Under non-stress condition, effects of exogenous nitric oxide (NO) on chlorophyll fluorescence parameters in detached leaves and leaf discs of potato (Solanum tuberosum L.) were surveyed. Results showed that the maximal quantum efficiency (Fv/Fm) and the effective quantum efficiency (F PSⅡ) of photosystem Ⅱ (PSⅡ) were reduced by exogenous NO under illumination (150 mmol.m-2.s-1, 25 ℃). This influence was related not only to the concentration of sodium nitroprusside (SNP, a NO donor) solution, but also to the active duration of NO on leaf tissue. Results with leaf discs showed that the effects of SNP on F PSⅡ could be prevented by bovine hemoglobin (a powerful NO scavenger), while a mixture of NO2- and NO3- (the decomposition product of NO or its donor SNP) had much less influence on F PSⅡ than SNP, indicating that effects of exogenous SNP on PSⅡ photochemical activity was mainly due to NO generation. Under light (150 mmol.m-2.s-1, 25 ℃) for 4 h or longer period, the non-photochemical quenching (NPQ) in SNP-soaked leaves was statistically similar to that in H2O-soaked control, but F PSⅡ and the proportion of open reaction centers (measured as qP) were lower than control, respectively. After 25 min dark-adaptation, the maximal fluorescence (Fm) in SNP treatment (8 and 12 h illumination duration) was significantly lower than the control, while the initial fluorescence (Fo) in SNP and H2O-treated leaves had no significant difference. Therefore this indicated that under the present experimental condition, the NO-affected site might not be the PSⅡ reaction centers. On the donor side of PSⅡ, NO putatively influenced the light-harvesting capacity of leaves under light; on the acceptor side, NO-affected sites were some components of electron transport chain after QA, i.e. NO enhanced the reductive degree of reaction centers through blocking the electron transport after QA, thus reducing the photochemical activity of PSⅡ.
The spatial heterogeneity, including distribution pattern, tree perimeter and height differentiation, and canopy structure heterogeneity, of Bruguiera gymnorrhiza (L.) Lamk populations at Yingluo Bay, South-China Coast was investigated using the positioning index (CE), differentiation index (TC and TH), Shannon-Wiener diversity index (D), and Ripley’s K -functions. Most populations showed random distribution and low differentiation in perimeters and heights of individuals, while a few showed clumped distribution and clear differentiation. Canopy and gap patches were analyzed at multiple horizontal and vertical scales using geographic information system (GIS). The mosaic patterns of canopy and gap patches are different among populations, and could be quantitatively described with the Shannon-Wiener diversity index based on crown projection. The spatial heterogeneity of the canopy structure changed with spatial scales, but this kind of change would remain relatively stable over a range of scales. This scale range could be regarded as the referenced scale for a regeneration or ecological management unit for the forest.
The toxic dinoflagellate — Alexandrium tamarense (Lebour) Balech, formed resting cysts in f/2 media with low nitrate concentrations. Among the concentrations tested, f/20 NO3- was the most effective to induction with an encystment percentage of 2.0 in batch culture. About 73.2% and 17.6% of cysts were produced on 8 and 9 d after transferring. Newly formed cysts developed accumulation body 3 d later and kept forming mucilaginous substance, which might help their dispersal and survival. The mandatory dormancy period of resting cysts was 15 and 10 d when stored at 15 and 20 ℃ respectively. The cysts could germinate without temperature change, with germination of 75.6% 20 d after formation at 20 ℃. The Alexandrium cyst density in the surface sediment of DG-26 station reached above 25 cysts/g in May and November of 2002, and dropped to 4.5 and 0.9 cysts/g in August of 2002 and February of 2003, suggesting that Alexandrium cysts might have germinated in spring and autumn 2002. Cysts produced during the bloom returned to water column soon, whatever the season and water temperature were. The cyst density in the surface sediment at DG-26 station in May, 2003 was only 3.3 cysts/g and the cysts were newly formed. In the Yangtse River estuary, the inoculum size was not a major factor to determine the outbreak of A. tamarense bloom.
