,还破坏了植株的光合系统,导致净光合速率、气孔导度、叶绿素含量和PSⅡ光化学效率显著降低。外源硅显著改善了盐胁迫下西葫芦幼苗的根系形态,提高了根系活力,并通过促进根系质膜水通道蛋白基因PIP1;2、PIP1;3、PIP1;5、PIP1;7、PIP2;1、PIP2;4、PIP2;6、PIP2;8、PIP2;9和PIP2;12的表达改善植株体内的水分状况,提高叶片含水量和水势,增强蒸腾作用;外源硅还通过提高叶片...     

柑橘木虱胁迫对柠檬叶代谢组挥发性成分的影响

柑橘木虱是柑橘黄龙病的自然传播媒介,为了解柑橘应对柑橘木虱胁迫的代谢组学变化,本文以柠檬为受体,进行柑橘木虱取食胁迫处理,分别于胁迫不同阶段(0、12、24、48、72和96 h)采集柠檬叶为试验材料,静态顶空-气相色谱-质谱联用检测其挥发性物质。主要结果如下:结合保留指数从柠檬叶中共检出37种化合物,包含15种萜类,6种醛类,6种醇类等;含量较高的挥发性成分有(+)-柠檬烯、桧烯、月桂烯等;受柑橘木虱取食胁迫后,柠檬叶中的挥发性化合物含量产生明显变化,萜类、醛类和醇类物质相对含量均呈升高趋势。桧烯、里那醇、(+)-香茅醛和橙花醇4种物质的含量在柑橘木虱取食胁迫96 h时分别升高2.1,2.9,7.8和3.2倍;α-石竹烯的含量下降1.9倍。(+)-柠檬烯、β-红没药烯和反式-α-香柑油烯等物质含量变化不明显,胁迫后的样品中新检出玫瑰呋喃氧化物、香叶醇和2-异丙基-5-甲基茴香醚等3种化合物。皮尔森相关性分析表明,桧烯、β-蒎烯、甲基庚烯酮、月桂烯、水芹烯等9种物质含量与柑橘木虱胁迫时间呈极显著正相关(P0.01),α-蒎烯、莰烯、松油烯、γ-萜品烯等10种物质含量与柑橘木虱胁迫时间呈显著正相关(P0.05),而邻甲氨基苯甲酸甲酯含量与柑橘木虱胁迫时间呈极显著负相关(P0.01)。聚类和热图进一步分析表明,胁迫不同时间的样品具有显著差异,且胁迫时柠檬叶挥发性化合物大部分呈现上升的趋势,尤其是胁迫48、72和96 h后,物质含量显著增加。研究结果为了解柑橘应对柑橘木虱等生物胁迫的代谢组学变化及柑橘木虱的生物防治提供了理论基础。     

水分胁迫对小麦叶片光合作用的影响及其与抗旱性的关系

在水分胁迫初期,两个小麦品种叶片光合速率,气孔导度和细胞间隙CO_2浓度降低,气孔限制值增加,光合速率的降低主要是气孔因素的限制。中度到严重水分胁迫使叶片光合速率、气孔导度和气孔限制值降低,细胞间隙CO_2浓度明显增加,且叶圆片放氧能力,叶绿体Hill反应、叶绿素荧光强度和表观量子产额降低,此时光合速率的降低主要是叶肉细胞光合活性的下降引起的。抗旱性弱的郑引一号叶肉细胞光合活性比抗旱性强的丰抗13更容易受到水分胁迫的影响。     

根际低氧胁迫对黄瓜幼苗根系呼吸代谢的影响

采用营养液栽培方法,研究了低氧胁迫对两个耐低氧能力不同的黄瓜品种根系呼吸代谢的影响.结果表明：低氧胁迫下,两个黄瓜品种根系三羧酸循环显著受阻,无氧呼吸代谢被促进.与耐低氧能力较弱的中农8号相比,耐低氧能力较强的绿霸春4号根系琥珀酸脱氢酶和异柠檬酸脱氢酶活性的降低幅度较小,乳酸脱氢酶活性、乳酸和丙酮酸含量的增加幅度较小,而丙酮酸脱羧酶、乙醇脱氢酶活性及乙醇、丙氨酸含量的增加幅度较大;低氧胁迫8 d时,与相应对照相比,绿霸春4号根系乙醇脱氢酶活性及乙醇和丙氨酸含量分别增加了409.30%、112.13%和30.64%,中农8号根系分别增加了110.42%、31.84%和4.78%,这是两个黄瓜品种耐低氧能力差异的主要生理原因.两品种幼苗根系丙氨酸氨基转移酶活性和乙醛含量没有显著差异.表明低氧胁迫下黄瓜根系乙醇发酵代谢途径的增强和丙氨酸的积累有利于防御低氧伤害.     

