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1.
Summary The photosynthetic pathways of 42 species of the genusEuphorbia growing wild, naturalized or cultivated in Egypt were investigated. The criteria used included the δ13C- and δD-values and Kranz anatomy of the leaves. There is a relationship between the photosynthetic pathway and the ecological conditions in the habitat of a particular species. All 4 CAM species are succulent shrubs, wild or cultivated. The 11 species with C4 pathways are mainly summer annuals of tropical origin and flourish under the hot summer conditions. The 27 C3 species are either winter annuals, perennials, perennials flourishing in winter or shrubs; the majority are Mediterranean, European or Saharo-Arabian. Summer annuals with C3 pathways grow under the shade of the summer crops. Generally, C3 plants grow under conditions of relatively better water resources and lower temperature than the C4 plants. The majority of the CAM and C4 species occur in the southern part of the country, where high temperature is a common feature of the climate.  相似文献   

2.
Summary Laboratory and field gas exchange measurements were made on C3 (Scirpus olneyi Gray) and C4 (Spartina patens (Ait.) Mahl., Distichlis spicata (L.) Green) species from an irregularly flooded tidal marsh on the Chesapeake Bay. Laboratory measurements were made on plants grown from root stocks that were transplanted to a greenhouse and grown under high light and high nutrient conditions. The two C4 species were similar in their laboratory gas exchange characteristics: both had higher net carbon exchange rates, higher mesophyll conductances, higher photosynthetic temperature optima and lower leaf conductances than the C3 species. The laboratory photosynthetic water use efficiency of the C4 species was approximately three times that of the C3 species.Field gas exchange responses of the above species were measured in situ a Chesapeake Bay tidal marsh. Despite differences in biological potential measured in the laboratory, all three species had similar in situ carbon exchange rates on a leaf area basis. On a dry weight basis, leaves of the two C4 species had about 1.4 times higher light saturated CO2 assimilation rates than the C3 species. Light saturation of CO2 exchange occurred at photosynthetic photon flux densities of 80 n Einstein cm-2s-1, compared with 160 n Einstein cm -2s-1 in the laboratory grown plants. Spartina patens and Scirpus olneyi had similar daily CO2 assimilation rates, but the daily transpiration rate of the C3 species was almost twice that of the C4 species. Spartina patens showed greater seasonal decrease in photosynthesis than Distichlis spicata and Scirpus olneyi. The two C4 grass species maintained higher mesophyll conductances and photosynthetic water use efficiencies than the C4 sedge.  相似文献   

3.
The photosynthetic pathway of plant species collected at Menyuan, Henan, and Maduo sites, east of Tibetan Plateau, China, during the growing season were studied using stable carbon isotopes in leaves. The 232 samples leaves analyzed belonged to 161 species, 30 families, and 94 genera. The δ13C values (from −24.6 to − 29.2 ‰) indicated that all the considered species had a photosynthetic C3 pathway. The absence of plant species with C4 photosynthetic pathway might be due to the extremely low air temperature characterizing the Tibetan Plateau. The average δ13C value was significantly (p<0.05) different between annuals and perennials at the three considered study sites. Hence the longer-lived species had greater water-use efficiency (WUE) than shorter-lived species, that is, longer-lived species are better adapted to the extreme environmental conditions of the Tibetan Plateau.  相似文献   

4.
Abstract

Ecological aspects of C3, C4 and CAM photosynthetic pathways. - Three different photosynthetic CO2 fixation pathways are known to occur in higher plants. However all three pathways ultimately depend on the Calvin-Benson cycle for carbon reduction. The oxygenase activity of RuBP carboxilase is responsible for photorespiratory CO2 release. Both C4 and CAM pathways behave as a CO2 concentrating mechanism which prevent photorespiration. The CO2-concentrating mechanism in C4 plants is based on intracellular symplastic transport of C4 dicarboxylic acids from mesophyll-cells to the adjacent bundle-sheath cells. On the contrary in CAM plants the CO2-concentrating mechanism is based on the intracellular transport of malic acid into and out of the vacuole.

The C4 photosynthetic pathway as compared to the C3 pathway permits higher rates of CO2 fixation in high light and high temperature environments at low costs in terms of water loss, given the stability of the photosynthetic apparatus under such conditions.

