Caragana has a temperate Asian distribution. Based on the phylogeny and 13 distributional areas of this genus, its ancestral area was studied via the ancestral area analysis suggested by Bremer (1992), Ronquist (1994) and Hausdorf (1997). The results indicate that three areas, Far East-Northeast China, Altai-Sayan and North China-Qinling Mountains (Mts) are likely the ancestral areas. Linking to the viewpoints of the Holarctic origin for north temperate flora, Far East-Northeast China seems more likely to be the ancestral area. According to the three ancestral areas isolated geographically and the analysis in the present study, as well as former biogeographical analysis of this genus, it is suggested that Caragana speciation is mainly in the mode of vicariance rather than dispersal, and dispersed is often in short distance.
The typical steppe ecosystems in China are now being increasingly degraded due mainly to overgrazing. To determine the limiting nutrients is of significance in order to find out ways of successfully restoring the degraded steppe. In addition to field fertilization experiments, N:P stoichiometry is an alternative, but argumentative tool to study nutrient limitation. In this study, we used these two approaches to identify the most limiting nutrient element at the species level. Furthermore, nutrient addition experiment provides an effective means to test our hypothesis that N:P stoichiometry will remain constant because relatively narrow range of N:P ratio in tissues of the terrestrial plants is an important adaptive mechanism for plants to survive on earth. For these purposes, we designed a field experiment to examine the responses of biomass and N:P stoichiometry of the two dominant species — Leymus chinensis (Trin.) Tzvel. and Carex korshinskyi Kom. — to N fertilization at rates of 0, 5, 15, 30, 50 and 80 g NH4NO3.m-2.a-1 in two adjacent sites, one being excluded animal grazing for 22 years (site A), and another being free of grazing for only two years (site B) before the experiment was carried out. No effects of N fertilization were detected in the first year as reflected by the aboveground biomass and P concentrations of the two species. The regression analysis showed that N:P ratios of two species of both sites remained constant in the second year. N fertilization significantly increased the N concentrations of two species in both years, while only significantly increased the P contents of the two species in the second year. N and P contents of the two species were significantly correlated in all cases in 2001. Our results suggest that the L. chinensis was in short of N in site B while the growth of C. korshinskyi was limited by P in site A, and there is a significant synergistic relationship between tissue N and P concentrations in 2001. Our hypothesis was valid on the species level since N:P ratio of the two species remained constant with increasing N application rates after two years of fertilization. We argue that it may be inappropriate to define an ecosystem which is limited by certain nutrient elements since the responses of coexisting species present in a community to nutrient additions can vary tremendously.
The flowering phenology, pollination ecology and breeding system of Caesalpinia crista L. were studied in Dinghushan Nature Reserve, Guangdong, China. The species started blooming in February or March, then last till late April. It took about one week from first flower appearance to its full blooming, which lasted for 2-4 d. The pollen-ovule ratio was 18 000±500. The breeding system was self-incompatible, and protogynous xenogamy. Hymenoptera constituted the major group of pollinators. The pollination type is ambophily, the species could be pollinated by wind if the pollinators were unavailable: this is the first record of ambophily in the genus Caesalpinia. The floral structure adaptation to the pollinating behavior of carpenter bees was described. The influences of artificial treatments in pollination biological studies on the flowering and fruiting of the plants were also discussed.
The fate of 15N-labeled ammonium and nitrate was determined in a Kobresia pygaea C. B. Clarke meadow after 11-13 months following 15N additions in order to understand the role of alpine meadows in retention of deposited nitrogen (N). It was shown that the fate of NO3--15N or NH4+-15N was distinctly different. In 11-13 months after 15N additions, total 15N recovery of NO3--15N was 92.83%, 92.64% and 79.96% while 15N recovery of NH4+-15N was 49.6%, 63.33% and 66.22%. Their different fates were obviously shown on partitioning of 15N among different components in alpine meadows. After 11-13 months following 15N additions, more NO3--15N was recovered in plants than in soil organic matter or in soil microorganisms. 15N retained in soil organic matter was also high and increased with time. 15N immobilized in soil microorganisms was close to that retained in soil organic matter within 11-12 months while it decreased significantly after 13 months. When NH4+-15N was added, more 15N was retained in soil organic matter than in plants or in soil microorganisms. 15N taken up by plants was constant while that immobilized in soil microorganisms altered greatly. Eleven to thirteen months after 15N additions, plants and soil microorganisms took up more NO3--15N than NH4+-15N while soil organic matter recovered more NH4+-15N than NO3--15N. It indicates that alpine meadows play different roles in retention of deposited NO3- and NH4+ after a long time.
