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1.
C 4 photosynthesis is a complex trait that boosts productivity in warm environments. Paradoxically, it evolved independently in numerous plant lineages, despite requiring specialised leaf anatomy. The anatomical modifications underlying C 4 evolution have previously been evaluated through interspecific comparisons, which capture numerous changes besides those needed for C 4 functionality. Here, we quantify the anatomical changes accompanying the transition between non‐C 4 and C 4 phenotypes by sampling widely across the continuum of leaf anatomical traits in the grass Alloteropsis semialata. Within this species, the only trait that is shared among and specific to C 4 individuals is an increase in vein density, driven specifically by minor vein development that yields multiple secondary effects facilitating C 4 function. For species with the necessary anatomical preconditions, developmental proliferation of veins can therefore be sufficient to produce a functional C 4 leaf anatomy, creating an evolutionary entry point to complex C 4 syndromes that can become more specialised. 相似文献
2.
C4-like plants represent the penultimate stage of evolution from C3 to C4 plants. Although Coleataenia prionitis (formerly Panicum prionitis) has been described as a C4 plant, its leaf anatomy and gas exchange traits suggest that it may be a C4-like plant. Here, we reexamined the leaf structure and biochemical and physiological traits of photosynthesis in this grass. The large vascular bundles were surrounded by two layers of bundle sheath (BS): a colorless outer BS and a chloroplast-rich inner BS. Small vascular bundles, which generally had a single BS layer with various vascular structures, also occurred throughout the mesophyll together with BS cells not associated with vascular tissue. The mesophyll cells did not show a radial arrangement typical of Kranz anatomy. These features suggest that the leaf anatomy of C. prionitis is on the evolutionary pathway to a complete C4 Kranz type. Phosphoenolpyruvate carboxylase (PEPC) and pyruvate, Pi dikinase occurred in the mesophyll and outer BS. Glycine decarboxylase was confined to the inner BS. Ribulose 1,5-bisphosphate carboxylase/oxygenase (Rubisco) accumulated in the mesophyll and both BSs. C. prionitis had biochemical traits of NADP-malic enzyme type, whereas its gas exchange traits were close to those of C4-like intermediate plants rather than C4 plants. A gas exchange study with a PEPC inhibitor suggested that Rubisco in the mesophyll could fix atmospheric CO2. These data demonstrate that C. prionitis is not a true C4 plant but should be considered as a C4-like plant. 相似文献
3.
The biochemistry and leaf anatomy of plants using C 4 photosynthesis promote the concentration of atmospheric CO 2 in leaf tissue that leads to improvements in growth and yield of C 4 plants over C 3 species in hot, dry, high light, and/or saline environments. C 4 plants like maize and sugarcane are significant food, fodder, and bioenergy crops. The C 4 photosynthetic pathway is an excellent example of convergent evolution, having evolved in multiple independent lineages of land plants from ancestors employing C 3 photosynthesis. In addition to C 3 and C 4 species, some plant lineages contain closely related C 3–C 4 intermediate species that demonstrate leaf anatomical, biochemical, and physiological characteristics between those of C 3 plants and species using C 4 photosynthesis. These groups of plants have been extremely useful in dissecting the modifications to leaf anatomy and molecular biology, which led to the evolution of C 4 photosynthesis. It is now clear that great variation exists in C 4 leaf anatomy, and diverse molecular mechanisms underlie C 4 biochemistry and physiology. However, all these different paths have led to the same destination—the expression of a C 4 CO 2 concentrating mechanism. Further identification of C 4 leaf anatomical traits and molecular biological components, and understanding how they are controlled and assembled will not only allow for additional insights into evolutionary convergence, but also contribute to sustainable food and bioenergy production strategies. 相似文献
4.
