共查询到20条相似文献,搜索用时 31 毫秒
1.
K. M. Zhang X. M. Wang J. X. Cui J. O. Ogweno K. Shi Y. H. Zhou J. Q. Yu 《Biologia Plantarum》2011,55(2):361-364
To determine the effects of leaf colour on gas exchange and chlorophyll fluorescence, two genotypes of Begonia semperflorens with green leaves or red leaves were compared. The red leaves showed a high accumulation of anthocyanins and high absorbance
at 282 and 537 nm while the green leaves exhibited a higher net photosynthetic rate and lower thermal dissipation of light
energy. It seems likely that anthocyanins in the vacuoles restricted the absorption of green light to the chloroplasts, leading
to a decrease in the efficiency of excitation capture by open PS 2 centres, photochemical quenching and CO2 assimilation. 相似文献
2.
The impact of powdery (Uncinula necator) and downy mildew (Plasmopara viticola) on grapevine leaf gas exchange was analysed. Gas exchange measurements (assimilation A, transpiration E, stomatal conductance gs, intercellular concentration of CO2Ci) were made on three different leaf materials: (i) healthy tissue of diseased leaves, (ii) infected tissue of diseased leaves, (iii) healthy tissue of healthy leaves (control treatment). Using the same source of leaf tissue, photosynthetic pigment concentration (chlorophyll a, b) and fluorescence levels (minimal fluorescence F0, maximal fluorescence Fm and the optimal quantum yield [Fm ? F0]/Fm) were determined to explain the mechanism of action of the two diseases on leaf assimilation. The results indicated that powdery and downy mildew reduced the assimilation rates, not only through a reduction in green leaf area (visual lesions), but also through an influence on gas exchange of the remaining green leaf tissues, determining a ‘virtual lesion’. The ratios between virtual and visual lesions were higher in powdery mildewed leaves than in the downy mildewed leaves. The photosynthetic fluorescence level (Fv/Fm) was affected by neither of the two pathogens. The reduction in intercellular concentration of CO2 and photosynthetic pigment may explain the lower assimilation rates in the healthy tissues of powdery and downy mildewed leaves respectively. 相似文献
3.
为了解竹柏(Podocarpus nagi)的光合特性,以3 a生全绿叶和花叶竹柏为材料,测定其光合色素含量和气体交换参数。结果表明,全绿叶竹柏叶片的叶绿素a、叶绿素b、类胡萝卜素、叶绿素a+b、叶绿素a/b和叶绿素a+b/类胡萝卜素均显著高于花叶竹柏;全绿叶竹柏叶片的初始量子效率、最大光合速率和暗呼吸速率均显著高于花叶,而光饱和点和光补偿点均显著低于花叶;全绿叶竹柏叶片的初始羧化效率、光合速率、CO2饱和点和光呼吸速率均高于花叶,而CO2补偿点低于花叶。2种颜色叶片的气孔导度、蒸腾速率和水分利用效率均随着光合有效辐射的增大而增大,且均表现为全绿叶花叶,而胞间CO2浓度则相反,表现为花叶全绿叶。因此,全绿叶竹柏利用弱光的能力强于花叶竹柏,而花叶竹柏利用强光的能力更强,在园林绿化配置中,可根据2种颜色叶片的光合特性合理配置。 相似文献
4.
Zheng-He Lin Li-Song Chen Rong-Bing Chen Fang-Zhou Zhang Huan-Xin Jiang Ning Tang 《BMC plant biology》2009,9(1):43
Background
Although the effects of P deficiency on tea (Camellia sinensis (L.) O. Kuntze) growth, P uptake and utilization as well as leaf gas exchange and Chl a fluorescence have been investigated, very little is known about the effects of P deficiency on photosynthetic electron transport, photosynthetic enzymes and carbohydrates of tea leaves. In this study, own-rooted 10-month-old tea trees were supplied three times weekly for 17 weeks with 500 mL of nutrient solution at a P concentration of 0, 40, 80, 160, 400 or 1000 μM. This objective of this study was to determine how P deficiency affects CO2 assimilation, Rubisco, carbohydrates and photosynthetic electron transport in tea leaves to understand the mechanism by which P deficiency leads to a decrease in CO2 assimilation. 相似文献5.
