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1.
One of the key steps in developing transgenic plants for the phytoremediation of metal containing soils is to develop plants that accumulate metals in the aerial tissues. With the goal of changing the distribution of phytochelatin (PC)-dependent cadmium accumulation from roots to the leaves, the phytochelatin synthase (PCS) deficient cad1-3 mutant and wild type (Col-0) Arabidopsis plants were transformed with an Arabidopsis phytochelatin synthase (AtPCS1) under the control of a leaf-specific promoter. Three independent transformant lines from each genetic background were chosen for further analysis and designated cad-PCS and WT-PCS. PCS activity in the cadPCS lines was restored in the leaves, but not in the roots. Additionally, when whole plants were treated with cadmium, PCs were found only in the leaves of cad-PCS plants. Although the inserted AtPCS1 gene was leaf-specific, cad-PCS lines showed an overall decrease in cadmium toxicity evidenced by a partial amelioration of the "brown-root" phenotype and root growth was restored to wild type levels when treated with cadmium and arsenate. WT-PCS lines showed an increase in leaf PCS activity but had only wild type PC levels. In addition, cadmium uptake studies indicated that there was no difference in cadmium accumulation among all types tested. So, while we were able to protect the plants against cadmium by expressing PC synthase only in the leaves, we were not able to limit cadmium accumulation to aerial tissues. 相似文献
2.
Biomass production, leaf number and area, photosynthetic and dark respiration rates, leaf concentration of photosynthetic pigments, nitrate reductase activity, as well as cadmium concentrations in leaves, stem, and roots were measured in poplar clones PE 4/68, B-229, 665, and 45/51. Plants were grown hydroponically under controlled conditions and treated with two different cadmium (Cd) concentrations (10(-5) and 10(-7) M) in the same background solution (Hoagland's solution). The presence of Cd did not cause serious disturbance of growth and physiological parameters in the studied poplar clones. Cd concentrations in plant tissues reflected external concentrations. In treated plants, root contents increased from 38.57 to 511.51 ppm, leaf contents from 0.91 to 7.50, while stem contents ranged from 1.37 to 9.50 ppm. 相似文献
3.
The rapid induction of photosynthesis is critical for plants under light‐fleck environment. Most previous studies about photosynthetic induction focused upon single leaf, but they did not consider the systemic integrity of plant. Here, we verified whether systemic signalling is involved in photosynthetic induction. Rumex K‐1 ( Rumex patientia × Rumex tianschaious) plants were grown under light‐fleck condition. After whole night dark adaptation, different numbers of leaves (system leaf or SL) were pre‐illuminated with light, and then the photosynthetic induction of other leaves (target leaf or TL) was investigated. This study showed that the pre‐illumination of SL promoted photosynthetic induction in TL. This promotion was independent of the number of SL, the light intensity on SL and the distance between SL and TL, indicating that this systemic signalling is non‐dose‐dependent. More interestingly, the photosynthetic induction was promoted by only the pre‐illumination of morphological upper leaf rather than the pre‐illumination of morphological lower leaf, indicating that the transfer of this signal is directional. The results showed that the transfer of this systemic signalling depends upon the phloem. This systemic signalling helps plants to use light energy more efficiently under light flecks. 相似文献
4.
Experiments were conducted to determine the influence of glyphosate[ N-(phosphonomethyl)glycine] on extractable nitrate reductaseactivity during light and dark growth of soybean ( Glycine max)seedlings. Glyphosate (5?10 4 M), applied via root-feedingto three-day-old etiolated seedling, significantly reduced enzymeactivity in roots (48 to 96 h) and leaves (96 h) of seedlingsplaced in the light, but had little effect on enzyme activityin cotyledons compared to enzyme levels in tissues of untreatedseedlings. During dark-growth, nitrate reductase activity increasedwith time in cotyledons of untreated seedlings (activity about85-fold less than in cotyledons of light-grown plants) but muchlower enzyme levels were found in cotyledons of glyphosate-treatedseedlings after 72 and 96 h. In leaves of dark-grown seedlings,glyphosate reduced nitrate reductase levels by 95%. Most inhibitionof extractable enzyme activity occurred in newly developingorgans (leaves and roots) which correlates well with reportsthat glyphosate is rapidly translocated to these sites. However,the fact that glyphosate inhibits growth prior to lowering enzymeactivity levels indicates a secondary effect on nitrate reductase. (Received May 18, 1984; Accepted February 12, 1985) 相似文献
5.