Plants using the C 4 photosynthetic pathway have greater water use efficiency (WUE) than C 3 plants of similar ecological function. Consequently, for equivalent rates of photosynthesis in identical climates, C 4 plants do not need to acquire and transport as much water as C 3 species. Because the structure of xylem tissue reflects hydraulic demand by the leaf canopy, a reduction in water transport requirements due to C 4 photosynthesis should affect the evolution of xylem characteristics in C 4 plants. In a comparison of stem hydraulic conductivity and vascular anatomy between eight C 3 and eight C 4 herbaceous species, C 4 plants had lower hydraulic conductivity per unit leaf area ( KL) than C 3 species of similar life form. When averages from all the species were pooled together, the mean KL for the C 4 species was 1.60 × 10 ?4 kg m ?1 s ?1 MPa ?1, which was only one‐third of the mean KL of 4.65 × 10 ?4 kg m ?1 s ?1 MPa ?1 determined for the C 3 species. The differences in KL between C 3 and C 4 species corresponded to the two‐ to three‐fold differences in WUE observed between C 3 and C 4 plants. In the C 4 species from arid regions, the difference in KL was associated with a lower hydraulic conductivity per xylem area, smaller and shorter vessels, and less vulnerable xylem to cavitation, indicating the C 4 species had evolved safer xylem than the C 3 species. In the plants from resource‐rich areas, such as the C 4 weed Amaranthus retroflexus, hydraulic conductivity per xylem area and xylem anatomy were similar to that of the C 3 species, but the C 4 plants had greater leaf area per xylem area. The results indicate the WUE advantage of C 4 photosynthesis allows for greater flexibility in hydraulic design and potential fitness. In resource‐rich environments in which competition is high, an existing hydraulic design can support greater leaf area, allowing for higher carbon gain, growth and competitive potential. In arid regions, C 4 plants evolved safer xylem, which can increase survival and performance during drought events. 相似文献
5.
- Leaf venations have elements with relatively lower elasticity than other leaf tissue components, which are thought to contribute to leaf biomechanics. A better mechanistic understanding of relationships between vein traits and leaf mechanical properties is essential for ecologically relevant interpretation of leaf structural variations.
- We investigated 13 major (first to third order) and minor (>third order) vein traits, six leaf mechanical properties and other structural traits across 58 woody species from a subtropical forest to elucidate how vein traits contribute to leaf biomechanics.
- Across species, vein dry mass density (ρv), total vein dry mass per leaf area (VMA) and minor vein diameter (VDmin), but not the lower‐order vein density (VLA1?2), were positively correlated with leaf force to punch (Fp) and force to tear (Ft). Structural equation models showed that ρv and VDmin not only contribute to leaf mechanical properties directly (direct pathway), but also had impacts on leaf biomechanics by influencing leaf thickness and leaf dry mass per area (indirect pathway).
- Our study demonstrated that vein dry mass density and minor vein diameter are the key vein properties for leaf biomechanics. We also suggest that the mechanical characteristics of venations are potential factors influencing leaf mechanical resistance, structure and leaf economics spectrum.
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6.
Photosynthesis underpins the viability of most ecosystems, with C 4 plants that exhibit ‘Kranz’ anatomy being the most efficient primary producers. Kranz anatomy is characterized by closely spaced veins that are encircled by two morphologically distinct photosynthetic cell types. Although Kranz anatomy evolved multiple times, the underlying genetic mechanisms remain largely elusive, with only the maize scarecrow gene so far implicated in Kranz patterning. To provide a broader insight into the regulation of Kranz differentiation, we performed a genome‐wide comparative analysis of developmental trajectories in Kranz (foliar leaf blade) and non‐Kranz (husk leaf sheath) leaves of the C 4 plant maize. Using profile classification of gene expression in early leaf primordia, we identified cohorts of genes associated with procambium initiation and vascular patterning. In addition, we used supervised classification criteria inferred from anatomical and developmental analyses of five developmental stages to identify candidate regulators of cell‐type specification. Our analysis supports the suggestion that Kranz anatomy is patterned, at least in part, by a SCARECROW/SHORTROOT regulatory network, and suggests likely components of that network. Furthermore, the data imply a role for additional pathways in the development of Kranz leaves. 相似文献
7.