Gas exchange, water relations and leaf chemical characteristics were examined of two dominant psammophytes: Artemisia frigida Willd and A. halodendron Turcz. ex Bess in Horqin sandy land, Nei Mongol, China under different water regimes. The measurements were conducted by submitting the plants to five different irrigation levels. A. frigida was characterized by lower photosynthetic rate (Pn), lower transpiration rate (TR) and lower shoot water potential (Yw) relative to A. halodendron. Foliage of A. frigida had higher values of relative water deficit (RWD), bound water content (BWC), ratio of bound water content to free water content (BWC/FWC) and integrated drought-resistant index (DI) than that of A. halodendron. Water relations differed significantly between two species in response to soil water availability. Yw, BWC and BWC/FWC ratio of A. halodendron exhibited large variation with gradual decrease of soil moisture. However, in terms of these parameters, A. frigida was characterized by higher capacity of water holding and drought tolerance relative to A. halodendron. Proline and total soluble sugar contents of A. frigida and A. halodendron tended to increase with decrease of soil moisture and the former had a larger increase amplitude than the latter. This shows that A. frigida has a higher osmotic regulation ability than A. halodendron. Under the extreme drought conditions, Yw, RWD, BWC and BWC/FWC of two species were approximate, but soluble proteins degraded largely. A large amount of accumulation of organic matter, proline and total soluble sugars were observed in both A. halodendron and A. frigida. The increase in proline and total soluble sugar contents and soluble protein degradation of A. frigida far exceeded those of A. halodendron. We believe that the accumulated materials at this moment are mostly of nutrient substances available for the recovery of plants after the drought. This is one of the reasons why A. halodendron plants died while A. frigida plants survived under extremely drought condition. Our results suggest that these ecophysiological features of A. frigida are favorable to its growth in the fixed sandy land compared with A. halodendron, which often lost its dominance due to weak competition for water sources under lower soil water availability and are major factors resulting in replacement of A. halodendron by A. frigida in the later stage of sandy vegetation succession in Horqin.
In plants, triose phosphate/phosphate translocator (TPT) is the first regulation point for partitioning of photosynthate between source and sink. Studies on the characteristic of TPT and its regulation on the distribution of assimilates are critical for improving the utilization rate of photosynthetic assimilates. Chloroplasts with intactness of more than 91% and high purity were isolated from wheat (Triticum aestivum L. cv. Jing 411) leaves. Analysis of SDS-PAGE and labeling with an irreversible specific inhibitor, [H3]2-DIDS (4, 4''-diisothiocyano-2, 2''-stilbenedisulfonate, DIDS) demonstrated that wheat TPT was a chloroplast membrane protein with a 35 kD molecular weight, which comprised about 15% of the total membrane proteins of chloroplasts. Western blotting analysis showed that wheat TPT is uniquely distributed in the envelope membrane of chloroplasts, but not detected in the membranes of vacuoles and mitochondria. The silicone-oil-layer centrifugation system was employed to study the kinetic properties of TPT. The results showed that the maximal transport activity of TPT was the highest for dihydroxyacetone phosphate (DHAP)/inorganic phosphate (Pi), then for phosphoenolpyruvate (PEP)/Pi and glucose-6-phosphate (G6P)/Pi. The Km value of TPT was the lowest for DHAP, followed by Pi, PEP and G6P, therefore the most preferred substrate of TPT is DHAP. The transport of wheat TPT to DHAP was strongly inhibited by DIDS with a degree of 95%. Inhibition of TPT transport activity led to an obvious accumulation of starch in chloroplasts, therefore the TPT protein of wheat controls the export of TP out of chloroplasts into cytosol. Except for the need of participating in the Calvin cycle, the ratio of TP exported out of chloroplast to the one used for synthesizing starch was at least 93.6:6.4. The TPT protein from wheat has much high transport efficiency, which plays an important role in the regulation of the distribution of assimilates in wheat chloroplasts.
