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1.
Photoinhibition of photosynthesis was investigated in grapevine (Vitis vinifera L.) exposed to 2 or 4h of high irradiance (HI) (1 700–1 800 mol m–2 s–1) leaves under field conditions at different sampling time in a day. The degree of photoinhibition was determined by means of the ratio of variable to maximum chlorophyll fluorescence (Fv/Fm) and photosynthetic electron transport measurements. When the photochemical efficiency of photosystem 2 (PS2), Fv/Fm, markedly declined, F0 increased in both 2 (HI2) and 4 h (HI4) HI leaves sampled at midday. When various photosynthetic activities were followed on isolated thylakoids, HI4 leaves showed significantly higher inhibition of whole chain and PS2 activity than the HI2 leaves sampled at midday. Later, the leaves reached maximum PS2 efficiencies similar to those observed early in the morning during sampling at evening. The artificial exogenous electron donor Mn2+ failed to restore PS2 activity in both variants of leaves, while DPC and NH2OH significantly restored PS2 activity in HI4 midday leaf samples. Quantification of the PS2 reaction centre protein D1 and 33 kDa protein of water splitting complex following midday exposure of leaves showed pronounced differences between HI2 and HI4 leaves. The marked loss of PS2 activity noticed in midday samples was mainly due to the marked loss of D1 protein in HI2, while in HI4 it was mainly 33-kDa protein. 相似文献
2.
M. A. Sobrado 《Photosynthetica》2008,46(2):202-207
In six dominant species of the Amazonian ‘Bana’ vegetation, leaf blade characteristics, pigment composition, and chlorophyll (Chl) fluorescence parameters were measured in young and mature leaves under field conditions. Leaf δ13C was comparable in the six species, which suggested that both expanding and expanded leaves contained organic matter fixed under similar intercellular and ambient CO2 concentration (C i/C a). High leaf C/N and negative δ15N values found in this habitat were consistent with the extreme soil N-deficiency. Analysis of Chl and carotenoids showed that expanding leaves had an incomplete development of photosynthetic antenna when compared to adult leaves. Dynamic inactivation of photosystem 2 (PS2) at midday was observed at both leaf ages as Fv/Fm decreased compared to predawn values. Adult leaves reached overnight Fv/Fm ratios typical of healthy leaves. Overnight recovery of Fv/Fm in expanding leaves was incomplete. F0 remained unchanged from midday to predawn and Fv tended to increase from midday to predawn. The recovery from midday depression observed in adult leaves suggested an acclimatory down-regulation associated with photo-protection and non-damage of PS2. 相似文献
3.
4.
The content of cytokinins (CKs), the plant inhibitors of the final phase of plant development, senescence, is effectively
controlled by irreversible degradation catalysed by cytokinin oxidase/dehydrogenase (CKX). In transgenic tobacco, denoted
as AtCKX, with over-expressed CKX causing lowered CK content, we investigated changes in the time courses of chlorophyll (Chl)
and xanthophyll (violaxanthin, antheraxanthin, zeaxanthin, neoxanthin, and lutein) contents. We also determined parameters
of slow Chl fluorescence kinetics such as minimum Chl fluorescence yield in the darkadapted state F0, maximum quantum yield of PS2 photochemistry (Fv/Fm), maximum ratio of quantum yields of photochemical and concurrent non-photochemical processes in photosystem 2 (PS2), Fv/F0, non-photochemical quenching (NPQ), and effective quantum yield of photochemical energy conversion in PS2 (Φ2). We used three different developmental leaf stages, old, mature, and young, and compared this with time courses of these
characteristics in leaves with natural CK levels. The parameters Fv/Fm, Fv/F0, and Φ2 were unchanged during ageing in AtCKX plants in contrast to control ones where a significant decrease in old leaves was found.
In control plants F0 increased during ageing, but in the oldest leaf a considerable decrease was observed. This could indicate progressive damage
to PS2 reaction centres and then detachment and rapid degradation of Chl. This is in agreement with time course of Chl content.
NPQ decreased with age and was similar in both plant types. We observed a decline of xanthophyll contents in the oldest leaves
in both plant types, but the contents were enhanced in AtCKX compared to control plants, especially of neoxanthin. The higher
xanthophyll contents in the transgenic plants contribute to a better photoprotection and the fluorescence parameters indicated
that photosynthetic apparatus was in better condition compared to control and it consequently postponed the onset of leaf
senescence. 相似文献
5.