Photosynthetic pathway characteristics were studied in nine species of Heliotropium ( sensu lato, including Euploca), using assessments of leaf anatomy and ultrastructure, activities of PEP carboxylase and C 4 acid decarboxylases, and immunolocalization of ribulose 1·5‐bisphosphate carboxylase/oxygenase (Rubisco) and the P‐subunit of glycine decarboxylase (GDC). Heliotropium europaeum, Heliotropium calcicola and Heliotropium tenellum are C 3 plants, while Heliotropium texanum and Heliotropium polyphyllum are C 4 species. Heliotropium procumbens and Heliotropium karwinskyi are functionally C 3, but exhibit ‘proto‐Kranz’ anatomy where bundle sheath (BS) cells are enlarged and mitochondria primarily occur along the centripetal (inner) wall of the BS cells; GDC is present throughout the leaf. Heliotropium convolvulaceum and Heliotropium greggii are C 3–C 4 intermediates, with Kranz‐like enlargement of the BS cells, localization of mitochondria along the inner BS wall and a loss of GDC in the mesophyll (M) tissue. These C 3–C 4 species of Heliotropium probably shuttle photorespiratory glycine from the M to the BS tissue for decarboxylation. Heliotropium represents an important new model for studying C 4 evolution. Where existing models such as Flaveria emphasize diversification of C 3–C 4 intermediates, Heliotropium has numerous C 3 species expressing proto‐Kranz traits that could represent a critical initial phase in the evolutionary origin of C 4 photosynthesis. 相似文献
8.
Rapid metabolite diffusion across the mesophyll (M) and bundle sheath (BS) cell interface in C 4 leaves is a key requirement for C 4 photosynthesis and occurs via plasmodesmata (PD). Here, we investigated how growth irradiance affects PD density between M and BS cells and between M cells in two C 4 species using our PD quantification method, which combines three‐dimensional laser confocal fluorescence microscopy and scanning electron microscopy. The response of leaf anatomy and physiology of NADP‐ME species, Setaria viridis and Zea mays to growth under different irradiances, low light (100 μmol m ?2 s ?1), and high light (1,000 μmol m ?2 s ?1), was observed both at seedling and established growth stages. We found that the effect of growth irradiance on C 4 leaf PD density depended on plant age and species. The high light treatment resulted in two to four‐fold greater PD density per unit leaf area than at low light, due to greater area of PD clusters and greater PD size in high light plants. These results along with our finding that the effect of light on M‐BS PD density was not tightly linked to photosynthetic capacity suggest a complex mechanism underlying the dynamic response of C 4 leaf PD formation to growth irradiance. 相似文献
9.
C 4 photosynthesis is thought to be an adaptation to warm environments, involving complex changes in the expression of genes governing photosynthesis, intermediary metabolism, and leaf anatomy and histology. Such complexity should be difficult to evolve, yet the pathway has arisen multiple times in the history of the flowering plants and at least four times in the grass family alone. We have used immunolocalization techniques to compare photosynthetic gene expression across all four origins, to determine which genetic changes occur in parallel and which are unique to a particular lineage. The only gene expression patterns common to all origins of the pathway are up-regulation of PEP carboxylase and down-regulation of RuBisCO in mesophyll cells. Both NAD-malic enzyme and NADP-malic enzyme are expressed in bundle sheaths. Expression patterns of light-harvesting chlorophyll a/b binding proteins and pyruvate orthophosphate dikinase appear to be lineage specific, and may be localized to bundle sheaths or to mesophyll or expressed throughout the photosynthetic tissue of the leaf. We suggest that future studies of parallel origin of the C 4 pathway concentrate on regulation of the two carboxylases, as well as the increased density of vascular tissue, which is the only histological characteristic common to all origins of the pathway. 相似文献
10.
The species Arundinella hirta L. posseses a striking variation of the leaf anatomy that is characteristic of C 4 grasses. In addition to a sheath of large, bright green cells around the vascular bundles, there are strands of large parenchyma cells which appear identical to the bundle sheath cells and which run parallel to the vascular bundles, but which are not associated with any vascular tissue. This species may be useful for studying the cellular compartmentalization associated with the C 4 pathway and should provide interesting material for determining the role of translocation in the functioning of the C 4 system. 相似文献
11.
