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1.
In search for new forestation tree species for future Central European climate conditions, Mediterranean evergreen oak taxa
are investigated for their summer drought- and winter frost-hardiness. Here we report on the winter performance of the photosynthetic
apparatus of Quercus × hispanica Lam. and its evergreen parental species Q. suber L. under extraordinary harsh winter conditions. Both taxa showed a strong decline of photosystem II (PSII) quantum efficiency
(Fv/Fm) with a concomitant increase in the deepoxidation state (DES) of the xanthophyll pigments depending on (severe) frost events
during winter, and these parameters significantly correlated with minimum air temperatures during periods of chronic photoinhibition
at mid-winter, but not at the onset of winter in response to the first frost nights. Fv/Fm and DES correlated with each other in both taxa throughout the winter. 相似文献
2.
Climate change is one of the major issues nowadays, and Mediterranean broadleaf species have been suggested to fill possible future gaps created by climate change in Central European forests. To provide a scientific‐based foundation for such practical strategies, it is important to obtain a general idea about differences and similarities in the physiology of Central European and Mediterranean species. In the present study, we evaluated the onset of leaf senescence of a broad spectrum of oak species under the Central European climate in a common garden experiment. Degradation of the photosynthetic apparatus of evergreen (Quercus ilex, Q. suber), semi‐evergreen (Q. × turneri, Q. × hispanica) and deciduous oaks (Q. robur, Q. cerris, Q. frainetto, Q. pubescens) was monitored as chlorophyll content and analysed chlorophyll fluorescence induction transients. In the deciduous species, a significant decline in chlorophyll content was observed during autumn/winter, with Q. pubescens showing the slowest decline. Analysis of fluorescence induction transients revealed a significant decline in quantum efficiency of the primary photochemistry and reaction centre density and later, a decrease in quantum efficiency of end acceptor reduction. Alterations in fluorescence parameters were compared to the decline in chlorophyll content, which occurred much more slowly than expected from the fluorescence data. The evergreen species showed no decline in chlorophyll content, nor different chlorophyll a fluorescence induction behaviour despite temperature falling below 0 °C. The hybrids showed intermediate behaviour between their parental evergreen and deciduous taxa. 相似文献
3.
Leaf development of Quercus robur (deciduous), Q. ilex (evergreen) and of their hybrid Q. × turneri was assessed under Central European climate conditions. In all three taxa, development of maximum photosynthetic capacity
was slow, although whole chain electron transport, grana development, the xanthophyll cycle and the biochemical capacity for
photosynthesis were already completely present at day 7 after budbreak (DAB 7). In the course of the following 30 days, shifts
in the levels of metabolites of the photosynthetic dark reactions were observed, indicating a change from ribulose bisphosphate
(RubP) regeneration limitation towards RubP consumption limitation of photosynthesis. At the same time, electron transport
rates had strongly increased and the capacity of the light reactions did not seem to limit photosynthesis. Sucrose levels
in the leaves increased strongly, indicating sink limitation of photosynthesis, which might be responsible for the observed
slow development of maximum photosynthetic capacity in all three taxa. 相似文献
4.
Cavender-Bares J 《Photosynthesis research》2007,94(2-3):437-453
Sensitivity to cold and freezing differs between populations within two species of live oaks (Quercus section Virentes Nixon) corresponding to the climates from which they originate. Two populations of Quercus virginiana (originating from North Carolina and north central Florida) and two populations of the sister species, Q. oleoides, (originating from Belize and Costa Rica) were grown under controlled climate regimes simulating tropical and temperate conditions.
Three experiments were conducted in order to test for differentiation in cold and freezing tolerance between the two species
and between the two populations within each species. In the first experiment, divergences in response to cold were tested
for by examining photosystem II (PS II) photosynthetic yield (ΔF/F
m′) and non-photochemical quenching (NPQ) of plants in both growing conditions after short-term exposure to three temperatures
(6, 15 and 30°C) under moderate light (400 μmol m−2 s−1). Without cold acclimation (tropical treatment), the North Carolina population showed the highest photosynthetic yield in
response to chilling temperatures (6°C). Both ecotypes of both species showed maximum ΔF/F
m′ and minimum NPQ at their daytime growth temperatures (30°C and 15°C for the tropical and temperate treatments, respectively).
