植物向光性运动机理的新见解

向光性反应是植物器官适应环境,向有利方向生长的一种良好的生物学特性。1880年,Charles Darwin和Francis Darwin首先发现这个现象,并认为是某些物质引起的。1928年,Went证明燕麦芽鞘经单侧光照后,背光一侧芽鞘顶部扩散到琼脂的生长刺激活性是向光一侧的一倍。1924年,     

高等植物的向光性信号转导

对高等植物向光性信号转导的最新研究进展进行了综述,并对向光素的性质、结构和可能的作用方式及其下游可能的信号传递途径作了分析讨论.     

玉米幼苗向光性实验设计与探究

生物学教学和高考对实验有了更高的要求．集中表现在开放性实验设计上。现以高中《生物》必修教材中的“植物向性运动实验设计与观察”为例,以玉米幼苗为实验材料,对玉米幼苗向光性进行实验设计和探究。     

对燕麦胚芽鞘"向光性"解释的一点看法

中学课本中 ,通过燕麦胚芽鞘的向光性实验说明 :“胚芽鞘的尖端能产生生长素 ,并从尖端运输到下部 ,能促使下部生长”。而对生长素为什么能使植物显示出向光性是这样解释的 :“这与单侧光引起的生长素分布不均匀有关。光线能改变生长素的分布 :向光的一侧生长素分布得少 ,背光的一侧生长素分布得多。因此 ,向光的一侧 ,细胞生长得慢 ,背光的一侧 ,细胞生长得快。结果 ,茎朝向生长慢的一侧弯曲 ,也就是朝向光源的一侧弯曲 ,使植物的茎表现出向光性。”受单侧光的照射发生生长素分布不均的部位究竟是胚芽鞘尖端、胚芽鞘下部、还是整个部分 ,在…     

复习课“生长素与向光性”的教学构思与实践

在高考备考复习中,需要回顾课本,夯实基础。但从求知欲的角度而言,猎新、猎奇是学生求知的欲望,可是复习是重温旧知识,教与学的矛盾凸现,如何调动学生的兴趣,提高学生综合应用知识的能力,实现有效地备考,教学中就需要发掘教材中的学习新资源,并通过复习让学生梳理知识、建构知识网络,形成专业的学科概念,形成学科的知识结构体系。     

向光素调节植物向光性及其与光敏色素/隐花色素的相互关系

蓝光受体向光素(PHOT1/PHOT2)调节蓝光诱导的植物运动反应, 包括植物向光性、叶绿体运动、气孔运动和叶片伸展等。其中, 向光素介导的植物向光性能够促使植物弯向光源, 确保其以最佳取向捕获光源, 优化光合作用。光敏色素和隐花色素作为光受体也参与植物的向光性调节。该文综述了向光素介导的拟南芥(Arabidopsis thaliana)下胚轴向光弯曲信号转导及其与光敏色素、隐花色素协同作用的分子机制, 以期为改造植物光捕获能力及提高光利用效率提供理论基础。     

玉米胚芽鞘向光性运动的一些特性

利用云母片分隔、ＨＰＬＣ分析等方法研究了玉米胚芽鞘向光性运动的特性。云母片阻隔生长素的移动后并不能阻止胚芽鞘的向光性变弯曲。     

植物的向性运动

植物在空间的取向,除受植物携带的遗传指令的控制外,还受外界环境条件例如光照、重力、水分以及化学物质等刺激的影响。在这些外界单方向的刺激下,植物产生的定向生长运动,称为向性运动。根据外界刺激的不同,可以相应地称为向光性、向重力性、向水性和向化性等。那么,植物是怎样感受外界环境刺激,并做出相应的反应呢?多年来,人们为探讨此奥秘,进行了大量的研究工作。向光性早在一百年前,达尔文就发现金丝雀(?)草的茎尖,在单方向光照下,会发生向光弯曲。植物这种随光的方向而发生弯曲的能力,叫向光性。许多窗台上生长着的植物,都具有这种能力。由于这种茎的生长取向于光照较强的一面,故称之为正向光性。而有些植物例如向日     

植物向性微观机理的能量新说

此文是对本刊 2 0 0 0年第 2期“植物向地性的一种新解释”一文的争论和补充 ,这是很好的事 ,一方面说明读者关心我们的刊物 ,一方面也可使问题越争论越深入     

小麦胚芽鞘和青菜幼苗的向光性探究实验

“小麦（Triticum aestivum L．）胚芽鞘的向光弯曲”是经典实验,该实验对于提高学生的学习兴趣,培养学生的探究能力,学习科学家严密的科学思维和追求真理的精神具有重要的意义。从小麦种子的处理、胚芽鞘尖端剪切的长度、观察时间等方面对该实验进行了改进,取得良好的实验效果。以青菜（Brassica chinensis L．）为材料进行了拓展探究,发现青菜幼苗是可用于向光性演示实验的好材料。     