Grazing in grassland ecosystems affects plant growth by removing biomass and depositing excretal nutrients. However, grazing is not uniformly distributed in space. The spatial pattern of defoliation and excretion deposition by herbivores across vegetation mosaics has been frequently discussed, but rarely spatially quantified. A 60-day field experiment in a native semiarid grassland community was conducted to examine the responses of plant growth to simulated grazing pattern and varying nitrogen levels. Plants were subjected to five defoliation treatments determined by circularly clipped patches of different size (0, 10, 20, 40, 80 cm in radius), and four nitrogen supply levels in soils (0, 5, 10, 20 g N/m2). It was detected that defoliation had reduced primary productivity by 41.5% whereas fertilization had increased it by 57.8%. The negative effect of defoliation was greater in the smallest, fertilized patches. N addition had been found to have altered the effect of defoliation, as plants growing at higher nitrogen levels were more negatively affected by defoliation than plants with no supplementary application of nitrogen. These results indicated that the magnitude of defoliation response for an individual plant was modulated by not only defoliation itself, but also other factors, such as nutrient availability. The increase in the ratio of live to dead plant parts suggested that urine deposition delayed the senescence of plants. The results also showed that (1) the effect of defoliation on primary productivity was affected by the patch size, and (2) nitrogen addition (simulated urine deposition) could increase primary productivity and affect the response to defoliation more obviously in the smaller patches than in the larger ones.
Plasma membrane (PM) vesicles of the leaves of two ecotypes of reed (Phragmites communis Trin.), swamp reed (SR) and heavy salt meadow reed (HSMR) growing in the desert region of Northwest China, were purified by two-phase partitioning and the properties of their PM H+-ATPases (EC 184.108.40.206) were compared. The specific activity of this enzyme was greater in HSMR than in SR and the Km lower (1.27 mmol/L in SR and 0.30 mmol/L in HSMR), and the Vmax of ATP hydrolysis activity showed no significant difference between the two ecotypes. The PM H+-ATPase was more sensitive to denaturing temperatures in HSMR than in SR, and the pH profile also showed a slight difference, suggesting that the catalytic mechanism of this enzyme was different in HSMR compared with that in SR. The p -nitrophenyl phosphate (PNPP) hydrolysis activity of H+-ATPase was higher in HSMR than in SR at low concentrations of PNPP, but showed no difference at high PNPP concentration. The Km for PNPP hydrolysis was 3.61 mmol/L and 1.92 mmol/L in SR and HSMR, respectively. And the Vmax of PNPP hydrolysis showed no significant difference in the two reed ecotypes. An experiment with the inhibitor vanadate showed that the catalytic mechanisms of the phosphatase domain of the ATPase were different in the two ecotypes. The data obtained following trypsin treatment showed a difference in the enzyme activity pattern, suggesting that there existed a possible change in the C-terminus of the ATPase, either in the structure or in the property or both of them. In addition, compared with SR, the ATP-dependent H+ pumping activity of ATPase and the coupling between proton transport and ATP hydrolysis in HSMR were increased. These results indicated that the properties of PM H+-ATPase were changed in HSMR with compared to those in SR, which might include enzyme modifications and different isoforms expressed. The alterations of the properties of this enzyme might be an adaptive response to the habitat.
Effects of nitric oxide (NO) donor sodium nitroprusside (SNP), NO specific scavenger c-PTIO and nitric oxide synthase (NOS) inhibitor L-NAME on the rooting of mung bean (Vigna radiata L.) hypocotyl cuttings were studied. The spatio-temporal changes of NO and NADPH-diaphorase in the basal part of cutting were also detected during the adventitious rooting process. The results showed that SNP significantly enhanced the adventitious rooting in the range of concentrations tested. NADPH-diaphorase activity (commonly employed as a marker for NOS) and the fluorescence of NO were respectively observed in the zone between the vascular bundles of the basal part of cuttings at 24 h and 36 h after cutting. The root primordium became discernible at 48 h after cutting in the same region, and became more elongate at 60 h. NADPH-diaphorase activity and NO fluorescence gradually increased during 48-60 h and mainly distributed in root meristem. L-NAME treatment delayed adventitious root emergency and significantly reduced the NADPH-diaphorase staining and the fluorescence of NO. The specific NO scavenger, c-PTIO, also suppressed the fluorescence and inhibited the formation of adventitious roots. These results suggest that endogenous NO appears to play a key role in the generation and development of adventitious roots, and the production of NO in this process may be catalyzed by NOS-like enzyme.
Water channel proteins facilitate water flux across cell membranes and play important roles in plant growth and development. By GUS histochemical assay in RWC3 promoter-GUS transgenic rice (Oryza sativa L. cv. Shenxiangjin 4), one of the members of water channel proteins in rice, RWC3, was found to distribute widely in variety of organs, from vegetative and reproductive organs. Further studies showed that gibberellin (GA) enhanced the GUS activity in the transgenic calli, suspension cells and leaves, whereas ancymidol (anc), an inhibitor of GA synthesis, reduced the GUS activity. Sucrose was found to inhibit the effects induced by addition of GA, suggesting a possible cross-talk between GA and sucrose signaling on regulation of the RWC3 gene expression.
