Annals of Botany 91: 149-154, 2003
© 2003 Annals of Botany Company
Light-dependent Anaerobic Induction of the Maize Glyceraldehyde-3-Phosphate Dehydrogenase 4 (GapC4) Promoter in Arabidopsis thaliana and Nicotiana tabacum
1 Botanical Institute, Technical University of Braunschweig, Humboldtstr. 1, D-38106 Braunschweig, Germany and 2 Institute of Genetics, Technical University of Braunschweig, Spielmannstr. 7, D-38106 Braunschweig, Germany
* For correspondence. Tel +49 (0)531–391–5772, Fax +49 (0)531–391–5765, e-mail r.hehl{at}tu-bs.de
Received: 10 September 2001; Returned for revision: 3 December 2001; Accepted: 16 January 2002
 |
ABSTRACT |
|---|
 TOP ABSTRACT INTRODUCTIONMATERIALS AND METHODSRESULTSDISCUSSIONLITERATURE CITED |
|---|
The maize glyceraldehyde-3-phosphate dehydrogenase 4 (GapC4) promoter confers strong and specific anaerobic gene expression in tobacco (Nicotiana tabacum) and potato (Solanum tuberosum). Here we show that the promoter is also anaerobically induced in Arabidopsis thaliana. Histochemical analysis demonstrates that the promoter is anaerobically induced in roots, leaves, stems and flower organs. Surprisingly, the strong anaerobic induction of the promoter is dependent on light and on the substitution of oxygen with carbon dioxide. High carbon dioxide concentration alone does not induce the promoter in the presence of oxygen and light. If anaerobic conditions are generated under complete darkness or if plants are submerged, no induction above background is observed. When transgenic tobacco harbouring a GapC4 promoter–reporter gene construct is analysed for light dependent anaerobic induction, the results are indistinguishable from those with arabidopsis. The implications for using the GapC4 promoter as an anaerobic reporter for monitoring alterations in the anaerobic signal transduction pathway are discussed.
Key words: Carbon dioxide, reporter gene expression, submergence, transgenic plant.
|
INTRODUCTION |
|---|
|
TOPABSTRACTINTRODUCTIONMATERIALS AND METHODSRESULTSDISCUSSIONLITERATURE CITED |
|---|
In the presence of excess soil water the low diffusion rate of free oxygen in combination with respiration of microorganisms causes a rapid depletion of oxygen. The ability of plants to survive periods of low oxygen conditions depends on their level of adaptation (Blom and Voesenek, 1996; Drew, 1997). Most crop plants are unable to withstand prolonged oxygen deficiency (Dennis et al., 2000).
A comprehensive understanding of the anaerobic signal transduction pathway is required before transgenic crop plants may be engineered for increased tolerance to waterlogging (Dennis et al., 2000). The plant has to sense the lack of oxygen before inducing a variety of responses that enable plants to cope with periods of flooding. Anaerobic conditions result in the synthesis of a new set of polypeptides or anaerobic stress proteins in maize (Sachs et al., 1980). Many of the anaerobic proteins are enzymes engaged in the glycolytic and fermentative pathways because the lack of oxidative phosphorylation requires the plant to regenerate ATP and NAD anaerobically. The anaerobic stress proteins are induced at the level of transcription and translation (Bailey-Serres and Freeling, 1990). Alterations in the ribosomal acidic phosphoprotein complex may be involved in the selective translation of mRNA in flooded roots (Bailey-Serres et al., 1997). Changes in splicing efficiency may also contribute to anaerobic gene expression (Köhler et al., 1996a).
The combination of anaerobic promoters with a histochemically detectable reporter gene adds to our understanding of the spatial and temporal induction of the anaerobic response genes. Furthermore, such reporter gene constructs can be employed to monitor alterations in the anaerobic signal transduction pathway and to isolate anaerobic response mutants.
The promoter from the maize Adh1 gene in transgenic rice shows low constitutive expression of a ß-glucuronidase (GUS) reporter gene in root caps and no expression in leaves (Kyozuka et al., 1991). A high level of constitutive GUS expression was found in some flower organs. Under anaerobic conditions GUS activity in roots was only induced in rice. In tobacco the promoter of the arabidopsis GapC gene confers the highest constitutive GUS activity to the root caps (Yang et al., 1993). However, aerobic GUS activity was also found in leaves and stems. Anaerobic induction was detected mainly in roots. The promoter of the arabidopsis Adh gene was tested in transgenic arabidopsis (Dolferus et al., 1994). Constitutive GUS activity was detected only in roots, while no activity was found in the green plant parts, except in the apical meristem region. Again, anaerobic induction results in an increase of GUS expression mainly in the roots.