Under the temperate treatment where plants were allowed to acclimate to cold, the Q. virginiana populations showed greater NPQ under chilling temperatures than Q. oleoides populations, suggesting enhanced mechanisms of photoprotective energy dissipation in the more temperate species. In the second
and third experiments, inter- and intra-specific differentiation in response to freezing was tested for by examining dark-adapted
F
v/F
m before and after overnight freezing cycles. Without cold acclimation, the extent of post-freezing declines in F
v/F
m were dependent on the minimum freezing temperature (0, −2, −5 or −10°C) for both populations in both species. The most marked
declines in F
v/F
m occurred after freezing at −10°C, measured 24 h after freezing. These declines were continuous and irreversible over the
time period. The North Carolina population, however, which represents the northern range limit of Q. virginiana, showed significantly less decline in F
v/F
m than the north central Florida population, which in turn showed a lower decline in Fv/F
m than the two Q. oleoides populations from Belize and Costa Rica. In contrast, after exposure to three months of chilling temperatures (temperate treatment),
the two Q. virginiana populations showed no decline in F
v/F
m after freezing at −10°C, while the two Q. oleoides populations showed declines in F
v/F
m reaching 0.2 and 0.1 for Costa Rica and Belize, respectively. Under warm growth conditions, the two species showed different
F
0 dynamics directly after freezing. The two Q. oleoides populations showed an initial rise in F
0 30 min after freezing, followed by a subsequent decrease, while the Q. virginiana populations showed a continuous decrease in F
0 after freezing. The North Carolina population of Q. virginiana showed a tendency toward deciduousness in response to winter temperatures, dropping 58% of its leaves over the three month
winter period compared to only 6% in the tropical treatment. In contrast, the Florida population dropped 38% of its leaves
during winter. The two populations of the tropical Q. oleoides showed no change in leaf drop during the 3-months winter (10% and 12%) relative to their leaf drop over the same timecourse
in the tropical treatment. These results indicate important ecotypic differences in sensitivity to freezing and cold stress
between the two populations of Q. virginiana as well as between the two species, corresponding to their climates of origin. 相似文献
5.
Tropical plants are sensitive to chilling temperatures above zero but it is still unclear whether photosystem I (PSI) or photosystem
II (PSII) of tropical plants is mainly affected by chilling temperatures. In this study, the effect of 4°C associated with
various light densities on PSII and PSI was studied in the potted seedlings of four tropical evergreen tree species grown
in an open field, Khaya ivorensis, Pometia tomentosa, Dalbergia odorifera, and Erythrophleum guineense. After 8 h chilling exposure at the different photosynthetic flux densities of 20, 50, 100, 150 μmol m−2 s−1, the maximum quantum yield of PSII (F
v
/F
m) in all of the four species decreased little, while the quantity of efficient PSI complex (P
m) remained stable in all species except E. guineense. However, after chilling exposure under 250 μmol m−2 s−1 for 24 h, F
v
/F
m was severely photoinhibited in all species whereas P
m was relative stable in all plants except E. guineense. At the chilling temperature of 4°C, electron transport from PSII to PSI was blocked because of excessive reduction of primary
electron acceptor of PSII. F
v
/F
m in these species except E. guineense recovered to ~90% after 8 h recovery in low light, suggesting the dependence of the recovery of PSII on moderate PSI and/or
PSII activity. These results suggest that PSII is more sensitive to chilling temperature under the moderate light than PSI
in tropical trees, and the photoinhibition of PSII and closure of PSII reaction centers can serve to protect PSI. 相似文献
6.