Changes in Chlorophyll Fluorescence in Maize Plants with Imposed Rapid Dehydration at Different Leaf Ages 总被引:2,自引:0,他引:2
Z. Z. Xu G. S. Zhou Y. L. Wang G. X. Han Y. J. Li 《Journal of Plant Growth Regulation》2008,27(1):83-92
A comparison of the effects of a rapidly imposed water deficit with different leaf ages on chlorophyll a fluorescence and gas exchange was performed in maize (Zea mays L.) plants. The relationships between photosynthesis and leaf relative turgidity (RT) and ion leakage were further investigated.
Leaf dehydration substantially decreased net photosynthetic rate (A) and stomatal conductance (G
s), particularly for older leaves. With dehydration time, F
v
/F
m maintained a relatively stable level for youngest leaves but significantly decreased for the older leaves. The electron transport
rate (ETR) sharply decreased with intensifying dehydration and remained at lower levels during continuous dehydration. The
photochemical quenching of variable chlorophyll fluorescence (q
P) gradually decreased with dehydration intensity for the older leaves but increased for the youngest leaves, whereas dehydration
did not affect the nonphotochemical chlorophyll fluorescence quenching (NPQ) for the youngest leaves but remarkably decreased
it for the older leaves. The leaf RT was significantly and positively correlated with its F
v
/F
m, ETR, and q
P, and the leaf ion leakage was significantly and negatively correlated with F
v
/F
m and NPQ. Our results suggest that the photosynthetic systems of young and old leaves decline at different rates when exposed
to rapid dehydration. 相似文献
6.
The Cause of the Difference in Leaf Net Photosynthetic Rate between Two Soybean Cultivars 总被引:2,自引:0,他引:2
To explore the cause of difference in photosynthetic performance between different cultivars of crops, leaf net photosynt rate (P
N) and photosystem 2 (PS2) photochemical efficiency (Fv/Fm), apparent quantum yield of carbon assimilation (c), electron transport rate, photophosphorylation activity, etc. were measured in two soybean cultivars, Heinong 42 and Heinong 37. At pod setting and filling, significant differences in P
N between them were observed. The former with a higher P
N (from 7 to 38 %) had a significantly higher leaf thickness, leaf dry mass/area (LMA), chlorophyll content, soluble protein content, apparent quantum yield of electron transport through PS2 (e), carboxylation efficiency (CE), and ribulose-1,5-bisphosphate carboxylase (RuBPC) activity. The significantly higher P
N of Heinong 42 is mainly due to its higher content and activity of RuBPC. 相似文献
7.
Photosynthetic responses and proline content of mature and young leaves of sunflower plants under water deficit 总被引:4,自引:0,他引:4
In mature and young leaves of sunflower (Helianthus annuus L. cv. Catissol-01) plants grown in the greenhouse, photosynthetic rate, stomatal conductance, and transpiration rate declined
during water stress independently of leaf age and recovered after 24-h rehydration. The intercellular CO2 concentration, chlorophyll (Chl) content, and photochemical activity were not affected by water stress. However, non-photochemical
quenching increased in mature stressed leaves. Rehydration recovered the levels of non-photochemical quenching and increased
the Fv/Fm in young leaves. Drought did not alter the total Chl content. However, the accumulation of proline under drought was dependent
on leaf age: higher content of proline was found in young leaves. After 24 h of rehydration the content of proline returned
to the same contents as in control plants. 相似文献
8.