The maize cytosolic glyceraldehyde-3-phosphate dehydrogenase 4 gene (GapC4) is up-regulated under anaerobic conditions in maize (Köhler et al., 1995; Köhler et al., 1996a; Manjunath and Sachs, 1997). The GapC4 promoter is strongly and specifically induced under anaerobic conditions in tobacco and potato (Köhler et al., 1996b; Bülow et al., 1999). The promoter contains a complex arrangement of cis-regulatory sequences that are located between –386 and –196 relative to the transcription start site (Manjunath and Sachs, 1997; Geffers et al., 2000). Within this region a 50 bp weak anaerobic response element interacts with anaerobiosis specific nuclear factors and confers anaerobic reporter gene expression to a GapC4 minimal promoter. Essential components of this anaerobic minimal promoter are the TATA-box and a Myb binding site (Geffers et al., 2001). The Myb binding site was identified by mutagenesis and by a database-assisted approach to analyse plant transcription factor binding to a predicted and mutated cis-acting sequence (Geffers et al., 2001; Hehl and Wingender, 2001).
The ubiquitous induction of the maize GapC4 promoter in heterologous species is very intriguing and may indicate its usefulness as a reporter for alterations in the anaerobic signal transduction pathway. Towards this ends a GapC4 promoter–reporter gene construct was introduced into the plant Arabidopsis thaliana. It is shown that the promoter is induced under anaerobic conditions in all seedling tissues. However, the strong anaerobic induction depends on light and on oxygen replacement by CO2. By reinvestigating transgenic tobacco we also found that the strong anaerobic induction of the GapC4 promoter in tobacco is light dependent. These results have important implications for the use of the GapC4 promoter as an anaerobic reporter.
|
MATERIALS AND METHODS |
|---|
|
TOPABSTRACTINTRODUCTIONMATERIALS AND METHODSRESULTSDISCUSSIONLITERATURE CITED |
|---|
Plant material
The plants used in these studies were germinated on soil and grown on soil or in hydroponic culture in a Heraeus growth chamber. The day/night-regime for A. thaliana ecotype Columbia (10 h/14 h) and N. tabacum cv. GAT (14 h/10 h) at 25 °C/20 °C, a relative humidity of 80 % and 250–300 µE m–2 s–1 were used. In hydroponic culture, a well-aerated nutrient solution with the composition, 3·4 mM NO3–, 1·7 mM NH4+, 2·0 mM K+, 2·5 mM Ca2+, 1·2 mM Mg2+, 0·5 mM H2PO4–, 1·2 mM SO42–, 10 µM FeEDTA, 10 µM H3BO3, 0·5 µM Mn2+, 0·5 µM Zn2+, 0·1 µM Cu2+, 0·07 µM MoO42–, was used and changed three times a week. The tobacco line 4030-5 harbouring the 785 bp GapC4 promoter–uidA (ß-glucuronidase) construct in pUK4030 was described earlier (Köhler et al., 1996b).
Agrobacterium mediated transformation of A. thaliana
For transformation of Arabidopsis thaliana (ecotype Columbia), Agrobacterium tumefaciens harbouring plasmid construct pUK4030 was employed. The construction of pUK4030 was described earlier (Köhler et al., 1996b). Transformation of Arabidopsis thaliana was done by in planta vacuum infiltration according to Bechtold and Pelletier (1998). Sixteen independent transformants were selected on kanamycin and grown to maturity. Seed material was produced by self-pollination. Kanamycin resistant T1 and T2 generations were subjected to enzymatic assays.
Anaerobic induction
For anaerobic induction, plants were incubated in an airtight glass container (Merck) together with Anaerocult A (Merck) for 15 h. In another experiment the air was replaced by 100 % nitrogen or supplemented with 20 % carbon dioxide. The glass container was either incubated under constant light (200 µE m–2 s–1) or in complete darkness. Alternatively, plantlets were submerged for 24 h in water that had been previously flushed with nitrogen.