CAM is interpreted as an adaptation to arid environments because it enables carbon assimilation to take place at very low water costs during the night when the evaporative demand is low. Nevertheless many aquatic species of Isoetes and some relatives are CAM, suggesting the adaptive role of CAM to environments which become depleted in CO2.

The photosynthetic carbon fixation pathway certainly contributes to the ecological success of plants in different environments. However the distribution of plants may also reflect their biological history. On the other hand plants with different photosynthetic pathways coexist in many communities and tend to share resources in time. In any case some generalizations are possible: C4 plants enjoy an ecological advantage in hot, moist, high light regions while the majority of species in desert environments are C3; CAM plants are more frequent in semiarid regions with seasonal rainfall, coastal fog deserts, and in epiphytic habitats in tropical rain forests.  相似文献   

5.
Naturalization of alien plants in China   总被引:3,自引:0,他引:3  
Naturalization (the establishment of a self-sustaining population for at least a decade) is a fundamental precondition for plant invasion and so compiling a complete inventory of naturalized alien species is necessary for predicting and hence preventing such invasion. However, nationwide information on naturalized plants in China is still lacking. We compiled a nationwide list of the naturalized plant species of China, based on various literature reports. The list comprised a total of 861 naturalized plant species belonging to 110 families and 465 genera. The three most dominant families were Compositae, Poaceae, and Leguminosae, accounting for 16, 13 and 12% of naturalized plants, respectively. Among genera, Euphorbia and Solanum had the most naturalized species, followed by Ipomoea, Amaranthus, Oenothera, and Trifolium. Over half of all aliens were of American origin (52%), followed by those with European (14%) and Asian (13%) origins. Annuals and perennial herbs were prevalent among naturalized species; comparison to other studies suggests however that the invasive potential is higher among plants with longer life cycles than those of annuals. The taxonomic pattern of plant naturalization in China is similar to patterns worldwide. However, the low proportion of naturalized plants within the Chinese flora overall suggests that the potential for plant invasions in China may be high. Therefore, greater attention should be focused on naturalization of alien plants in China, especially concerning species of dominant families or genera, and those with a perennial life cycle.  相似文献   

6.
Hydrogen and carbon isotope ratios of cellulose nitrate and oxygen isotope ratios of cellulose from C3, C4, and Crassulacean acid metabolism (CAM) plants were determined for plants growing within a small area in Val Verde County, Texas. Plants having CAM had distinctly higher deuterium/hydrogen (D/H) ratios than plants having C3 and C4 metabolism. When hydrogen isotope ratios are plotted against carbon isotope ratios, each photosynthetic mode separates into a distinct cluster of points. C4 plants had many D/H ratios similar to those of C3 plants, so that hydrogen isotope ratios cannot be used to distinguish between these two photosynthetic modes. Portulaca mundula, which may have a modified photosynthetic mode between C4 and CAM, had a hydrogen isotope ratio between those of the C4 and CAM plants. When oxygen isotope ratios are plotted against carbon isotope ratios, no distinct clustering of the C4 and CAM plants occurs. Thus, oxygen isotope ratios are not useful in distinguishing between these metabolic modes. A plot of hydrogen isotope ratios versus oxygen isotope ratios for this sample set shows considerable overlap between oxygen isotope ratios of the different photosynthetic modes without a concomitant overlap in the hydrogen isotope ratios of CAM and the other two photosynthetic modes. This observation is consistent with the hypothesis that higher D/H ratios in CAM plants relative to C3 and C4 plants are due to isotopic fractionations occurring during biochemical reactions.  相似文献   

7.
R.Z. Wang 《Photosynthetica》2005,43(4):535-549
Of the total 570 species, 194 species in 116 genera and 52 families were found with C3 photosynthesis, 24 species in 17 genera and 6 families with C4 photosynthesis, and 2 species in 1 genera and 1 family with CAM photosynthesis. 90 % of the total species can be found in Changbai Mountain flora, more a half (69 %) in North China flora, and about 1/3 in Mongolian flora and Xinan flora, respectively. The occurrence of C4 species was not as common as that in adjacent grasslands and deserts, but relatively more than in the adjacent forests. Of the total 24 C4 species, 63 % C4 species (15 of 24) was found in Gramineae. Nine life form types can be found, reflecting the moist climate in the region, especially the occurrence of epiphyte and liana forms. Relatively more geophyte life form plants suggested the winter in the region was much colder than in grasslands. These indicated that both ecological studies and land management decisions must take into account plant photosynthetic pathway and life form patterns, for both of them are closely related to climatic changes and land use.  相似文献   