Photoinhibition of photosynthesis was investigated in Vitis berlandieri and Vitis rupestris leaves under field conditions at different sampling time in a day. The degree of photoinhibition was determined by means of the ratio of variable to maximum chlorophyll fluorescence (Fv/Fm) and photosynthetic electron transport measurements. When the photochemical efficiency of PS2, Fv/Fm, markedly declined, F0 increased significantly in leaves of V. berlandieri, while F0 did not increase in V. rupestris leaves. Isolated thylakoids of leaves of V. berlandieri showed significant inhibition of whole chain and PS2 activities at midday. A smaller inhibition was observed for V. rupestris. Later, the leaves reached maximum PS2 efficiencies similar to those observed early in the morning during sampling at evening. The artificial exogenous electron donor Mn2+ failed to restore PS2 activity in both species, while DPC and NH2OH significantly restored PS2 activity in V. rupestris midday leaf samples. Quantification of the PS2 reaction centre protein D1 and 33 kDa protein of water splitting complex following midday exposure of leaves showed pronounced differences between V. berlandieri and V. rupestris leaves. The marked loss of PS2 activity noticed in midday samples was mainly due to the marked loss of D1 protein in V. berlandieri while in V. rupestris it was the 33 kDa protein. 相似文献
9.
Gas exchange, photochemical efficiency, and leaf water potential (l) of Salix matsudana (non-indigenous species), S. microstachya and S. gordejevii (indigenous species) were studied in Hunshandak Sandland, China. l of all the three species decreased from 06:00 to 12:00, and increased afterwards. S. matsudana showed higher values of l than others. Net photosynthetic rate (P
N) and stomatal conductance (g
s) of S. matsudana were the lowest among all, with the maximum P
N at 10:00 being 75% of that of S. gordejevii. Compared with the indigenous species, the non-indigenous S. matsudana had also lower transpiration rate (E) and water use efficiency (WUE). The values of Fv/Fm in all the species were lower from 06:00 to 14:00 than those after 14:00, indicating an obvious depression in photochemical efficiency of photosystem 2 in both non-indigenous and native species. However, it was much more depressed in S. matsudana, the non-indigenous tree. P
N was positively correlated to g
s and negatively related to l. The relationship between g
s and vapour pressure difference (VPD) was exponential, while negative linear correlation was found between g
s and l. 相似文献
10.
Adult trees of Quercus petraea were submitted to controlled water shortage in a natural stand near Nancy, France. Diurnal course of net CO2 assimilation rate (A) was measured in situ together with chlorophyll a fluorescence determined on dark adapted leaves. In 1990, trees experienced a strong water stress, with predawn and midday leaf water potentials below –2·0 and –3·0 MPa, respectively. Diurnal course of A of well-watered trees exhibited sometimes important midday decreases in A related to high temperature and vapour pressure deficit. Decreases in initial (Fo) and maximal (Fm) fluorescence and sometimes in photochemical efficiency of photosystem II (Fv/Fm) were observed and probably revealed the onset of mechanisms for thermal de-excitation. These mechanisms were shown to be sensitive to dithiothreitol. All these effects were reversible and vanished almost completely overnight. Therefore, they may be considered as protective mechanisms adjusting activity of photosystem II to the electron requirement for photosynthesis. Water stress amplified these reactions: A was strongly decreased, showing important midday depression; diurnal reductions in Fm and Fv/Fm were enhanced. The same trends were observed during summer 1991, despite a less marked drought. These protective mechanisms seemed very effective, as no photoinhibitory damage to PS II could be detected in either water stressed or control trees. 相似文献
11.
CO2 assimilation, xanthophyll cycle pigments and PSII efficiency in pumpkin plants as affected by ozone fumigation 总被引:2,自引:0,他引:2
Stefania Ciompi Antonella Castagna Annamaria Ranieri Cristina Nali Giacomo Lorenzini Gian Franco Soldatini 《Physiologia plantarum》1997,101(4):881-889
CO2 assimilation, xanthophyll cycle pigments and PSII efficiency were analyzed in two different ages of pumpkin leaves (Cucurbita pepo L. cv. Ambassador) exposed to 150 nmol mol-1 of ozone (5 days, 5 h day-1). Gas-exchange measurements revealed a reduction in CO2 assimilation and stomatal conductance, accompanied by an increase in the intercellular CO2 concentration both in young and in mature leaves as compared to their respective controls. In both leaves, F0 remained unchanged, while Fm and the Fv/Fm ratio decreased after O3 fumigation, indicating that ozone may induce an alteration in the capability of photosystem II (PSII) to reduce the primary acceptor QA. In the mature leaves the photochemical quenching (qp) was significantly lowered by the pollutant, but this was not the case in the young leaves where qp did not change. In both mature and young ozonated pumpkin leaves, the development of non-photochemical quenching caused a decrease in the PSII photochemical rate, as shown by the correlation between Fv/Fm and the de-epoxidation state of dark-adapted leaves. Decreases in the Fv/Fm ratio are generally attributed to damage to the PSII reaction centre, apart from the down-regulation of the capacity of PSII electron transport. While in young ozonated leaves the decrease in the Fv/Fm ratio was not associated with damage to the D1 protein, in mature ozonated pumpkin leaves, the decrease in the Fv/Fm was accompanied by a significant decline in the D1 content. In conclusion, ozone exposure induces alterations in the light reactions of photosynthesis in both young and mature leaves. However, in young leaves the engagement of the xanthophyll cycle appears to counteract ozone effects against the photosynthetic apparatus as demonstrated by the absence of damage to the D1 protein. On the other hand, the loss of D1 protein in mature fumigated leaves suggests that the activation of the xanthophyll cycle is not sufficient to prevent photoinhibition, probably because a physiological state of senescence adds to the oxidative stress. 相似文献
12.
