In the past decade, our understanding of the mechanisms of water uptake by plant roots at the cell, tissue, and whole-plant levels rapidly progressed due to the introduction of new techniques and concepts. Some aspects of this work were reviewed, mainly including the composite structure of roots and effects of the distribution of roots in the soil. The nature of water flow in plant roots was discussed. A link was provided between root hydraulics and the expression and function of aquaporins. This was related to the regulation of water transport and to the signaling between roots and shoots. The composite transport model of root was mentioned which represents a physical model of water uptake. This is part of a comprehensive analysis of recent findings of studies on water uptake by plant roots and contributes to our current understanding of the basic mechanisms that govern the water uptake by roots.
Sonneratia alba J.Smith is a widely distributed mangrove species. Leaf samples of one hundred individuals from four natural and one introduced populations in Hainan Island, China, were collected. Genetic variation among the five populations was evaluated using inter-simple sequence repeats (ISSR) markers. Eleven ISSR primers gave rise to 133 discernible DNA fragments of which 103 (77.44%) were polymorphic, indicating a considerable genetic variation at the species level. However, the polymorphism at the population level was relatively low, with the percentage of polymorphic bands from 51.88% to 65.41%. The mean expected heterozygosity and Shannon’s information index were 0.227 1 and 0.348 9 respectively at the species level, 0.183 7 and 0.277 5 at the population level. Based on Nei’s Gst value, a large proportion of genetic variance (81.02%) was resided among individuals within populations, however, only 18.98% genetic variance was resided among populations. AMOVA analysis also indicated a similar genetic structure. The genetic identity between populations was 0.934 2 on average. UPGMA cluster analysis based on Nei’s genetic distance divided the populations into two main groups: Linshui population (LS) and Sanya population (SY) formed one group, Qionghai population (QH), Wenchang population (WC) and Dongzhai Harbor population (DZ) were in the other group. The Mantel test showed that genetic distance was significantly correlated with geographical distance.
Consecutive investigations in 1994, 1996, 1998, and 2002 in the permanent plots established in Futian Mangrove Reserve of Shenzhen, Guangdong Province, revealed that the breaking, drying and death of the individual plants or branches in the mangrove communities were significant and the number of plants in plots covering an area of 200 m2 was 417, 341, 196 and 132; the average density of population per square meter is 2.08, 1.70, 0.98 and 0.66; the death rate between the interval of two investigations is 18.2%, 42.5% and 32.6% respectively. The individuals of population exhibit an obvious diameter at breast height (DBH) growth. For example, the maximum increment of individual DBH was up to 3.63, 2.45, and 4.52 cm in the dominant populations Aegiceras corniculatum (L.) Blanco (Ac), Kandelia candel (L.) Druce (Kc), and Avicennia marina (Forsk.) Vierh. (Am), respectively. At the same time, growth of individual height was also prominent. In the second investigation, 233 out of the 341 individuals exhibit a height growth; whereas the number under the third and fourth investigations was 127 out of 196 and 74 out of 132, respectively. During a 2-year interval, the maximum height growth was 1.5 m in Ac, 1.9 m in Kc, and 1.8 m in Am. The biomass also showed a relative change in the mangrove communities. The total biomass of stems and leaves decreased with time but occasionally an increase was found in the second and third investigations and finally a decrease in the fourth investigation. However, the average biomass of the survived individuals usually increased with time. In terms of the total biomass, the results of the four investigations were similar to the previous research in which the data were calculated by the methods of standardized timbers, etc. being 7.57, 8.36, 5.15 and 7.71 kg/m2 during 1994, 1996, 1998 and 2002, respectively. The above analysis indicates that self-thinning of mangrove communities is an important evolutionary process, characterized by drying, breaking, and death of individuals/ramifications. During the process of evolution, fewer new seedlings developed, and individual height growth, DBH growth, breaking and death from dryness maybe closely related to the composition, structure, and density of population in the mangrove communities.
