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101.
102.
Adams WW Watson AM Mueh KE Amiard V Turgeon R Ebbert V Logan BA Combs AF Demmig-Adams B 《Photosynthesis research》2007,94(2-3):455-466
The potential role of foliar carbon export features in the acclimation of photosynthetic capacity to differences and changes
in light environment was evaluated. These features included apoplastic vs. symplastic phloem loading, density of loading veins,
plasmodesmatal frequency in intermediary cells, and the ratio of loading cells to sieve elements. In initial studies, three
apoplastic loaders (spinach, pea, Arabidopsis thaliana) exhibited a completely flexible photosynthetic response to changing light conditions, while two symplastic loaders (pumpkin,
Verbascum phoeniceum), although able to adjust to different long-term growth conditions, were more limited in their response when transferred
from low (LL) to high (HL) light. This suggested that constraints imposed by the completely physical pathway of sugar export
might act as a bottleneck in the export of carbon from LL-acclimated leaves of symplastic loaders. While both symplastic loaders
exhibited variable loading vein densities (low in LL and high in HL), none of the three apoplastic loaders initially characterized
exhibited such differences. However, an additional apoplastic species (tomato) exhibited similar differences in vein density
during continuous growth in different light environments. Furthermore, in contrast to the other apoplastic loaders, photosynthetic
acclimation in tomato was not complete following a transfer from LL to HL. This suggests that loading vein density and loading
cells per sieve element, and thus apparent loading surface capacity, play a major role in the potential for photosynthetic
acclimation to changes in light environment. Photosynthetic acclimation and vein density acclimation were also characterized
in the slow-growing, sclerophytic evergreen Monstera deliciosa. This evergreen possessed a lower vein density during growth in LL compared to HL and exhibited a more severely limited potential
for photosynthetic acclimation to increases in light environment than the rapidly-growing, mesophytic annuals. 相似文献
103.
Peter J. Fashing Felix Mulindahabi Jean-Baptiste Gakima Michel Masozera Ian Mununura Andrew J. Plumptre Nga Nguyen 《International journal of primatology》2007,28(3):529-550
With group sizes sometimes >300 individuals, the Angolan black-and-white colobus (Colobus angolensis ruwenzorii) population
in Nyungwe Forest, Rwanda is an intriguing exception to the tendency for folivores to live in smaller groups than expected
relative to body size. Researchers have hypothesized that the unusually high quality of foliage at Nyungwe allows colobus
there to avoid intragroup feeding competition, releasing constraints on the formation of large groups (Fimbel et al., 2001). We collected data on the activity and ranging patterns of a >300-member Nyungwe colobus group and compared our results
to those from smaller groups in other black-and-white colobus (Colobus spp.) populations. Colobus at Nyungwe spent far more
time feeding and moving (62%) and far less time resting (32%) than black-and-white colobus at any other site. The annual home
range of the Nyungwe colobus was also many times larger (95% minimum convex polygon: 20.7 km
2
; 95% fixed kernel: 24.4 km
2
) than those for other populations. We terminated our research after the group engaged in an unprecedented migration among
black-and-white colobus by moving 13 km south of their former range. Our results suggest that intragroup scramble competition
may be more intense than originally believed within the large colobus groups at Nyungwe and that long periods of resource
renewal may be necessary after a large colobus group passes through an area, thereby potentially helping to explain their
wide ranging patterns. We discuss the socioecological convergence between the Nyungwe colobus and Chinese snub-nosed monkeys
(Rhinopithecus spp.) and suggest directions for future research on the unique black-and-white colobus population at Nyungwe.
相似文献
Peter J. FashingEmail: |
104.