Barbara Demmig-Adams William W. Adams III Klaus Winter Angelika Meyer Ulrich Schreiber João S. Pereira Almuth Krüger Franz-Christian Czygan Otto L. Lange 《Planta》1989,177(3):377-387
During the midday depression of net CO2 exchange in the mediterranean sclerophyllous shrub Arbutus unedo, examined in the field in Portugal during August of 1987, several parameters indicative of photosynthetic competence were strongly and reversibly affected. These were the photochemical efficiency of photosystem (PS) II, measured as the ratio of variable to maximum chlorophyll fluorescence, as well as the photon yield and the capacity of photosynthetic O2 evolution at 10% CO2, of which the apparent photon yield of O2 evolution was most depressed. Furthermore, there was a strong and reversible increase in the content of the carotenoid zeaxanthin in the leaves that occurred at the expense of both violaxanthin and -carotene. Diurnal changes in fluorescence characteristics were interpreted to indicate three concurrent effects on the photochemical system. First, an increase in the rate of radiationless energy dissipation in the antenna chlorophyll, reflected by changes in 77K fluorescence of PSII and PSI as well as in chlorophyll a fluorescence at ambient temperature. Second, a state shift characterized by an increase in the proportion of energy distributed to PSI as reflected by changes in PSI fluorescence. Third, an effect lowering the photon yield of O2 evolution and PSII fluorescence at ambient temperature without affecting PSII fluorescence at 77K which would be expected from a decrease in the activity of the water splitting enzyme system, i.e. a donor side limitation.Abbreviations and symbols ci
concentration of CO2 within the leaf
- Fo
instantaneous fluorescence emission
- FM
maximum fluorescence emission
- Fv
variable fluorescence emission
- PFD
photon flux density (400–700 nm)
- PSI, II
photosystem I, II
- TL
leaf temperature 相似文献
13.
George T. Byrd T. Loboda Clanton C. Black Jr. R. Harold Brown 《Photosynthesis research》1995,44(3):253-260
Onion (Allium cepa L.) plants were examined to determine the photosynthetic role of CO2 that accumulates within their leaf cavities. Leaf cavity CO2 concentrations ranged from 2250 L L–1 near the leaf base to below atmospheric (<350 L L–1) near the leaf tip at midday. There was a daily fluctuation in the leaf cavity CO2 concentrations with minimum values near midday and maximum values at night. Conductance to CO2 from the leaf cavity ranged from 24 to 202 mol m–2 s–1 and was even lower for membranes of bulb scales. The capacity for onion leaves to recycle leaf cavity CO2 was poor, only 0.2 to 2.2% of leaf photosynthesis based either on measured CO2 concentrations and conductance values or as measured directly by 14CO2 labeling experiments. The photosynthetic responses to CO2 and O2 were measured to determine whether onion leaves exhibited a typical C3-type response. A linear increase in CO2 uptake was observed in intact leaves up to 315 L L–1 of external CO2 and, at this external CO2 concentration, uptake was inhibited 35.4±0.9% by 210 mL L–1 O2 compared to 20 mL L–1 O2. Scanning electron micrographs of the leaf cavity wall revealed degenerated tissue covered by a membrane. Onion leaf cavity membranes apparently are highly impermeable to CO2 and greatly restrict the refixation of leaf cavity CO2 by photosynthetic tissue.Abbreviations Ca
external CO2 concentration
- Ci
intercellular CO2 concentration
-
CO2 compensation concentration
- PPFR
photosynthetic photon fluence rate 相似文献
14.