It is reported that chromosome 1R of rye (Secale cereale L.) convey phosphorus use efficient gene (s), and 1RS/1BL translocation genotype Lovrin No.10 is P use efficient. So we hypothesized whether P efficient gene(s) locate on 1RS, and the high P efficiency of Lovrin No.10 is from 1RS? To test this hypothesis, we investigated the P use efficiency (PUE) of a doubled haploid (DH) population with 61 lines derived from anther culture of F1 hybrid between Lovrin No.10 and phosphorus uptake inefficient genotype Chinese Spring to see whether PUE differs between DH line with and without 1RS/1BL translocation. Acidic polyacrylamide-gel electrophoresis (A-PAGE) of gliadin and genomic DNA in situ hybridization (GISH) were employed to discriminate 1RS/1BL translocation DH lines from the normal 1B DH lines. Among the 61 DH lines investigated, A-PAGE analysis showed that 34 lines contained the 1RS/1BL translocation chromosome, which was characterized by the presence of a 1RS-specific Sec-1 marker bands. Further verification with GISH proved that 33 in the 34 lines contained a pair of homozygous 1RS/1BL translocation chromosomes, only one line was a 1RS/1BL monosomic line. A field experiment was carried out on P deficient soil to investigate grain yield, biomass, numbers of spikes per plant (SPP), P uptake efficiency (PUpE), and P utilization efficiency (PUtE) of the DH lines and their parents under -P (nil P applied) and +P (60 kg P/hm2 applied) at maturity. Results showed soil P deficiency decreased the values of the first four traits in Lovrin No.10, but were more severe for Chinese Spring. Lovrin No.10 had higher values of all the above tested traits at both -P and +P than Chinese Spring did, but had similar PUtE with Chinese Spring. These five traits segregated, and differed greatly among DH lines under both -P and +P conditions. Although the variations among DH lines exceeded the difference between the two parents, the average values of the DH lines were between the two parents. The average of the above five traits, and P deficiency tolerance (PDT) (measured by relative grain yield of -P/+P) were not different between the DH lines with and without 1RS/1BL translocation. This indicated that there was no association between 1RS and PUE and PDT in Lovrin No.10, and 1RS may not have P efficient gene(s). Therefore, in the offspring of Lovrin No.10, it is possible to combine high PUE and PDT with good quality without the negative effect of 1RS on flour quality.
Transmission electron microscopy (TEM) observation of pollen grains of 18 species belonging to 18 respective genera of the tribe Peucedaneae Drude revealed distinct ultrastructural difference in the pollen exine, including the thickness and features of tectum, columnar layer, foot layer and endexine. The systematic position of those 18 species are re-evaluated based on their ultrastructural characteristics of pollen exine observed in this study. Seven genera related to Angelica L. in Angelicinae Drude have been deduced to genus Angelica L. For example, Ostericum grosseserratum (Maxim.) Kitagawa was changed to Angelica L. by some authors, but it differs from Angelica sinensis (Oliv.) Diels in having well developed tectum which is thicker than the columnar layer and foot layer. Its columnar layer is quite well-developed with long and branched columellae. Besides its surface is tuberculated. Evidently, its development exceeds that of Angelica sinensis. However, it is only a moderate evolutional species in its genus, and the Angelica sinensis accounts as the most advanced species in Angelica Diels, thus, placing genus Ostericum Hoffm. in Angelica L. is not suitable, it may be more appropriate to keep its original position. In addition, Ferula akitschkensis B. Fedtsch. ex K.-Pol. differs greatly from those of Talassia transiliensis (Herd.) Korov. and Schumannia turcomnnia Kuntze, because of its very well-developed columnar layer, being about four to five times thicker than the total of tectum and foot layer, tuberculated tectum surface and complicated structure of columnellae. As another species Heracleum forrestii Wolff also differs from Semenovia rubtzovii (Schischk.) Monden. in having an even thickness of exine and well-developed columnar layer, it seems suitable that they should also be treated as two independent genera.
The stigma initiation and development of Cucumis sativus L. female flower was studied using electron microscopy. The differentiation of stigmatic cells could be recognized when the floral bud was about 1 mm in length. After the pinnate structure of the stigma appeared, three regions indicating the papillae, the transmitting tissue and the secretory tissue were observed. The pinnate stigma was characterized as a partition structure for naming immature and mature stigma in the following investigation. The ultrastructure of various tissue cells of the stigma during the development was observed using transmission electron microscopy. Throughout the whole developmental process the cytoplasm of papillae and secretory tissue cells was filled with many endoplasmic reticula (ER). Most of the ER was tube-like and rough with enlarged cisterna from which many vesicles were produced. In the mature stigma, numbers of plasmodesmata were found between the secretory and the transmitting tissue cells. The papillae and secretory tissue cells are highly vacuolated and the plasmalemma was invaginated or exvaginated. The nuclear envelope of secretory tissue cells was enlarged, which led to the formation of plurivalvis nucleus during stigma development. Apparently, nuclear envelope became more strongly lamellate at mature stage. In different tissue cells of mature stigma, ATPase activity was localized along the plasmalemma and vacuole membrane. The PM-H+-ATPase specific activity increased during stigma development. Our results revealed the glandular characteristics of the developing stigma of cucumber female flowers.