8.
Summary The photosynthetic processes of two ecologically-matched, herbaceous Atriplex species differed in their response to SO2 fumigations. Atriplex triangularis, a C3 species, was more sensitive than the C4 species, A. sabulosa. This difference in sensitivity can be attributed in part to the higher conductance of the C3 species in normal air and saturating light as well as greater stimulation of stomatal opening following exposure to SO2. In addition, photosynthetic mechanisms of the C3 species had higher intrinsic SO2 sensitivity than the C4 species. Differences between photosynthetic responses of these two species may also reflect differences in morphological configuration of mesophyll tissues and greater SO2 sensitivity of the initial photosynthetic carboxlating enzyme of the C3 species. It is likely that certain of the differences in photosynthetic SO2 sensitivity of these contrasting C3 and C4 Atriplex species are characteristic of C3 and C4 plants in general.Abbreviations PEP carboxylase phosphoenolpyruvate carboxylase - RuBP carboxylase ribulose-1,5-bisphosphate carboxylase  相似文献   

9.
Summary Common generalizations concerning the ecologic significance of C4 photosynthesis were tested in a study of plant gas exchange, productivity, carbon balance, and water use in monospecific communities of C3 and C4 salt desert shrubs. Contrary to expectations, few of the hypotheses concerning the performance of C4 species were supported. Like the C3 species, Ceratoides lanata, the C4 shrub, Atriplex confertifolia, initiated growth and photosynthetic activity in the cool spring months and also exhibited maximum photosynthetic rates at this time of year. To compete successfully with C3 species, Atriplex may have been forced to evolve the capacity for photosynthesis at low temperatures prevalent during the spring when moisture is most abundant. Maximum photosynthetic rates of Atriplex were lower than those of the C3 species. This was compensated by a prolonged period of low photosynthetic activity in the dry late summer months while Ceratoides became largely inactive. However, the annual photosynthetic carbon fixation per ground area was about the same in these two communities composed of C3 and C4 shrubs. The C4 species did not exhibit greater leaf diffusion resistance than the C3 species. The photosynthesis/transpiration ratios of the two species were about the same during the period of maximum photosynthetic rates in the spring. During the warm summer months the C4 species did have superior photosynthesis/transpiration ratios. Yet, since Ceratoides completed a somewhat greater proportion of its annual carbon fixation earlier in the season, the ratio of annual carbon fixation/transpiratory water loss in the two communities was about the same. Atriplex did incorporate a greater percentage of the annual carbon fixation into biomass production than did Ceratoides. However, this is considered to be a reflection of properties apart from the C4 photosynthetic pathway. Both species displayed a heavy commitment of carbon to the belowground system, and only about half of the annual moisture resource was utilized in both communities.  相似文献   

10.
Photosynthetic carbon gain in plants using the C3 photosynthetic pathway is substantially inhibited by photorespiration in warm environments, particularly in atmospheres with low CO2 concentrations. Unlike C4 plants, C3 plants are thought to lack any mechanism to compensate for the loss of photosynthetic productivity caused by photorespiration. Here, for the first time, we demonstrate that the C3 plants rice and wheat employ a specific mechanism to trap and reassimilate photorespired CO2. A continuous layer of chloroplasts covering the portion of the mesophyll cell periphery that is exposed to the intercellular air space creates a diffusion barrier for CO2 exiting the cell. This facilitates the capture and reassimilation of photorespired CO2 in the chloroplast stroma. In both species, 24–38% of photorespired and respired CO2 were reassimilated within the cell, thereby boosting photosynthesis by 8–11% at ambient atmospheric CO2 concentration and 17–33% at a CO2 concentration of 200 µmol mol?1. Widespread use of this mechanism in tropical and subtropical C3 plants could explain why the diversity of the world's C3 flora, and dominance of terrestrial net primary productivity, was maintained during the Pleistocene, when atmospheric CO2 concentrations fell below 200 µmol mol?1.  相似文献   