The wettability of leaf surface, commonly represented by contact angle (CA), affects various physiological and
physical processes. The present study aims to better understand the wettability of tea leaves and elucidate its influence on the energy barrier of the droplet condensation process. The CA values of different leaf ages (young,
mature and old) of five famous tea cultivars (Maolu, longjing 43, Huangjinya, Zhongcha 108 and Anji Baicha)
were measured via the sessile drop method, and the micro-morphology of two cultivars leaves (Maolu, Zhongcha
108) was investigated by a 3D super depth-of-field digital microscope. Specifically, two radically distinctive types
of CA trends were observed, one was the decreased firstly and then increased slightly with the increase of leaf age,
while the other stayed constant. The valley depth or maximum height (RZ) of Maolu leaf surface increased with
the leaf age while the RZ of Zhongcha 108 leaf remained unchanged by comparing the microscopic features. The
Maolu mature leaf CA decline attributed to the young leaf was hydrophilic (θ < 90°), and it was considered that
surface structures like folds and pits on old leaf played a crucial role in making CA increased. Small deviation in
CA can lead to significant error in calculation of the contact angle function of energy barrier in phase change. It
will have great significant for simulating and better understanding the formation of frost on tea leaves. 相似文献
15.
Growth rates of seasonal leaf flushes of Valenciaorange [Citrus sinensis (L.) Osbeck] were measured and waterrelations characteristics of young (new) and over-wintered (old)citrus leaves were compared. New flush leaves had lower specificleaf weights and lower midday leaf water potentials than comparablyexposed old leaves. Spring and summer flush new leaves had higherosmotic potentials than old leaves. These differences becamenon-significant as the new leaves matured. During summer conditions,water-stressed new leaves reached zero turgor and stomatal conductancealso began to decrease in them at higher leaf water potentialsthan in old leaves. Old leaves were capable of maintaining openstomata at lower leaf water potentials. Opened flowers and newflush leaves lost more water, on a dry weight basis, than flowerbuds, fruit or mature leaves. The results illustrate differencesin leaf water potential and stomatal conductance which can beattributed to the maintenance of leaf turgor by decreases inleaf osmotic potentials as leaves mature. These changes in citrusleaf water relations are especially important since water stressresulting from high water loss rates of new tissues could reduceflowering and fruit set. Citrus sinensis (L.) Osbeck, orange, Citrus paradisi Macf., grapefruit, growth rate, leaf water relations, osmotic potential, water potential, stomatal conductance 相似文献
16.
M. Dutta V. Arunachalam A. Bandyopadhyay K. Vinod Prabhu 《TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik》1986,71(4):662-666
Summary Seeds of 4 crosses of groundnut (Arachis hypogaea L.), Robut 33-1 x Chico, Robut 33-1 x NC Ac 17090, Robut 33-1 x PI 298115 and MK 374 x GAUG 1, were irradiated with 30 kR. In the F1, some branches of each plant were intermated with other plants at random and others selfed in each cross to produce S2 and F2 seeds. They were evaluated for pod yield, shelling percentage and 100-kernel weight. The frequency of plants superior to F[in1] was much higher in S2 than in F2, which was, in general, true for the values of yield and its components. The S2 and F2 were advanced to third generation by selfing. The families descending from S2 showed clear superiority over those from F2. The reason for such superiority was suggested to be the recombination of genes from the upper and lower ends of the genotypic distribution under intermating. 相似文献
17.
18.