The responses of field-grown Fagus engleriana seedlings to light and soil nutrient availability were investigated. Two-year-old seedlings were grown for two growing seasons under six treatment conditions, including three light levels (L1: 1%-2% of full sunlight; L2: 18% of full sunlight; L3: 100% of full sunlight), with and without , fertilizer addition (F1 and F0) for each light level. The results showed that light and nutrients had significant effect on seedling growth as measured in terms of shoot height, stem basal diameter and biomass; the mean increments of shoot height over two growing seasons were significantly less in L1 than in L2 and L3 (P ＜0.001), and in L3 than in L2 (P ＜0.01), but the increments during the first growing season were not significantly different among the treatments; the increments of stem basal diameter and biomass components were significantly less in L1 than in L2 and L3 (P ＜0.001); the increments of stem basal diameter and whole plant biomass were not statistically different between L2 and L3; adding fertilizer did not affect the seedling growth under closed forest canopy, but had effect in the environments with more sunlight. The results suggest that (1) two-year-old F. engleriana seedlings could survive the conditions of closed forest canopy, but their growth might be severely inhibited; (2) the seedlings could grow as well as or even better in small forest gaps than in open sites; and (3) fertile soil might enhance seedling growth in forest gaps and open sites, but not under closed forest canopy.
Photosynthetic C4-microcycle and its function in different genotype rices were explored comparatively using PEPC transgenic rice and homozygous wild genotype (WT) rice (Oryza sativa L. subsp. japonica Kitaake) as experimental material. In untransformed WT, there existed an intact C4 photosynthetic enzyme system detected by the activities of enzymes of photosynthetic C4 pathway, i.e. phosphoenolpyruvate carboxylase (PEPC), NADP+-malic enzyme (NADP+-ME), NADP+-malate dehydrogenase (NADP+-MDH), pyruvate orthophosphate dikinase (PPDK), and indicating that there is a primitive photosynthetic C4-pathway with increased photosynthetic rate in leaf discs or chloroplasts fed with exogenous oxaloacetate (OAA) or malate (MA). Furthermore, photosynthetic C4 microcycle was promoted in a great range in transgenic rice introduced a maize specific PEPC gene. Enhancement of photosynthetic C4-microcycle further played some role in raising the net photosynthetic rates (Pn) and debasing the ratio of Pr/Pn by comparing the CO2 gas exchange rates in different genotype rices, WT rice and PEPC transgenic rice. Analyzing the chlorophyll a fluorescence characteristics showed that increase of photosynthetic C4-microcycle companied with the raising PSⅡmaximum photochemical efficiency (Fv/Fm) and photochemical quenching (qP), and the lowering of non-photochemical quenching (qN). These results will provide scientific evidence for genetic breeding to improve photosynthetic efficiency in crops by gene engineering.
The diurnal photosynthesis and photoinhibition in the photoperiod-sensitive genic male-sterile rice (Oryza sativa L.), Nongken 58S (NK58S), were investigated in this paper. From 06:00 to 09:00, no remarkable photoinhibition occurred, and the down-regulation of photosynthesis might be due to the running of xanthophylls cycle. From 10:00 to 12:00, the specific energy flux for dissipation (DIo/RC) and the net rate of reaction centers (RCs) closure (dV/dto) were increased, while the probability of electron transport at the acceptor side (yo) and the density of active RCs (Do) were decreased. These indicated that the photoinhibition of NK58S was exacerbated with the inactivation of PSⅡ RCs. Fluorescence dark relaxation analysis and inhibitor treatment suggested that all of state transition, xanthophyll cycle and inactivation of PSⅡ RCs could contribute to protect NK58S against photodamage. Compared with the inactivation of PSⅡRCs, xanthophyll cycle had an immediate response to high light stress, which functioned mainly in the period of relatively low light intensity. However, the inactivation of PSⅡ RCs played an important role in protecting the remaining active RCs when xanthophyll cycle was saturated.
Incorporating C3 plants with C4 photosynthesis traits by genetic engineering are available for improving plant productivity. Although rattans are a special and big group of plants including 13 genera and ca. 600 species in the world and have been studied since the mid-nineteenth century, the knowledge of its photosynthetic pathway is still lacking. Therefore, it is meaningful to determine the photosynthetic pathway of rattans. It was reported that chlorophyll a/b value, ratio of stomata occurrence on upper to lower epidermis, activities of phosphoenolpyruvate carboxylase (PEPC) and pyruvate phosphate dikinase (PPDK), and stable carbon isotope ratio in leaves of C3 plants were lower than those of C4 plants, thus this study tested them with seedlings and adult plants of the three rattan species, Daemonorops margaritae (Hance) Becc., Calamus simplicifolius C. F. Wei and C. tetradactylus Hance occurring in South China. The results showed that values of these indices were rather low, falling into the ranges of other C3 plants, so it was concluded that three rattan species were C3 plants.