11.
Summary The C4 species, Euphorbia forbesii, and the C3 species, Claoxylon sandwicense, occupy cool, shaded habitats in Hawaii. Both of these species exhibit the photosynthetic characteristics of typical shade plants: low light-saturated photosynthetic rates, low dark respiration rates, low light levels for saturation of photosynthesis, and low light compensation points. In addition, the quantum yields of the two species are similar at leaf temperatures near 22°C, reflecting a significant increase in the quantum yield of E. forbesii over that of C4 species from open habitats. C. sandwicense has a lower dark respiration rate than E. forbesii. Hence, since the quantum yields of the two species are similar at cool temperatures, C. sandwicense has a higher photosynthetic rate than E. forbesii at low incident photon flux densities. As a consequence, C. sandwicense should have a greater carbon gain than E. forbesii under the diffuse radiation conditions of their native habitat. However, since E. forbesii has a higher light-saturated photosynthetic rate than C. sandwicense, E. forbesii may have a greater carbon gain than C. sandwicense during sunflecks.  相似文献   

12.
Summary Mono-specific communities of the C3 sedge, Scirpus olneyi and the C4 grass, Spartina patens, were exposed to normal ambient or elevated CO2, (ca. 680 l l–1) throughout the 1987 and 1988 growing seasons in open-top field chambers located on a tidal marsh. Single stems of C3 plants grown in ambient or elevated CO2 showed an increased photosynthetic rate when tested at elevated CO2 for both seasons. This increase in photosynthetic response in the C3 species was maintained throughout the 1987 and 1988 growing season. The stimulation of photosynthesis with elevated CO2 appeared to increase as temperature increased and decreased as photosynthetic photon flux (PPF) increased. Analysis of the photosynthetic response of the C3 species during the 1988 season indicated that significant differences in light-saturated photosynthetic rate between ambient and elevated CO2 conditions continued until October. In contrast to the C3 sedge, the C4 grass showed no significant photosynthetic increase to elevated CO2 except at the beginning of the 1988 season.  相似文献   

13.
Summary Field measurements of photosynthetic CO2 exchange were made on saplings of a C4 tree species, Euphorbia forbesii, and a C3 tree species, Claoxylon sandwicense, in a shaded mesic forest on Oahu, Hawaii. Both species had light responses typical of those generally found in shade plants. Light saturated photosynthetic rates were 7.15 and 4.09 mol m2 s1 and light compensation points were 6.3 and 1.7 mol m2 s1 in E. forbesii and C. sandwicense, respectively. E. forbesii maintained a higher mesophyll conductance and a higher water use efficiency than C. sandwicense as is typically found in comparisons of C4 and C3 plants. Under natural light regimes, both species maintained positive CO2 uptake rates over essentially the entire day because of low respiration rates and light compensation points. However, photosynthesis during sunflecks accounted for a large fraction of the daily carbon gain. The results show that the carbon-gaining capacity of E. forbesii is comparable to that of a C3 species in a moderately cool, shaded forest environment. There appears to be no particular advantage or disadvantage associated with the C4 photosynthetic pathway of E. forbesii in this environment.  相似文献   

14.
Carbon and hydrogen isotope ratios of cellulose nitrate and oxygen isotope ratios of cellulose from species of greenhouse plants having different photosynthetic modes were determined. When hydrogen isotope ratios are plotted against carbon isotope ratios, four clusters of points are discernible, each representing different photosynthetic modes: C3 plants, C4 plants, CAM plants, and C3 plants that can shift to CAM or show the phenomenon referred to as CAM-cycling. The combination of oxygen and carbon isotope ratios does not distinguish among the different photosynthetic modes. Analysis of the carbon and hydrogen isotope ratios of cellulose nitrate should prove useful for screening different photosynthetic modes in field specimens that grew near one another. This method will be particularly useful for detection of plants which show CAM-cycling.  相似文献   

15.
Family Chenopodiaceae is an intriguing lineage, having the largest number of C4 species among dicots, including a number of anatomical variants of Kranz anatomy and three single-cell C4 functioning species. In some previous studies, during the culture of Bienertia cycloptera Bunge ex Boiss., carbon isotope values (δ13C values) of leaves deviated from C4 to C3−C4 intermediate type, raising questions as to its mode of photosynthesis during growth in natural environments. This species usually co-occurs with several Kranz type C4 annuals. The development of B. cycloptera morphologically and δ13C values derived from plant samples (cotyledons, leaves, bracts, shoots) were analyzed over a complete growing season in a salt flat in north central Iran, along with eight Kranz type C4 species and one C3 species. For a number of species, plants were greenhouse-grown from seeds collected from the site, in order to examine leaf anatomy and C4 biochemical subtype. Among the nine C4 species, the cotyledons of B. cycloptera, and of the Suaeda spp. have the same respective forms of C4 anatomy occurring in leaves, while cotyledons of members of tribe Caroxyloneae lack Kranz anatomy, which is reflected in the δ13C values found in plants grown in the natural habitat. The nine C4 species had average seasonal δ13C values of −13.9‰ (with a range between species from −11.3 to −15.9‰). The measurements of δ13C values over a complete growing season show that B. cycloptera performs C4 photosynthesis during its life cycle in nature, similar to Kranz type species, with a seasonal average δ13C value of −15.2‰. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.  相似文献   