植物功能性状与外来植物入侵

揭示影响外来植物入侵性的功能性状及其生态机制是入侵植物生态学的核心任务之一。本文综述了植物功能性状与外来植物入侵性的研究进展, 通过分析植物功能性状对外来植物入侵的贡献以及外来植物的不同入侵阶段对其功能性状的需求, 探讨植物功能性状与外来植物入侵的相关性及其入侵机理。迄今研究较多的影响外来植物入侵性的功能性状主要包括形态性状、生长性状、生理性状、繁殖性状、种子性状、克隆性状、表型可塑性和遗传变异等。这些功能性状对外来植物入侵的贡献随着入侵阶段的不同而变化。在传播到达阶段, 种子性状对入侵具有重要影响; 在定居建群阶段, 与植物抗逆性和适应性相关的生理性状和繁殖性状发挥主要作用; 在扩散入侵阶段, 克隆性状和影响植物竞争能力的生理性状对植物成功入侵具有重要贡献。由于植物入侵性是其功能性状和环境因素互作的结果, 且功能性状的作用随环境因素和入侵阶段不同而异, 因此, 结合外来植物入侵阶段, 并考虑功能性状与环境因子的互作, 是入侵生物学中植物功能性状研究的发展趋势。     

The role of mutants in the search for the photoreceptor for phototropism in higher plants

Early attempts to identify the chromophore of the photoreceptor for phototropism are reviewed. Carotenoids and flavins were the principal candidates, but studies with grass coleoptiles devoid of carotenoids suggest that at least in these organs carotenoids are most unlikely to play that role. The status of characterization of a gene for a putative photoreceptor protein is also reviewed. As the action spectrum for phototropism resembles the absorption spectrum of a flavoprotein, flavoproteins are attractive candidates at present, especially since the CRY1 photoreceptor in Arabidopsis thaliana that mediates blue light-dependent hypocotyl growth suppression has flavin adenine dinucleotide as one of its two chromophores. As the second chromophore appears to be pterin, pterins should not be ruled out as candidate chromophores for the photoreceptor for phototropism.     

The relationship between rhizosphere nitrification and nitrogen-use efficiency in rice plants

Two different rice cultivars, Yangdao 6 [Indica rice cultivar with high nitrogen-use efficiency (NUE)] and Nongken 57 (Japonica rice cultivar with low NUE) were used to study the relationship between NUE and nitrification activity in the rice seedling rhizosphere soil using a rhizobox with three compartments, and a soil-slicing method. The roots of both rice cultivars developed aerenchyma tissue [expressed as percentage porosity of root (POR)], but Yangdao 6 showed better development than Nongken 57. This root morphology change results in more radial oxygen loss (ROL) into the rhizosphere. Leaf glutamine synthetase activity (GSA) and nitrate (NO3-) reductase activity (NRA) of Yangdao 6 were significantly higher than those of Nongken 57, while there was no significant difference in root NRA between the cultivars. The nitrification activities were maximal in rhizosphere soil, followed by those in the bulk soil and the root surface for both cultivars. The rhizosphere nitrification activity, NO3- concentration and abundance of ammonia-oxidizing bacteria (AOB) associated with Yangdao 6 were always higher than those of Nongken 57. Therefore, we conclude that the greater N uptake by Yangdao 6 when compared to Nongken 57 can be mainly attributed to the bigger capacity for nitrification in Yangdao 6.     

中国种子植物属的地理成分分布格局及其与气候和地理的关系

基于覆盖了全中国各地理区的204个地区植物区系研究资料和这些地区的841个气象站资料,我们对中国种子植物属的地理成分分布格局及其与气候、经纬度分布的关系进行了研究,并结合这些分布格局探讨了中国植被分带和植物区系分区。结果如下：（1）除世界分布、栽培和入侵成分外,大部分中国种子植物属的地理成分的分布与地理相关密切;（2）热带分布属（泛热带分布、热带亚洲至热带美洲间断分布、旧世界热带分布、热带亚洲至热带大洋洲分布、热带亚洲至热带非洲分布及热带亚洲分布合计）占各地方植物区系的0．84％到94．38％,其最低值出现在中国西北部的新疆和青海地区,最高值出现在中国云南南部和海南;（3）热带分布属在〈北纬30°的地区占优势,除热带亚洲至热带美洲间断分布外,其它热带成分随纬度增加迅速减少;（4）温带分布属（北温带分布、东亚和北美间断分布、旧世界温带分布、温带亚洲分布、地中海区、西亚到中亚分布、中亚分布和东亚分布合计）占各地方植物区系的5．1％至98．83％,其最高值出现在中国西北部的新疆地区,最低值出现在中国云南南部和海南;（5）除东亚和北美间断分布、东亚分布和中国特有分布外,其它温带成分随纬度增加迅速增加;（6）在温带成分中,东亚和北美间断分布及东亚分布属主要出现在中国亚热带到暖温带地区,北温带分布、旧世界温带分布和温带亚洲分布属在中国北部占优势,而地中海区、西亚到中亚分布和中亚分布属则在中国西北部占优势;（7）除世界分布、东亚和北美间断分布、东亚分布和中国特有分布外,所有其他成分都显示了与气候因素（主要是气温和降雨量）密切相关,其中,北温带分布属与年均温和年降雨量最为密切相关。中国种子植物属的地理成分的分布格局与现行的中国植被分带和植物区系分区密切匹配。支持现行的中国植被分带和植物区系分区方案。     

