Granier sap flow system is one of the most commonly used techniques for measurements of whole-tree water use in ecophysiological and forest hydrological studies. However, in the literature there is not one paper that exclusively reviews the Granier method. In this paper, we recapitulate the theoretical basis of the Granier sap flow system and review recent developments in calibration and modification of the sensor probes. Practical issues, such as the determination of the non-flow signal values, natural thermal gradient, wounding effect, reversed sap flow pattern and extrapolation of individual measurement of sap flux density to whole-tree sap flow, are discussed in detail. In the perspectives, new approaches are put forward to use the strong coupling between photosynthesis and transpiration or canopy conductance, via the measurement of 13C discrimination, to estimate whole-canopy carbon assimilation.
Plant receptor-like kinases (RLKs) have been shown to be critical components in plant cellular processes. To provide a valid basis to evaluate the evolutionary relationships among RLKs from Arabidopsis and rice, a genome-wide search for RLKs-related sequences was conducted. By doing BLASTP through the database of rice (Oryza sativa L. subsp. indica) genome at Beijing Genomics Institute (BGI), we identified 267 putative RLK genes. All RLKs were classified into different structural groups based on their extracellular structures. The phylogenetic analysis of RLKs in rice and Arabidopsis showed that the different groups of RLKs had different characteristics of sequence conservation and of evolutionary relationship. The multi-sequences alignment of rice RLKs and Arabidopsis Brassinosteroid-insensitive 1 (BRI1) suggested that the putative autophosphorylation sites of rice RLKs were dissimilar to those in BRI1.
A relatively high resolution pollen record and data of loss of ignition (LOI), grain size and susceptibility of the Daxigou profile in the head area of the Urumqi River, central Tianshan Mountains, revealed new information about vegetation changes and environmental evolution since 3.6 ka BP. Results showed that from 3.6 ka BP to present, climate was unstable with multi-changes of warming-cooling and wetting-drying. From ca. 3.6 to 3.2 ka BP, climate was warmer and more humid than today. Climate changed to cooler and drier between ca. 3.2 and 2.0 ka BP, coinciding with a glacier advance in the head area of the Urumqi River. From ca. 2.0 to 1.4 ka BP, climate became warmer and more humid again. From ca. 1.4 to 0.5 ka BP temperature and humidity went on increasing and a period of Climatic Optimum since 3.6 ka BP might occur. A few limnetic hydrophytes pollen are counted for all zones, indicating a freshwater habitat since 3.6 ka BP in this region. Based on synthetically analysis of ecological characteristics and dispersal of spruce pollen, the abundance of Picea is influenced by treeline moving upward, valley wind and glacier ablation. Statistics of charcoal concentration and susceptibility further suggest that fires may have occurred in this region since 0.5 ka BP and the peak value of charcoal might be related to human activities.
The variation in airborne pollen concentration of the Zonguldak region, Turkey was studied for two consecutive years 2001-2002 using a Durham sampler. During this period, a total of 61 304 pollen grains belonging to 43 taxa were recorded. Of these 43 taxa, 26 belonged to arboreal and 17 to non-arboreal plants. The main pollen types were Pinaceae, Populus, Carpinus, Betula, Corylus, Fagus orientalis, Castanea sativa, Alnus glutinosa, Quercus, Cupressaceae, Chenopodiaceae and Gramineae, representing 96.7% of the pollen spectrum. Pollen concentration reached the highest level in March.
Haloxylon ammodendron (CA Mey.) Bunge, the dominant tree species in many xerophytic deserts of Asia, plays an important role in the maintenance of the structure and function of these ecosystems. Despite its ecological and economic importance, nearly nothing is known about its genetic attributes. In this study, RAPD and ISSR markers were used to investigate the genetic diversity and structure of four natural populations of H. ammodendron. Five RAPD primers amplified 61 bands with 51 (83.6%) polymorphic and eight ISSR primers amplified 195 bands with 175 (89.7%) polymorphic. The genetic diversity, estimated by Shannon’s index, was 0.333 (by RAPDs) and 0.367 (by ISSRs). Both RAPD and ISSR analyses revealed a high level of genetic diversity in natural populations of H. ammodendron. Furthermore, analysis of molecular variance (AMOVA) was used to apportion the variation within and between populations. The proportion of variation attributable to within-population differences was very high (138.2% by RAPDs; 89.4% by ISSRs). No genetic differentiation was detected among populations using RAPDs (P = 0.999), while only a small amount of variation (10.6%) was detected among populations using ISSRs. We suggest that the present genetic structure is due to high levels of gene flow.