Inorganic phosphate (Pi)-limited chemostat cultures of the green alga Selenastrum minutum were employed to investigate interactions between Pi assimilation, respiration and photosynthetic processes. Changes in net and gross gas exchange rates indicated that O2 evolution decreases during photosynthetic Pi assimilation. Room temperature and 77K Chi a fluorescence measurements revealed that this photosynthetic suppression is correlated with a transition from state 1 to state 2. Substantial photosynthetic Pi uptake rates occur in the presence of DCMU and KCN. Additionally, the cellular ratio of ATP:NADPH increases following Pi enrichment, suggesting that the ratio of cyclic to linear electron flow is enhanced in response to the high energy requirements of Pi uptake. Net starch degradation was observed during photosynthetic Pi assimilation and the cellular pool size of 3-phosphoglycerate increased; however, gross gas exchange parameters and cellular metabolite pool sizes indicated that mitochondrial respiration plays a smaller role during Pi assimilation in the light than it does in the dark. These observations were used to formulate a model depicting possible interactions between photosynthetic electron flow, photosynthetic and respiratory carbon metabolism and metabolite exchange between the chloroplast, cytosol and mitochondrion during photosynthetic Pi assimilation. 相似文献
6.
The hypothesis that CO2 gas exchange and chlorophyll a fluorescence (ChlaF) of lichens vary according to the light regimes of their original habitat, as observed in vascular plants, was tested by
analysing the photosynthetic performance of 12 populations of seven dorsoventral, foliose lichens collected from open, south-exposed
rocks to densely shaded forests. Light response curves were induced at optimum thallus water content and ChlaF emission curves at the species-specific photon flux at which the quantum yield of CO2 assimilation is the highest and is saturating the photosynthetic process. Photosynthetic pigments were quantified in crude
extracts. The results confirm that the maximum rate of gross photosynthesis is correlated with the chlorophyll content of
lichens, which is influenced by light as well as by nitrogen availability. Like leaves, shade tolerant lichens emit more ChlaF than sun-loving ones, whereas the photosynthetic quantum conversion is higher in the latter. 相似文献
7.
Seasonal relationships between leaf nitrogen content (photosynthetic capacity) and leaf canopy light exposure in peach (Prunus persica) 总被引:4,自引:3,他引:1
Abstract Field gas exchange measurements on intact peach (Prunus persica (L.) Batsch) leaves indicate that leaf nitrogen content (NL) and leaf weight per unit leaf area (Wa) are highly correlated with CO2 assimilation rate (A) and mesophyll conductance (gm). Therefore, NL and Wa were used to study seasonal relationships between leaf carboxylation capacity and natural light exposure in tree canopies. From mid-season onwards, NL and Wa were linearly correlated with light exposure expressed as the amount of time during a clear day that a leaf was exposed to a photosynthetic photon flux density (Q) of ≥ 100 μmol m?2 s?1. The data support the hypothesis that whole-tree photosynthesis is optimized by partitioning of photosynthetic capacity among leaves in deciduous tree canopies with respect to natural light exposure. 相似文献
8.
9.