Early leafing and extended leaf longevity can be important mechanisms for the invasion of the forest understory. We compared
the leaf phenology and photosynthetic characteristics of Berberis thunbergii, an early leafing invasive shrub, and two co-occurring native species, evergreen Kalmia latifolia and late leafing Vaccinium corymbosum, throughout the 2004 growing season. Berberis thunbergii leafed out 1 month earlier than V. corymbosum and approximately 2 weeks prior to the overstory trees. The photosynthetic capacity [characterized by the maximum carboxylation
rate of Rubisco (V
cmax) and the RuBP regeneration capacity mediated by the maximum electron transport rate (J
max)] of B. thunbergii was highest in the spring open canopy, and declined with canopy closure. The 2003 overwintering leaves of K. latifolia displayed high V
cmax and J
max in spring 2004. In new leaves of K. latifolia produced in 2004, the photosynthetic capacity gradually increased to a peak in mid-September, and reduced in late November.
V. corymbosum, by contrast, maintained low V
cmax and J
max throughout the growing season. In B. thunbergii, light acclimation was mediated by adjustment in both leaf mass per unit area and leaf N on a mass basis, but this adjustment
was weaker or absent in K. latifolia and V. corymbosum. These results indicated that B. thunbergii utilized high irradiance in the spring while K. latifolia took advantage of high irradiance in the fall and the following spring. By contrast, V. corymbosum generally did not experience a high irradiance environment and was adapted to the low irradiance understory. The apparent
success of B. thunbergii therefore, appeared related to a high spring C subsidy and subsequent acclimation to varying irradiance through active N
reallocation and leaf morphological modifications. 相似文献
105.
Chamorovsky SK Chamorovsky CS Knox PP Chizhov IV Zubov BV 《European biophysics journal : EBJ》2007,36(6):601-608
Laser-induced temperature jump experiments were used for testing the rates of thermoinduced conformational transitions of
reaction center (RC) complexes in chromatophores of Chromatium minutissimum. The thermoinduced transition of the macromolecular RC complex to a state providing effective electron transport from the
multiheme cytochrome c to the photoactive bacteriochlorophyll dimer within the temperature range 220–280 K accounts for tens of seconds with activation
energy 0.166 eV/molecule. The rate of the thermoinduced transition in the cytochrome–RC complex was found to be three orders
of magnitude slower than the rate of similar thermoinduced transition of the electron transfer reaction from the primary to
secondary quinone acceptors studied in the preceding work (Chamorovsky et al. in Eur Biophys J 32:537–543, 2003). Parameters of thermoinduced activation of the electron transfer from the multiheme cytochrome c to the photoactive bacteriochlorophyll dimer are discussed in terms of cytochrome c docking onto the RC. 相似文献
106.
We consider a function-valued trait z(t) whose pre-selection distribution is Gaussian, and a fitness function W that models optimizing selection, subject to certain natural assumptions. We show that the post-selection distribution of
z(t) is also Gaussian, compute the selection differential, and derive an equation that expresses the selection gradient in terms
of the parameters of W and of the pre-selection distribution. We make no assumptions on the nature of the “time” parameter t.
相似文献
107.
以昆明小白鼠为实验动物,对类球红细菌Z1、沼泽红假单胞菌Z2及光合细菌分离株C2采用急性毒性试验、骨髓细胞微核试验和精子畸形试验进行安全性评定。结果表明,急性毒性试验:实验组小白鼠的一般状况、器官含水量、器官系数及血常规检查,与对照组差异均无显著性(P>0.05);骨髓细胞微核试验和精子畸形试验实验组与阴性对照组(生理盐水)差异均无显著性(P>0.05),与阳性对照组(环磷酰胺40 mg/kg)比较,骨髓细胞微核试验差异有极显著性(P<0.01),精子畸形率试验差异有显著性(P<0.05)。以上结果说明,三株光合细菌均不具有毒性。 相似文献
108.
Total concentrations of algal pigments, organic C, C, N, P and S were determined in surface sediments from the littoral zone
of 21 lakes in ice-free areas of northern Victoria Land (Antarctica) with different climatic and environmental conditions.