When the CO2 concentration was kept at 360 mL/L (ambient) and 5 000 mL/L (elevated), the effects of UV-B stress on photosynthesis, lipid peroxidation and antioxidative enzymes of marine microalgae Platymonas subcordiformis (Wille) Hazen were examined. The experiment indicated that: (1) UV-B alone significantly decreased dry weight, photosynthetic rate, chlorophyll a (Chl a) and carotenoid (Car.) contents; CO2 enrichment alone enhanced dry weight and photosynthetic rate, but Chl a content and Car. content had no major difference compared with those of ambient UV-B and ambient CO2; the dry weight and photosynthetic rate of P. subcordiformis grown under the combination of UV-B and CO2 had no major difference compared with that under ambient UV-B and ambient CO2; while the Chl a content and Car. content significantly decreased compared to those of P. subcordiformis grown under ambient UV-B and ambient CO2. (2) Both UV-B alone and CO2 enrichment alone significantly decreased soluble protein content, when UV-B and CO2 were in combination, the soluble protein content was higher than that of UV-B alone. Changes in soluble protein content of algae grown in high CO2 could be largely due to a decline in Rubisco protein. (3) UV-B alone significantly increased the rate of O2-. production, H2O2 and malondialdehyde (MDA) content, CO2 enrichment alone significantly decreased the rate of O2-. production, H2O2 and MDA contents, when UV-B and CO2 were in combination, the rate of O2-. production, H2O2 and MDA contents were significantly lower than those of UV-B alone. The results suggested that CO2 enrichment could reduce oxidative stress of reactive oxygen species to P. subcordiformis, and reduce the lipid peroxidation damage of UV-B to P. subcordiformis. And (4) UV-B alone significantly increased SOD, POD, CAT, GR and GPX activities, CO2 enrichment alone significantly decreased the activities of SOD, POD and GR, while the CAT and GPX activities were decreased a little but not changed significantly compared to ambient UV-B and ambient CO2. The SOD, POD, CAT, GR and GPX activities of P. subcordiformis grown under the combination of UV-B and CO2 were much lower than those of P. subcordiformis grown under UV-B alone. The results indicated that CO2 enrichment showed a protective effect against the oxidative damage of UV-B-induced stress. Therefore, elevated CO2 can be favor of enhancing the capacity of stress resistance.
In order to investigate the possible role of silicon in rice (Oryza sativa L.) leaves resistance to ultraviolet-B (UV-B), experiments were conducted by using rice plants solution-cultured with or without silicon supplementation. Results showed that under high UV-B irradiation the silicon-deficient leaves exhibited obvious brown spots and strips of UV damage symptoms, but the silicon-treated leaves were not affected. A 21% and 67% increase in soluble and insoluble UV-absorbing compounds was observed in the epidermis of silicon-treated leaves, respectively. Furthermore, fluorescence microscopy revealed that a great deal of insoluble UV-absorbing compounds was enriched in silicon bodies that were formed in the cell walls and cell lumina of epidermis of silicon-treated leaves, whereas the insoluble UV-absorbing compounds were less in the epidermis of non-silicon-treated leaves. Based on these results, it is concluded that the elevated UV resistance of silicon-treated leaves is due to the increase of phenolic compounds in epidermis induced by silicon.
Two rice (Oryza sativa L.) varieties, Ootikara with big grain (36 mg/grain) and Habataki with small grain (18 mg/grain), were used to study the factors that control caryopsis development. We compared the differences of caryopsis weight, the number of endosperm cell, the structures of pericarp and endosperms, changes of physiological activities, and so forth during the caryopsis development. The main results showed that the growth period of the cell of ovary wall and the caryopsis of Ootikawa was longer compared with that of Habataki, resulting in the formation of more endosperm cells and heavier cell weight. In Ootikawa, it has a longer period of maintaining a high level of dehydrogenase and catalase activities, and higher level of respiratory rate of the ears, the degree of greening and photosynthetic rate of the flag leaf, and a longer functional maintenance period of the dorsal carpellary bundles in the ovary. And all these features indicated that the larger capacity and the longer active period of the caryopsis in Ootikara would lead to the notable expansion of the caryopsis.
