THE TIMING OF BIRDS' BREEDING SEASONS

Examination of survival rdtes of nestlings and fledglings of some species show that there is a strong tendency for those young which are hatched earliest in the season to have the greatest chance of surviving to breed. Since natural selection so strongly favours parents who leave many surviving young, the question arises as to why other birds breed later than the date at which they could most successfully raise their young.
It is suggested that the food supply for the breeding females immediately prior to the breeding season may limit their ability to form eggs and the females may thus not be able to lay at the time which would result in young being in the nest at the best time for raising them, but as soon after this time as the female is able to produce her eggs. Not all species are likely to be prevented, by food shortage, from breeding at the best time for raising young and the groups of birds most likely to be affected are discussed.     

臭氧对真菌杀灭作用的初步研究

以根霉 ,黑曲霉 ,青霉 ,酵母菌等为研究对象 ,测定了放电时间与致死率的曲线关系 ,并观察了与空白对照后其菌落形态的变化。实验结果表明 ,随着放电时间的增长 ,致死率明显升高 ,且能够达到完全杀菌。     

植物病原真菌毒素的研究现状

近几年来,关于寄主专化性毒素(Host-Specific Toxin,HST)的作用机制及分子生物学方面的研究有了新进展;在14种寄主专化性毒素中,以Alternaria属的病原菌产生的专化性毒素的研究更为深入。非寄主专化性毒素(Non-Host-Specific Toxin,NHST)的研究着重在毒素产生的条件、生物活性测定、抗性鉴定以及检测被感染植物体的毒素含量等。本文综述了一些能产生专化性毒素和非专化性毒素的植物病原真菌,有链格孢(Alternaria)、镰孢(Fusarium)、尾孢(Cercospora)、轮枝孢(Verticillium)、梨孢(Pyricularia)、疫霉(Phytophthora)、长蠕孢(Helminthosporium)、黑团孢(Periconia)和核盘菌(sclerotinia)等属的病原菌。从所发表的文献表明真菌毒素在植物病害发展中起着重要作用。     

4株溶磷细菌和真菌溶解磷矿粉的特性

溶磷微生物广泛地分布在土壤,根际等生态环境中,了解这些微生物溶解难溶性磷酸盐如磷矿粉的特性,对于开发利用这些微生物,提高磷素利用效率具有重要作用,研究发现;真菌比细菌溶解磷矿粉的能力要强得多,培养基中的铁,镁,锰,钠等成分可以提高真菌的溶磷量,但降低了细菌的溶磷量,培养基中磷矿粉用量越高,溶磷量越低;碳源物质浓度高于3%将显地降低溶磷量,微生物能够破坏磷矿粉的结构。使其中的磷在以后的培养过程中更加容易释放出来,可见利用微生物活化磷矿粉中的磷,具有良好前景。     

水杨酸在AM真菌侵染和诱导植物抗病性中的作用

水杨酸（SA）是一种广泛存在于高等植物体内的酚类物质,是肉桂酸的衍生物,在植物许多生理过程中发挥重要作用（原永兵和曹宗巽,1994）,如诱导某些植物开花和气孔关闭;导致天南星科植物的佛焰花序产热;促进侧芽萌发;抑制乙烯的生物合成;调节某些植物的光周期;影响黄瓜的性别分化等（Wang＆Tsao,1979）;因而Raskin提出SA是一种新的植物激素（Raskin,1992）.许多试验证明SA是重要的能够激活植物过敏反应（HR）和系统获得抗性（SAR）的内源信号分子（Malamy et a1.,1990）,能诱导烟草和黄瓜等植物对细菌、真菌、病毒等多种病害的抗病性（原永兵等,1997）.