Summary The scale insect, Toumeyella sp., feeds exclusively on the subtropical hammock tree lignum vitae (Guaiacum sanctum L.). The combined effects of scale herbivory and shading on leaf gas exchange characteristics and growth of lignum vitae trees were studied using a factorial design. Trees grown in full sun or in 75% shade were manually infested with scale or left noninfested. Beginning 4 weeks after infestation, net CO2 assimilation, stomatal conductance, transpiration, internal partial pressure of CO2, and water-use efficiency were determined on single-leaves at 4-week intervals for trees in each treatment. At the end of the experiment, net CO2 assimilation was determined for whole plants. Total leaf area, leaf, stem, and root dry weights, and leaf chlorophyll and nitrogen concentrations were also determined. Scale infested trees generally had lower net CO2 assimilation, stomatal conductance, and transpiration rates as well as less leaf area, and root, stem, and leaf dry weights than noninfested trees. Twenty four weeks after the shade treatment was imposed, sun-grown trees had approximately twice the leaf area of shade-grown trees. Shade-grown trees compensated for the reduced leaf area by increasing their photosynthetic efficiency. This resulted in no difference in light saturated net CO2 assimilation on a whole plant basis between sun-grown and shade-grown trees. Chlorophyll and nitrogen concentrations per unit leaf area were greater in leaves of shade-grown trees than in leaves of sun-grown trees. Shading and herbivory by Toumeyella sp. each resulted in decreased growth of Guaiacum sanctum. Scale insect herbivory did not result in greater detrimental effects on leaf gas exchange characteristics for shade-grown than for sun-grown trees. Herbivory by Toumeyella resulted in a greater decrease in tree growth for sun-grown than for shade-grown trees. 相似文献
10.
Analyses of CO2 exchange and chlorophyll fluorescence were carried out to
assess photosynthetic performance during senescence of maize leaves.
Senescent leaves displayed a significant decrease in CO2 assimilatory
capacity accompanied by a decrease in stomatal conductance and an increase
in intercellular CO2 concentration. The analyses of fluorescence quenching
under steady-state photosynthesis showed that senescence resulted in an
increase in non-photochemical quenching and a decrease in photo-chemical
quenching. It also resulted in a decrease in the efficiency of excitation
energy capture by open PSII reaction centres and the quantum yield of PSII
electron transport, but had very little effect on the maximal efficiency of
PSII photochemistry. The results determined from the fast fluorescence
induction kinetics indicated an increase in the proportion of
QB-non-reducing PSII reaction centres and a decrease in the rate of QA
reduction in senescent leaves. Theoretical analyses of fluorescence
parameters under steady-state photosynthesis suggest that the increase in
the non-photochemical quenching was due to an increase in the rate constant
to thermal dissipation of excitation energy by PSII and that the decrease
in the quantum yield of PSII electron transport was associated with a
decrease in the rate constant of PSII photochemistry. Based on these
results, it is suggested that the decrease in the quantum yield of PSII
electron transport in senescent leaves was down-regulated by an increase in
the proportion of QB-non-reducing PSII reaction centres and in the
non-photochemical quenching. The photosynthetic electron transport would
thus match the decreased demand for ATP and NADPH in carbon assimilation
which was inhibited significantly in senescent leaves.Key words:
Chlorophyll fluorescence, gas exchange, maize (Zea
mays L.), photochemical and non-photochemical quenching,
photosystem II photochemistry.
相似文献
11.
Summary Routine field determination of the parameters characterizing the activity of the photosynthetic apparatus is often difficult when attached branches of tall trees have to be used for gas exchange measurement. If severed twigs could be used, determining these parameters would be greatly facilitated. Because stomatal conductance changes when twigs or leaves are detached, CO2 assimilation is usually altered. Thus, measurements made at ambient CO2 concentration fail to accurately assess the activity of the photosynthetic apparatus because photosynthetic rates greatly depend on the supply of carbon dioxide. However, when photosynthetic carboxylation reactions are saturated by increased CO2 partial pressure in the mesophyll, CO2 assimilation rates no longer depend on instantaneous stomatal conductance, as shown by gas exchange measurements of spruce (Picea abies) twigs prior to and following detachment. Because net photosynthesis following detachment at saturating CO2 remains constant for a minimum of 15 min, photosynthetic measurements of severed twigs may be reliable. This length of time is sufficient for detaching and recutting the twig, assembling a portable minicuvette system, re-establishing steady-state conditions with the gas analyser system, and reading the data over a reasonable period of time. The method described measures the maximal photosynthetic CO2 assimilation of spruce needles of a single age-class from detached spruce twigs under the following conditions: saturating light, saturating external CO2-partial pressure, standardized temperature and air humidity in the field. The method is applicable as a routine procedure to characterize the status of the photosynthetic apparatus of spruce trees that may be damaged in the process of forest decline. 相似文献
12.