Alternative respiratory pathway was investigated in rice seedlings grown under total darkness, light/dark cycle, or continuous light. The capacity of the alternative pathway was relatively higher in leaves that had longer light exposure. An analysis of rice AOX1 multigene family revealed that AOX1c, but not AOX1a and AOX1b, had a light-independent expression. The alternative oxidase (AOX) inhibitor, salicylhydroxamic acid (SHAM, 1mM), inhibited nearly 68% of the capacity of the alternative pathway in leaves grown under different light conditions. The plants grown under different light periods were treated with SHAM and then were exposed to illumination for 4h. The transition from dark to 4h of light stimulated the capacity of alternative pathway in etiolated rice seedlings and in those grown under light/dark cycle, whereas the capacity of the alternative pathway was constant in seedlings grown under continuous light with additional 4h of illumination. Etiolated leaves did not show any CO(2) fixation after 4h of illumination, and the increase in chlorophyll content was delayed by the SHAM pretreatment. When seedlings grown under light/dark cycle were moved from dark and exposed to 4h of light, increases in chlorophyll content and CO(2) fixation rate were reduced by SHAM. Although these parameters were stable in plants grown under continuous light, SHAM decreased CO(2) fixation rate but not the chlorophyll content. These results indicate that the role and regulation of AOX in light are determined by the developmental stage of plant photosynthetic apparatus. 相似文献
6.
Summary The protein synthesis inhibitors chloramphenicol and terramycin, and light of low intensity were used to retard the rate of chlorophyll formation in illuminated dark grown pea leaves. In the control leaves the onset of photosynthesis, as measured by carbon dioxide exchange of the whole leaves, and reduction of ferricyanide and metmyoglobin and photo-oxidation of ascorbate in isolated chloroplasts, was observed after 2–4 hours illumination. The photosynthetic activity of the treated leaves did not commence until 10–12 hours illumination had elapsed. In both the control and treated leaves the onset of photosynthesis occurred when the total chlorophyll content was 0.04 mg/g fresh weight. The precise point of photosynthetic inception was apparently more related to the attainment of a specific total chlorophyl content than to the ratio of chlorophyll a to chlorophyll b. A marked increase in the evolution of carbon dioxide in the light was observed in the treated leaves during the first 10 hours of greening. This observation could not be ascribed to photorespiration since the leaves did not possess an active photosystem. It is suggested that the enhanced respiration may have been due to the light-induced activation of synthetic pathways responsible for the formation of chloroplast constituents.The following abbreviations are used CMU
3(3-chlorophenyl)-1, 1-dimethylurea
- DCIP
dichlorophenol indophenol
- PMS
phenazine methosulphate
- TRIS
2-amino-2-hydroxymethyl propane-1, 3-diol
This work was supported by a Science Research Council studentship granted to R. J. Dowdell and submitted for the degree of Ph. D. of Bath University of Technology. 相似文献
7.