Apoptosis, both in animal and plant cells, is usually analyzed by observing and detecting the characteristic morphological and biochemical changes in nuclei, organelles such as mitochondria and cell membranes. Using 1H-NMR we have found a correlation between the progression of apoptosis and 1H-NMR methylene signal intensity in cultured tobacco (Nicotiana tabacum L. cv. BY-2) and carrot (Daucus carota L.) cells. The increase in the methylene resonance signal intensity which reflects the alterations in membrane lipids and accordingly in the biophysical and biochemical characteristics of cell membrane during apoptosis was found to be closely associated with nuclear changes as detected by DNA laddering assay and the TUNEL procedure. The rise of methylene resonance signal intensity was evident in apoptotic plant cells induced by various factors including nicotinamide, menadione, heat shock and hydroxyl radicals, but it was not found in necrotic cells. To our knowledge, this is the first report of the 1H-NMR detection of apoptosis which is closely associated with the increase in methylene resonance signal intensity in plants.
Pollen of Nicotiana tabacum L. is bicellular type, a generative cell and a vegetative cell in a mature pollen grain. To isolate sperm cells pollen tube should be induced in advance. Using an in vivo-in vitro technique, the style was pollinated and kept in vivo growing for 37 h and then cut about 3.5-4.0 cm long to be cultured in a medium containing 15% (W/V) sucrose, 0.01% (W/V) boric acid, 0.01% (W/V) CaCl2, 0.01% (W/V) KH2PO4, at pH 5.0. A numerous pollen tubes grew out of the cut end of the style after being cultured for 3-5 h. When the pollen tubes were transferred to a broken solution just containing 9% mannitol some tubes broke and released the tube content into the broken solution including two sperm cells. Two sperm cells just released from the tube are connected with vegetative nucleus (VN) of pollen tube consisting of a male germ unit (MGU). Two sperm cells of tobacco are dimorphism: one is big and the other small. The small one (Svn) connects with vegetative nucleus and the big one only associates with the small one. Two isomorphic sperm cells might be selective fusion with egg cell and central cell during in vivo fertilization (preferential fertilization). When two associated sperm cells were transferred into a solution containing 0.01% cellulase, 0.008% pectinase and 9% mannitol, the association between two brother sperm cells disappeared, and both cells could be easily separated using a micromanipulator. To probe the mechanism of preferential fertilization two sperm cells from one pollen tube have to be separated each other to find the differences at the molecular level. Two sperm cells were respectively collected into two individual populations, each containing over thousand big sperm cells or small one, using a micromanipulator. The two sperm populations will offer a possibility to find the differences between two sperm cells in genes and proteins by using molecular methods, which will help us to understand the mechanism of preferential fertilization and gametic recognition of higher plants, especially in the species with bicellular pollen.
A new Coix aquatica Roxb. cyto-type, found in the southwest of Guangxi Zhuang Autonomous Region in China, was identified and analyzed by acetocarmine squashing and fluorescence in situ hybridization (FISH) technique including genomic in situ hybridization (GISH). This new C. aquatica cyto-type was different from other C. aquatica cyto-types reported in chromosome structure. It was 2n = 30 in chromosome number, and ten bivalents plus ten univalents were formed in meiotic prophase and metaphaseⅠ. GISH results indicated that its 20 chromosomes were highly homologous to chromosomes of allotetraploid species C. lacryma-jobi L. (2n = 20). The 45S and 5S rDNA were respectively located on the two different chromosomes of the C. aquatica. One of chromosomes carrying 45S rDNA showed its chromosome shape and signal location in the C. aquatica as the same as that in C. lacryma-jobi. So did one of chromosomes carrying 5S rDNA. It could be deducted that one of parental candidates for the new C. aquatica cyto-type may be C. lacryma-jobi. The other parental candidate may be allooctopolyploid C. aquatica (2n = 40), which is similar to the new cyto-type of C. aquatica in aquatic habit and plant morphology.
A new method was developed to determine the acting paths of elicitors based on the analysis of intermediate response mode in suspension cultures. It was found that the acting path of an elicitor, defined as the biosynthesis step whose rate was significantly enhanced upon the addition of the elicitor, was located between two adjacent intermediates whose concentrations changed in opposite directions. The validity of this method was verified in the biosynthesis of taxol from suspension cultures of Taxus chinensis (Pilg.) Rehd. var. mairei (Lemee et Levl.) Cheng et L. K. Fu. The acting paths of methyl jasmonate, silver nitrate and ammonium citrate were determined to be located at the step from baccatin Ⅲ to 10-deacyl taxol. There are three possibilities for salicylic acid and arachidonic acid: (1) improving the biosynthesis of 10-deactyl baccatin Ⅲ (10-DAB), (2) inhibiting the degradation of taxol and (3) inhibiting the degradation of cephalomannine. But it is difficult to elucidate the exact acting paths of these two elicitors based on the present method.
