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991.
Victoria López-Rodas Antonio Flores-Moya Emilia Maneiro Nieves Perdigones Fernando Marva Marta E. García Eduardo Costas 《Evolutionary ecology》2007,21(4):535-547
Adaptation of Microcystis aeruginosa (Cyanobacteria) to resist the herbicide glyphosate was analysed by using an experimental model. Growth of wild-type, glyphosate-sensitive
(Gs) cells was inhibited when they were cultured with 120 ppm glyphosate, but after further incubation for several weeks, occasionally
the growth of rare cells resistant (Gr) to the herbicide was found. A fluctuation analysis was carried out to distinguish between resistant cells arising from rare
spontaneous mutations and resistant cells arising from other mechanisms of adaptation. Resistant cells arose by rare spontaneous
mutations prior to the addition of glyphosate, with a rate ranging from 3.1 × 10−7 to 3.6 × 10−7 mutants per cell per generation in two strains of M. aeruginosa; the frequency of the Gr allele ranged from 6.14 × 10−4 to 6.54 × 10−4. The Gr mutants are slightly elliptical in outline, whereas the Gs cells are spherical. Since Gr mutants have a diminished growth rate, they may be maintained in uncontaminated waters as the result of a balance between
new resistants arising from spontaneous mutation and resistants eliminated by natural selection. Thus, rare spontaneous pre-selective
mutations may allow the survival of M. aeruginosa in glyphosate-polluted waters via Gr clone selection. 相似文献
992.
Starvation resistance is an important trait related to survival in many species and often involves dramatic changes in physiology
and homeostasis. The tropical African butterfly Bicyclus anynana lives in two seasonal environments and has evolved phenotypic plasticity. The contrasting demands of the favourable, wet
season and the harsh, dry season have shaped a remarkable life history, which makes this species particularly interesting
for investigating the relationship between starvation resistance, metabolism, and its environmental modulation. This study
reports on two laboratory experiments to investigate the effects of pre-adult and adult temperatures that mimic the seasonal
environments, on starvation resistance and resting metabolic rate (RMR) in adult B. anynana. In addition, we investigate starvation resistance in wet and dry seasonal form genotypes; artificial selection on eyespot
size has yielded lines that only produce one or the other of the seasonal forms across all rearing environments. As expected,
the results show a large effect of adult temperature. More relevant, we show here that both pre-adult temperature and genetic
background also influence adult starvation resistance, showing that phenotypic plasticity in this species includes starvation
resistance. The dry season form genotype has a higher starvation resistance when developed at dry season temperatures, indicating
a genetic modulation of starvation resistance in relation to temperature. Paradoxically, dry season pre-adult temperatures
reduce starvation resistance and raise RMR. The high overall association of RMR and starvation resistance in our experiments
suggests that energy expenditure and survival are linked, but that they may counteract each other in their influence on fitness
in the dry season. We hypothesize that metabolism is moderating a trade-off between pre-adult (larval) survival and adult
survival in the dry season. 相似文献
993.
994.
995.
We investigated the responses of photon-saturated photosynthesis rate (P
sat) and its simultaneous acclimation of anatomy and nitrogen use patterns of current needles of Korean pine (Pinus koraiensis) seedlings grown under factorial combinations of two nitrogen levels and irradiances. Although N supply resulted in a significant
increase of N content in needles under both irradiances, the increase of P
sat tended to be suppressed only in shade (S). The significant increase of P
sat in full sunlight (O) was associated with the increase of ribulose-1,5-bisphosphate carboxylase/oxygenase (RuBPCO) and chlorophyll
(Chl) contents. In contrast, small increase of Chl content and no increase of RuBPCO content were found in S (90 % cut of
full irradiance), which would result in a small increase of P
sat. This result suggests that extra N is stocked in needles under shade for the growth in next season. With N supply, a significant
decrease of specific leaf area (SLA) was detected only in O. This decrease of SLA was due to the increase of density of needle.
Furthermore, the increase of needle density was not due to the increased number and size of mesophyll cells, but the increased
density of each mesophyll cell. Therefore, although SLA changed in O, the change did not involve anatomical adaptation to
use increased N effectively, at least observable by light microscopy. Hence, even though the SLA would change, N deposition
will improve the photosynthetic capacity of Korean pine seedlings, not through the development of needle anatomy but through
improvement of the allocation of N in both irradiances. 相似文献
996.
J. Moutinho-Pereira N. Magalhães B. Gonçalves E. Bacelar M. Brito C. Correia 《Photosynthetica》2007,45(2):202-207
Optical characteristics, contents of photosynthetic pigments, total soluble sugars, and starch, rates of gas exchange, chlorophyll (Chl) a fluorescence, and leaf water relations were analysed in three Vitis vinifera L. cultivars, Tinto Cão (TC), Touriga Nacional (TN), and Tinta Roriz (TR), grown in Mediterranean climate. Chl content was significantly lower in TC than in TN and TR leaves, while the Chl a/b ratio was higher. TR had the lowest net photosynthetic rate, stomatal conductance, and contents of soluble sugars and starch than TN and TC. In spite of low Chl content, TC showed the lowest photon absorbance and the highest photochemical efficiency of photosystem 2. TC had the lowest predawn and midday leaf water potential. The capability for osmotic adjustment was similar among cultivars and the calculated modulus of elasticity was higher in TC leaves. The typical lighter green leaves of TC seemed to be an adaptive strategy to high irradiance and air temperature associated to water stress. 相似文献
997.
One-year-old olive trees (cv. Koroneiki) were grown in plastic containers of 50 000 cm3 under full daylight and 30, 60, and 90 % shade for two years. The effects of shade on leaf morphology and anatomy, including
stomatal density and chloroplast structure, net photosynthetic rate (P
N), stomatal conductance (g
s), and fruit yield were studied. Shade reduced leaf thickness due to the presence of only 1–2 palisade layers and reduced
the length of palisade cells and spongy parenchyma. The number of thylakoids in grana as well as in stroma increased as shade
increased, while the number of plastoglobuli decreased in proportion to the reduced photosynthetically active radiation (PAR).
The higher the level of shade, the lower the stomatal and trichome density, leaf mass per area (ALM), g
s, and P
N. Shade of 30, 60, and 90 % reduced stomatal density by 7, 16, and 27 %, respectively, while the corresponding reduction in
P
N was 21, 35, and 67 %. In contrast, chlorophyll a+b per fresh mass, and leaf width, length, and particularly area increased under the same shade levels (by 16, 33, and 81 %
in leaf area). P
N reduction was due both to a decrease in PAR and to the morphological changes in leaves. The effect of shade was more severe
on fruit yield per tree (32, 67, and 84 %) than on P
N indicating an effect on bud differentiation and fruit set. The olive tree adapts well to shade compared with other fruit
trees by a small reduction in stomatal and trichome density, palisade parenchyma, and a significant increase in leaf area. 相似文献
998.
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
999.
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
1000.
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