Five-year-old trees of deciduous Quercus robur L., evergreen Q. ilex L., and their semideciduous hybrid, Q. × turneri Willd. (var. pseudoturneri), growing in pots, were subjected to drought stress by withholding water for 18–22 days, until leaf water potentials decreased below ?2 MPa. Gas-exchange rates, oxygen evolution, and modulated chlorophyll (Chl) fluorescence measurements revealed that by strong stomata closure and declining photosynthetic capacity down to approximately 50%, all three taxa responded with strongly reduced photosynthesis rates. In Q. robur, photochemical quenching of the drought-stressed plants was much lower than in nonstressed controls. Dissection of the occurring events in the photosynthetic electron transport chain by fast Chl fluorescence induction analysis with the JIP-test were discussed. 相似文献
7.
We analyzed the physiological response of the Mediterranean evergreen species (Arbutus unedo L., Cistus incanus L., Erica arborea L., Erica multiflora L., Phillyrea latifolia L., Pistacia lentiscus L., Quercus ilex L., and Rosmarinus officinalis L.) to winter low air temperatures. In occasion of two cold events, in February 2005 (T
min = 1.8 °C), and January 2006 (T
min = 3.1 °C and minimum T
air = −0.40 °C during the nights preceding the measurements), R. officinalis, C. incanus, and E. multiflora had the highest net photosynthetic rate (P
N) decrease (73 %, mean value) with respect to the winter P
N maximum, followed by A. unedo (62 %), P. latifolia and P. lentiscus (54 %, mean value), E. arborea (49 %), and Q. ilex (44 %). Among the considered species, Q. ilex was able to maintain P
N near the maximum for 150 min during the day, A. unedo, P. lentiscus, E. arborea, P. latifolia, E. multiflora, and R. officinalis for 60 min, and C. incanus for 30 min. The calculated mean winter daily P
N ranged from 7.9±0.6 (Q. ilex) to 2.8±0.5 (R. officinalis) μmol(CO2) m−2 s−1. During the study period, chlorophyll (Chl) content decreased by 36 % on an average in the two cold events, and the carotenoid
(Car) to Chl ratio increased by 133 % in Q. ilex, having the highest value in January 2006. Principal component analysis underlined the highest cold resistance of Q. ilex by high P
N and high Car/Chl ratio. On the contrary, R. officinalis and C. incanus had the lowest cold resistance by the highest P
N decrease and the lowest Car/Chl (C. incanus). Thus, winter stress could be an additional limitation to Mediterranean evergreen species production, and the capacity of
the species to maintain P
N near 90–100 % during winter is determinant for biomass accumulation. 相似文献
8.
The relationship between net photosynthetic (P
N) and leaf respiration (R) rates of Quercus ilex, Phillyrea latifolia, Myrtus communis, Arbutus unedo, and Cistus incanus was monitored in the period February 2006 to February 2007. The species investigated had low R and P
N during winter, increasing from March to May, when mean air temperature reached 19.2 °C. During the favourable period, C. incanus and A. unedo had a higher mean P
N (16.4±2.4 μmol m−2 s−1) than P. latifolia, Q. ilex, and M. communis (10.0±1.3 μmol m−2 s−1). The highest R (1.89±0.30 μmol m−2 s−1, mean of the species), associated to a significant P
N decrease (62 % of the maximum, mean value of the species), was measured in July (mean R/P
N ratio 0.447±0.091). Q10, indicating the respiration sensitivity to short-term temperature increase, was in the range 1.49 to 2.21. Global change
might modify R/P
N determining differences in dry matter accumulation among the species, and Q. ilex and P. latifolia might be the most favoured species by their ability to maintain sufficiently higher P
N and lower R during stress periods. 相似文献
9.