ß-Glucuronidase assays
For the fluorimetric GUS assay approx. 100 mg plant tissue was homogenized, and incubated with the substrate 4-methylumbelliferyl-ß-D-glucuronide (MUG; Duchefa, The Netherlands) at 37 °C. Quantification of the fluorescence and determination of protein concentrations were done according to established protocols (Bradford, 1976; Jefferson et al., 1987). The GUS activity was measured in three independent experiments as photometrically measured fluorescence and displayed as pmoles 4-MU per mg protein and hour. For histochemical staining, intact plant material was vacuum infiltrated with 1 mM X-gluc (5-bromo-4-chloro-3-indolyl-ß-D-glucuronic acid CHA salt; Duchefa) and incubated overnight at 37 °C (Beeckman and Engler, 1994). After staining the tissue was cleared with 70 % ethanol. As negative control wild-type A. thaliana ecotype Columbia and as positive control Nicotiana tabacum cv. GAT plants stably transformed with pRT99-GUS (Töpfer et al., 1988) via protoplasts was used.
|
RESULTS |
|---|
|
TOPABSTRACTINTRODUCTIONMATERIALS AND METHODSRESULTSDISCUSSIONLITERATURE CITED |
|---|
Anaerobic induction of the maize GapC4 promoter in A. thaliana
Sixteen transgenic A. thaliana plants harbouring the 785 bp GapC4–GUS reporter gene construct in pUK4030 were generated. The arabidopsis lines were tested for aerobic and anaerobic induction using quantitative GUS assays. As shown in Table 1, aerobic expression in all of the lines is in the range of nonspecific background obtained for an untransformed plant. Under anaerobic conditions that were generated with the Anaerocult system, most of the transgenic lines show GUS expression values 10–1000-fold over nonspecific background, demonstrating that reporter gene expression is induced in the experimental set-up under anaerobic conditions. In these early experiments we noticed that sometimes the anaerobic induction was not reproducible. This lack of induction was always observed when the quantitative GUS assays were performed after a prolonged dark period (see below).
|
Tissue specificity of anaerobic induction of the maize Gapc4 promoter in arabidopsis
To analyse the spatial pattern of reporter gene expression, anaerobically induced transgenic arabidopsis plants (T2 generation) were subjected to histochemical GUS assays and compared with uninduced plant material (Fig. 1A and B). As shown in Fig. 1B and in the magnifications in Figs 1C–E anaerobic reporter gene expression is detected in all organs such as roots, flowers and leaves. No differences between younger or older leaf material or leaf type were noticed. As in tobacco the GapC4 promoter seems to be wound-induced because some histochemical staining was always observed at wounded areas under normal conditions (data not shown).
|
Anaerobic expression of the GapC4 promoter in arabidopsis and tobacco is light dependent
During the course of the analysis of anaerobic reporter gene expression we noticed that the anaerobic induction was not observed when the analysis was performed immediately after a prolonged dark period. This led us to perform specific experiments to analyse the anaerobic induction in the presence and absence of light. Plants were anaerobically induced with the Anaercult system (Merck) and incubated once under constant light and in parallel under complete darkness. As shown in Fig. 1F, only those arabidopsis plants subjected to anaerobic conditions in the light show GUS reporter gene expression. This demonstrates that the anaerobic induction of the GapC4 promoter in arabidopsis is light dependent.
This result prompted us to reinvestigate transgenic tobacco harbouring a GapC4 promoter–reporter gene construct for light dependence of the anaerobic induction [line 4030-5 (Köhler et al., 1996b)]. As shown in Fig. 1G, the results with transgenic tobacco are indistinguishable from those obtained in arabidopsis.
The light dependent anaerobic induction of the GapC4 promoter is also CO2 dependent
The system to induce anaerobic conditions, Anaerocult A (Merck), contains components which chemically bind oxygen quickly and completely, creating an oxygen-free (anaerobic) milieu within 50 min and a CO2 atmosphere. This system is often used to generate anaerobic environments for analysis of microorganisms. Alternatively, anaerobic conditions can be generated with nitrogen or by submerging the plants in water.
Therefore we also analysed if flooding can induce reporter gene expression. Towards these ends we submerged arabidopsis and tobacco plants in light for 24 h in tap water that was previously flushed with nitrogen. Under these conditions neither transgenic arabidopsis nor tobacco shows anaerobic induction of the GapC4 promoter–reporter gene construct in histochemical assays (Fig. 1F or G, sub-light). In another control experiment we found that 20 % CO2 alone, which is comparable with the CO2 concentration in the Anaerocult system, and 100 % N2 cannot induce the GapC4 promoter in arabidopsis (data not shown).