The Chenopodiaceae is one of the families including C4 species among eudicots. In this family, the genus Chenopodium is considered to include only C3 species. However, we report here a transition from C3 photosynthesis to proto-Kranz to C3–C4 intermediate type in Chenopodium. We investigated leaf anatomical and photosynthetic traits of 15 species, of which 8 species showed non-Kranz anatomy and a CO2 compensation point (Γ) typical of C3 plants. However, 5 species showed proto-Kranz anatomy and a C3-like Γ, whereas C. strictum showed leaf anatomy and a Γ typical of C3–C4 intermediates. Chenopodium album accessions examined included both proto-Kranz and C3–C4 intermediate types, depending on locality. Glycine decarboxylase, a key photorespiratory enzyme that is involved in the decarboxylation of glycine, was located predominantly in the mesophyll (M) cells of C3 species, in both M and bundle-sheath (BS) cells in proto-Kranz species, and exclusively in BS cells in C3–C4 intermediate species. The M/BS tissue area ratio, number of chloroplasts and mitochondria per BS cell, distribution of these organelles to the centripetal region of BS cells, the degree of inner positioning (vacuolar side of chloroplasts) of mitochondria in M cells, and the size of BS mitochondria also changed with the change in glycine decarboxylase localization. All Chenopodium species examined were C3-like regarding activities and amounts of C3 and C4 photosynthetic enzymes and δ13C values, suggesting that these species perform photosynthesis without contribution of the C4 cycle. This study demonstrates that Chenopodium is not a C3 genus and is valuable for studying evolution of C3–C4 intermediates. 相似文献
12.
The non-graminaceous wild flora of Hungary was screened for C 4 plants by using the stable carbon isotope ratio, the leaf anatomy and the photosynthetic carbon dioxide compensation concentration
to determine the photosynthetic pathway type. On the whole, 31 C 4 species (native or naturalized) were found in the Amaranthaceae, Chenopodiaceae, Cyperaceae, Euphorbiaceae, Portulacaceae and Zygophyllaceae families. Together with the 26 C 4 grass species ( Poaceae) reported earlier (Kalapos 1991), a total of 57 wild C 4 species occur in Hungary, which forms 2.6 % of the country's angiosperm flora. This figure is somewhat higher than what was
expected on climatic grounds, a fact probably due to certain edaphic conditions favouring C 4 plant growth. In Hungary, the C 4 species are predominantly annuals growing in open habitats such as dry grasslands, inland saline areas, temporarily exposed
riverbeds and disturbed sites. In comparison with C 3 plants, the C 4 species have higher temperature and light preferences, and their phenology lags behind that of the C 3 plants. These differences might account for C 4 plants being usually excluded from productive biotopes in Hungary, where the C 3 canopy may become closed during the growing season before C 4 plants can start their ontogenetic development. Ecological properties of C 3 and C 4 plants differ considerably in the Cyperaceae, but much less in the Chenopodianceae family. Among C 4 annuals naturalized aliens are common, most of which colonized hungary in the last two centuries. Increasing preponderance
of
C 4 plants is anticipated in the future as a consequence of possible climate changes and the ever increasing human impact on
terrestrial vegetation.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
15.
