Effect of temperature on growth of some avirulent fungi and cross-protection against the wheat take-all fungus

The linear growth rates of Gaeumannomyces graminis var. graminis, G. graminis var. tritici, Phialophora radicicola var. graminicola and a lobed hyphopodiate Phialophora sp. were studied on agar at various temperatures between 5 and 30 °C and on wheat roots at two temperature regimes (12 h at 7°/12 h at 13 °C and 12 h at 17°/12 h at 23 °C). On agar at 30 °C, the isolates of G. graminis graminis grew faster than those of G. graminis tritici and Phialophora sp. but three isolates of G. g. graminis grew more slowly than the other two fungi at 5 and 10 °C. Two other isolates of G. g. graminis were cold-tolerant and had growth rates comparable to those of G. g. tritici and Phialophora sp. at 10 °C. The growth rates of Australian isolates of P. radicicola graminicolu were similar to that of a British isolate and were about a third to a half those of the other three fungi at most temperatures. The growth rates of the fungi on wheat roots at the low and high temperature regimes were correlated with the growth rates on agar at 10 and 20 °C respectively. The correlation was better at low temperatures r= 0.81) than at high temperatures (r = 0.62). Cross-protection experiments using two G. g. graminis isolates which grow poorly at temperatures below 15 °C and a cold-tolerant isolate each of G. g. graminis and Phialophora sp. showed that, while all four fungi protected wheat against take-all at high temperatures (17/23 °C) as evidenced by less severe disease and significantly greater dry weights, only the cold-tolerant fungi were effective at low temperatures (7/13 °C). The use of cold-tolerant isolates of avirulent fungi in field experiments may result in better protection in the early stages of wheat growth when Australian soil temperatures are mostly below 15 °C.     

Hormone Action and the Levels of Cyclic AMP and Prostaglandins in the Toad Bladder

THERE is overwhelming evidence to connect cyclic 3′,5′-adenos-ine monophosphate (cyclic AMP) with hormone action in various tissues¹. For example, the toad bladder responds to neurohypophyseal hormones (ADH) with an increase in water permeability² and with an increase in the mucosal to serosal transport of sodium³. ADH also causes an increase in cyclic AMP levels in the tissue⁴ and the actions of the hormone can be mimicked by addition of the cyclic nucleotide^2,5. Orloff and Handler⁵ have suggested that cyclic AMP directly affects the permeability of the mucosal face of the epithelial cells to water and to sodium and that there are two separate adenyl cyclase systems responsible for controlling the permeability to water and to sodium^6,7.     

关于植物营养生态学

植物营养学与植物生态学发展的前沿交叉正形成了植物营养生态学,植物营养生态学是探讨植物营养利用策略的科学,包括植物体内营养的合理利用策略和植物对无机营养环境的改造以利于营养吸收的各种可能策略。其研究内容主要包括养分利用效率、植物体内营养的再利用、体内营养含量格局和植物对土壤无机营养环境的改造。植物营养生态学以植物种群为研究对象。它的发展对深刻理解种群的生态行为特征具有重要意义,同时对如何增进人工混交群落的营养协调性具有实践上的指导意义。营养生态机理的各个方面是相互协调和相互补充的整体,营养生态机理的效率决定了种群营养合理利用的程度和在营养资源上的竞争力。目前,研究上尚缺少营养策略与其它生态策略的关联性的探讨,随着各种营养策略研究上的深入,这种关联性探讨将成为今后植物营养生态学的主要发展趋势。     

中国香港17种植物新记录

报道了香港17种植物新记录:无配膜叶铁角蕨[Hymenasplenium apogamum(N.Murak.&Hatan.)Nakaike]、似薄唇蕨(Leptochilus decurrens Blume)、穿心藤[Amydrium hainanense(H.Li,Y.Shiao&S.L.Tseng)H.Li]、毛背...     