热激锻炼对高温胁迫下菊花生理代谢的影响

以菊花(Chrysanthemum morifolium)品种'神马'的扦插苗为试验试材,在40℃下对其进行8 h的热激锻炼,然后在50℃下分别进行0、 1、 1.5、 2、 2.5、4 h不同时间的高温胁迫.通过对其相对电导率、丙二醛(MDA)、脯氨酸和可溶性蛋白质含量及过氧化物歧化酶(POD)和超氧化物歧化酶(SOD)活性的测定,研究了热激锻炼对菊花耐热性的影响.结果表明,热激锻炼的菊花叶片相对电导率比对照减小,MDA含量也比对照减小,而可溶性蛋白质和脯氨酸含量及POD和SOD活性比对照增加,说明热激锻炼在一定程度上提高了菊花幼苗的耐热性.     

锰胁迫对商陆(Phytolacca acinosa)保护酶的影响

对室内栽培的商陆(Phytolacca acinosa)幼苗分别经4、12、36mmol/L的锰(Mn2 )溶液处理30d后,用聚丙烯酰胺凝胶电泳(PAGE)分离了根和叶片过氧化物酶(POD)同工酶和超氧化物歧化酶(SOD)同工酶,并测定了其酶活性.结果表明:(1)经不同浓度的Mn2 溶液处理,根POD同工酶(RP1)消失,而12、36mmoL/L Mn2 溶液处理根新的POD同工酶(RP5,RP8)出现,根POD酶活性出现先降低后升高的变化趋势;叶片POD同工酶(LP)有3种,与对照的相同,但其酶活性随Mn2 浓度增加而随之升高.(2)12、36mmol/L Mn2 溶液处理,根新的SOD同工酶(RS5-RS7)出现,SOD酶活性上升;36mmol/L Mn2 溶液处理,叶片SOD同工酶(LS2-LS5)消失,叶片SOD酶活性下降.推断,商陆根和叶片同工酶的表达调控的机制不同.认为,商陆在Mn2 胁迫中,POD发挥更重要的作用.     

Cell-wall lysing enzymes and products of cell-wall digestion elicit ethylene in citrus

Ethylene production was induced in Valencia oranges [ Citrus sinensis (L.) Osbcck] by injection of the fungal enzyme mixture Pectolyase ( Aspergillus japonicus ) which contains pectolytic enzymes into the peel. The mixture also stimulated production of 1-aminocyclopropane-1-carboxylic acid (ACC). Cycloheximide partially inhibited the Pectolyase-induced ethylene response. Pectin fragments, resulting from partial acid hydrolysis or Pectolyase digestion, caused an increase in ethylene production when injected into the peel of intact orange fruits. Pectic fragments produced by fungal enzymes are known to be elicitors of phytoalexins and in this study are shown to elicit ethylene in citurs.     

锌胁迫对两种柑橘幼苗光合特性日变化及其相关性的影响

通过砂培试验,采用C I-340型便携式光合测定系统研究了不同锌处理（0.05mg/L Zn为对照,0.5mg/L Zn为锌过量,0mg/L Zn为锌缺乏）对‘不知火’和‘椪柑’幼苗叶片光合特性日变化及其相关性的影响。结果表明,在锌胁迫条件下,‘不知火’叶片的净光合速率（Pn）日变化呈单峰曲线,对照为双峰曲线,而‘椪柑’与对照呈现相似的单峰型变化,且锌胁迫下两者平均的Pn均显著低于对照。简单相关分析表明,‘不知火’在锌胁迫下叶片Pn与光合有效辐射（PAR）、蒸腾速率（Tr）均呈显著的正相关,其对照Pn与各因子之间并无显著相关性,各锌处理下的‘椪柑’叶片Pn均与Gs呈显著正相关。逐步多元回归的分析结果与简单相关分析结果存在出入。还就锌胁迫对两品种柑橘的光合特性及其相关性的影响进行了讨论。     

Effect of soil moisture stress on legume-rhizobium symbiosis in soybeans

Summary In a pot culture experiment, the influence of soil moisture stress at different physiological stages of soybean, cv. Hark, on nodulation, symbiosis and nitrogen accumulation was studied. Moisture stress reduced leghemoglobin content of root nodules and nitrogen uptake by plants. It had no effect on number of bacteroids. Stress at mid bloom and rapid pod filling stages reduced yield and seed protein content. However, these parameters were not affected by stress at nodule initiation and early flowering stages, though, flower initiation and maturity of the plant were delayed. Moisture stress at any stage did not alter nitrogen status of roots.     

