浅谈对“探究二氧化碳是否是光合作用的原料”实验的改进

在传统的“探究二氧化碳是否是光合作用的原料”实验的基础上,对实验器材、装置、操作进行了改进,具有装置简单、材料易找,操作简便安全、耗时少,现象直观明显,节约环保、效率高等优点,打造了精致高效的实验课堂.     

“证明绿色植物光合作用释放氧气”实验的装置改进

利用1.25 L的饮料瓶、长颈漏斗、导管、乳胶管及铁夹制作"证明绿色植物光合作用产生氧气"的实验装置。     

“验证绿叶在光下吸收二氧化碳”的实验改进

将水生植物置于含有二氧化碳的溴麝香草酚蓝（BTB）溶液中,使其进行光合作用,通过观察BTB溶液颜色的变化,即能得出“绿叶在光下吸收二氧化碳”的实验结论,简化了实验器材和过程。通过创设一系列支架,降低实验操作难度,帮助学生在自主设计和分析实验的过程中,深入理解实验原理,培养科学思维和创新精神,达成了真实、高效的实验探究效果。     

叶绿素,光和二氧化碳是光合作用必要条件的一组快速实验

大多数高等绿色植物光合作用的主要产物为碳水化合物和氧气。依据绿色植物光合作用放出氧气的现象,设计下述实验来证明叶绿素、光和C（）2是光合作用必要条件,具有比常规实验简便、快速和经济的优点。l实验方法与步骤见．王将适当浇水、盆栽的健壮金心大叶黄杨;或从校园内种植的金心大叶黄杨植株上取下健壮枝条,插于盛有清水的户口瓶中,置于室内,备用。互．2选摘枝条上部较大、光合功能强,且绿色和黄色部分比例适用的较嫩叶1～2片,用剪刀沿叶边缘将锯齿剪去,把绿色和黄色的部分分别剪下。而后,视具体情况尽可能剪裁下较大而形状…     

对“检验光合作用需要二氧化碳”实验的改进

生物学教学的目标是提高学生的生物科学素养,凸显对生物学重要概念的理解和传递。本改进实验简单易行,且实验现象明显,便于学生观察,用时较短,材料廉价易得;将原来的教师演示实验改为学生的自主探究,更能体现课标要求,凸显对重要概念的理解,从而提高学习效率。     

大气二氧化碳浓度升高对光合作用的影响（上）

随着工农业生产的发展和人口的迅速增长,人类对能源和木材等的需求量剧增,这便导致化石燃料（煤、石油和天然气等）的大量消耗和森林的不断砍伐。因此,大气中的ＣＯ２浓度正在持续不断地增加,从工业革命前的２７０μｍｏｌ·ｍｏｌ-１（ｐｐｍ）已上升到了目前的３５０μ?..     

验证光合作用需要CO2实验的改进

验证光合作用需要CO2实验是初中生物学内容的重点,而且为高中生物的教学奠定基础,在整个中学生物学知识中占有十分重要的地位。这个实验按教材提示的做法所需的实验时间较长,整个实验过程无法在课堂上完成,教师往往只好事先做好或让部分学生参与实验过程,大部分学生只能观察到实验结果,     

光合作用底物二氧化碳中氧代谢途径的教学探讨

培养学生的探究意识和探究能力是作为创新人才培养基地的高校义不容辞的责任.本文以光合作用底物二氧化碳中氧代谢途径的教学为例,探讨一下在植物生理教学中如何培养学生的探究意识和能力.     

“光合作用产生氧气”实验改进

<正>人教版初中生物学7年级上第3单元第5章"绿色植物与生物圈中碳——氧平衡"一节,有一个演示实验,证明光合作用产生氧气。教材中的实验是利用金鱼藻、漏斗、试管等收集氧气。实验时需要     

Effect of oxygen concentration on leaf photosynthesis and resistances to carbon dioxide diffusion

Summary Net photosynthesis of tropical legume leaves increased by 44% and that of tropical grass leaves was unaffected when oxygen concentration was reduced from 21 to 0.2%. Stomatal resistance to carbon dioxide diffusion was unaltered in both cases but mesophyll resistance of legume leaves decreased with oxygen concentration. It is proposed that the decrease in mesophyll resistance is accompanied by decreases in excitation and carboxylation resistances.     

