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991.
O. Urban A. Ač J. Kalina T. Priwitzer M. Šprtová V. Špunda M. V. Marek 《Photosynthetica》2007,45(3):392-399
Temperature responses of carbon assimilation processes were studied in four dominant species from mountain grassland ecosystem,
i.e. Holcus mollis (L.), Hypericum maculatum (Cr.), Festuca rubra (L.), and Nardus stricta (L.), using the gas exchange technique. Leaf temperature (T
L) of all species was adjusted within the range 13–30 °C using the Peltier thermoelectric cooler. The temperature responses
of metabolic processes were subsequently modelled using the Arrhenius exponential function involving the temperature coefficient
Q
10. The expected increase of global temperature led to a significant increase of dark respiration rate (R
D; Q
10 = 2.0±0.5), maximum carboxylation rate (V
Cmax; Q
10 = 2.2±0.6), and maximum electron transport rate (J
max; Q
10 = 1.6±0.4) in dominant species of mountain grassland ecosystems. Contrariwise, the ratio between J
max and V
Cmax linearly decreased with T
L [y = −0.884 T
L + 5.24; r
2 = 0.78]. Hence temperature did not control the ratio between intercellular and ambient CO2 concentration, apparent quantum efficiency, and photon-saturated CO2 assimilation rate (P
max). P
max primarily correlated with maximum stomatal conductance irrespective of T
L. Water use efficiency tended to decrease with T
L [y = −0.21 T
L + 8.1; r
2 = 0.87]. 相似文献
992.
We determined the interactive effects of irradiance, elevated CO2 concentration (EC), and temperature in carrot (Daucus carota var. sativus). Plants of the cv. Red Core Chantenay (RCC) were grown in a controlled environmental plant growth room and exposed to 3
levels of photosynthetically active radiation (PAR) (400, 800, 1 200 μmol m−2 s−1), 3 leaf chamber temperatures (15, 20, 30 °C), and 2 external CO2 concentrations (C
a), AC and EC (350 and 750 μmol mol−1, respectively). Rates of net photosynthesis (P
N) and transpiration (E) and stomatal conductance (g
s
) were measured, along with water use efficiency (WUE) and ratio of internal and external CO2 concentrations (C
i/C
a). P
N revealed an interactive effect between PAR and C
a. As PAR increased so did P
N under both C
a regimes. The g
s
showed no interactive effects between the three parameters but had singular effects of temperature and PAR. E was strongly influenced by the combination of PAR and temperature. WUE was interactively affected by all three parameters.
Maximum WUE occurred at 15 °C and 1 200 μmol m−2 s− 1 PAR under EC. The C
i
/C
a
was influenced independently by temperature and C
a. Hence photosynthetic responses are interactively affected by changes in irradiance, external CO2 concentration, and temperature. EC significantly compensates the inhibitory effects of high temperature and irradiance on
P
N and WUE. 相似文献
993.
The effect of elevated carbon dioxide (600±50 cm3 m−3; C600) on growth performance, biomass production, and photosynthesis of Cenchrus ciliaris L. cv. 3108 was studied. This crop responded significantly by plant height, leaf length and width, and biomass production
under C600. Leaf area index increased triple fold in the crops grown in the open top chamber with C600. The biomass production in term of fresh and dry biomass accumulation increased by 134.35 (fresh) and 193.34 (dry) % over
the control (C360) condition where the crops were grown for 20 d. The rate of photosynthesis and stomatal conductance increased by 24.51 and
46.33 %, respectively, in C600 over C360 plants. In comparison with C360, the rate of transpiration decreased by 6.8 % under C600. Long-term exposure (120 d) to C600 enhanced photosynthetic water use efficiency by 34 %. Also the contents of chlorophylls a and b significantly increased in C600. Thus C. ciliaris grown in C600 throughout the crop season may produce more fodder in terms of green biomass. 相似文献
994.
Groups of Actinidia deliciosa A. Chev. C.F. Liang et A.R. Ferguson var. deliciosa kiwifruit plants were subjected to soil water shortage (D), while other groups were well irrigated (I). Variations in chlorophyll
(Chl) a fluorescence indices and leaf gas exchange were determined once plants were severely stressed (25 d after the beginning of
the D-cycle). Daily maximum values of photosynthetic photon flux density (PPFD) were ca. 1 650 μmol(photon) m−2 s−1, while air temperatures peaked at 34.6 °C. High irradiance per se did not greatly affect the efficiency of photosystem (PS) 2, but predisposed its synergistic reduction by D co-occurrence.
Fluorescence showed transient photodamage of PS2 with a complete recovery in the afternoon in both D and I plants. Upon re-watering
the efficiency of PS2 was suboptimal (95 %) at day 2 after irrigation was reinitiated. At early morning of the day 5 of re-watering,
photosynthesis and stomatal conductance recovered at about 95 and 80 % of I vines, respectively, indicating some after-stress
effect on stomatal aperture. Once excessive photons reached PS2, the thermal dissipation of surplus excitation energy was
the main strategy to save the photosynthetic apparatus and to optimize carbon fixation. The rather prompt recovery of both
Chl a fluorescence indices and net photosynthetic rate during re-watering indicated that kiwifruit photosynthetic apparatus is
prepared to cope with temporary water shortage under Mediterranean-type-climates. 相似文献
995.
We found differences between true leaves (TL) and phyllodes (Ph) during ontogeny of Acacia mangium plants as reflected in chlorophyll (Chl) and carotenoid contents, gas exchange, Chl fluorescence, and growth. The production
of TL enhanced the relative growth rate of the A. mangium seedlings, allowing the plants to accumulate enough dry biomass for later growth, while the production of thicker Ph in the
later growth stage of A. mangium could help plants to cope with higher irradiance in their natural growth conditions. 相似文献
996.