To elucidate the effect of ionizing radiation on the non-photochemical quenching (NPQ) oir chlorophyll fluorescence, we analyzed
the buildup and release of NPQ in Arabidopsis wild-type (WT) and npq1- 2 mutant plants after gamma-irradiation. The npqi- 2 mutant cannot normally induce the buildup of NPQ by a mutation in the violaxamthin de-epoxidase gene. A dose of 50 Gy h for
4 h significantly suppressed such buildup in the mutant and, more noticeably, in the WT. Both the initial rise and maximum
level of NPQ were gradually inhibited after gamma-irradiation. In contrast, the release of NPQ and the maximum photochemical
efficiency (Fv/Fm) of Photosystem II were largely unaffected in either genotype. This inhibition of NPQ buildup could be partly
attributable to a significant decrease in the content of carotenoids, including xanthophyll pigments. Moreover, inhibition
that was dependent on the xanthophyll cycle substantially enhanced the sensitivity of irradiated leaves to a photoinhibitory
illumination of 800 |imol photons m 2 s"1. The difference in Fv/Fm values between the WT and npq1- 2 under that photoinhibitory level of illumination was much smaller in the irradiated leaves than in the control. However,
NPQ inhibition did not cause a significant difference in efficiency between WT and mutant when both were treated with UV-B
irradiance of 2.4 W m 2. Therefore, we suggest that a significant decrease in carotenoid content after gamma-irradiation should
partially contribute to the enhanced sensitivity of irradiated plants, at least to high-ligtil photoinhibition. This is accomplished
by suppressing the thermal dissipation of excess light absorbed by photosynthetic pigments. 相似文献
8.
Etiolated bean leaves supplied δ-amino-levulinic acid in the dark synthesize large amounts of protochlorophyllide which is not converted to chlorophyllide upon illumination of the leaves. The fine structure of the proplastids is not affected by the treatment. When leaves containing "inactive" protochlorophyllide are exposed to light of 700 ft-c for 3 hours, they lose practically all their green pigments. During this period large stacks of closed membrane structures are built up in the region of the prolamellar body. These lamellar structures remain even when no or only traces of pigment are left in the leaves. In untreated control leaves the pigment content remained constant during similar illumination and the structural changes in the plastids consisted of a rearrangement of the vesicles from the prolamellar bodies into strands dispersed through the stroma; lamellae and grana formation occurred later. 相似文献
9.
Both light and NO3- are necessary for the appearance of nitrate reductase (NR) activity (NRA) in photosynthetic tissues. To define the light effect more precisely, we examined the response to light/dark transitions on NRA, NR protein (NRP), and NR mRNA in 6-d-old maize (Zea mays cv W64A x W182E) seedlings that had been grown in a light/dark regime for 5 d and then induced with 5 mM KNO3 for 24 h. The decay of NRA and NR mRNA in the shoot was immediate, but there were only minor changes in NRP during the initial 4 h in the dark. In root tissues, in contrast, there was a 4-h delay in the loss of NRA, NRP, and NR mRNA after transfer to the dark. When the seedlings were returned to light after a 2-h interval in the dark, shoot NRA reached 92% of the initial levels within 30 min of illumination. These results indicate that in the shoots (a) NR message production requires light and (b) the NRP that appears with light treatment and that is active is inactivated in the dark. The NRP can be reactivated when the light is turned on after short periods of darkness (2 h). Root tissues, on the other hand, probably respond to the supply of photosynthetically produced metabolites rather than to immediate products of the light reactions of photosynthesis. 相似文献
10.
分别用不同浓度的铜试剂和百草枯对水稻幼苗进行叶面喷施后,于4,24,48,72h分别测定叶片中叶绿素和类胡萝卜素含量的动态变化.结果表明,处理后叶片中光合色素含量降低.铜试剂及百草枯对叶绿素和类胡萝卜素含量的影响有相似的规律.在处理后的4h,光合色素含量开始发生变化,铜试剂处理后幼苗叶片中光合色素含量在72h最低,百草枯处理后幼苗叶片光合色素含量在48h达最低,降低的幅度与铜试剂及百草枯的浓度成正相关. 相似文献
11.