Effect of copper hydroxide sprays for citrus canker control on wild-type Escherichia coli

Aims: To show that application of copper hydroxide citrus sprays mixed with field source water (possibly contaminated) will not support Escherichia coli on plant surfaces. Environmental stresses of transient phyllosphere bacteria and presence of copper will eradicate these bacteria before harvest. Methods and Results: Studies were performed in vitro with bacteria grown in broth and then subjected to field spray copper hydroxide concentrations in the broth and on citrus leaves. Escherichia coli exposed to copper hydroxide in vitro were eradicated from the broth within 6–8 h depending on the broth pH. Even with near neutral pH (7·2), cells began to die immediately after exposure to copper. No E. coli survived on leaf surfaces sprayed with copper. Conclusions: Copper field sprays mixed with water that may contain E. coli can help eliminate E. coli from plant surfaces. Significance and Impact of the Study: HACCP mandates are becoming more restrictive because of the increased illness resulting from food pathogens on fresh produce. Use of potable water in fields, a proposed mandate, is not feasible for large grove owners. These data show that copper sprays aimed at reducing citrus canker also affect E. coli and may help to ease water quality mandates.     

覆盖材料对云贵高原柑橘园土壤理化性质和细菌群落特征以及柑橘品质的影响

采用田间试验,研究了玉米秸秆覆盖(JF)、白色地膜覆盖(BF)、黑色地膜覆盖(HM)和园艺地布覆盖(YD),以及清耕作为对照(CK)对云贵高原柑橘园土壤理化性质、细菌群落特征及柑橘品质的影响。结果表明,与CK相比,不同覆盖处理下柑橘产量、单果重、果汁率、可食率、维生素C含量和可溶性固形物等指标均提高,可滴定酸含量则有所降低,进而提高了固酸比,其中以JF处理效果最显著。BF、HM和YD处理降低了土壤pH值,JF处理则相反,不同覆盖处理均能提高土壤温度、含水量、有机质和养分含量,JF处理对土壤有机质、全氮、全磷、全钾、有效磷和速效钾含量的提升作用最明显,BF处理下土壤温度最高。JF、HM和YD处理均能显著提高Chao1指数和Observed species指数,而BF处理则相反。在门水平上,覆盖提高了有益菌放线菌门的相对丰度,降低了致病菌拟杆菌门的相对丰度;在属水平上,覆盖提高了有益菌热酸菌属、朱氏杆菌属、Babeliales、红杆菌属和脱氯单胞菌属的相对丰度,降低了致病菌Saccharimonadales、成对杆菌属、金黄色杆菌属、芽孢八叠球菌属和丛毛单胞菌属的相对丰度。此外,覆盖还使土壤细菌共生网络变得简单而稳定。冗余分析结果表明,土壤全氮和细菌群落红杆菌属是提升柑橘产量和品质的关键因子,其解释率分别为45.67%和39.40%。方差分解分析结果表明,土壤理化性质和细菌群落的共同作用对柑橘产量和品质提升的贡献最大,其解释率为45.0%。综上所述,覆盖能有效改善土壤理化性质,提升土壤养分供应水平,优化细菌群落结构,提高柑橘产量和品质,其中,玉米秸秆覆盖可优先作为云贵高原柑橘园土壤的地表覆盖措施。     

Differences in water relations among the citrus leafminer and two different populations of its parasitoid inhabiting the same apparent microhabitat

The water balance relationships of adult females and pupae of two populations (Australian and Taiwan) of the parasitic wasp Ageniaspis citricola, a biological control agent of the citrus leafminer Phyllocnistis citrella, were compared to determine whether habitat preferences might differ between them. No differences were detected between Australian and Taiwan strains of the wasp during the pupal stage, but adult females from the Australian strain had lower net water loss rates than the parasitoid adults from Taiwan. This implies a greater moisture requirement by adults of the Taiwan strain, which should be considered before they are released into a new environment in classical biological control programs.     

Effect of soil moisture on bioremediation of chlorophenol-contaminated soil

A chlorophenol-contaminated soil was tested for the biodegradability in a semi-pilot scale microcosm using indigenous microorganisms. More than 90% of 4-chlorophenol and 2,4,6-trichlorophenol, initially at 30 mg kg^–1, were removed within 60 days and 30 mg pentachlorophenol kg^–1 was completely degraded within 140 days. The chlorophenols were degraded more effectively under aerobic condition than under anaerobic condition. Soil moisture had a significant effect with the slowest degradation rate of chlorophenols at 25% in the range of 10–40% moisture content. At 25–40%, the rate of chlorophenol degradation was directly related to the soil moisture content, whereas at 10–25%, it was inversely related. Limited oxygen availability through soil agglomeration at 25% moisture content might decrease the degradation rate of chlorophenols.     

The movement and distribution of citrus tristeza virus and citrus exocortis viroid in citrus seedlings1

The systemic movement of citrus tristeza virus (CTV) in sour orange (Citrus aurantium) seedlings and of citrus exocortis viroid (CEVd) in Etrog citron (C. medica) seedlings was studied. The movement of the two pathogens was analysed by detection in sections of roots and stems at different time intervals. Both pathogens were detected initially in the basal parts and the roots and subsequently spread to the shoot. CTV and CEVd moved in young citrus seedlings at similar rates. The findings are consistent with long distance phloem transport of the virus and the viroid. The practical implications of the pattern of systemic movement for diagnosis of infected trees are discussed.