Low genetic variation of invasive Fallopia spp. in their northernmost European distribution range
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Anne‐Kari Holm Abdelhameed Elameen Benedikte W. Oliver Lars O. Brandsæter Inger S. Fløistad May B. Brurberg 《Ecology and evolution》2018,8(1):755-764
Knowledge about the reproduction strategies of invasive species is fundamental for effective control. The invasive Fallopia taxa (Japanese knotweed s.l.) reproduce mainly clonally in Europe, and preventing spread of vegetative fragments is the most important control measure. However, high levels of genetic variation within the hybrid F. × bohemica indicate that hybridization and seed dispersal could be important. In Norway in northern Europe, it is assumed that these taxa do not reproduce sexually due to low temperatures in the autumn when the plants are flowering. The main objective of this study was to examine the genetic variation of invasive Fallopia taxa in selected areas in Norway in order to evaluate whether the taxa may reproduce by seeds in their most northerly distribution range in Europe. Fallopia stands from different localities in Norway were analyzed with respect to prevalence of taxa, and genetic variation within and between taxa was studied using amplified fragment length polymorphism (AFLP). Taxonomic identification based on morphology corresponded with identification based on simple sequence repeats (SSR) and DNA ploidy levels (8× F. japonica, 6× F. × bohemica and 4× F. sachalinensis). No genetic variation within F. japonica was detected. All F. × bohemica samples belonged to a single AFLP genotype, but one sample had a different SSR genotype. Two SSR genotypes of F. sachalinensis were also detected. Extremely low genetic variation within the invasive Fallopia taxa indicates that these taxa do not reproduce sexually in the region, suggesting that control efforts can be focused on preventing clonal spread. Climate warming may increase sexual reproduction of invasive Fallopia taxa in northern regions. The hermaphrodite F. × bohemica is a potential pollen source for the male‐sterile parental species. Targeted eradication of the hybrid can therefore reduce the risk of increased sexual reproduction under future warmer climate. 相似文献
10.
Involvement of betacyanin in chilling-induced photoinhibition in leaves of <Emphasis Type="Italic">Suaeda salsa</Emphasis> 总被引:1,自引:0,他引:1
Seeds of Suaeda salsa were cultured in dark for 3 d and betacyanin accumulation in seedlings was promoted significantly. Then the seedlings with
accumulated betacyanin (C+B) were transferred to 14/10 h light/dark and used for chilling treatment 15 d later. Photosystem
2 (PS2) photochemistry, D1 protein content, and xanthophyll cycle during the chilling-induced photoinhibition (exposed to
5 °C at a moderate photon flux density of 500 μmol m−2 s−1 for 3 h) and the subsequent restoration were compared between the C+B seedlings and the control (C) ones. The maximal efficiency
of PS2 photochemistry (Fv/Fm), the efficiency of excitation energy capture by open PS2 centres (Fv′/Fm′), and the yield of PS2 electron transport (ΦPS2) of the C+B and C leaves both decreased during photoinhibition. However, smaller decreases in Fv/Fm, Fv′/Fm′, and ΦPS2 were observed in the C+B leaves than in C ones. At the same time, the deepoxidation state of xanthophyll cycle, indicated
by (A+Z)/(V+A+Z) ratio, increased rapidly but the D1 protein content decreased considerably during the photoinhibition. The
increase in rate of (A+Z)/(V+A+Z) was higher but the D1 protein turnover was slower in C+B than C leaves. After photoinhibition
treatment, the plants were transferred to a dim irradiation (10 μmol m−2 s−1) at 25 °C for restoration. During restoration, the chlorophyll (Chl) fluorescence parameters, D1 protein content, and xanthophyll
cycle components relaxed gradually, but the rate and level of restoration in the C+B leaves was greater than those in the
C leaves. The addition of betacyanins to the thylakoid solution in vitro resulted in similar changes of Fv/Fm, D1 protein content, and (A+Z)/(V+A+Z) ratio during the chilling process. Therefore, betacyanin accumulation in S. salsa seedlings may result in higher resistance to photoinhibition, larger slowing down of D1 protein turnover, and enhancement
of non-radiative energy dissipation associated with xanthophyll cycle, as well as in greater restoration after photoinhibition
than in the control when subjected to chilling at moderate irradiance. 相似文献
11.