Mechanical stimulation of plants can be caused by various abiotic and biotic environmental factors. Apart from the negative consequences, it can also cause positive changes, such as acclimatization of plants to stress conditions. Therefore, it is necessary to study the physiological and biochemical mechanisms underlying the response of plants to mechanical stimulation. Our aim was to evaluate the response of model plant Arabidopsis thaliana to a moderate force of 5 N (newton) for 20 s, which could be compared with the pressure caused by animal movement and weather conditions such as heavy rain. Mechanically stimulated leaves were sampled 1 h after exposure and after a recovery period of 20 h. To study a possible systemic response, unstimulated leaves of treated plants were collected 20 h after exposure alongside the stimulated leaves from the same plants. The effect of stimulation was assessed by measuring oxidative stress parameters, antioxidant enzymes activity, total phenolics, and photosynthetic performance. Stimulated leaves showed increased lipid peroxidation 1 h after treatment and increased superoxide dismutase activity and phenolic oxidation rate after a 20-h recovery period. Considering photosynthetic performance after the 20-h recovery period, the effective quantum yield of the photosystem II was lower in the stimulated leaves, whereas photochemical quenching was lower in the unstimulated leaves of the treated plants. Nonphotochemical quenching was lower in the stimulated leaves 1 h after treatment. Our study suggested that plants sensed moderate force, but it did not induce pronounced change in metabolism or photosynthetic performance. Principal component analysis distinguished three groups–leaves of untreated plants, leaves analysed 1 h after stimulation, while stimulated and unstimulated leaves of treated plants analysed 20 h after treatment formed together the third group. Observed grouping of stimulated and unstimulated leaves of treated plants could indicate signal transduction from the stimulated to distant leaves, that is, a systemic response to a local application of mechanical stimuli. 相似文献
12.
Changes in photosynthetic activity, redox state of photosystem I (PSI) and photosystem II (PSII), as well as starch and sucrose content were studied on the source leaves of 18- to 20-day-old radish ( Raphanus sativus L.) plants that were dark-adapted for 12 h and then exposed to continuous white light (170 mol quanta/(m 2 s)). The kinetic pattern of photosynthetic activity comprised three phases. Within the first 6 h of light adaptation (first phase), the maximum photosynthetic rate and the quantum yield of photosynthesis increased 1.6 times in the illuminated leaves compared to the leaves of plants placed in darkness. Further illumination led to the decrease of both photosynthetic indices by about 20% (12 h after the onset of light exposure, second phase) and finally increased them to the level observed after 6-h light exposure (72 h, third phase). The stationary photooxidation level of PSI primary donor was relatively low within the first 6 h of light adaptation, and then it steeply increased. The linear relationship between the amounts of photoreduced PSII primary acceptor and photooxidized PSI primary donor did not change during prolonged light adaptation, showing a highly coordinated functioning of both photosystems. The amount of sucrose in leaves attained its peak after 12 h of light adaptation and did not change further on. The starch content increased to its peak within 24 h of illumination and decreased gradually upon longer exposures. It is concluded that, despite active export of assimilates to the developing storage organ, the source leaves exhibit a nonmonotonic temporal course of endogenously regulated photosynthetic activity, which was related to changes in the effectiveness and, possibly, the number of the components of photosynthetic apparatus. 相似文献
13.
The photoreduction of protochlorophyllide was studied in leaves and isolated chloroplasts of barley. Leaves of plants which had been preilluminated for varying lengths of time were incubated with [ 14C]-δ- aminolevulinic acid for 2 h in the dark. The subsequent photoreduction of [ 14C]-protochlorophyllide was analyzed by high performance liquid chromatography of pigments extracted from illuminated leaves and plastids. The plastids used in this study were isolated in the dark from leaves at the end of the 2 h labelling period. Three major results were obtained: - 1
The extent of protochlorophyllide reduction in vivo was rapidly reduced as a function of the preillumination period. In 24 h preilluminated plants only a small fraction of the radioactively labelled protochlorophyllide was reduced during the subsequent light period. - 2
The amount of NADPH-protochlorophyllide oxidoreductase (EC 1.6.99.-) present in plastids of fully-green plants was drastically reduced relative to levels in plastids of dark-grown plants as estimated by the methods of immunoblotting of plastid proteins and immunogold labelling of ultrathin sections of the leaf tissue. - 3
In etiolated plants light seemed to affect the reduction of protochlorophyllide directly through the excitation of protochlorophyllide. In fully green plants, however, light also affected chlorophyll formation indirectly by the supply of NADPH via photosynthetic electron transport. 相似文献
14.