Anatomical studies of the culm of Triticum aestivum L. cv. Xiaoyan 81, a comparatively lodging resistant cultivar, from its maternal parent Xiaoyan 54 and paternal parent 8602, was carried out by means of various microscopic techniques coupled with chemical analysis. It was found that the culm of Xiaoyan 81 possessed shorter diameter, thicker width, higher thickness-diameter ratio and higher percentage of mechanical tissue, comparing with its parents. Furthermore, the lignin content was determined by Klason’s method and semi-quantitatively analyzed with confocal laser scanning microscopy (CLSM), histochemical staining, and Fourier transform infrared spectroscopy (FTIR), and the results revealed a much higher lignin content in the culm of Xiaoyan 81 than that in the Xiaoyan 54 and 8602. All of these findings provided anatomical and chemical evidence for a better quality in biomechanics of culm in cv. Xiaoyan 81 than that in its parents.
OsZFP1 (Oryza sativa zinc finger protein No.1) gene encodes a protein containing three putative Cys2/Cys2-type zinc-finger domains, and is negatively regulated by salt stress. The plant expres-sion vector carrying the OsZFP1 gene was constructed under the control of 35S promoter in pCAMBIA1300, and then transformed into Arabidopsis plants and rice calli to overexpress OsZFP1 gene. Both the transgenic Arabidopsis plants and the transgenic rice calli were more sensitive to salt treatment than the wild type. This result implies that OsZFP1 gene may function as a repressor, which probably inhibits the expression of some salt-inducible genes. The transgenic Arabidopsis plants also bolted later than wild type plants upon ABA treatment, suggesting that the function of the OsZFP1 gene may be regulated by ABA.
An extended investigation was carried out for further demonstrating single-embryo RT-PCR technique, which was previously established in our laboratory as a useful tool on study of gene expression of Arabidopsis thaliana (L.) Heynh. Based on the previous work some important technical aspects in the application of the technique were mainly discussed in the present report. The dynamic expression of three selected genes, shoot-meristemless (STM), monppteros (MP) and Arabidopsis shaggy-like kinase etha (ASKh), during the embryogenesis were carefully compared. It was revealed that the technique was especially useful for tracing the expression dynamics of specific genes during embryogenesis. However, the quantity of starting material and the duration of DNaseⅠ treatment are critical points for successful application of the technique. The best condition for eliminating the possible influence of genomic DNA on data analysis was also tested and discussed.
Ty1/copia-like sequences were amplified from mung bean (Vigna radiata (L.) Wilczek) genomic DNA, by PCR with degenerate oligonucleotide primers corresponding to highly conserved domains in the Ty1/copia-like retrotransposons. PCR fragments of roughly 270 bp were isolated and cloned, and forty clones were sequenced. Thirty-six of the forty clones had unique nucleotide sequences, and eighteen clones had a frameshift, a stop codon, or both. Alignment of the nucleotide sequences indicated that these clones, denoted Tvr, fell into nine subgroups and nine ungrouped sequences. The nucleotide sequence similarity between these elements ranged from 8% to 100%, which indicates high level of sequence heterogeneity among these clones. A phylogenetic analysis comparing these clones with corresponding sequences from other plant species showed that some of the Tvr clones are more closely related to Ty1/copia-like retrotransposons from other species than to other Tvr clones. Dot blot analysis revealed that Ty1/copia-like retrotransposons comprise about 9.3% of the mung bean genome.