These results demonstrate that expression of the GapC4 promoter is light dependent. Furthermore, the induction depends on anaerobic conditions generated by replacing oxygen with CO2.
|
DISCUSSION |
|---|
|
TOPABSTRACTINTRODUCTIONMATERIALS AND METHODSRESULTSDISCUSSIONLITERATURE CITED |
|---|
An anaerobic reporter gene construct has many potential applications for studying the anaerobic signal transduction pathway. For example, it could be possible to isolate anaerobic signal transduction mutants that no longer induce anaerobic reporter gene expression or that allow expression of anaerobic genes under normal aerobic conditions. Such an approach has been taken for isolation of an arabidopsis mutation that causes superinduction of cold responsive genes. This mutation was identified by using the firefly luciferase reporter gene under the control of a cold-responsive promoter (Ishitani et al., 1998). Furthermore, aerobic expression of genes involved in anaerobic signal transduction may cause altered expression of anaerobically induced genes. It may be possible to monitor such effects with anaerobic promoter–reporter gene constructs. It has been suggested that the expression or function of AtMyb2, a low oxygen induced transcription factor of arabidopsis (Hoeren et al., 1998), can be modified to amplify the expression of the fermentation pathway genes and possibly other metabolic genes (Dennis et al., 2000).
Is the GapC4 promoter a suitable reporter to monitor changes in anaerobic gene expression? When we compared the properties of the maize GapC4 promoter in heterologous host plants with those of other anaerobic promoters we found it remarkable that the gene was induced ubiquitously and strongly in all tissues of transgenic tobacco (Köhler et al., 1996b; Geffers et al., 2000). However, the experiments with the GapC4 promoter were all performed under an anaerobic CO2 environment with a 12 h day and 12 h night regime. Constant light or constant darkness was only tested under aerobic conditions and was found not to induce the GapC4 promoter (Köhler et al., 1996b).
In the light of the experiments presented here, the anaerobic induction of the GapC4 promoter in tobacco and arabidopsis seems to be more complex. Although CO2 concentrations similar to that produced in the Anaerocult system are unable to induce the GapC4 promoter in the presence of otherwise normal oxygen conditions, the promoter is strongly induced anaerobically by replacing oxygen with CO2 in the presence of light. Submergence and the replacement of oxygen by nitrogen does not have a histochemically detectable effect on gene expression.
The specific induction of the GapC4 promoter under anaerobiosis generated by CO2 leads to the important question if such conditions are present in nature? The ambient CO2 concentration in air is about 0·03 % suggesting that the 20 % CO2 used in the experiments presented here is nonphysiological. However, in the field CO2 concentration can reach 50 % of the total soluble gas in flooded soybean fields where CO2 is released from the soil (G. Boru et al., unpubl. res.). In fact, the susceptibility of soybean to flooding is caused by these elevated CO2 levels. In river systems CO2 concentrations can rise above normal levels during flooding when flood water contacts marshes. Dissolved free CO2 was oversaturated with respect to the atmosphere with values higher on the floodplain than in the river (Villar and Bonetto, 2000). Data on free CO2 in a small acidic headwater stream in NE Scotland show that high CO2 concentrations are maintained by continually high inputs of CO2-rich water from tributaries (Dawson et al., 2001). These examples show that higher CO2 concentrations in flood water can occur and it will be interesting to learn at which CO2 concentration the maize GapC4 promoter is induced anaerobically in arabidopsis and tobacco.
On the molecular and physiological levels there are only a few reports of different effects between anaerobic CO2 and N2 environments. Different effects of anaerobic conditions generated by CO2 and N2 have been observed in yeast. An additional 18-kDa version of a centromere-binding factor was found in anaerobic cells grown under an atmosphere of purified nitrogen, but not when CO2 was used to establish anaerobiosis (Oechsner and Bandlow, 1998). When tomato fruit was given a short-term (24 h) high CO2 (80 %) or N2 (100 %) treatment and then transferred to air storage at 20 °C, the CO2 treatment stimulated 1-aminocyclopropane-1-carboxylic acid (ACC) oxidase activity and ethylene production, whereas the N2 treatment increased ACC content but did not increase ethylene production (Terai et al., 1998).