The aim of the present study was to investigate the in vitro and in vivo acaricidal effects of an essential oil of Cinnamomum zeylanicun leaves on Psoroptes cuniculi, a mange mite. In vitro, 2.5 ml of the essential oil diluted at different concentrations, from 10% to 0.03%, in paraffin oil were added to Petri dishes containing all motile stages of P. cuniculi. Mites mortality observed in these dishes was compared with that observed in untreated and treated (AcaCerulen R) control plates. In vivo, one group of six P. cuniculi infected rabbits was topically treated two times at seven days interval with two ml of the essential oil at the concentration of 2.5% in paraffin oil and compared with untreated and treated (AcaCerulen R) control groups of six rabbits each. After 24 h of contact, all concentrations of essential oil between 0.10 and 10% showed a good in vitro acaricidal efficacy if compared with the untreated controls (p<0.01), but only the concentrations between 0.16 and 10% turned out as active as the drug. In vivo, the treatment with the essential oil cured all infested rabbits and no statistical differences were observed with the treated control group. 相似文献
15.
This study aims to elucidate the molecular mechanism for the transient increase in the O 2‐uptake rate in tobacco ( Nicotiana tabacum cv Xanthi) leaves after turning off actinic lights (ALs). The photosynthetic O 2 evolution rate reaches a maximum shortly after the onset of illumination with ALs and then decreases to zero in atmospheric CO 2/O 2 conditions. After turning off the ALs, tobacco leaves show a transient increase in the O 2‐uptake rate, the post‐illumination transient O 2‐uptake, and thereafter, the O 2‐uptake rate decreases to the level of the dark‐respiration rate. Photosynthetic linear electron flow, evaluated as the quantum yield of photosystem II [Y(II)], maintained a steady‐state value distinct from the photosynthetic O 2‐evolution rate. In high‐[CO 2] conditions, the photosynthetic O 2‐evolution rate and Y(II) showed a parallel behavior, and the post‐illumination transient O 2‐uptake was suppressed. On the other hand, in maize leaves (a C4 plant), even in atmospheric CO 2/O 2 conditions, Y(II) paralleled the photosynthetic O 2‐evolution rate and the post‐illumination transient O 2‐uptake was suppressed. Hypothesizing that the post‐illumination transient O 2‐uptake is driven by C3 plant photorespiration in tobacco leaves, we calculated both the ribulose 1,5‐bisphosphate carboxylase‐ and oxygenase‐rates (Vc and Vo) from photosynthetic O 2‐evolution and the post‐illumination transient O 2‐uptake rates. These values corresponded to those estimated from simultaneous chlorophyll fluorescence/O 2‐exchange analysis. Furthermore, the H +‐consumption rate for ATP synthesis in both photosynthesis and photorespiration, calculated from both Vc and Vo that were estimated from chlorophyll fluorescence/CO 2‐exchange analysis, showed a positive linear relationship with the dissipation rate of the electrochromic shift signal. Thus, these findings support our hypothesis. 相似文献
16.