We studied carotenoid composition and chlorophyll fluorescence in two-year-old needles from Siberian spruce (Picea obovata (L.) Karst.), Siberian fir (Abies sibirica L.), and common juniper (Juniperus communis L.). The highest values of maximum PSII photochemical activity (F
v/F
m) equaling 0.82–0.85 were observed in July–September. The decrease in F
v/F
m in December–March was more pronounced in juniper (down to 0.15) than in spruce and fir (0.45–0.50). In May, we observed a
nearly complete recovery in maximum PSII photochemical activity in fir and spruce (0.72–0.77), while in juniper, the F
v/F
m value was notably lower (0.65–0.67). The amount of thermal dissipation of energy absorbed by PSII LHC did not exceed 30%
in summer and equaled 60–90% in winter and early spring. The carotenoid pool consisted mainly of xanthophylls, among which
lutein (70%), neoxanthin (7–10%), and a violaxanthin cycle (VXC) component — violaxanthin (3–15%) were constantly present.
The accumulation of two other VXC pigments—zeaxanthin and antheraxanthin, was noted in December–March. In July, these xanthophylls
were not identified. We discovered a direct connection between VXC pigment de-epoxidation level and light energy thermal dissipation
in boreal conifer leaves. Such association reflects the non-species-specific character of the mechanism for quenching zeaxanthin-dependent
nonphotochemical chlorophyll fluorescence in PSII LHC in winter and spring. 相似文献
12.
Wen-Jun Wang Fei-Jiu Wang Jian-Yi Zhu Xiu-Tao Sun Chun-Yan Yao Pu Xu 《Journal of applied phycology》2011,23(6):1017-1022
In January and February 2010, heavy sea ice formed along the coast of the Bohai Sea and the northern Yellow Sea, China. Intertidal
organisms were subjected to serious freezing stress. In this study, we investigated the freezing tolerance of the upper intertidal
economic seaweed Porphyra yezoensis. The maximum photochemical efficiency of PS II (F
v/F
m) in undehydrated thalli remained high after 24 h at −2°C and that in dehydrated thalli decreased in a proportion to thallial
water loss. F
v/F
m dropped sharply after 24 h at −20°C, regardless of absolute cellular water content (AWC). The F
v/F
m in frozen thalli recovered rapidly at 0–20°C. A wide range of water loss in the thalli enhanced their tolerance to freezing.
F
v/F
m values in undehydrated thalli dropped sharply after 3 d at −2°C or 10 d at −20°C while those in dehydrated thalli (20–53%
AWCs) remained at high levels after 9 d at −2°C or 30 d at −20°C. These results indicate that P. yezoensis has high freezing tolerance by means of dehydration during the ebb tide and rapid recovery of F
v/F
m from freezing. A strategy of P. yezoensis industry to avoid heavy loss during freezing season is discussed based on these findings. 相似文献
13.
Photochemical efficiency of photosystem 2 (PS2), assessed from in situ chlorophyll (Chl) fluorescence measurements, was seasonally
monitored in five evergreen sclerophyll and five malacophyllous drought semi-deciduous species, co-occurring in the same Mediterranean
field site. In evergreen sclerophylls, a considerable drop in the variable (Fv) to maximum (Fm) Chl fluorescence ratio coincided with the lowest winter temperatures, indicating low PS2 efficiency during this period.
Summer drought caused a comparatively slight decrease in Fv/Fm and only in three of the five evergreen sclerophyll species tested. In drought semi-deciduous shrubs, the winter drop in
Fv/Fm was much less conspicuous. During the summer, and in spite of the severe and prolonged desiccation of their malacophyllous
leaves, Fv/Fm was maintained high and only in one species the PS2 efficiency was transiently suppressed, when the leaf relative water content
became lower than 30 %. Thus evergreen sclerophylls are more prone to photoinhibition by low winter temperatures, while the
sensitivity of drought semi-deciduals depends on the extent and duration of summer drought.
This revised version was published online in September 2006 with corrections to the Cover Date. 相似文献
14.