Given the CO2 and light-dependent anaerobic induction of the GapC4 promoter, many interesting questions await answers. The light- and CO2-dependent induction of the GapC4 promoter will stimulate experiments that aim to elucidate the role of photosynthesis for anaerobic induction. Furthermore it will be interesting to see if the anaerobiosis specific nuclear protein complex that was previously found to interact with the GapC4 promoter in tobacco is light specific (Geffers et al., 2000). The different promoter deletions that were tested for anaerobic induction in tobacco can now be reinvestigated to see if cis-regulatory elements for anaerobic and light-dependent expression can be distinguished (Geffers et al., 2000).
If the GapC4 promoter is used to monitor alterations in the anaerobic signal transduction pathway it will be important to see if these components are induced anaerobically by CO2 and/or N2. The GapC4 promoter may still be useful for generating submergence-tolerant plants, because flooding seems to be acompanied with high CO2 concentrations in the flood water. In the light of the CO2 poisoning of submerged soybeans (G. Boru et al., unpubl. res.) the genes mediating flooding tolerance should rather counteract senescence than increase glycolysis or fermentation (Zhang et al., 2000).
|
ACKNOWLEDGEMENTS |
|---|
We are grateful to Michael Wettern for critical comments on the manuscript and to Katharina Nowak for excellent technical assistance. This work was supported by a grant through the Forschungsschwerpunkt Agrarbiotechnologie des Landes Niedersachsen.
|
LITERATURE CITED |
|---|
|
TOPABSTRACTINTRODUCTIONMATERIALS AND METHODSRESULTSDISCUSSIONLITERATURE CITED |
|---|
-
Bailey-Serres J, Freeling M. 1990. Hypoxic stress-induced changes in ribosomes of maize seedling roots. Plant Physiology 94: 1237–1243.
Bailey-Serres J, Vangala S, Szick K, Lee CH. 1997. Acidic phosphoprotein complex of the 60S ribosomal subunit of maize seedling roots. Components and changes in response to flooding. Plant Physiology 114: 1293–1305.[Abstract]
Bechtold N, Pelletier G. 1998. In planta Agrobacterium-mediated transformation of adult Arabidopsis thaliana plants by vacuum infiltration. Methods in Molecular Biology 82: 259–266.[Medline]
Beeckman T, Engler G. 1994. An easy technique for the clearing of histochemically stained plant tissue. Plant Molecular Biology Reporter 12: 37–42.[CrossRef]
Blom CWPM, Voesenek LACJ. 1996. Flooding: the survival strategies of plants. Trends in Ecology and Evolution 11: 290–295.[CrossRef]
Bradford MM. 1976. A rapid and sensitive method for the quantitation of microgram quantities of protein utilizing the principle of protein-dye binding. Analytical Biochemistry 7: 248–254.[CrossRef]
Bülow L, Köhler U, Cerff R, Hehl R, Düring K. 1999. Induction of the maize GapC4 promoter in transgenic potato under anaerobiosis and in Erwinia carotovora-inoculated tuber tissue. Molecular Plant-Microbe Interaction 12: 182–188.
Dawson JJC, Bakewell C, Billett MF. 2001. Is in-stream processing an important control on spatial changes in carbon fluxes in headwater catchments? Science of the Total Environment 265: 153–167.[Medline]
Dennis ES, Dolferus R, Ellis M, Rahman M, Wu Y, Hoeren FU, Grover A, Ismond KP, Good AG, Peacock WJ. 2000. Molecular strategies for improving waterlogging tolerance in plants. Journal of Experimental Botany 51: 89–97.
Dolferus R, Jacobs M, Peacock WJ, Dennis ES. 1994. Differential interactions of promoter elements in stress responses of the Arabidopsis Adh gene. Plant Physiology 105: 1075–1087.[Abstract]
Drew MC. 1997. Oxygen deficiency and root metabolism: injury and acclimation under hypoxia and anoxia. Annual Review of Plant Physiology and Plant Molecular Biology 48: 223–250.[CrossRef][Web of Science][Medline]
Geffers R, Cerff R, Hehl R. 2000. Anaerobiosis specific interaction of tobacco nuclear factors with cis-regulatory sequences in the maize GapC4 promoter. Plant Molecular Biology 43: 11–21.[CrossRef][Web of Science][Medline]
Geffers R, Sell S, Cerff R, Hehl R. 2001. The TATA box and a Myb binding site are essential for anaerobic expression of a maize GapC4 minimal promoter in tobacco. Biochimica et Biophysica Acta 1521: 120–125.[Medline]
Hehl R, Wingender E. 2001. Database-assisted promoter analysis. Trends in Plant Science 6: 251–255.[CrossRef][Web of Science][Medline]
Hoeren FU, Dolferus R, Wu Y, Peacock WJ, Dennis ES. 1998. Evidence for a role for AtMYB2 in the induction of the Arabidopsis alcohol dehydrogenase gene (ADH1) by low oxygen. Genetics 149: 479–490.
