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171.
Y.-P. Guo M.-J. Hu H.-F. Zhou L.-C. Zhang J.-H. Su H.-W. Wang Y.-G. Shen 《Photosynthetica》2006,44(3):333-337
Spraying low concentrated (0.5–5.0 mM) solutions of NaHSO3 on Satsuma mandarin (Citrus unshiu Marc.) leaves resulted in enhancement (maximal about 15 % at 1 mM NaHSO3) of net photosynthetic rate (P
N) for 6 d. The potential photochemical efficiency of photosystem 2 (PS2, Fv/Fm) and the quantum yield of PS2 electron transport (ΦPS2) were increased under strong photon flux density (PFD). The slow phase of millisecond delayed light emission (ms-DLE) was
increased, showing that the transmembrane proton motive force related to photophosphorylation was enhanced. We also observed
that low concentrations of NaHSO3 promoted the production of ATP in irradiated leaves. We suggest that the increase in P
N in Satsuma mandarin leaves caused by low concentrations of NaHSO3 solution may have been due to the stimulation of photophosphorylation and, hence, the increase in photochemical efficiency
through speeding-up of PS2 electron transport. Photoinhibition of photosynthesis in leaves was modified by NaHSO3 treatment under high PFD. Hence the increase in leaf dry mass seems to be associated with the mitigation of photoinhibition
caused by strong PFD. 相似文献
172.
Olmo-Mira MF Cabello P Pino C Martínez-Luque M Richardson DJ Castillo F Roldán MD Moreno-Vivián C 《Archives of microbiology》2006,186(4):339-344
A nas gene region from Rhodobacter capsulatus E1F1 containing the putative nasB gene for nitrite reductase was previously cloned. The recombinant His6-NasB protein overproduced in E. coli showed nitrite reductase activity in vitro with both reduced methyl viologen and NADH as electron donors. The apparent K
m
values for nitrite and NADH were 0.5 mM and 20 μM, respectively, at the pH and temperature optima (pH 9 and 30°C). The optical spectrum showed features that indicate the presence of FAD, iron-sulfur cluster and siroheme as prosthetic groups, and nitrite reductase activity was inhibited by sulfide and iron reagents. These results indicate that the phototrophic bacterium R. capsulatus E1F1 possesses an assimilatory NADH-nitrite reductase similar to that described in non-phototrophic organisms. 相似文献
173.
V. V. Maksimov E. V. Shchetinina O. V. Kraykivskaya E. A. Maksimova 《Microbiology》2006,75(6):653-657
The survival rate, metabolic activity, and ability for growth of microbial communities of Lake Baikal have been first studied after exposure to extremely low temperatures (freeze-thawing) for different lengths of time. It has been shown that short-term freezing (1–3 days) inhibits the growth and activity of microbial communities. The quantity of microorganisms increased after 7-and 15-day freezing. In the periods of maximums, the total number of microorganisms in the test samples was twice as high as in the control. It was established that after more prolonged freezing the microorganisms required more time after thawing to adapt to new conditions. In the variants with 7-and 15-day freezing, the activities of defrosted microbial communities were three or more times higher than in the control. The survival rate and activity of Baikal microorganisms after freeze-thawing confirms the fact that the Baikal microbial communities are highly resistant to this type of stress impact. 相似文献
174.
Water relations and gas exchange in olive trees under regulated deficit irrigation and partial rootzone drying 总被引:2,自引:1,他引:1
J. E. Fernández A. Díaz-Espejo J. M. Infante P. Durán M. J. Palomo V. Chamorro I. F. Girón L. Villagarcía 《Plant and Soil》2006,284(1-2):273-291
It is widely believed that partial root drying (PRD) reduces water losses by transpiration without affecting yield. However,
experimental work carried out to date does not always support this hypothesis. In many cases a PRD treatment has been compared
to a full irrigated treatment, so doubt remains on whether the observed benefits correspond to the switching of irrigation
or just to PRD being a deficit irrigation treatment. In addition, not always a PRD treatment has been found advantageous as
compared to a companion regulated deficit irrigation (RDI) treatment. In this work we have compared the response of mature
‘Manzanilla‘ olive trees to a PRD and an RDI treatment in which about 50% of the crop evapotranspiration (ETc) was supplied daily by localised irrigation. We alternated irrigation in the PRD treatment every 2 weeks in 2003 and every
3 weeks in 2004. Measurements of stem water potential (Ψstem), stomatal conductance (g
s) and net CO2 assimilation rate (A) were made in trees of both treatments, as well as in trees irrigated to 100% of ETc (Control trees) and in Rain-fed trees. Sap flow was also measured in different conductive organs of trees under both PRD
and RDI treatments, to evaluate the influence of alternating irrigation on root water uptake and tree water consumption. We
found small and random differences in Ψstem, g
s and A, which gave no evidence of PRD causing a positive effect on the olive tree performance, as compared to RDI. Stomatal conductance
decreased in PRD trees as compared to Control trees, but a similar decrease in g
s was also recorded in the RDI trees. Sap flow measurements, which reflected water use throughout the irrigation period, also
showed no evidence of g
s being more reduced in PRD than in RDI trees. Daily water consumption was also similar in the trees of the deficit irrigation
treatments, for most days, throughout the irrigation period. Alternating irrigation in PRD trees did not cause a change in
either water taken up by main roots at each side of the trees, or in the sap flow of both trunk locations and main branches
of each side. Results from this work, and from previous work conducted in this orchard, suggest that transpiration is restricted
in trees under deficit irrigation, in which roots are left in drying soil when water is applied by localised irrigation, and
that there is no need to alternate irrigation for achieving this effect.
Section Editor: R. E. Munns 相似文献
175.