LOCALIZATION AND DISTRIBUTION OF PITUITARY ADENYLATE CYCLASE-ACTIVATING POLYPEPTIDE IN THE RAT EPIDIDYMIS

Previous investigation has provided evidence for the control of electrogenic chloride secretion by pituitary adenylate cyclase-activating polypeptide (PACAP) across the rat epididymal epithelium using electrophysiological measurement of transepithelial transport in cultured epididymal system. Hence, it suggests that epididymal and sperm functions are subject to control by a local PACAP system in the rat epididymis. In the present study, localization and distribution of PACAP in the rat epididymal duct was studied by an indirect immunofluorescence technique in conjunction with confocal laser scanning microscopy. Immunoreactivity for PACAP was found in all regions of the epididymal duct. However, the intensity of immunoreactivity for PACAP was stronger in the caput and corpus regions when compared to that of the cauda epididymidis. Much weaker immunostaining for PACAP, as compared to those found in other regions, was observed in the cauda epididymidal tubules which are in close proximity to the vas deferens. No immunoreactivity for PACAP was found in epididymal spermatozoa. Together with the previous finding, the present results suggest that PACAP may exhibit a regional difference in its expression along the epididymal duct and it may act in a paracrine or autocrine fashion in the regulation of epididymal chloride secretion and hence fluid secretion, thus regulating epididymal and sperm functions along the epididymal duct.     

Evaluation of models of leaf water 18O enrichment using measurements of spatial patterns of vein xylem water, leaf water and dry matter in maize leaves

The effectiveness of several leaf water models (‘string‐of‐lakes’, ‘desert river’ and the Farquhar–Gan model) are evaluated in predicting the enrichment of leaf water along a maize leaf at different humidities. Progressive enrichment of both vein xylem water and leaf water was observed along the blade. At the tip, the maximum observed enrichment for the vein water was 17.6‰ at 50% relative humidity (RH) whereas that for the leaf water was 50‰ at 34% RH and 19‰ at 75% RH. The observed leaf water maximum was a fraction (0.5–0.6) of the theoretically possible maximum. The ‘string‐of‐lakes’ and ‘desert river’ models predict well the variation of leaf water enrichment pattern with humidity but overestimate the average enrichment of bulk leaf water. However, the Farquhar–Gan model gives good prediction for these two aspects of leaf water enrichment. Using the anatomical dimensions of vein xylem overestimates the effective longitudinal Péclet number (P_l). Possible explanations for this discrepancy between the effective and the xylem‐based estimate of P_l are discussed. The need to characterize the heterogeneity of transpiration rate over the leaf surface in studies of leaf water enrichment is emphasized. The possibility that past atmospheric humidity can be predicted from the slope of the Δ¹⁸O spatial variation of leaf macrofossils found in middens is proposed.     

CC趋化因子偶联受体信号途径

Thechemokinesareafamilyofproinflammatorycytokinesthatactthroughcellsurfacereceptorstoregulatenumerousroutinephysiologicalandpathophysiologicalprocesses,includinghematopoiesis,T cellactivation ,angiogenesis,inflammatorydiseasesaswellasHIV 1infection[1,2 ].Thesesmallpeptidesaretypicallycomposedof 70 - 1 30aminoacidsandarecharacterizedbythepresenceoftwodisulphidebondsformedbetweenfourconservedcysteineresidues.Chemokinesareclassifiedintofoursubfamiliesaccordingtothepatternofconservedcysteinesinth…     

蒙新河狸夏季夜间活动节律和时间分配

2011 年7 ～8 月和2012 年7 ～ 8 月,采用瞬时扫描取样法和焦点动物取样法研究了新疆布尔根河狸保护区蒙新河狸夏季夜间行为节律和时间分配,结果表明:夏季蒙新河狸活动高峰呈晨昏型。觅食和移动行为分别占69.5% 和24.5% ,修饰、警戒和其他行为的时间比例依次是3.4% 、0.4% 、2.2% 。利用Pearson’s correlation 检验发现移动和警戒行为之间存在显著正相关,而觅食行为分别与移动、修饰和其他行为之间呈极显著负相关,与警戒存在显著负相关;Mann-Whitney U 检验表明年龄因素对河狸各种行为的影响不显著(P > 0. 05)。