Xylem vulnerability to cavitation and hydraulic efficiency are directly linked to fine‐scale bordered pit features in water‐conducting cells of vascular plants. However, it is unclear how pit characteristics influence water transport and carbon economy in tropical species. The primary aim of this study was to evaluate functional implications of changes in pit characteristics for water relations and photosynthetic traits in tropical Ficus species with different growth forms (i.e. hemiepiphytic and non‐hemiepiphytic) grown under common conditions. Intervessel pit characteristics were measured using scanning electron microscopy in five hemiepiphytic and five non‐hemiepiphytic Ficus species to determine whether these traits were related to hydraulics, leaf photosynthesis, stomatal conductance and wood density. Ficus species varied greatly in intervessel pit structure, hydraulic conductivity and leaf physiology, and clear differences were observed between the two growth forms. The area and diameter of pit aperture were negatively correlated with sapwood‐specific hydraulic conductivity, mass‐based net assimilation rate, stomatal conductance ( gs), intercellular CO 2 concentration ( Ci) and the petiole vessel lumen diameters ( Dv), but positively correlated with wood density. Pit morphology was only negatively correlated with sapwood‐ and leaf‐specific hydraulic conductivity and Dv. Pit density was positively correlated with gs, Ci and Dv, but negatively with intrinsic leaf water‐use efficiency. Pit and pit aperture shape were not significantly correlated with any of the physiological traits. These findings indicate a significant role of pit characteristics in xylem water transport, carbon assimilation and ecophysiological adaptation of Ficus species in tropical rain forests. 相似文献
16.
Background and AimsCrassulacean acid metabolism (CAM) is often considered to be a complex trait, requiring orchestration of leaf anatomy and physiology for optimal performance. However, the observation of trait correlations is based largely on comparisons between C 3 and strong CAM species, resulting in a lack of understanding as to how such traits evolve and the level of intraspecific variability for CAM and associated traits. MethodsTo understand intraspecific variation for traits underlying CAM and how these traits might assemble over evolutionary time, we conducted detailed time course physiological screens and measured aspects of leaf anatomy in 24 genotypes of a C 3+CAM hybrid species, Yucca gloriosa (Asparagaceae). Comparisons were made to Y. gloriosa’s progenitor species, Y. filamentosa (C 3) and Y. aloifolia (CAM). Key ResultsBased on gas exchange and measurement of leaf acids, Y. gloriosa appears to use both C 3 and CAM, and varies across genotypes in the degree to which CAM can be upregulated under drought stress. While correlations between leaf anatomy and physiology exist when testing across all three Yucca species, such correlations break down at the species level in Y. gloriosa.ConclusionsThe variation in CAM upregulation in Y. gloriosa is a result of its relatively recent hybrid origin. The lack of trait correlations between anatomy and physiology within Y. gloriosa indicate that the evolution of CAM, at least initially, can proceed through a wide combination of anatomical traits, and more favourable combinations are eventually selected for in strong CAM plants. 相似文献
17.
The leafless amphibious sedge Eleocharis vivipara develops culms with C 4 traits and Kranz anatomy under terrestrial conditions, but develops culms with C 3 traits and non-Kranz anatomy under submerged conditions. The culms of the terrestrial form have high C 4 enzyme activities, while those of the submerged form have decreased C 4 enzyme activities. The culms accumulate ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco) in the mesophyll cells
(MC) and the bundle sheath cells. The Rubisco in the MC may be responsible for the operation of the C 3 pathway in the submerged form. To verify the presence of the C 3 cycle in the MC, we examined the effects of 3,3-dichloro-2-(dihydroxyphosphinoylmethyl) -propenoate (DCDP), an inhibitor
of phospho enolpyruvate carboxylase (PEPC), on photosynthesis in culms of the terrestrial forms of E. vivipara and related amphibious species, E. baldwinii and E. retroflexa ssp. chaetaria. When 1 mM DCDP was fed via the transpiration stream to excised leaves, photosynthesis was inhibited completely in Fimbristylis dichotoma (C 4 control), but by only 20% in potato (C 3 control). In the terrestrial Eleocharis plants, the degree of inhibition of photosynthesis by DCDP was intermediate between those of the C 4 and C 3 plants, at 58–81%. These results suggest that photosynthesis under DCDP treatment in the terrestrial Eleocharis plants is due mainly to fixation of atmospheric CO 2 by Rubisco and probably the C 3 cycle in the MC. These features are reminiscent of those in C 4-like plants. Differential effects of DCDP on photosynthesis of the 3 Eleocharis species are discussed in relation to differences in the degree of Rubisco accumulation and C 3 activity in the MC.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
18.