J. P. Maroco M. S. B. Ku & G. E. Edwards & G. E. Edwards 《Plant, cell & environment》2000,23(1):115-121
The combined effects of O2 on net rates of photosynthesis, photosystem II activity, steady‐state pool size of key metabolites of photosynthetic metabolism in the C4 pathway, C3 pathway and C2 photorespiratory cycle and on growth were evaluated in the C4 species Amaranthus edulis and the C3 species Flaveria pringlei. Increasing O2 reduced net CO2 assimilation in F. pringlei due to an increased flux of C through the photorespiratory pathway. However, in A. edulis increasing O2 up to 5–10% stimulated photosynthesis. Analysis of the pool size of key metabolites in A. edulis suggests that while there is some O2 dependent photorespiration, O2 is required for maximizing C4 cycle activity to concentrate CO2 in bundle sheath cells. Therefore, the response of net photosynthesis to O2 in C4 plants may result from the balance of these two opposing effects. Under 21 versus 5% O2, growth of A. edulis was stimulated about 30% whereas that of F. pringlei was inhibited about 40%. 相似文献
13.
Stem and leaf gas exchange and their responses to fire in a north Australian tropical savanna 总被引:3,自引:0,他引:3
We measured stem CO2 efflux and leaf gas exchange in a tropical savanna ecosystem in northern Australia, and assessed the impact of fire on these processes. Gas exchange of mature leaves that flushed after a fire showed only slight differences from that of mature leaves on unburned trees. Expanding leaves typically showed net losses of CO2 to the atmosphere in both burned and unburned trees, even under saturating irradiance. Fire caused stem CO2 efflux to decline in overstory trees, when measured 8 weeks post-fire. This decline was thought to have resulted from reduced availability of C substrate for respiration, due to reduced canopy photosynthesis caused by leaf scorching, and to priority allocation of fixed C towards reconstruction of a new canopy. At the ecosystem scale, we estimated the annual above-ground woody-tissue CO2 efflux to be 275 g C m(-2) ground area year(-1) in a non-fire year, or approximately 13% of the annual gross primary production. We contrasted the canopy physiology of two co-dominant overstory tree species, one of which has a smooth bark on its branches capable of photosynthetic re-fixation (Eucalyptus miniata), and the other of which has a thick, rough bark incapable of re-fixation (Eucalyptus tetrodonta). Eucalyptus miniata supported a larger branch sapwood cross-sectional area in the crown per unit subtending leaf area, and had higher leaf stomatal conductance and photosynthesis than E. tetrodonta. Re-fixation by photosynthetic bark reduces the C cost of delivering water to evaporative sites in leaves, because it reduces the net C cost of constructing and maintaining sapwood. We suggest that re-fixation allowed leaves of E. miniata to photosynthesize at higher rates than those of E. tetrodonta, while the two invested similar amounts of C in the maintenance of branch sapwood. 相似文献
14.