以谷子(Setaria italica(L)Beauv.)为对象,从拔节期开始持续给予低氮(1.875 mmol/L)和高氮(15 mmol/L)两种氮供应条件并从抽穗期开始进行26 d两种强度(4.29、7.12 kJ·m-2·d-1)的增强UV-B辐射处理,研究了谷子叶中光合色素含量、类黄酮含量和苯丙氨酸解氨酶(PAL)活性的变化.结果表明:与高氮供应条件相比,低氮供应条件明显降低了谷子叶中光合色素含量但提高了类胡萝卜素/叶绿素含量比值;在开花期中段和灌浆期中段,高氮供应条件下谷子叶中光合色素含量对增强UV-B辐射比低氮供应条件下的谷子更敏感.从灌浆期开始到处理结束,两种影响因子对谷子叶中类黄酮含量均有显著影响,增强UV-B辐射导致谷子叶中类黄酮含量逐渐升高,且相同增强UV-B辐射强度下低氮供应条件下的谷子叶中类黄酮含量明显高于高氮供应条件下的谷子.谷子叶中PAL活性对两种影响因子的响应较类黄酮含量更加敏感,低氮供应条件使谷子叶中PAL活性明显提高.结合上述指标的相关性分析结果可知,低氮供应条件加强了处于繁殖期主要阶段的谷子叶中类黄酮的积累,并使谷子叶中的类胡萝卜素/叶绿素含量比值明显提高,进而有助于维持谷子叶中光合色素含量在增强UV-B辐射条件下的相对稳定性,对植株抵抗UV-B辐射伤害有利. 相似文献
17.
Red light (R) pretreatment of etiolated cucumber seedlings ( Cucumis sativus L. var. Elem) followed by prolonged dark incubation prior to white light (WL) exposure, had an adverse effect on the greening of the cotyledons. The effect was photoreversible by far-red (FR) light. Cotyledons which were dark incubated for 24 h following the R pulse greened more rapidly when exposed to WL than did the controls, while total chlorophyll (Chl) accumulation after 24 h in the light was about the same in both. However, after 48 h post-R dark incubation greening of the treated cotyledons was delayed, and their amount of Chl which accumulated after 24 h WL was about one half of that in non-treated seedlings. As the length of the post-R dark incubation period was extended Chl production became slower, so that after 96 h post-R dark incubation the Chl level in the treated cotyledons after 24 h WL was approximately 20% of the controls. No significant differences in amounts of protochlorophyll could be detected between seedlings preilluminated with R or R followed by FR. Seedlings 4-, 5- and 6-days-old at the time of R treatment showed similar degrees of impaired Chl synthesis following prolonged post-R dark incubation. 相似文献
18.
The 2 major photosynthetic products and translocated carbohydrates in celery ( Apium graveolens L.) are sucrose and the sugar alcohol, mannitol. Sucrose is produced and utilized in leaves of all ages. Mannitol, however, is synthesized primarily in mature leaves, utilized in young leaves and stored in all leaves. Here we show that mannitol export was lower from young, expanding leaves than from older leaves. After a 10 min pulse of 14CO 2 and a 2 h chase in the light or dark there was more radioactivity in sucrose than in mannitol in petiole tissues from leaves of all ages. However, after a chase of 15 h in the dark or 6 h in the light followed by 9 h in the dark, mannitol was the predominant [ 14C]-labeled carbohydrate remaining in all leaf and petiole tissues. Thus, newly synthesized sucrose was apparently exported at a faster rate than mannitol and more mannitol was partitioned into vacuolar storage pools than was sucrose. It also appears that in the light both sucrose and mannitol were exported, but in the dark, once sucrose pools were depleted, mannitol remained as the predominant substance translocated. Both mannitol and sucrose were unloaded into petiole storage parenchyma tissue, but sucrose was hydrolyzed prior to storage. 相似文献
19.