The relationship between nuclear DNA content and leaf strategy in seed plants

BACKGROUND AND AIMS: Species' 2C-values (mass of DNA in G(1) phase 2n nuclei) vary by at least four orders of magnitude among seed plants. The 2C-value has been shown to be co-ordinated with a number of other species traits, and with environmental variables. A prediction that species 2C-values are negatively related to leaf life span (LL) and leaf mass per area (LMA) is tested. These leaf traits are components of a major dimension of ecological variation among plant species. METHODS: Flow cytometry was used to measure the 2C-values for 41 Australian seed plant species, 40 of which were new to the literature. Where possible, LL and LMA data from the global literature were combined with 2C-values from our data set and online C-value databases. KEY RESULTS: Across all species, weak positive relationships were found between 2C-values and both LL and LMA; however, these did not reflect the relationships within either angiosperms or gymnosperms. Across 59 angiosperm species, there were weak negative relationships between 2C-values and both LL (r2 = 0.13, P = 0.005) and LMA (r2 = 0.15, P = 0.002). These relationships were the result of shifts to longer LL and greater LMA in woody compared with herbaceous growth forms, with no relationships present within growth forms. It was not possible to explain a positive relationship between 2C-values and LMA (r2 = 0.30, P = 0.024) across 17 gymnosperm species. The 2C-value was not related to LL or LMA either across species within orders (except for LMA among Pinales), or as radiation divergences in a model phylogeny. CONCLUSIONS: Gymnosperms appear to vary along a spectrum different from angiosperms. Among angiosperms, weak negative cross-species relationships were associated with growth form differences, and traced to a few divergences deep in the model phylogeny. These results suggest that among angiosperms, nuclear DNA content and leaf strategy are unrelated.     

The relationship between genome size and synaptonemal complex length in higher plants

There appears to be only a weak correlation between genome size and the corresponding total length of a complete set of synaptonemal complexes (SCs) based on published evidence for several fungal, plant, and animal species. This result is unexpected, considering the strong positive correlations between genome size (DNA amount) and total chromosome length and volume and between relative lengths of chromosomes and SCs. Because the observed weak correlation was based on limited data, we systematically investigated the relationship between genome size and SC length, using ten higher plant species. Two-dimensional spreads of SCs from primary microsporocytes at pachytene were prepared using a hypotonic bursting technique. The SC spreads were examined either by light or electron microscopy, and the lengths of at least ten complete sets of SCs were measured for each of the ten species. Additionally, the genome size of each species was determined from pollen tetrad protoplasts using flow cytometry. A strong correlation (r = 0.97) between total SC length and genome size was observed for higher plants, indicating a constant amount of DNA is associated with a given length of SC, at least when averaged over the whole genome.     

The relationship between cytokinins and the amount of nitrogen in the wintering organs of herbaceous plants

The dynamics of cytokinin content and the total protein and nonprotein forms of nitrogen in tissues of wintering organs of clary sage Salvia sclarea L. and cinquefoil Potentilla alba L. in abnormally cold (2005–2006 years) and abnormally warm (2006–2007 years) winters in Moscow have been studied. A direct correlation between the content of total cytokinins and the total and protein nitrogen forms in tissues of wintering leaves and buds has been determined. A correlation link between the level of single cytokinins and the protein nitrogen forms has been found.     

Interaction between gravitropism and phototropism in sporangiophores of Phycomyces blakesleeanus

The interaction between gravitropism and phototropism was analyzed for sporangiophores of Phycomyces blakesleeanus. Fluence rate-response curves for phototropism were generated under three different conditions: (a) for stationary sporangiophores, which reached photogravitropic equilibrium; (b) for sporangiophores, which were clinostated head-over during phototropic stimulation; and (c) for sporangiophores, which were subjected to centrifugal accelerations of 2.3g to 8.4g. For blue light (454 nm), clinostating caused an increase of the slope of the fluence rate-response curves and an increase of the maximal bending angles at saturating fluence rates. The absolute threshold remained, however, practically unaffected. In contrast to the results obtained with blue light, no increase of the slope of the fluence rate-response curves was obtained with near-ultraviolet light at 369 nm. Bilateral irradiation with near-ultraviolet or blue light enhanced gravitropism, whereas symmetric gravitropic stimulation caused a partial suppression of phototropism. Gravitropism and phototropism appear to be tightly linked by a tonic feedback loop that allows the respective transduction chains a mutual influence over each other. The use of tropism mutants allowed conclusions to be drawn about the tonic feedback loop with the gravitropic and phototropic transduction chains. The results from clinostating mutants that lack octahedral crystals (implicated as statoliths) showed that these crystals are not involved in the tonic feedback loop. At elevated centrifugal accelerations, the fluence-rate-response curves for photogravitropic equilibrium were displaced to higher fluence rates and the slope decreased. The results indicate that light transduction possesses a logarithmic transducer, whereas gravi-transduction uses a linear one.