Jen-Hsien Weng Kuan-Ming Lai Tien-Szu Liao Mon-Yuan Hwang Yaw-Nan Chen 《Trees - Structure and Function》2009,23(2):347-356
We investigated the relationships of photosynthetic capacity (P
nsat, near light-saturated net photosynthetic rate measured at 1,200 μmol m−2 s−1 PPFD) to photosystem II efficiency (F
v/F
m) and to photochemical reflectance index [PRI = (R
531 − R
570)/(R
531 + R
570)] of Pinus taiwanensis Hay. needles at high (2,600 m a.s.l) and low-elevation (800 m a.s.l) sites through different seasons. Results indicate that
at high-elevation site, P
nsat, F
v/F
m and PRI (both measured at predawn) paralleled in general with the air temperature. On the coolest measuring day with the
minimum air temperature dropping to −2°C, P
nsat could decrease to ca. 15% of its highest value, which was measured in autumn. At low-elevation site, with the minimum air
temperature of 10–12°C in cooler season and almost no seasonal variation of F
v/F
m, P
nsat dropped to ca. 65% of its highest value and PRI decreased ca. 0.02 in winter. Even though seasonal variation of P
nsat was affected by many factors, it was still closely related to PRI based on statistical analyses using data from both sites,
through different seasons. On the contrary, seasonal variation of F
v/F
m of P. taiwanensis needles was influenced mainly by low temperature at high elevation. Therefore, the correlation of P
nsat − F
v/F
m was lower than that of P
nsat − PRI when data combined from both high- and low-elevation sites were analyzed. It is concluded that predawn PRI could be
used as an indicator to estimate the seasonal potential of photosynthetic capacity of P. taiwanensis grown at low- and high-elevations of sub-tropical Taiwan. 相似文献
15.
M. Angélica Casanova-Katny Gustavo E. Zúñiga Luis J. Corcuera Leon Bravo Miren Alberdi 《Polar Biology》2010,33(4):477-483
Primary photochemistry of photosystem II (F
v/F
m) of the Antarctic hair grass Deschampsia antarctica growing in the field (Robert Island, Maritime Antarctic) and in the laboratory was studied. Laboratory plants were grown
at a photosynthetic photon flux density (PPFD) of 180 μmol m−2 s−1 and an optimal temperature (13 ± 1.5°C) for net photosynthesis. Subsequently, two groups of plants were exposed to low temperature
(4 ± 1.5°C day/night) under two levels of PPFD (180 and 800 μmol m−2 s−1) and a control group was kept at 13 ± 1.5°C and PPFD of 800 μmol m−2 s−1. Chlorophyll fluorescence was measured during several days in field plants and weekly in the laboratory plants. Statistically
significant differences were found in F
v/F
m (=0.75–0.83), F
0 and F
m values of field plants over the measurement period between days with contrasting irradiances and temperature levels, suggesting
that plants in the field show high photosynthetic efficiency. Laboratory plants under controlled conditions and exposed to
low temperature under two light conditions showed significantly lower F
v/F
m and F
m. Moreover, they presented significantly less chlorophyll and carotenoid content than field plants. The differences in the
performance of the photosynthetic apparatus between field- and laboratory-grown plants indicate that measurements performed
in ex situ plants should be interpreted with caution. 相似文献
16.
Close relationship between the state of the xanthophyll cycle pigments and photosystem II efficiency during recovery from winter stress 总被引:7,自引:0,他引:7
Amy S. Verhoeven William W. Adams III Barbara Demmig-Adams 《Physiologia plantarum》1996,96(4):567-576
The potential involvement of the xanthophyll cycle in photoprotection of overwintering evergreen plants was investigated. Leaves from five evergreen species. Pseudotsuga menziesii, Pinus panderosa, Euonyums kiautschovicus. Mahonia repens and Malva neglecta, were collected from the field predawn during winter and transferred to the laboratory where chlorophyll fluorescence emission as well as the chlorophyll and carotenoid composition were ascertained periodically for 4.5 days. Leaves and needles from all species were found to have retained large amounts of the xanthophyll cycle pigments zeaxanthin and antheraxanthin, and they exhibited sustained low values of the intrinsic efficiency of photosystem II (PSII; measured as the ratio of variable to maximal fluorescence, Fv/Fm) upon collection. The increase in PSII efficiency was biphasic, with a rapid phase (requiring several hours) and a slow phase (requiring several days). Changes in the conversion state of the xanthophyll cycle were found to correlate with increases in PSII efficiency in both phases, with the latter phase involving large increases in both Fm (maximal fluorescence) and Fo (minimal fluorescence) throughout the period of recovery. The relationship between Fm quenching (expressed as nonphotochemical or Stern-Volmer quenching [NPQ] of Fm, i.e. Fm/ Fm–1) and Fo quenching (Fo/Fo–1) was linear, as expected for changes in xanthophyll cycle-dependent energy dissipation in the antenna complexes. Furthermore, the relationship between Fv/Fm and NPQ during recovery followed the theoretical relationship predicted for changes in the rate constant for energy dissipation in the antenna complexes. This fit between the theoretical relationship and the actual data indicates that all changes in NPQ or Fv/Fm can be accounted for by changes in this rate constant. The results suggest a role for the photoprotective xanthophyll cycle-dependent dissipation process in the lowered efficiency of PSII observed in coldstressed evergreen plants in the field. 相似文献
17.