Using reverse transcription-polymerase chain reaction (RT-PCR) and rapid amplification of cDNA ends (RACE) strategies, two chalcone synthase (CHS) cDNAs were cloned from developing seeds of blue-grained wheat, both of the deduced peptides contain 394 amino acids, and share 98.9% of amino acid sequence identity and the nucleotide sequences have the identity of 96%, and one flavonoid 3''5''-hydroxylase (F3 ''5 ''H) 3''-end cDNA was isolated. Four CHS genomic DNAs were cloned from Thinopyrum ponticum (ThpCHS.tg), blue-grained wheat (TaCHS.bg), white-grained offspring of light blue-grained wheat (TaCHS.wg) and Chinese Spring (2n=42)(TaCHS.csg), respectively. Although these four genomic DNAs were isolated from different materials, they are very highly homologous and each has one intron. The difference of the four CHS genomic DNAs mainly exists in intron. Through DNA alignment we found that one CHS cDNA (TaCHS.t1) came from one of the parents, Th. ponticum, the other one (TaCHS.w1) had the identity of 100% with white-grained parent. This indicated that CHS genes from two parents expressed at the same developing stage in blue-grained wheat. Southern blotting analysis showed that they have at least four copies in wheat, the copy numbers in different color grains are not significantly different, but they are different from that of Th. ponticum. CHS in blue-grained wheat belongs to a CHS multifamily. Reverse Northern analysis indicated that the CHS expressed strongly in the developing blue-grained seeds at early stage (15 d after flowering, DAF), but F3 ''5 ''H and dihydroflavonol 4-reductase (DFR) transcripts accumulated less than that of CHS at early stage. However, at the later developing stage (21 DAF), F3 ''5''H and DFR transcripts accumulated more than that of CHS, the transcripts of CHS could hardly be detected. The expression order of the three genes is the same as the order of the biosynthetic steps in anthocyanin biosynthesis. At the same time, CHS genes cloned from seeds have not been detected in leaves of blue-grained wheat, but F3 ''5 ''H and DFR expressed strongly in leaves. This showed that the expression of CHS genes cloned by us had tissue specificity. RT-PCR indicated that the transcripts of F3 ''5''H accumulated a lot in the developing seeds of blue- and white-grained wheats at 21 DAF, but the transcripts of CHS and DFR accumulated in the blue-grained wheat more than those of white-grained wheat and Chinese Spring at the same developing stage. Therefore, we proposed that anthocyanin biosynthetic pathway existed in blue-grained wheat and the expression of the secondary structure genes in anthocyanin biosynthetic pathway was coordinately regulated by regulatory gene(s) during the period of blue pigment formation.
Soybean (Glycine max (L.) Merrill) is one of the recalcitrant crops to be manipulated in vitro. To improve Agrobacterium-mediated soybean cotyledonary node transformation efficiency, a new solidliquid medium selection system based on using the bar gene as the selectable marker has been developed. The cotyledonary nodes were first cultured in MS solid medium modified with 2 mg/L 6-BA and 5 mg/L glufosinate for two weeks, and the surviving explants were transferred into a liquid selection medium with 2 mg/L glufosinate and 0.01 mg/L thidanzuron (TDZ) instead of 6-BA for further selection. The liquid medium was changed every week until the transgenic shoots were regenerated from the liquid selection medium. Several factors affecting the transformation efficiency have also been evaluated. GUS assay and Southern blotting analyses confirmed the integration of the transgenes into the soybean genome. This transformation system is genotype-independent and efficient, and has less escape due to the tight selection.
One new compound named smilglaside F (1) and five known ones (2-6) were isolated from the EtOAc portion of the 95% ethanolic extract of Smilax perfoliata Lour. by silica gel and ODS column chromatography. On the basis of chemical and spectral methods, they were identified as 1, 6-O diferuloyl- (3-O-p-coumaroyl)-b-D-fructofuranosyl-(2→1)-2-O-acetyl-a-D-glucopyranoside (1), rutin (2), narcissin (3), cassiamin A (4), cassiamin B (5) and 1, 2, 3-trimethoxy-5-hydroxyphenol-1-O-b-D glucopyranoside (6), respectivety. Compounds 1, 3-6 were obtained from the genus Smilax for the first time.
A new phenolic glucoside, curculigoside C (3), was isolated from the rhizomes of Curculigo orchioides Gaertn., together with three known compounds, curculigoside (1), curculigoside B (2), and 2,6-dimethoxyl benzoic acid (4). The structure of the new compound (3) was elucidated as 5-hydroxy-2-O-b-D-glucopyranosyl benzyl-3''-hydroxy-2'', 6''-dimethoxybenzoate by using spectroscopic methods.
Five new cyclopeptides named arcticumin A (1), arcticumin B (2), arcticumin C (3), regelin A (4) and crassipin B (5) were isolated from three arctic Caryophyllaceae species (＜100 g), Cerastium arcticum Lange. C. regelii Ostenf. and Stellaria crassipes Hult., with structures elucidated primarily by FAB+-MS and amino acids analysis. Based on the comparison of Caryophyllaceae cyclopeptides from both the Qinghai-Xizang (Tibet) Plateau and Arctic region, it is proposed that cyclopeptides are characteristic components of Caryophyllaceae and Arctic region is one part of the distribution center of Caryophyllaceae.
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