16.
Most plants show considerable capacity to adjust their photosynthetic characteristics to their growth temperatures (temperature acclimation). The most typical case is a shift in the optimum temperature for photosynthesis, which can maximize the photosynthetic rate at the growth temperature. These plastic adjustments can allow plants to photosynthesize more efficiently at their new growth temperatures. In this review article, we summarize the basic differences in photosynthetic reactions in C3, C4, and CAM plants. We review the current understanding of the temperature responses of C3, C4, and CAM photosynthesis, and then discuss the underlying physiological and biochemical mechanisms for temperature acclimation of photosynthesis in each photosynthetic type. Finally, we use the published data to evaluate the extent of photosynthetic temperature acclimation in higher plants, and analyze which plant groups (i.e., photosynthetic types and functional types) have a greater inherent ability for photosynthetic acclimation to temperature than others, since there have been reported interspecific variations in this ability. We found that the inherent ability for temperature acclimation of photosynthesis was different: (1) among C3, C4, and CAM species; and (2) among functional types within C3 plants. C3 plants generally had a greater ability for temperature acclimation of photosynthesis across a broad temperature range, CAM plants acclimated day and night photosynthetic process differentially to temperature, and C4 plants was adapted to warm environments. Moreover, within C3 species, evergreen woody plants and perennial herbaceous plants showed greater temperature homeostasis of photosynthesis (i.e., the photosynthetic rate at high-growth temperature divided by that at low-growth temperature was close to 1.0) than deciduous woody plants and annual herbaceous plants, indicating that photosynthetic acclimation would be particularly important in perennial, long-lived species that would experience a rise in growing season temperatures over their lifespan. Interestingly, across growth temperatures, the extent of temperature homeostasis of photosynthesis was maintained irrespective of the extent of the change in the optimum temperature for photosynthesis (T opt), indicating that some plants achieve greater photosynthesis at the growth temperature by shifting T opt, whereas others can also achieve greater photosynthesis at the growth temperature by changing the shape of the photosynthesis–temperature curve without shifting T opt. It is considered that these differences in the inherent stability of temperature acclimation of photosynthesis would be reflected by differences in the limiting steps of photosynthetic rate.  相似文献   

17.
Summary Pure and mixed cultures of the dicotyledons Atriplex hortensis L. (C3 plant) and Amaranthus retroflexus L (C4) on the one hand and of the grasses Avena sativa L (C3) and Panicum miliaceum L. (C4) on the other hand were maintained in a standard soil with different ground water tables. After 12 weeks the length, dry weight and nitrogen-content of the aboveground and belowground parts of the plants, and in addition the carbon-and ash-content and the 13C value of the aboveground parts were determined. It turned out that the length and the dry weight of the shoots of the C3 species showed on increasing tendency with increased water supply, while the values of the C4 species were drastically diminished at the highest water level only. The roots showed in most cases an increased length and dry weight at drier conditions, more pronounced in the C4 than in the C3 species. The nitrogen content of the shoots was mostly higher in the shoots of the C3 plants and in the roots of the C4 plants; it changed in a non-regular manner with variations in water supply. Since the carbon content did not change markedly, the C/N ratio was variable. There was a slight tendency for a higher carbon content and mostly also for a higher C/N-ratio in the shoots of C4 plants. The 13C values of both C3 as C4 plants were in general not at all influenced by the water supply; they were fixed genetically. The ash content of the analyzed species did not show a clear relationship to the type of photosynthetic CO2-fixation or to the water regime.The influence of light intensity was studied with mixed cultures of all four plant species, again with different water supply. There was a strong effect of light intensity on the competitive behaviour of the C3 and C4 plants under modified water conditions. The wild C3 plant Atriplex hortensis was most successful under conditions of relatively low light intensity and high water availability, while the cultivated artificial species Avena sativa showed much less differences between full-light grown and shadow plants. The C4 plant Amaranthus retroflexus is most successful under competitive conditions at high water stress in full light. The C4 grass Panicum miliaceum showed maximum shoot growth in light, but was successful under competitive conditions especially also with good water supply. The light intensity had no effect on the 13C values. — There was no indication that the soil-type as such has a distinct influence on the success of C3 or C4 plants in mixed cultures.Dedicated to Prof. Dr. M. Evenari, Jerusalem, and to Dr. K.F. Springer, Heidelberg  相似文献   