Nonhost resistance is durable and broad-spectrum, which attracts more and more attention for its great potential to be exploited in crop protection against diseases. However, mechanism of nonhost resistance is largely unknown. Previously a cDNA clone of tomato leaf mould pathogen Cladosporium fulvum Cooke was isolated. It is highly homologous in sequence to bZIP transcription factors. Upon expression it results in necrosis in its host tomato (Lycopersicon esculentum Mill.) and nonhost Nicotiana spp. and confers resistance to potato virus X, and thus is named CfHNNI1 (C. fulvum host and nonhost necrosis inducer 1). The present paper reports the results on mutational analyses of the relationship between the amino acid sequences of putative DNA-binding and leucine zipper domains of CfHNNI1 and the necrosis-inducing function of CfHNNI1. Deletion of six amino acids R112-N117 (RKRQRN) or substitution of alanines for arginines R125 and R127 of DNA-binding domain almost completely abolished or severely lowered the necrosis-inducing activity of CfHNNI1, while substitution of alanines for leucine L149 or L163 of leucine zipper domain partially impaired the necrosis-inducing activity of CfHNNI1. Adding of tobacco PR-1a signal peptide to CfHNNI1 so that the mature product CfHNNI1 was secreted into extracellular compartment resulting in complete loss of the necrosis-inducing activity. It was concluded that amino acids R112-N117, R125 and R127, L149 and L163 of putative DNA-binding and leucine zipper domains of CfHNNI1 and inner cellular localization of mature protein were required for full necrosis-inducing function of CfHNNI1.
According to the conservative region of resistance gene homologue (RGH) family of the barley Mla locus, we synthesized four pairs of family primers. RT-PCR with the series of family-specific primers was used to analyze the differential expression of genes between the inoculated seedlings and the uninoculated seedlings of a wheat (Triticum aestivum L.) line which showed high resistance to powdery mildew. As a result, a putative resistance gene fragment, RJ-3-3L, expressed specifically in the inoculated condition, was isolated and then, its full-length cDNA, designated as TaMla1, was obtained using rapid amplification of cDNA ends (RACE). By alignment analysis and functional-motif scanning, the TaMla1 shared high similarity to Mla alleles in barley and coded a typical CC-NBS-LRR (coiled-coil, nucleotide binding site, Leu-rich repeat) resistance protein. Subsequently, by Southern blot using a series of nulli-tetrasomics of wheat, the TaMla1 was located on wheat chromosome 1A, where the ortholog of the barley Mla locus lies. These findings showed that TaMla1 is one of the Mla-like alleles in wheat. In addition, another gene fragment, RW-2-3L, its transcription remarkably inhibited in the inoculated seedlings, was isolated and homology analysis showed that it was also highly similar to Mla members in barley. We inferred that the gene derived RW-2-3L was also a Mla-like allele and probably acted as a powdery mildew susceptible gene or a negative factor for resistance to powdery mildew.
Acetyl-CoA carboxylase (ACCase) is a biotinylated enzyme that catalyzes the first committed step in fatty acid biosynthesis. Graminaceous ACCase in plastid is the target site of two classes of graminicide herbicides. Two full-length cDNAs of plastid ACCase from sethoxydim-resistant and sensitive Setaria italica Beauv., named foxACC-R and foxACC-S, have been cloned. cDNA sequencing showed that they encode a protein of 2 321 amino acids long with a pI of 5.89 and a calculated molecular mass of 256 kD. The sequences of foxACC-R and foxACC-S have been compared with their homologs from other plants and analyzed for conserved amino acid regions and their functional domains. It is found that the amino acid at position 1 780 is Leu in foxACC-R other than Ile in foxACC-S and other cereal plastid ACCase. It is suspected that the change of Ile to Leu residue is critical for interaction of plastid ACCase with cereal herbicides APPs and CHDs. According to Southern hybridization, foxACC-R and foxACC-S are both estimated to be single copy in the genome of S. italica.
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