Photoinhibition of colonial and unicellular <Emphasis Type="Italic">Microcystis</Emphasis> cells in a summer bloom in Lake Taihu 总被引:1,自引:0,他引:1
To evaluate the photoinhibition of colonial and unicellular cells of Microcystis aeruginosa under natural conditions, the maximum and effective quantum yields of photosystem II were measured from variable chlorophyll
a fluorescence in samples from Lake Taihu during a summer bloom from June 19 to 21, 2006. Diurnal changes in the photoinhibition
of Microcystis cells incubated immediately below the surface in clear bottles for 30 min and in situ samples under natural conditions were
measured. At solar noon during the three days, the mean values of maximum quantum yield (F
v/F
m) and effective quantum yield (ΔF/F
m′) for unicellular cells (F
v/F
m = 0.15, ΔF/F
m′ = 0.10) were lower than those for colonial cells (F
v/F
m = 0.25, ΔF/F
m′ = 0.15). For in situ samples, the values of F
v/F
m and ΔF/F
m′ for colonial cells at solar noon on the three days (F
v/F
m 0.30, 0.25, 0.29; ΔF/F
m′ 0.24, 0.21, 0.22) were also higher than those of unicellular cells (F
v/F
m 0.26, 0.18, 0.25; ΔF/F
m′ 0.15, 0.11, 0.14). The results indicate that colony formation has a protective effect on Microcystis cells by reducing the occurrence of photoinhibition under high light intensities. 相似文献
18.
P. Giorio 《Photosynthetica》2011,49(3):371-379
Tomato and pepper leaves were clipped with black leaf clips for dark adaptation under solar radiation in the late spring or
early summer 2010 in southern Italy. The leaves showed highly variable maximum PSII quantum yield (Fv/Fm = 0.026−0.802) using a continuous-excitation fluorometer Pocket PEA. These results were confirmed using the modulated fluorometer FMS1 on tomato leaves in mid summer, with Fv/Fm as low as 0.222 ± 0.277 due to nearly equal minimum (Fo) and maximum (Fm) fluorescence emission. A significant clip effect on Fv/Fm occurred after only 12 (tomato) or 25 (pepper) min. Increasing the leaf temperature from 25 to 50°C reportedly induced an
Fo increase and Fm decrease so that Fv/Fm approached zero. The hypothesis that black leaf clips overheated under intense solar irradiance was verified by shrouding
the clipped leaves with aluminum foil. In clipped leaves of pepper, Fv/Fm with the black clip/Pocket-PEA was 0.769 ± 0.025 (shrouded) and as low as 0.271 ± 0.163 (nonshrouded), the latter showing
a double Fo and 32% lower Fm. An 8% clip effect on Fv/Fm was observed with the white clip/FMS1. To avoid the clip effect in high irradiance environments, Fv/Fm measurements with black clip/Pocket PEA system required leaf dark adaptation with radiation-reflecting shrouds. It would be useful if manufacturing companies could
develop better radiation-reflecting leaf clips for the Pocket PEA fluorometer. 相似文献
19.