Grifola umbellata (Pers.) Pilat is a fungus whose sclerotium has potent pharmaceutical values. The present study shows that its sclerotia can be reproduced from the hyphae, in addition to its traditional mode of reproduction from sclerotia. On a culture medium, the hyphae first become swollen and enlarged followed by differentiation to form a highly organized structure, sclerotia. We demonstrate that at a microscopic level, sclerotia derived from hyphae and sclerotia obtained in the field are similar, both having cortex and medullary substances.
Hairpin RNA (hpRNA) can induce post-transcriptional gene silencing, and was constructed with 128-754 bp of segment 8 of rice dwarf virus then placed under the control of the CaMV35S promoter and used to transform rice cultivar “Zhonghua 11” via Agrobacterium tumefaciens. A total of 12 independent lines containing hpRNA were obtained as demonstrated by Southern blotting analysis. Challenge inocula-tion with rice dwarf virus (RDV) viruliferous leafhoppers (Nephotettix cincticeps) showed that T1 plants containing the hpRNA transgene displayed high resistance or delayed and attenuated viral symptoms. In contrast, transgenic lines expressing sense RNA showed severe symptoms similar to control plants trans-formed with the vector alone. These results suggest that hpRNA confers high resistance to RDV in transgenic rice.
It is well accepted that S type of cytoplasmic male sterility (CMS) in maize (Zea mays L.) is associated with R region in mitochondrial genome. R region includes two open reading frames — orf355 and orf77 and it is speculated that orf77 is an important candidate gene of CMS. RT-PCR showed that both DNA strands of R region are transcribed. Nuclear background or developing stages of plant do not influence the transcription of R region in the strand which also acts as template strand of coxⅠ/coxⅡ locating just upstream of R region, but they do influence the transcription of R region in the other strand (template strand of orf355-orf77). In tassel with nuclear background of rf3rf3, transcription of the template strand of orf355-orf77 is different from that in etiolated shoots with nuclear background of Rf3- or rf3rf3 and tassel with nuclear background of Rf3-. Compared to the same other three, it is truncated at about 238 base from the 5'' end of R region. Rabbit antiserum against putative ORF77 expressed in Escherichia coli was prepared but Western blot did not detect ORF77 in plant materials. It seems that double-strand transcription of R region inhibits the translation of orf77 and the transcribing mode of R region may be associated with male sterility.
A stable transformation system for the expression of foreign genes in the unicellular green marine alga (Dunaliella salina Teod.) was established. Using electroporation, the alga was transformed with a plasmid containing the hepatitis B surface antigen (HBsAg) gene and the chloramphenicol acetyltransferase (CAT) gene as a selectable gene. PCR and Southern blotting analysis indicated that the HBsAg gene was integrated into the D. salina genome. Northern dotting analysis showed that the HBsAg gene was expressed at the mRNA level. The stable expression of HBsAg protein in transformants was confirmed by HBsAg enzyme-linked immunosorbent assay (HBsAg ELISA) and Western blotting analysis. Also, PCR and Southern blotting analyses showed that the CAT gene was integrated into the D. salina genome, and CAT ELISA indicated that CAT protein was stably expressed in the cells. The introduced HBsAg DNA and HBsAg protein expression were stably maintained for at least 60 generations in media devoid of chloramphenicol. This is the first report of the stable expression of foreign genes in D. salina .