Background and AimsLeaf venation in many C 4 species is characterized by high vein density, essential in facilitating rapid intercellular diffusion of C 4 photosynthetic metabolites between different tissues (mesophyll, bundle sheath). Greater vein density has been hypothesized to be an early step in C 4 photosynthesis evolution. Development of C 4 vein patterning is thought to occur from either accelerated or prolonged procambium formation, relative to ground tissue development. MethodsCleared and sectioned tissues of phylogenetically basal C 3 Flaveria robusta and more derived C 4 Flaveria bidentis were compared for vein pattern in mature leaves and vein pattern formation in developing leaves. Key ResultsIn mature leaves, major vein density did not differ between C 3 and C 4 Flaveria species, whereas minor veins were denser in C 4 species than in C 3 species. The developmental study showed that both major and minor vein patterning in leaves of C 3 and C 4 species were initiated at comparable stages (based on leaf length). An additional vein order in the C 4 species was observed during initiation of the higher order minor veins compared with the C 3 species. In the two species, expansion of bundle sheath and mesophyll cells occurred after vein pattern was complete and xylem differentiation was continuous in minor veins. In addition, mesophyll cells ceased dividing sooner and enlarged less in C 4 species than in C 3 species. ConclusionsLeaf vein pattern characteristic to C 4 Flaveria was achieved primarily through accelerated and earlier offset of higher order vein formation, rather than other modifications in the timing of vein pattern formation, as compared with C 3 species. Earlier cessation of mesophyll cell division and reduced expansion also contributed to greater vein density in the C 4 species. The relatively late expansion of bundle sheath and mesophyll cells shows that vein patterning precedes ground tissue development in C 4 species.Key words: Bundle sheath, C4 photosynthesis evolution, Flaveria, heterochrony, leaf development, mesophyll, vein density, vein pattern formation 相似文献
19.
Summary The leaf anatomy was investigated with respect to the arrangement of cells involved in photosynthesis. The full-grown leaf has one vascular bundle consisting mainly of phioem cells. In similarity to terrestrial C 4 plants the vascular bundle is surrounded by mesophyll bundle sheath cells. However, in contrast to C 4 plants, these cells do not contain chlorophyll or starch in Ceratophyllum. The early products in photosynthesis (10 seconds 14C labelling) were analyzed. Although no complete separation of all radioactivity in the plant extracts was reached, it was clear that malate was the major labelled component, indicating C 4 activity in the plants. No light saturation could be proven in Ceratophyllum in several stages of post-dormancy in a statistically significant way, although a tendency to light saturation was observed at intensities higher than 36 Wm –2. The photosynthetic activity was only slightly depressed by enhancement of the O 2 concentration in the medium. 相似文献
20.
Question: Are trait differences between grasses along a gradient related to climatic variables and/or photosynthetic pathway? Location: Temperate grassland areas of South and North America. Methods: In a common garden experiment, we cultivated C 3 and C 4 grasses from grasslands under different climatic conditions, and we measured a set of 12 plant traits related to size and resource capture and utilization. We described (1) interspecific plant trait differences along a climatic gradient defined by the precipitation and temperature at the location where each species is dominant and (2) the association between those plant trait differences and the photosynthetic pathway of the species. Results: Trait differences between grasses were related to the precipitation at the area where each species is dominant, and to the photosynthetic pathway of the species. Leaf length, leaf width, plant height, leaf area per tiller, specific leaf area, leaf δ 13C ratio, and nitrogen resorption efficiency increased while leaf dry matter content and nitrogen concentration in senesced leaves decreased as precipitation increased. A proportion of these changes along the gradient was related to the photosynthetic pathway because dominant grass species in cold areas with low precipitation are mainly C 3 and those from warm and wet areas are C 4. Conclusions: A previous worldwide analysis showed that traits of graminoid species measured in situ changed slightly along climatic gradients (< 10% variance explained). In contrast, under a common environment we observed that (1) grass traits changed strongly along a climatic gradient (30‐85% variance explained) and, (2) a proportion of those changes were related to the association between photosynthetic pathway of the species and precipitation. 相似文献
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