Thick sun leaves have a larger construction cost per unit leaf area than thin shade leaves. To re-evaluate the adaptive roles
of sun and shade leaves, we compared the photosynthetic benefits relative to the construction cost of the leaves. We drew
photosynthetically active radiation (PAR)-response curves using the leaf-mass-based photosynthetic rate to reflect the cost.
The dark respiration rates of the sun and shade leaves of mulberry (Morus bombycis Koidzumi) seedlings did not differ significantly. At irradiances below 250 μmol m−2 s−1, the shade leaves tended to have a significantly larger net photosynthetic rate (P
N) than the sun leaves. At irradiances above 250 μmol m−2 s−1, the P
N did not differ significantly. The curves indicate that plants with thin shade leaves have a larger daily CO2 assimilation rate per construction cost than those with thick sun leaves, even in an open habitat. These results are consistently
explained by a simple model of PAR extinction in a leaf. We must target factors other than the effective assimilation when
we consider the adaptive roles of thick sun leaves. 相似文献
997.
Münzbergová Z 《Annals of botany》2007,100(6):1259-1270
BACKGROUND AND AIMS: Despite the recent enormous increase in the number of studies on polyploid species, no studies to date have explored the population dynamics of these taxa. It is thus not known whether the commonly reported differences in single life-history traits between taxa of different ploidy levels result in differences in population dynamics. METHODS: This study explores differences in single life-history traits and in the complete life cycle between populations of different ploidy levels and compares these differences with differences observed between different habitat types and years. Diploid and hexaploid populations of a perennial herb, Aster amellus, are used as the study system. Transition matrix models were used to describe the dynamics of the populations, and population growth rates, elasticity values and life-table response experiments were used to compare the dynamics between populations and years. KEY RESULTS: The results indicate that between-year variation in population dynamics is much larger than variation between different ploidy levels and different habitat conditions. Significant differences exist, however, in the structure of the transition matrices, indicating that the dynamics of the different ploidy levels are different. Strong differences in probability of extinction of local populations were also found, with hexaploid populations having higher probability than diploid populations, indicating strong potential differences in persistence of these populations. CONCLUSIONS: This is the first study on complete population dynamics of plants of different ploidy levels. This knowledge will help to understand the ability of new ploidy levels to spread into new areas and persist there, and the interactions of different ploidy levels in secondary contact zones. This knowledge will also contribute to understanding of interactions of different ploidy levels with other plant species or other interacting organisms such as pollinators or herbivores. 相似文献
998.
Day length affects the dynamics of leaf expansion and cellular development in Arabidopsis thaliana partially through floral transition timing 总被引:2,自引:0,他引:2
Background and Aims: Plant aerial development is well known to be affected by daylength in terms of the timing and developmental stage of floraltransition. Arabidopsis thaliana is a long dayplant in which the time to flower is delayed by short days andleaf number is increased. The aim of the work presented herewas to determine the effects of different day lengths on individualleaf area expansion. The effect of flower emergence per se onthe regulation of leaf expansion was also tested in this study. Methods: Care was taken to ensure that day length was the only sourceof micro-meteorological variation. The dynamics of individualleaf expansion were analysed in Ler and Col-0 plants grown underfive day lengths in five independent experiments. Responsesat cellular level were analysed in Ler plants grown under variousday lengths and treatments to alter the onset of flowering. Key Results: When the same leaf position was compared, the final leaf areaand both the relative and absolute rates of leaf expansion weredecreased by short days, whereas the duration of leaf expansionwas increased. Epidermal cell number and cell area were alsoaltered by day-length treatments and some of these responsescould be mimicked by manipulating the date of flowering. Conclusions: Both the dynamics and cellular bases of leaf development arealtered by differences in day length even when visible phenotypesare absent. To some extent, cell area and its response to daylength are controlled by whole plant control mechanisms associatedwith the onset of flowering. 相似文献
999.
1000.
Martin Hossann Alenka Schwerdt Nicole Teichert Rolf D. Issels Lars H. Lindner 《生物化学与生物物理学报:生物膜》2007,1768(10):2491-2499
Recently, we reported that 1,2-dipalmitoyl-sn-glycero-3-phosphoglyceroglycerol (DPPGOG) prolongs the circulation time of thermosensitive liposomes (TSL). Since the only TSL formulation in clinical trials applies DSPE-PEG2000 and lysophosphatidylcholine (P-lyso-PC), the objective of this study was to compare the influence of these lipids with DPPGOG on in vitro stability and heat-induced drug release properties of TSL. The content release rate was significantly increased by incorporating DPPGOG or P-lyso-PC in TSL formulations. DPPC/DSPC/DPPGOG 50:20:30 (m/m) and DPPC/P-lyso-PC/DSPE-PEG2000 90:10:4 (m/m) did not differ significantly in their release rate of carboxyfluorescein with > 70% being released within the first 10s at their phase transition temperature. Furthermore, DPPC/DSPC/DPPGOG showed an improved stability at 37 °C in serum compared to the PEGylated TSL. The in vitro properties of DPPGOG-containing TSL remained unchanged when encapsulating doxorubicin instead of carboxyfluorescein. The TSL retained 89.1 ± 4.0% of doxorubicin over 3 h at 37 °C in the presence of serum. The drug was almost completely released within 120s at 42 °C. In conclusion, DPPGOG improves the in vitro properties in TSL formulations compared to DSPE-PEG2000, since it not only increases the in vivo half-life, it even increases the content release rate without negative effect on TSL stability at 37 °C which has been seen for DSPE-PEG2000/P-lyso-PC containing TSL. 相似文献