Ishitani M, Xiong L, Lee H, Stevenson B, Zhu JK. 1998. HOS1, a genetic locus involved in cold-responsive gene expression in arabidopsis. Plant Cell 10: 1151–1161.
Jefferson RA, Kavanagh TA, Bevan MW. 1987. GUS fusions: ß-glucuronidase as a sensitive and versatile gene fusion marker in higher plants. EMBO Journal 6: 3901–3907.[Web of Science][Medline]
Köhler U, Liaud M-F, Mendel RR, Cerff R, Hehl R. 1995. The maize GapC4 promoter confers anaerobic reporter gene expression and shows homology to the maize anthocyanin regulatory locus C1. Plant Molecular Biology 29: 1293–1298.[CrossRef][Web of Science][Medline]
Köhler U, Donath M, Mendel RR, Cerff R, Hehl R. 1996a. Intron-specific stimulation of anaerobic gene expression and splicing efficiency in maize cells. Molecular and General Genetics 251: 252–258.
Köhler U, Mendel RR, Cerff R, Hehl R. 1996b. A promoter for strong and ubiquitous anaerobic gene expression in tobacco. Plant Journal 10: 175–183.[CrossRef]
Kyozuka J, Fujimoto H, Izawa T, Shimamoto K. 1991. Anaerobic induction and tissue-specific expression of maize Adh1 promoter in transgenic rice plants and their progeny. Molecular and General Genetics 228: 40–48.
Manjunath S, Sachs MM. 1997. Molecular characterization and promoter analysis of the maize cytosolic glyceraldehyde 3-phosphate dehydrogenase gene family and its expression during anoxia. Plant Molecular Biology 33: 97–112.[CrossRef][Web of Science][Medline]
Oechsner U, Bandlow W. 1998. Growth-regulated formation of hetero meric complex of the centromere and promoter factor, Cbf1p, in yeast. Molecular and General Genetics 260: 417–425.
Sachs MM, Freeling M, Okimoto R. 1980. The anaerobic proteins of maize. Cell 20: 761–767.[CrossRef][Web of Science][Medline]
Terai H, Tsuchida H, Mizuno M, Matsui N. 1998. Influence of short-term treatment with high CO2 and N2 on ethylene biosynthesis in tomato fruit. Hortscience 33: 103–104.
Töpfer R, Schell J, Steinbiss HH. 1988. Versatile cloning vectors for transient gene expression and direct gene transfer in plant cells. Nucleic Acids Research 16: 8725.
Villar CA, Bonetto C. 2000. Chemistry and nutrient concentrations of the Lower Parana River and its floodplain marshes during extreme flooding. Archiv für Hydrobiologie 148: 461–479.
Yang Y, Kwon H-B, Peng H-P, Shih M-C. 1993. Stress responses and metabolic regulation of glyceraldehyde-3-phosphate dehydrogenase genes in Arabidopsis. Plant Physiology 101: 209–216.[Abstract]
Zhang J, Van Toai T, Huynh L, Preiszner J. 2000. Development of flooding-tolerant Arabidopsis thaliana by autoregulated cytokinin production. Molecular Breeding 6: 135–144.[CrossRef]
CiteULike 
Connotea 
Del.icio.us What's this?
This article has been cited by other articles:
|
|
 |
|
  J. BAILEY-SERRES and R. CHANG Sensing and Signalling in Response to Oxygen Deprivation in Plants and Other Organisms Ann. Bot., September 1, 2005; 96(4): 507 - 518. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
E. J. W. VISSER, L. A. C. J. VOESENEK, B. B. VARTAPETIAN, and M. B. JACKSON Flooding and Plant Growth Ann. Bot., January 2, 2003; 91(2): 107 - 109. [Abstract] [Full Text] [PDF]
|
|
| ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||