This paper reports the cloning and expression analysis of a high-affinity nitrate transporter in wheat (Triticum aestivum L.). A full-length cDNA, TaNRT2.3 (accession number AY053452), was isolated from NO3–-induced roots of wheat. The cDNA encodes a polypeptide with 507 amino acids and 12 transmembrane domains, belongs to nitrate/nitrite porter (NNP) family within the major facilitator superfamily (MFS), and is closely related to other NRT2 proteins from plants. The expressions of TaNRT2 genes in wheat tissues were analyzed using Northern blot, results indicated that TaNRT2 were induced specifically in roots but not in shoots in response to both low (5-200 mmol/L) and high (2.0 mmol/L) concentrations of NO3–. TaNRT2 transcripts were undetectable in N-deprived or NH4+-grown plant roots. The significant correlation between the time course of TaNRT2 transcription accumulation in the roots of wheat plants grown in 0.2 mmol/L NO3– and the time course of the nitrate uptake rates by wheat plants grown under the same conditions suggested that TaNRT2 played an important role in high-affinity NO3– uptake. Using the split root system, we found that supplying NO3– to one part of the roots induced the expression of TaNRT2 in the other part not supplied with NO3– or supplied with NH4+, which implied that N cycling within plants acted as a regulatory signal for N uptake.
Xyloglucan endotransglycosylase (XET) is thought to be involved in fruit softening through disassembly of xyloglucan, which is the predominant hemicellulose of cell wall. To study the relationship between fruit softening and XET during banana (Musa acuminata Colla cv. Grand Nain) fruit ripening, a full length cDNA (1 095 bp) encoding an XET, MA-XET1, was isolated from ripening banana fruit using RT-PCR and RACE-PCR (rapid amplification of cDNA ends) methods. Sequence analysis showed that the cDNA contains 5'' untranslated region of 66 bp, 3'' untranslated region of 189 bp and ORF of 840 bp, encoding a predicted polypeptide of 280 amino acids, including DEIDFEFL motif, which is a presumptive catalytic domain conserved in XETs. DNA gel blot analysis demonstrated that MA-XET1 is encoded by a multi-copy family in the banana genome. RNA gel blot analysis revealed that the level of MA-XET1 transcript in the pulp was undetectable, increased and decreased slightly at the preclimacteric, climacteric and postclimacteric stages, respectively. In the peel, accumulation of MA-XET1 transcript was low, increased dramatically and then decreased rapidly, at preclimacteric, climacteric and postclimacteric stages, respectively. Treatment of fruit with propylene, an analog of ethylene, decreased the firmness and enhanced the accumulation of MA-XET1 transcript in the peel and pulp. These results suggest that MA-XET1 is involved in softening of the peel and pulp during banana fruit ripening and its expression is regulated by ethylene at transcriptional level.
To isolate seed-expressed sequences, a cDNA library was constructed using wheat (Triticum aestivum L.) seed tissues at 12 d after pollination. Plasmid DNAs of 10 000 clones randomly picked out from the library were prepared. The preparation of high density filters were made with the Biomek 2000 HDRT system, and then hybridized separately with three probes prepared by reverse transcription of RNA of unpollinated ovary, embryo and endosperm. Based on the hybridization results, 800 clones expressed in embryo and/or endosperm were chosen for further analysis of expressed sequence tags (ESTs). Finally, 216 different genes were identified preliminarily. Of them, 24 (11.5%) were considered identical to known wheat genes, 122 (56%) were identified as putative new plant genes which may be involved in seed storage proteins, biochemical metabolisms, development, and other biological processes of seeds, while 70 (32.5%) sequence identities could not be determined.
A phytochemical investigation of the bark of Erythrophleum fordii Oliv. furnished five compounds. One is a new triterpenoid, namely 20S, 24S-epoxy-23S, 25-dihydroxy-dammarane-3-one (1), and four are known, identified to be 20S , 25-epoxy-24R -hydroxydammarane-3-one (2), 20S, 24S -epoxydammarane-3b,25-diol (3), betulinic acid (4), morolic acid acetate (5). All the known compounds were isolated from the species for the first time. The structure of compound 1 was elucidated on the basis of spectroscopic analyses.
A novel C30 sterol, (22E, 24x)-24-n-propylcholest-7, 22-dien-3b-ol (racemosol, 1), along with scopoletin (2), scopolin (3), umbelliferone (4), methyl b-D-frucopyranoside (5), syringaresinol-4-O-b-D-glucopyranoside (6), quercetin-3-O-b-D-glucopyranoside (7), quercetin-3-O-a-L-rhamnopyranoside(8), eupatilin (9), kaempferol-3-O-b-D-glucopyranoside (10) and (E)-N-2-(2,3-dihydroxyphenyl) ethyl cinnamamide (11), was isolated from the whole plants of Porana racemosa Roxb. Their structures were elucidated predominantly by spectral evidence.
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