Photosynthesis pathways,ecological characteristics,and the geographical distribution of the Cyperaceae in Japan

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.     

Distribution of South African C3 and C4 species of Cyperaceae in relation to climate and phylogeny

Abstract In this study the contribution of climatic factors and phylogenetic relationships affecting the geographical distribution of C₃ and C₄ genera of the Cyperaceae in South Africa was investigated. The δ¹³C values of herbarium specimens of 68 southern African species from 22 genera and eight tribes were used to assign the species to either the C₃ or C₄ photosynthetic pathway. Geographical distribution data for the Cyperaceae were used to investigate relationships between climatic factors and the number of species and proportional abundance of C₄ species per region. The number of Cyperaceae species per 2° × 2° square across South Africa varied from less than five in the north‐western regions to more than 15 in the south‐western and north‐eastern regions of South Africa where rainfall exceeds 800 mm y^‐1. Of the 68 species investigated, 28 had C₄ photosynthesis and these were scattered among nine genera of four tribes (Cypereae, Scirpeae, Abildgaardieae and Rhyncosporeae). The proportional abundance of C₄ species ranged from 14% in the winter rainfall regions of the south‐west of South Africa to 67% in the summer rainfall areas of the north‐east. The geographical distribution of species was related to their phylogenetic position such that the distributions of C₃ and C₄ species in Cypereae, Scirpeae and Schoeneae was quite distinct. Linear regression analysis showed that the transition temperatures (equal C₃ and C₄ species numbers) for the Cyperaceae were different to those obtained for the Poaceae from the same region. No strong relationships were found between the proportional abundance of C₄ species and other climate factors such as altitude and rainfall. Our analysis of the current geographical distribution of C₄ Cyperaceae in southern Africa in a phylogenetic context suggests that the ecological advantages conferred by the C₄ pathway differ amongst the different plant groups.     

C4 acid decarboxylation type in Eragrostis (Poaceae) patterns of variation in chloroplast position, ultrastructure and geographical distribution

Abstract We investigated the activity of C₄ acid decarboxylating enzymes, the PCR (‘photosynthetic carbon reduction’, or ‘Kranz’) bundle sheath anatomy and ultrastructure, and the geographical distribution of Australian species of the C₄ grass genus Eragrostis. Species had either the even sheath outline and centripetally located PCR cell chloroplasts characteristic of NAD-malic enzyme (NAD-ME) species (29 spp.), the uneven sheath outline and centrifugal PCR cell chloroplasts characteristic of PEP carboxykinase (PCK) species (28 spp.), or were intermediate between these types (7 spp.). The suberized lamella was present in PCR cell walls of species with PCK-like and intermediate anatomy, and absent from those of species with NAD-ME-like anatomy. Biochemical determination of C₄ type for 11 species, however, revealed only NAD-ME activity, irrespective of anatomical type; no PCK activity was detected. PCK-like species arc most numerous in northern, high rainfall, tropical Australia and also predominate in relatively humid coastal and subcoastal areas. NAD-ME-like species are numerically and proportionally dominant where rainfall is < 30 cm year^?1. Overall, as many species occur in high as in low rainfall areas. Results are discussed in relation to previously established anatomical/ultrastructural/geographical/biochemical correlations and to Infrageneric taxonomy.     

Leaf ultrastructure of C4 species possessing different Kranz anatomical types in the cyperaceae

The leaf ultrastructure of NADP-malic enzyme type C₄ species possessing different anatomical features in the Cyperaceae was examined: types were the Rhynchosporoid type, a normal Kranz type in which mesophyll cells are adjacent to Kranz cells, and Fimbristyloid and Chlorocyperoid types, unusual Kranz types in which nonchlorophyllous mestome sheath intervenes between the two types of green cells. They show structural characteristics basically similar to the NADP-malic enzyme group of C₄ grasses, that is, centrifugally located chloroplasts with reduced grana and no increase of mitochondrial frequency in the Kranz cells. However, the Kranz cell chloroplasts of the Fimbristyloid and Chlorocyperoid types exhibit convoluted thylakoid systems and a trend of extensive development of peripheral reticulum, although those of the Rhynchosporoid type do not possess such particular membrane systems. The suberized lamella, probably a barrier for CO₂ diffusion, is present in the Kranz cell walls of the Rhynchosporoid type and in the mestome sheath cell walls of the other two types, and tightly surrounds the Kranz cells (sheaths) that are the sites of the decarboxylation of C₄ acids. These ultrastructural features are discussed in relation to C₄ photosynthetic function.     