An improved method for disruption of microbial cells with pressurized carbon dioxide.

Disruption of microbial cells by pressurized carbon dioxide at both subcritical and supercritical temperatures has been previously investigated. This method differs in principle from other disruption techniques and was found to have potential applications for rupture of a variety of microorganisms. However, it is not as effective for some of the microbial cells, including yeast, of which the cell walls are extremely robust and rigid. This work suggests an alternative operation to improve the disruption rates of cells by repeatedly releasing the applied fluid pressure within the cells in the midst of a disruption process. The improvement is substantial at all the experimental conditions studied.     

An improved dynamic model of photosynthesis for estimation of carbon gain in sunfleck light regimes

A dynamic model of leaf photosynthesis for C₃ plants has been developed for examination of the role of the dynamic properties of the photosynthetic apparatus in regulating CO₂ assimilation in variable light regimes. The model is modified from the Farquhar-von Caemmerer-Berry model by explicitly including metabolite pools and the effects of light activation and deactivation of Calvin cycle enzymes. It is coupled to a dynamic stomatal conductance model, with the assimilation rate at any time being determined by the joint effects of the dynamic biochemical model and the stomatal conductance model on the intercellular CO₂ pressure. When parametrized for each species, the model was shown to exhibit responses to step changes in photon flux density that agreed closely with the observed responses for both the understory plant Alocasia macrorrhiza and the crop plant Glycine max. Comparisons of measured and simulated photosynthesis under simulated light regimes having natural patterns of lightfleck frequencies and durations showed that the simulated total for Alocasia was within ±4% of the measured total assimilation, but that both were 12–50% less than the predictions from a steady–state solution of the model. Agreement was within ±10% for Glycine max, and only small differences were apparent between the dynamic and steady–state predictions. The model may therefore be parametrized for quite different species, and is shown to reflect more accurately the dynamics of photosynthesis than earlier dynamic models.     

Restrictions to carbon dioxide conductance and photosynthesis in spinach leaves recovering from salt stress

Salt accumulation in spinach (Spinacia oleracea L.) leaves first inhibits photosynthesis by decreasing stomatal and mesophyll conductances to CO₂ diffusion and then impairs ribulose-1,5-bisphosphate carboxylase/oxygenase (S. Delfine, A. Alvino, M. Zacchini, F. Loreto [1998] Aust J Plant Physiol 25: 395–402). We measured gas exchange and fluorescence in spinach recovering from salt accumulation. When a 21-d salt accumulation was reversed by 2 weeks of salt-free irrigation (rewatering), stomatal and mesophyll conductances and photosynthesis partially recovered. For the first time, to our knowledge, it is shown that a reduction of mesophyll conductance can be reversed and that this may influence photosynthesis. Photosynthesis and conductances did not recover when salt drainage was restricted and Na content in the leaves was greater than 3% of the dry matter. Incomplete recovery of photosynthesis in rewatered and control leaves may be attributed to an age-related reduction of conductances. Biochemical properties were not affected by the 21-d salt accumulation. However, ribulose-1,5-bisphosphate carboxylase/oxygenase activity and content were reduced by a 36- to 50-d salt accumulation. Photochemical efficiency was reduced only in 50-d salt-stressed leaves because of a decrease in the fraction of open photosystem II centers. A reduction in chlorophyll content and an increase in the chlorophyll a/b ratio were observed in 43- and 50-d salt-stressed leaves. Low chlorophyll affects light absorptance but is unlikely to change light partitioning between photosystems.