Maize ( Zea mays L.) seedlings were grown in nutrient solution culture containing 0, 5, and 20 μM cadmium (Cd) and the effects on various
aspects of photosynthesis were investigated after 24, 48, 96 and 168 h of Cd treatments. Photosynthetic rate ( P
N) decreased after 48 h of 20 μM Cd and 96 h of 5μM Cd addition, respectively. Chl a and total Chl content in leaves declined under 48 h of Cd exposure. Chl b content decreased on extending the period of Cd exposure to 96 h. The maximum quantum efficiency and potential photosynthetic
capacity of PSII, indicated by F v/F m and F v/F o, respectively, were depressed after 96 h onset of Cd exposure. After 48 h of 5μM Cd and 24 h of 20 μM Cd treatments, the
activities of ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco, EC 4.1.39) and phospho enolpyruvate carboxylase (PEPC, EC 4.1.1.31) in the leaves started to decrease, respectively. We found that the limitation of
photosynthetic capacity in Cd stressed maize leaves was associated with Cd toxicity on the light and the dark stages. However,
Cd stress initially reduced the activities of Rubisco and PEPC and subsequently affected the PSII electron transfer, suggesting
that the Calvin cycle reactions in maize plants are the primary target of the Cd toxic effect rather than PSII. 相似文献
20.
Resynthesis of the photosynthetic apparatus and resumption of CO 2 assimilation upon rehydration is reported for the monocotyledonous and poikilochlorophyllous desiccation-tolerant (PDT) plant Xerophyta scabrida (Pax) Th. Dur. et Schinz (Velloziaceae). During desiccation there was a complete breakdown of chlorophylls whereas the total carotenoid content of air-dried leaves was reduced to about 22% of that of functional leaves. The prerequisites for the resynthesis of photosynthetic pigments and functional thylakoids were the reappearance of turgor and maximum leaf water content at 2 and 10 h after rehydration, respectively. The period of increased initial respiration after rewetting leaves (rehydration respiration) lasted up to 30 h and was thus 6 to 10 times longer than in homoiochlorophyllous desiccation-tolerant plants (HDTs) in which chlorophylls are retained during desiccation. Accumulation of chlorophylls a + b and total carotenoids (xanthophylls and carotene) started 10 h after rehydration. Normal levels of chlorophyll and carotenoids were obtained 72 h after rehydration. Values for the variable-fluorescence decrease ratio (Rfd690 values), an indicator of photochemical activity, showed that photochemical function started 10 h after rehydration, but normal values of 2.7 were reached only 72 h after rehydration. Net CO 2 assimilation started 24 h after rewetting and normal rates were reached after 72 h, at the same time as normal values of stomatal conductance were obtained. The increasing rates of net CO 2 assimilation were paralleled by decreasing values of the intercellular CO 2 concentration. All photosynthetic parameters investigated showed values normal for functional chloroplasts by 72 h after the onset of rehydration. Fully regreened leaves of the presumed C 3 plant X. scabrida exhibited a net CO 2 assimilation rate which was in the same range as that of other C 3 plants and higher than that of recovered HDT plants. The fundamental difference between air-dried PDT plants, such as X. scabrida, which have to resynthesize the photosynthetic pigment apparatus, and air-dried HDT plants, which only undergo a functional recovery, is discussed.Abbreviations c
-carotene
- c i
intercellular CO 2 concentration
- Car x + c
total carotenoid content x + c
- Chl a + b
total chlorophyll a + b content
- g s
stomatal conductance
- HDT
homoiochlorophyllous desiccation tolerant
- LWC
leaf-water content
- P N
net photosynthesis rate
- PDT
poikilochloro phyllous desiccation tolerant
- R d
dark respiration
- Rfd
variable fluorescence decrease ratio (Rfd = fd/fs)
- x
xanthophylls
The senior author thanks the Deutschem Akademischem Auslandsdienst (Bonn, Germany), Soros Foundation (Budapest, Hungary) and European Community (Brussels, Belgium) for providing fellowships for research periods at Karlsruhe. The research was also supported by the Hungarian Scientific Research Foundation (OTKA I/848, OTKA I/3.1545 and OTKA I/4.F.5359). We wish to thank Professor T. Pocs (Eger, Hungary — Morogoro, Tanzania) for collecting the plant material and to the linguist Mr. A. Jackson for correcting the English. 相似文献
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