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The size and de-epoxidation state of the xanthophyll cycle pool was measured in cultures of Nitzschia palea grown at six fluence rates in continuous light or with a 12 h photoperiod. In both series the size of the pool increased with increasing irradiance. The de-epoxidized form, diatoxanthin, was only present at fluence rates saturating for growth. The portion of diadinoxanthin, which was not readily de-epoxidized in saturating light, was constant and not related to the size of the pool. In the culture grown in a light-dark cycle at 300 μmol photons m-2 s-1 (PAR) increasing de-epoxidation took place in the latter half of the photoperiod, when the rate of photosynthesis was decreasing. A rapid, spectrophotometric method for measuring the extent of de-epoxidation of the xanthophyll cycle pool in a culture of diatoms is described. Upon addition of a small volume of hydrochloric acid to an extract of pigments in 90% acetone, the absorbance at 480 nm is reduced. The size of the reduction is a measure of the state of the xanthophyll cycle pool, since the absorbance of diatoxanthin is reduced by 5%, but the absorbance of diadinoxanthin by 87% due to an epoxide-furanoid rearrangement, which causes the absorption spectrum to be shifted by ca 20 nm towards shorter wavelengths.  相似文献   
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葡萄叶片光合速率与量子效率日变化的研究及利用   总被引:24,自引:0,他引:24  
  相似文献   
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丁俊祥  邹杰  唐立松  刘卫国 《生态学报》2015,35(16):5316-5323
对于田地区3种不同生境(沼泽、盐化沙丘过渡带和沙丘顶)芦苇的生长环境特征、光合特性、渗透调节及抗氧化系统的特征进行研究。结果表明:芦苇叶片的Pn日变化在沼泽生境呈单峰曲线,在盐化沙丘过渡带和沙丘顶部均为双峰曲线,光合"午休"现象明显,气孔导度降低是其主要原因。脯氨酸和可溶性糖含量随根区土壤水分减少和盐分加剧增加显著,其中可溶性糖含量变化剧烈,对抵御干旱和盐渍化危害的贡献较大。芦苇叶片超氧化物歧化酶(SOD)和过氧化氢酶(CAT)活性随干旱及盐分加剧增加显著,两者对水分亏缺的响应较盐分敏感,且可有效缓解沙丘生境由于缺水所造成的氧化损伤,使丙二醛(MDA)含量维持在相对较低水平。过氧化物酶(POD)活性在沙丘和盐渍化生境内都比较高,对抵抗盐渍化和干旱起着同样重要的作用。  相似文献   
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Tropical forest responses to climatic variability have important consequences for global carbon cycling, but are poorly understood. As empirical, correlative studies cannot disentangle the interactive effects of climatic variables on tree growth, we used a tree growth model (IBTREE) to unravel the climate effects on different physiological pathways and in turn on stem growth variation. We parameterized the model for canopy trees of Toona ciliata (Meliaceae) from a Thai monsoon forest and compared predicted and measured variation from a tree‐ring study over a 30‐year period. We used historical climatic variation of minimum and maximum day temperature, precipitation and carbon dioxide (CO2) in different combinations to estimate the contribution of each climate factor in explaining the inter‐annual variation in stem growth. Running the model with only variation in maximum temperature and rainfall yielded stem growth patterns that explained almost 70% of the observed inter‐annual variation in stem growth. Our results show that maximum temperature had a strong negative effect on the stem growth by increasing respiration, reducing stomatal conductance and thus mitigating a higher transpiration demand, and – to a lesser extent – by directly reducing photosynthesis. Although stem growth was rather weakly sensitive to rain, stem growth variation responded strongly and positively to rainfall variation owing to the strong inter‐annual fluctuations in rainfall. Minimum temperature and atmospheric CO2 concentration did not significantly contribute to explaining the inter‐annual variation in stem growth. Our innovative approach – combining a simulation model with historical data on tree‐ring growth and climate – allowed disentangling the effects of strongly correlated climate variables on growth through different physiological pathways. Similar studies on different species and in different forest types are needed to further improve our understanding of the sensitivity of tropical tree growth to climatic variability and change.  相似文献   