Azospirillum brasilense Tarrand, Krieg et Döbereiner is one of the important plant growth-promotion endophytes. A. brasilense Yu62 tagged with gfp gene was inoculated into roots of rice and tobacco seedlings, which were then, cultured in gnotobiotic condition. At a certain days after inoculation the different portions of the seedling were observed under laser confocal microscope, resulting in that A. brasilense Yu62 bacteria were colonized in epidermal and cortical cells, intercellular spaces and vascular system of stem and leaf tissue interiors besides in roots. Higher populations of the bacteria isolated from roots, stems and leaves indicated that A. brasilense Yu62 bacteria could ascend themselves from roots to stems and leaves of rice and tobacco. This observation lays down the foundation for ecology and cell morphology of bacterial migration inside plants, interaction between A. brasilense Yu62 bacteria and host cells as well as the plant-growth promotion, provides scientific basis for further application, and is of importance in science and practice.
The precise factors affecting stigma behavior in Campsis radicans (L.) Seem. ex Bureau. remain unclear up to now. In this study mechanical touch, self- and cross-pollination, and pollination with variable amounts of pollen grains separately contacting with stigmas have been conducted to determine the exact factor affecting the stigma behavior. Results show that mechanical touch alone cannot make the stigmas close permanently. It is the adequate pollen (＞350) deposition that causes the stigma permanent closure, which is in accordance with previous reports that sufficient pollen grains are necessary for fruit development. In addition, the stigma behavior does not display differences when pollinated with cross- or self-pollen separately; both self and cross pollen grains can germinate and grow successfully. Our results cannot demonstrate that the stigma behavior in C. radicans is an outcrossing mechanism, but strongly indicate it acts as a mechanism to facilitate pollination, and then enhance the reproductive success.
The ontogeny and vascular systems of female cones of the Fokienia, Cupressus, Chamaecyparis and Juniperus were investigated in detail using scanning electron microscopy (SEM) and conventional light microscopy. In the species examined, in the axils of the bracts, the first recognizable structure was a broad meristematic swelling, from which ovules developed. No ovuliferous scales developed during the ontogeny of the female cones. The number of ovules and ovule developing sequence displayed considerable variation in different species. However, development of the bracts was similar in all of the investigated species. Following pollination, the foliage-like bracts became peltate bract scales due to intercalary expansion, and global cones formed. In addition, the vascular system in the bract scales became intricate, and inverted vascular bundles emerged in the adaxial of the mature bracts. Based on these observations, a morphological interpretation and possible evolutionary trend of the Cupressaceae female reproductive structures was discussed.
Harpins are bacterial proteins that can enhance plant growth and defense against pathogens and insects. To elaborate whether harpins perform the diverse functions in coordination with the activa-tion of specific promoters that contain particular elements, we cloned pathogen-inducible plant promoters PPP1, PPP2, and PPP3 from tobacco and investigated their responses to harpinXoo or its truncated fragments DEG, DIR, and DPR (domains for enhancing plant growth, insect resistance and pathogen resistance). PPP1 contains an internal repeat composed of two tandem 111 bp fragments; 111 bp in the repeat was deleted in PPP2. PPP3 contains a bacteria-inducible element; PPP1 and PPP2 additionally contain TAC-1 and Eli boxes inducible correspondingly by salicylic acid (SA) and elicitors. Function of cloned PPPs was confirmed based on their activation in transgenic Arabidopsis plants by Ralstonia solanacearum (Ralston) or SA. HarpinXoo, DEG, DIR, or DPR activated PPP1 and PPP2 but not PPP3, consistent with the presence of Eli boxes in promoters. PPP1 was ca. 3-fold more active than PPP2, suggesting that the internal repeat affects levels of the promoter activation.
A cDNA library was created from stem apex tissue from Jonathan apples (Malus domestica Borkh.), harvested in June to August, during which the plant transitions from vegetative growth to reproductive growth. From this library, we isolated an expressed sequence tag (EST) sequence containing a zinc finger motif; using this sequence, a 779 bp cDNA fragment was obtained by using 5'' RACE, and a final full-length cDNA encoding an apple zinc finger protein (named MdZF1; GenBank accession number AB116545) was obtained by further PCR. This zinc finger motif of MdZF1 has high homology with INDETERMINATE 1(ID1) gene from maize which seemed to be involved in the transition to flowering. Northern blot and RT-PCR analyses showed that the MdZF1 expressed in the root, stem, leaves, shoot apex and floral organs of the apple, with expression levels higher in root, stem, leaves and floral shoot apex than that in floral organs (sepals, petals, stamens and pistils). Genomic Southern analysis showed that there was a single copy gene in apple genome.