Influence of nitrogen supply and growth irradiance on photoinhibition and recovery in Heuchera americana (Saxifragaceae) 总被引:1,自引:0,他引:1
Prior work demonstrated that Heuchera americana, an evergreen herb inhabiting the deciduous forest understory in the southeastern United States, has a 3-4-fold greater photosynthetic capacity under the low-temperature, strong-light, open canopies of winter compared to the high-temperature, weak-light, closed canopies of summer. Moreover, despite the reductions in soil nitrogen, the chilling temperatures, and the increased quantum flux associated with winter, chronic photoinhibition was not observed in this species at this time of the year. We were interested in the photosynthetic acclimation and photoinhibition characteristics of this species when grown under contrasting light and nitrogen regimes. Newly expanded shade-acclimated leaves of forest-grown plants exposed to strong light varying in intensity and duration at 25°C showed a reduction in Fv/Fm (the ratio of variable to maximum room temperature chlorophyll fluorescence measured after dark adaptation), which was correlated with a decline in øa (the intrinsic quantum yield of CO2-saturated O2 evolution on an absorbed light basis). Plants grown in the glasshouse under contrasting light (high and low light; HL and LL, respectively) and nitrogen supply (high and low nitrogen; HN and LN, respectively) regimes showed that photosynthetic acclimation to HL was impaired in LN regimes. The HL-LN plants also had the lowest values of Fv/Fm and of ø on both incident and absorbed light bases and had 50% less chlorophyll (per unit area) compared to plants from other growth regimes. Controlled exposure to bright light at low temperatures (2-3°C) for 3 h resulted in a sharp decrease in Fv/Fm (and rise in Fo, the minimum fluorescence yield) in all plants. Shade-grown plants from both N regimes were highly susceptible to chronic photoinhibition, as indicated by a greater reduction in Fv/Fm and incomplete recovery after 18 h in weak light at 25°C. The HL-HN plants were the least susceptible to chronic photoinhibition, having the smallest decrease in Fv/Fm with near full recovery within 6 h. The decline in Fv/Fm in HL-LN plants was comparable to that of shade-acclimated plants, but recovered fully within 6 h. Low-N plants from both light regimes displayed greater increases in Fo which did not return to pretreatment levels after 18 h of recovery. These studies indicate that HL-LN plants were sensitive to chronic photoinhibition and, at the same time, had a high capacity for dynamic photoinhibition. Experimental garden studies showed that H. americana grown in an open field in summer were photoinhibited and did not fully recover overnight or during extended periods of weak light. These results are discussed in relation to the photosynthetic acclimation of H. americana under natural conditions. 相似文献
20.
Photochemical efficiency, photosynthetic capacity, osmoprotectants, and relative water content (RWC) were recorded in saplings
of two evergreen plants (Boehmeria rugulosa Wedd. and Olea glandulifera Wall. ex G. Don) grown inside (GL) and outside (OP) a glasshouse during the winter season. The OP plants experienced 2.0–2.5 °C lower
air temperature and dew formation in comparison to GL plants. Diurnal observations indicated no change in RWC in the leaves
of GL and OP plants, while significant reduction in both transpiration and net photosynthetic (P
N) rates was observed in OP plants: the reduction in P
N was much more prominent as was also reflected by poor water use efficiency of these plants. Similarly, OP plants also showed
decrease in the apparent quantum yield and irradiance-saturated CO2 assimilation rate. The decrease in P
N was not associated with decreased stomatal conductance. However, a significant reduction in the ratio of variable to maximum
chlorophyll (Chl) fluorescence (Fv/Fm) and Chl content was recorded in the OP plants which also contained more total soluble saccharides but less proline contents.
The greater enhancement of P
N at 15 °C in comparison to measurements taken at 10 °C in OP plants over GL plants probably indicated an increase in mesophyll
capacity of the OP plants’ growth at increased temperature. Hence the enhanced growth and productivity of plants grown in
sheltered environments could be associated to their higher photosynthetic activity that may have important bearing on their
field establishment and productivity in the long run. The response varied with plant species; reduction in P
N was greater in B. rugulosa than in O. glandulifera. However, the recovery of OP plants in terms of Fv/Fm in the subsequent months revealed that photosynthetic system of these plants is revocable. 相似文献