《Environmental and Experimental Botany》2006,55(1-2):87-96
In order to fully understand the adaptive strategies of young leaves in performing photosynthesis under high irradiance, leaf orientation, chloroplast pigments, gas exchange, as well as chlorophyll a fluorescence kinetics were explored in soybean plants. The chlorophyll content and photosynthesis in young leaves were much lower than that in fully expanded leaves. Both young and fully expanded leaves exhibited down-regulation of the maximum quantum yield (FV/FM) at noon in their natural position, no more serious down-regulation being observed in young leaves. However, when restraining leaf movement and vertically exposing the leaves to 1200 μmol m−2 s−1 irradiance, more pronounced down-regulation of FV/FM was observed in young leaves; and the actual photosystem II (PS II) efficiency (ФPSII) drastically decreased with the significant enhancement of non-photochemical quenching (NPQ) and ‘High energy’ quenching (qE) in young leaves. Under irradiance of 1200 μmol m−2 s−1, photorespiration (Pr) in young leaves measured by gas exchange were obviously lower, whereas the ratio of photorespiration/gross photosynthetic rate (Pr/Pg) were higher than that in fully expanded leaves. Compared with fully expanded leaves, young leaves exhibited higher xanthophyll pool and a much higher level of de-epoxidation components when exposure to high irradiance. During leaf development, the petiole angle gradually increased all the way. Especially, the midrib angle decreased with the increasing of irradiance in young leaves; however, no distinct changes were observed in mature leaves. The changes of leaf orientation greatly reduced the irradiance on young leaf surface under natural positions. In this study, we suggested that the co-operation of leaf angle, photorespiration and thermal dissipation depending on xanthophyll cycle could successfully prevent young leaves against high irradiance in field. 相似文献
19.
The carbon-dioxide response of photosynthesis of leaves of Quercus suber, a sclerophyllous species of the European Mediterranean region, was studied as a function of time of day at the end of the summer dry season in the natural habitat. To examine the response experimentally, a standard time course for temperature and humidity, which resembled natural conditions, was imposed on the leaves, and the CO2 pressure external to the leaves on subsequent days was varied. The particular temperature and humidity conditions chosen were those which elicited a strong stomatal closure at midday and the simultaneous depression of net CO2 uptake. Midday depression of CO2 uptake is the result of i) a decrease in CO2-saturated photosynthetic capacity after light saturation is reached in the early morning, ii) a decrease in the initial slope of the CO2 response curve (carboxylation efficiency), and iii) a substantial increase in the CO2 compensation point caused by an increase in leaf temperature and a decrease in humidity. As a consequence of the changes in photosynthesis, the internal leaf CO2 pressure remained essentially constant despite stomatal closure. The effects on capacity, slope, and compensation point were reversed by lowering the temperature and increasing the humidity in the afternoon. Constant internal CO2 may aid in minimizing photoinhibition during stomatal closure at midday. The results are discussed in terms of possible temperature, humidity, and hormonal effects on photosynthesis.Abbreviations and symbols CE
carboxylation efficiency
- NP
net photosynthesis rate
- PAR
photosynthetically active radiation
- Pi
leaf internal CO2 partial pressure
- W
water vapor mole fraction difference between leaf and air
-
T
CO2 compensation pressure
Dedicated to Professor Dr. Hubert Ziegler on the occasion of his 60th birthday 相似文献
20.
Ralph Scheuermann Klaus Biehler Thomas Stuhlfauth Heinrich P. Fock 《Photosynthesis research》1991,27(3):189-197
Gas exchange and fluorescence measurements of attached leaves of water stressed bean, sunflower and maize plants were carried out at two light intensities (250 mol quanta m-2s-1 and 850 mol quanta m-2s-1). Besides the restriction of transpiration and CO2 uptake, the dissipation of excess light energy was clearly reflected in the light and dark reactions of photosynthesis under stress conditions. Bean and maize plants preferentially use non-photochemical quenching for light energy dissipation. In sunflower plants, excess light energy gave rise to photochemical quenching. Autoradiography of leaves after photosynthesis in 14CO2 demonstrated the occurrence of leaf patchiness in sunflower and maize but not in bean. The contribution of CO2 recycling within the leaves to energy dissipation was investigated by studies in 2.5% oxygen to suppress photorespiration. The participation of different energy dissipating mechanisms to quanta comsumption on agriculturally relevant species is discussed.Abbreviations Fo
minimal fluorescence
- Fm
maximal fluorescence
- Fp
peak fluorescence
- g
leaf conductance
- PN
net CO2 uptake
- qN
coefficient of non-photochemical quenching
- qP
coefficient of photochemical quenching 相似文献