Various aspects of the biochemistry of photosynthetic carbon assimilation in C3 plants are integrated into a form compatible with studies of gas exchange in leaves. These aspects include the kinetic properties of ribulose bisphosphate carboxylase-oxygenase; the requirements of the photosynthetic carbon reduction and photorespiratory carbon oxidation cycles for reduced pyridine nucleotides; the dependence of electron transport on photon flux and the presence of a temperature dependent upper limit to electron transport. The measurements of gas exchange with which the model outputs may be compared include those of the temperature and partial pressure of CO2(p(CO2)) dependencies of quantum yield, the variation of compensation point with temperature and partial pressure of O2(p(O2)), the dependence of net CO2 assimilation rate on p(CO2) and irradiance, and the influence of p(CO2) and irradiance on the temperature dependence of assimilation rate.Abbreviations RuP2
ribulose bisphosphate
- PGA
3-phosphoglycerate
- C=p(CO2)
partial pressure of CO2
- O=p(O2)
partial pressure of O2
- PCR
photosynthetic carbon reduction
- PCO
photorespiratory carbon oxidation 相似文献
15.
Y. Bashan T. Khaosaad B. G. Salazar J. A. Ocampo A. Wiemken F. Oehl Horst Vierheilig 《Trees - Structure and Function》2007,21(3):329-335
The mycorrhizal association with the boojum tree, Fouquieria columnaris (=Idria columnaris), was studied. This unusual tree is almost exclusively endemic to granite and volcanic soils in highly arid areas of the
Baja California Peninsula of Mexico. Soil and root samples from ten sites, covering the extent of geographic distribution
of the tree on the peninsula, were analyzed. The roots of the boojum tree contained all structures of an arbuscular mycorrhizal
(AM) association. Morphologically different species, 23 in number, were identified in close vicinity to the boojum tree indicating
that F. columnaris is associated with a high number of AM species of several AM genera and families. 相似文献
16.
Coupled response of stomatal and mesophyll conductance to light enhances photosynthesis of shade leaves under sunflecks
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Courtney E. Campany Mark G. Tjoelker Susanne von Caemmerer Remko A. Duursma 《Plant, cell & environment》2016,39(12):2762-2773
Light gradients within tree canopies play a major role in the distribution of plant resources that define the photosynthetic capacity of sun and shade leaves. However, the biochemical and diffusional constraints on gas exchange in sun and shade leaves in response to light remain poorly quantified, but critical for predicting canopy carbon and water exchange. To investigate the CO2 diffusion pathway of sun and shade leaves, leaf gas exchange was coupled with concurrent measurements of carbon isotope discrimination to measure net leaf photosynthesis (An), stomatal conductance (gs) and mesophyll conductance (gm) in Eucalyptus tereticornis trees grown in climate controlled whole‐tree chambers. Compared to sun leaves, shade leaves had lower An, gm, leaf nitrogen and photosynthetic capacity (Amax) but gs was similar. When light intensity was temporarily increased for shade leaves to match that of sun leaves, both gs and gm increased, and An increased to values greater than sun leaves. We show that dynamic physiological responses of shade leaves to altered light environments have implications for up‐scaling leaf level measurements and predicting whole canopy carbon gain. Despite exhibiting reduced photosynthetic capacity, the rapid up‐regulation of gm with increased light enables shade leaves to respond quickly to sunflecks. 相似文献
17.
18.
The photosynthetic rate of seed wings developed from sepals was compared with the leaf photosynthetic rate in nine dipterocarp tree species (Dipterocarpus pachyphyllus, Dryobalanops aromatica, Dryobalanops lanceolata, Shorea beccariana, Shorea ferruginea, Shorea macroptera ssp. bailonii, Shorea macroptera ssp. macropterifolia, Shorea pilosa, and Vatica spp.). The wings showed positive photosynthetic activity, but at much lower rates than in the leaves. The daily CO2 uptake of wings showed slightly negative values in diurnal gas exchange measurements, even in D. aromatica that showed the highest photosynthetic capacity of all nine species. This low photosynthetic rate in the wings may be the result of low nitrogen and chlorophyll contents in the wing compared with leaves. However, the wings had a higher C/N ratio than leaves, and were thicker. Hence, dipterocarp wings have physical strength and defence against herbivores as higher priorities than photosynthetic activity. 相似文献
19.