To investigate the possible function of the agglutinin from Amaranthus caudatus L. (ACA) in plant defending against insect pests, ACA cDNA was cloned by RT-PCR and the 5'' and 3'' sequences were confirmed by rapid amplification of cDNA ends (RACE). The phloem-specific expression vector of ACA gene, pBCACAc, was constructed based on the plant binary vector pBC438 and transfered into tobacco plants via Agrobacterium-mediated transformation method. Results from PCR and Southern blotting analysis showed that ACA gene was integrated into the genomes of transformed plants and the transgene integra-tion varied from one to four estimated copies per genome. Western blotting analysis indicated that ACA gene was transcribed and translated in the transgenic plants. The bioassay of Myzus persicae Sulzer on detached leaves demonstrated that the 78% transgenic tobacco plants displayed an average aphid-resistant rate of more than 75%. Some apterous progeny of M. persicae were found dead on the resistant plants. These results indicate that ACA gene should be an effective aphid-resistant gene and could be valuable for application in crop breeding for aphid resistance.
AtLH gene of Arabidopsis is a BcpLH (leafy head) homolog of Chinese cabbage, which encodes a double-stranded RNA-binding protein related to the curvature of folding leaf leading to the formation of leafy head. In order to elucidate the regulatory function of AtLH in the development of leaf curvature, we made a construct of 35S::AtLH and transformed it to Arabidopsis. In transgenic plants for sense-AtLH, transcripts of AtLH gene were increased significantly in leaves and flowers, giving rise to the AtLH-overexpressed plants in which the rosette leaves curved downward or outward in a manner of enhanced epinastic growth. Compared with normal plants, bolting and flowering time of the transgenic plants was significantly delayed. Moreover, the apical dominance of transgenic plants was weaker in vegetative shoots since more axillary shoots emerged from axil of rosette leaves, while stronger in flowering shoots because fewer cauline inflorescences were observed on the main inflorescence. In other aspects, these transgenic plants exhibited an increase in root-stimulating response to IAA and decrease in root-inhibi-tory reaction on ABA. It indicates that overexpression of AtLH causes downward curvature of transgenic plants.
Following differing periods of long-term subculture and selection, two types of calli of the same wheat (Triticum aestivum L. cv. Jinan 177) were obtained. The one (named Cha 9) grew fast and easily formed cell suspensions that were non-regenerable, but the protoplasts possessed a high division capacity. The other (named 176) was regenerable, but the derived protoplasts grew slowly. Fusion combination between either Cha 9 or 176 protoplasts and UV-treated wild millet (Setaria italica L. Beaur.) protoplasts failed to produce regenerated green plants. However, when the two types of wheat protoplasts were mixed together as recipient and fused with wild millet, green plants were obtained. The hybrid nature of regener-ated calli and plants was confirmed by the analysis of cytological, isozyme, 5S rDNA spacer sequences and random amplified polymorphic DNA (RAPD). The chloroplast genomes of hybrids were analyzed with several wheat-specific chloroplast microsatellite (simple sequence repeat, SSR) primers. A hybrid clone carrying recipient DNA of Cha 9 and 176, as well as both nuclear and chloroplast donor DNA had a high regeneration capacity and produced more vigorous green plants than did the other clones.
Five neolignans including four new ones were obtained from the seed endotheliums of Trewia nudiflora L. Their structures were determined to be 9''-methyl americanol A (1), 9''-methyl isoamericanol A (2), 9''-ethyl americanol A (3), 9''-butyl americanol A (4), and americanin (5). Two acetylated products 3,4-diacetyl americanin (5a) and 3,4,9-triacetyl americanin (5b) had been prepared from compound 5. All of these compounds were investigated on antibacterial assays when carbenicillin sodium, streptomycin sulfate and rifampicin were used as positive controls. Compounds 4 and 5 exhibited antibacterial activities against gram-positive bacterium Staphylococcus aureus and gram-negative bacterium Mycobacterium tuberculosis at the minimum inhibitory concentrations (MIC) of 50 mg/mL and 100 mg/mL, respectively, but 5a and 5b did not exhibit antibacterial activity at 200 mg/disk.
The structure of a bioactive fructan RCP isolated from the traditional Chinese medicinal herb Cyathula officinalis Kuan was determined by NMR, methylation, reductive-cleavage and GC-MS analyses. It was a highly branched fructan possessing a (2→1)-linked b-D-fructofuranosyl (Fruf ) backbone with (2→6)-linked b-D-Fruf side chains, belonging to neokestose family. Of the 93.17% b-D-Fruf residues, 24.15% was terminal, 26.24% was 1-linked, 20.46% was 6-linked, and 22.32% was 1,6-linked. Of the 6.83% a-D-glucopyranosyl (Glcp) residues, 2.14% was terminal and 4.69% was 6-linked. A structural model was postulated for a degree of polymerization (DP) of 15.
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