Hegde SG Nason JD Clegg JM Ellstrand NC 《Evolution; international journal of organic evolution》2006,60(6):1187-1197
If two previously isolated taxa mutually assimilate through hybridization and subsequent biparental introgression, and if their introgressed descendants have the same or higher fitness than their parents, then gene flow should result in the local extinction of parental taxa via replacement by hybrid derivatives. These dramatic events may occur rapidly, even in a few generations. Given the speed at which such extinction by hybridization may occur, it may be difficult to identify that the process has occurred. Thus, documented instances of extinction by hybridization are rare, and especially so for cases in which both parents are replaced by the hybrid lineage. Here we report morphological and allozyme evidence for the local extinction of two Raphanus species in California via replacement by their hybrid-derived descendants. The results from a greenhouse experiment demonstrate that California wild radishes have a specific combination of traits from their progenitors, and comparison of our results to that of an earlier report indicate that pure parental types are no longer present in the wild. Our results also show the hybrid-derived lineage has transgressive fruit weight compared to its parents. Allozyme analysis demonstrates that California wild radishes are derived from hybridization between the putative parental species. However, that analysis also demonstrates that California wild radish has now become an evolutionary entity separate from both of its parents. We suggest that the aggressive colonizing behavior of the hybrid-derived lineage probably results from a novel combination of parental traits, rather than genetic variability of the population per se. 相似文献
176.
A Bilitou N De Marco AM Bello L Garzia P Carotenuto M Kim C Campanella S Ohnuma M Zollo 《Gene》2012,509(1):93-103
The development of stratified retinal cell architecture is highly conserved in all vertebrates, implying that a common fundamental molecular mechanism is involved in the generation of the organized retina. However, the detailed molecular mechanisms of retinal development are not fully understood. Here we have identified the Xenopus ortholog of prune and show that it is expressed in both differentiating and differentiated retinal domains during development. Interestingly, these spatial and temporal expression patterns coincide with the expression of prune binding partners, the NM23 family members. Overexpression of prune in retinal precursor cells significantly increases the ratio of Müller glial cells as observed by modulation of NM23 activity (Mochizuki et al., 2009). However, a mutated form of prune that has replacement of four aspartate (D) residues (D'Angelo et al., 2004), essential for phosphodiesterase activity, does not exhibit gliogenic activity. Our observations suggest that Xenopus prune may regulate Müller gliogenesis through phosphodiesterase-mediated regulation of NM23 family members. 相似文献
177.
Hunt JH 《Journal of evolutionary biology》2012,25(1):1-19
In a model based on the wasp family Vespidae, the origin of worker behaviour, which constitutes the eusociality threshold, is not based on relatedness, therefore the origin of eusociality does not depend on inclusive fitness, and workers at the eusociality threshold are not altruistic. Instead, incipient workers and queens behave selfishly and are subject to direct natural selection. Beyond the eusociality threshold, relatedness enables 'soft inheritance' as the framework for initial adaptations of eusociality. At the threshold of irreversibility, queen and worker castes become fixed in advanced eusociality. Transitions from solitary to facultative, facultative to primitive, and primitive to advanced eusociality occur via exaptation, phenotypic accommodation and genetic assimilation. Multilevel selection characterizes the solitary to highly eusocial transition, but components of multilevel selection vary across levels of eusociality. Roles of behavioural flexibility and developmental plasticity in the evolutionary process equal or exceed those of genotype. 相似文献
178.
Effects of root temperature on leaf gas exchange and xylem sap abscisic acid concentrations in six Cucurbitaceae species 总被引:2,自引:0,他引:2
Roots of six Cucurbitaceae species were exposed to low (14 °C), middle (24 °C), and high (34 °C) temperatures while aerial
parts of plants were maintained at ambient temperatures between 23 and 33 °C. The highest dry mass (DM), photon-saturated
rate of net photosynthesis (P
Nsat), and stomatal conductance (g
s) were found at 14 °C in figleaf gourd and turban squash plants, at 24 °C in cucumber and melon plants, while bitter melon
and wax gourd plants had lower DM, P
Nsat, and g
s at 14 °C than at 24 or 34 °C. Sub-or supra-optimum root temperatures did not induce photoinhibition but induced slight changes
in the quantum efficiency of photosystem 2, PS2 (ΦPS2) and photochemical quenching (qp). Meanwhile, xylem sap abscisic acid (ABA) concentration followed a contrasting change pattern to that of g
s. Thus the change in P
Nsat was mainly due to the change in g
s and roots played an important role in the regulation of stomatal behaviour by delivering increased amount of ABA to shoots
at sub-or supra-optimum root temperatures. 相似文献
179.
To investigate how excess excitation energy is dissipated in a ribulose-1,5-bisphospate carboxylase/oxygenase activase antisense
transgenic rice with net photosynthetic rate (P
N) half of that of wild type parent, we measured the response curve of P
N to intercellular CO2 concentration (C
i), electron transport rate (ETR), quantum yield of open photosystem 2 (PS2) reaction centres under irradiation (Fv′/Fm′), efficiency of total PS2 centres (ΦPS2), photochemical (qP) and non-photochemical quenching (NPQ), post-irradiation transient increase in chlorophyll (Chl) fluorescence (PITICF), and
P700+ re-reduction. Carboxylation efficiency dependence on C
i, ETR at saturation irradiance, and Fv′/Fm′, ΦPS2, and qP under the irradiation were significantly lower in the mutant. However, NPQ, energy-dependent quenching (qE), PITICF, and P700+ re-reduction were significantly higher in the mutant. Hence the mutant down-regulates linear ETR and stimulates cyclic electron
flow around PS1, which may generate the ΔpH to support NPQ and qE for dissipation of excess excitation energy. 相似文献
180.