Concentrations of major ions and nutrients were also determined in water samples from the same lakes. The latter samples had
extremely variable chemical compositions; however, all the lakes resulted oligotrophic. Pigment concentrations in surface
sediments were comparable to those reported for other Antarctic lakes and lower than those in oligotrophic lakes at lower
latitudes. Cyanophyta, Chlorophyta and Bacillariophyta were the main taxa identified. These taxa correspond to those reported
in previous microscopy-based studies on Antarctic phytoplankton and phytobenthos. Discriminant Function Analysis and Canonical
Correspondence Analysis of data indicate that the distribution of pigments in these Victoria Land lakes depends mainly on
their geographical location (particularly the distance from the sea) and nutrient status. 相似文献
109.
Plant communities around natural CO2 springs have been exposed to elevated CO2 levels over many generations and give us a unique opportunity to investigate the effects of long-term elevated CO2 levels on wild plants. We searched for natural CO2 springs in cool temperate climate regions in Japan and found three springs that were suitable for studying long-term responses
of plants to elevated levels of CO2: Ryuzin-numa, Yuno-kawa and Nyuu. At these CO2 springs, the surrounding air was at high CO2 concentration with no toxic gas emissions throughout the growth season, and there was natural vegetation around the springs.
At each site, high-CO2 (HC) and low-CO2 (LC) plots were established, and three dominant species at the shrub layers were used for physiological analyses. Although
the microenvironments were different among the springs, dicotyledonous species growing at the HC plots tended to have more
starch and less nitrogen per unit dry mass in the leaves than those growing at the LC plots. In contrast, monocotyledonous
species growing in the HC and LC plots had similar starch and nitrogen concentrations. Photosynthetic rates at the mean growth
CO2 concentration were higher in HC plants than LC plants, but photosynthetic rates at a common CO2 concentration were lower in HC plants. Efficiency of water and nitrogen use of leaves at growth CO2 concentration was greatly increased in HC plants. These results suggest that natural plants growing in elevated CO2 levels under cool temperate climate conditions have down-regulated their photosynthetic capacity but that they increased
photosynthetic rates and resource use efficiencies due to the direct effect of elevated CO2 concentration. 相似文献
110.
J. Rodríguez-Calcerrada J. A. Pardos L. Gil I. Aranda 《Trees - Structure and Function》2007,21(1):45-54
Photosynthetic acclimation of two co-occurring deciduous oaks (Quercus petraea and Quercus pyrenaica) to a natural light gradient was studied during one growing season. In the spring of 2003, 90 seedlings per species were
planted along a transect resulting from a dense Pinus sylvestris stand, an adjacent thinned area and a 10-m-wide firebreak (16.5–60.9% Global Site Factor (GSF)). In two dates of the following
summer, we measured leaf gas exchange, carboxylation efficiency (CE), chlorophyll and nitrogen content, light–response curves
of chlorophyll a fluorescence parameters, and leaf mass per area (LMA). Summer was mild, as evidenced by leaf predawn water potential (Ψpd), which reduced the interactive effect of water stress on the response of seedlings to light. Q. pyrenaica had higher LMA, CE, stomatal conductance (g
s max) and photosynthesis per unit area than Q. petraea at all growth irradiances. , LMA, g
s max and electron transport rate (ETR) all increased with light availability (GSF) in a similar fashion in both species. Light
had also a clear effect on the organization of Photosystem II (PS II), as deduced by chlorophyll a fluorescence curves. Chlorophyll concentration (Chlm) decreased with increasing light availability in Q. pyrenaica but it did not in Q. petraea. Seedlings of Q. petraea acclimated to higher irradiances showed a greater non-photochemical quenching (NPQ) than those of Q. pyrenaica. This suggests a higher susceptibility to high light in Q. petraea, which would be consistent with a better adaptation to shade, inferred from the lower LMA or the lower rate of photosynthesis. 相似文献