18.
T. M. De Jong 《Oecologia》1978,34(3):343-351
Summary Laboratory gas exchange measurements were conducted on four pioneering beach species from southern California. Atriplex leucophylla (Moq.) D. Dietr., a C4 species, had a photosynthetic temperature optimum substantially higher than leaf temperatures normally experienced on the beach during the primary growing season. The C3 species, Cakile maritima Scop., Ambrosia chamissonis Less. and Abronia maritima Nutt. ex Wats., had photosynthetic temperature optima close to their growth temperature and higher photosynthetic rates than the C4 species at normal field growth temperatures. Atriplex leucophylla had higher mesophyll conductances which resulted in higher water use efficiencies at all measurement temperatures. Leaf chlorophyll and protein contents were not correlated with photosynthetic rates. The possible significance of water use efficiency is discussed in relation to the characteristics of the beach habitat.  相似文献   

19.
O. Ueno  T. Takeda 《Oecologia》1992,89(2):195-203
Summary The nature of the photosynthetic pathways of Cyperaceae found in Japan were investigated on the basis of Kranz anatomy, the CO2 compensation concentration and previously reported data. Among 301 species (96% of all cyperaceous species recorded in the region), 58 species were classified as being C4 plants. These C4 species were scattered among the tribes Fimbristylideae, Lipocarpheae, Cypereae and Rhynchosporeae in the subfamily Cyperoideae. The genera Cyperus, Eleocharis and Rhynchospora included, in Japan, both C3 and C4 species within a single genus. Using these data, an analysis was made of the ecological characteristics and geographical distribution of the C3 and C4 species in Japan. Although cyperaceous species grow in markedly different environments, the majority were found in wet and aquatic areas (61%) or shaded areas, such as forest floors (20%). Most of the C3 species were also hygrophytes (58%) and forest-living species (25%), and C3 species growing in mesic and dry areas were relatively rare. The C4 species inhabited wet and aquatic (75%), mesic (13%) and dry areas (6%) and showed marked ecological characteristics with respect to soil-moisture conditions, unlike other C4 plants, although they were absent from shaded habitats. In order to determine the climatic factors that influence the relative floristic abundance of C3 and C4 members of the Cyperaceae in Japan, the ratios of number of C4 species to the total number of members of Cyperaceae (C4 percentage) in 16 representative locales were examined in terms of various climatic variables. There were strong positive correlations between the C4 percentage and temperature. Among the C3 groups of three subfamilies, there were different distributional trends for various temperature regimes. The C3 subfamily Caricoideae increased its relative contribution to the cyperaceous flora with a decrease in mean annual temperature, while the C3 subfamily Sclerioideae exhibited the opposite pattern. The C3 group of the subfamily Cyperoideae did not show any marked change in pattern along temperature gradients, unlike the two other C3 subfamilies, and seemed to be heterogeneous in terms of its response to temperature. The relationships between the C4 biochemical subtypes and ecological characteristics are also discussed.  相似文献   

20.
Summary Diurnal patterns of CO2 exchange and titratable acidity were monitored in six species of evergreen rosette plants growing in controlled environment chambers and under outdoor environmental conditions. These patterns indicated that two of the species, Yucca baccata and Y. torreyi, were constituitive CAM plants while the other species, Y. elata, Y. campestris, Nolina microcarpa and Dasylirion wheeleri, were C3 plants. The C3 species did not exhibit CAM when grown in any of several different temperature, photoperiod, and moisture regimes. Both photosynthetic pathway types appear adapted to desert environments and all species show environmentally induced changes in their photosynthetic responses consistent with desert adaptation. The results of this study do not indicate that changes in the photosynthetic pathway type are an adaptation in any of these species.  相似文献   

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