R. VALENTINI D. EPRON P. DE ANGELIS G. MATTEUCCI E. DREYER 《Plant, cell & environment》1995,18(6):631-640
Diurnal time courses of net CO2 assimilation rates, stomatal conductance and light-driven electron fluxes were measured in situ on attached leaves of 30-year-old Turkey oak trees (Quercus cerris L.) under natural summer conditions in central Italy. Combined measurements of gas exchange and chlorophyll a fluorescence under low O2 concentrations allowed the demonstration of a linear relationship between the photochemical efficiency of PSII (fluorescence measurements) and the apparent quantum yield of gross photosynthesis (gas exchange). This relationship was used under normal O2 to compute total light-driven electron fluxes, and to partition them into fractions used for RuBP carboxylation or RuBP oxygenation. This procedure also yielded an indirect estimate of the rate of photorespiration in vivo. The time courses of light-driven electron flow, net CO2 assimilation and photorespiration paralleled that of photosynthetic photon flux density, with important afternoon deviations as soon as a severe drought stress occurred, whereas photochemical efficiency and maximal fluorescence underwent large but reversible diurnal decreases. The latter observation indicated the occurrence of a large non-photochemical energy dissipation at PSII. We estimated that less than 60% of the total photosynthetic electron flow was used for carbon assimilation at midday, while about 40% was devoted to photorespiration. The rate of carbon loss by photorespiration (R1) reached mean levels of 56% of net assimilation rates. The potential application of this technique to analysis of the relative contributions of thermal de-excitation at PSII and photorespiratory carbon recycling in the protection of photosynthesis against stress effects is discussed. 相似文献
20.
Hiroyuki Muraoka Yanhong Tang Ichiro Terashima Hiroshi Koizumi & Izumi Washitani 《Plant, cell & environment》2000,23(3):235-250
Diurnal changes in photosynthetic gas exchange and chlorophyll fluorescence were measured under full sunlight to reveal diffusional and non‐diffusional limitations to diurnal assimilation in leaves of Arisaema heterophyllum Blume plants grown either in a riparian forest understorey (shade leaves) or in an adjacent deforested open site (sun leaves). Midday depressions of assimilation rate (A) and leaf conductance of water vapour were remarkably deeper in shade leaves than in sun leaves. To evaluate the diffusional (i.e. stomatal and leaf internal) limitation to assimilation, we used an index [1–A/A350], in which A350 is A at a chloroplast CO2 concentration of 350 μ mol mol ? 1. A350 was estimated from the electron transport rate (JT), determined fluorometrically, and the specificity factor of Rubisco (S), determined by gas exchange techniques. In sun leaves under saturating light, the index obtained after the ‘peak’ of diurnal assimilation was 70% greater than that obtained before the ‘peak’, but in shade leaves, it was only 20% greater. The photochemical efficiency of photosystem II ( Δ F/Fm ′ ) and thus JT was considerably lower in shade leaves than in sun leaves, especially after the ‘peak’. In shade leaves but not in sun leaves, A at a photosynthetically active photon flux density (PPFD) > 500 μ mol m ? 2 s ? 1 depended positively on JT throughout the day. Electron flows used by the carboxylation and oxygenation (JO) of RuBP were estimated from A and JT. In sun leaves, the JO/JT ratio was significantly higher after the ‘peak’, but little difference was found in shade leaves. Photorespiratory CO2 efflux in the absence of atmospheric CO2 was about three times higher in sun leaves than in shade leaves. We attribute the midday depression of assimilation in sun leaves to the increased rate of photorespiration caused by stomatal closure, and that in shade leaves to severe photoinhibition. Thus, for sun leaves, increased capacities for photorespiration and non‐photochemical quenching are essential to avoid photoinhibitory damage and to tolerate high leaf temperatures and water stress under excess light. The increased Rubisco content in sun leaves, which has been recognized as raising photosynthetic assimilation capacity, also contributes to increase in the capacity for photorespiration. 相似文献