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渍水对冬小麦生长的危害及其生理效应   总被引:7,自引:0,他引:7  
小麦受渍后叶片的光合和蒸腾速率迅速下降,而后则显微弱的回升趋势。渍害不仅削弱小麦光合产物的积累,并且改变光合产物在地上部分和根系中的分配比例;植株根/冠比下降,而黄叶的发展与根/冠比的变化呈显著负相关;渍害改变小麦的发育进程,尤其是后期渍害明显促使小麦早衰。认为清水使叶片光合速率降低、光合有效面积损失和衰老加速,从而危害小麦的生长。  相似文献   
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Effect of fruiting and drought or flooding on carbon balance of apple trees   总被引:4,自引:0,他引:4  
The response of fruiting or deblossomed trees to water stress such as drought or flooding was investigated in six semi open-top cuvettes each containing one apple (Malus domestica Borkh. cv. Golden Delicious) tree. Xylem water potentials of leaves dropped from -1.2 to -4.1 MPa within 7 d of drought, the effect being enhanced by fruiting. Apple trees without fruits showed smaller reductions in net photosynthetic rate (P N ) and dark respiration rate (R D ) after 2 d of drought and hence more positive carbon balances relative to fruiting trees. Flooding for 4 d had a more pronounced effect on P N than on transpiration, resulting in a reduced water use efficiency (WUE). This reduction in WUE was greater in the non-fruiting trees. Flooding reduced P N of the whole apple canopies irrespective of fruiting; aple trees without fruits increased R D resulting in a less positive carbon balance relative to fruiting trees. Fruiting increased the sensitivity to drought of apple trees (R D and P N ), but decreased their sensitivity to flooding (R D and WUE), suggesting different adaptation mechanisms for the two forms of water stress. This revised version was published online in August 2006 with corrections to the Cover Date.  相似文献   
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Chlorophyll is synthesized from activated glutamate in the tetrapyrrole biosynthesis pathway through at least 20 different enzymatic reactions. Among these, the MgProto monomethylester (MgProtoME) cyclase catalyzes the formation of a fifth isocyclic ring to tetrapyrroles to form protochlorophyllide. The enzyme consists of two proteins. The CHL27 protein is proposed to be the catalytic component, while LCAA/YCF54 likely acts as a scaffolding factor. In comparison to other reactions of chlorophyll biosynthesis, this enzymatic step lacks clear elucidation and it is hardly understood, how electrons are delivered for the NADPH‐dependent cyclization reaction. The present study intends to elucidate more precisely the role of LCAA/YCF54. Transgenic Arabidopsis lines with inactivated and overexpressed YCF54 reveal the mutual stability of YCF54 and CHL27. Among the YCF54‐interacting proteins, the plastidal ferredoxin‐NADPH reductase (FNR) was identified. We showed in N. tabacum and A. thaliana that a deficit of FNR1 or YCF54 caused MgProtoME accumulation, the substrate of the cyclase, and destabilization of the cyclase subunits. It is proposed that FNR serves as a potential donor for electrons required in the cyclase reaction and connects chlorophyll synthesis with photosynthetic activity.  相似文献   
10.
Aims   总被引:2,自引:0,他引:2       下载免费PDF全文
互花米草(Spartina alterniflora)的入侵给海岸带盐沼生态系统的结构和功能带来了显著影响。互花米草盐沼中的硫含量高于附近的土著芦苇(Phragmites australis)盐沼。为探讨硫元素对互花米草和芦苇竞争过程的可能影响及其作用机制,以50mmol·L–1的Na2SO4和Na2S对互花米草和芦苇进行处理,分析处理前后5天内两种植物光合气体交换和叶绿素荧光指标变化的差异,实验另设等Na+浓度的Na Cl处理作为比较。研究发现:Na2S对互花米草和芦苇光合作用影响的差异最大,Na Cl次之,Na2SO4最小。Na2S处理后,互花米草净光合速率(Pn)出现显著上升,芦苇Pn值大幅度下降。互花米草的光饱和点(Isat)上升而芦苇的Isat值无变化。表明Na2S处理对互花米草的光合能力有促进作用,但对芦苇的光合能力有抑制作用。Na Cl处理后互花米草Pn值也出现小幅上升,而芦苇Pn值略有下降。Na2SO4处理对互花米草和芦苇的Pn值均无显著影响。除Na2SO4处理的互花米草外,不同盐处理后的互花米草和芦苇非光化学淬灭(NPQ)均出现上升趋势。研究结果表明互花米草对环境硫胁迫的适应能力显著高于芦苇,暗示盐沼高硫环境尤其是硫化物有助于互花米草相对于芦苇的竞争,也很可能是其形成单一植被的重要原因之一。  相似文献   
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