Anatomical features of species of Cyperaceae from northeastern Brazil

Seventy-three species from 17 genera of Cyperaceae were studied with the aim of identifying and confirming those species with Kranz anatomy. Among the species studied, 36 exhibited Kranz anatomy; 37 did not. Of the four types of Kranz anatomy recognized in Cyperaceae, three were encountered: the chlorocyperoid type in the genera Cyperus, Kyllinga, Lipocarpha, Pycreus, and Remirea; the fimbristyloid type in Abildgaardia, Bulbostylis, and Fimbristylis; and the rhynchosporoid type in Rhynchospora. Non-Kranz anatomy was confirmed in species of the following genera: Becquerelia, Calyptrocarya, Cyperus, Diplacrum, Eleocharis, Fuirena, Hypolytrum, Pleurostachys, Rhynchospora, and Scleria. The anatomical data obtained corroborate earlier studies of species of Cyperaceae as to the presence of Kranz anatomy and the anatomical types in several species and the “Kranzkette” pattern in Cyperus ligularis and Cyperus pohlli.     

The occurrence of C4 species in the genusRhynchospora and its significance in kranz anatomy of the cyperaceae

Rhynchospora rubra was found to have a low CO₂ compensation point, high δ¹³C value, Kranz leaf anatomy, starch present in the bundle sheath cells and narrow interveinal distance. These observations suggest thatR. rubra is a C₄ plant. A further anatomical survey revealed seven otherRhynchospora species presumably having the C₄ photosynthetic pathway. In the family Cypraceae C₄ plants therefore occur in the tribe Rhynchosporeae as well as in the Scirpeae and Cypereae. The C₄ species ofRhynchospora have a normal Kranz type of leaf anatomy, although the C₄ species ofCyperus andFimbristylis presently known have an abnormal one in which the mestome sheath without chloroplasts is interposed between the Kranz tissue and the rest of the chlorenchyma. Thus inRhynchospora the Kranz tissue is in direct contact with the rest of the chlorenchyma, and it is suggested that the Kranz tissue may be homologous with the mestome sheath.     

Distribution and evolution of C4 syndrome inRhynchospora (Rhynchosporeae-Cyperaceae)

In order to elucidate the evolution of C₄ syndrome, the taxonomic relationships, leaf anatomy, and ecological and global distribution of C₃ and C₄ species in the genusRhynchospora were investigated. The anatomical observation for 181 species revealed that 26 C₄ species occurred within theCapitatae group of the subgenusHaplostyleae, a natural group showing highly advanced morphological characteristics, together with several C₃ species. In spite of there being rather few C₄ species, they possessed two kinds of Kranz anatomical structure differing from each other in the location of Kranz cells. Some C₃ species ofCapitatae showed radial arrangement in mesophyll cells surrounding vascular bundles, which is distinguished from typical non-Kranz anatomy. The C₄ species extended their ecological ranges from wet habitats to dry savanna grasslands, while the C₃ species showed the best development in wet habitats. The C₃ species were widespread from tropical to temperate regions with partial range extension into subarctic regions of both hemispheres, showing conspicuously high concentration of species in the New World, but being absent from arid climatic regions. The C₄ species were distributed mostly in tropics and subtropics, showing two separate distributional centers in South and Central America and in Tropical Asia and Australia. The range of C₄ species was nearly completely included in the C₃ range. In conclusion, it seems that inRhynchospora the C₄ syndrome evolved relatively recently, and arose in at least two separate phylogenetic trends in the tropics and the subtropics, more probably in the Neotropics.     

Structural features of NAD-malic enzyme type C4 Eleocharis: An additional report of C4 acid decarboxylation types of the cyperaceae

The genusEleocharis, a blade-less sedge group, has been very recently recorded to include NAD-malic enzyme type C₄ species. The ultrastructural features of culms of two C₄ representatives in the genus were examined in relation to the C₄ acid decarboxylation type. They possessed non-chlorophyllous mestome sheath cells between mesophyll cells and Kranz cells, and were confirmed biochemically to be NAD-malic enzyme type. The oval or lenticular chloroplasts with well-developed grana are scattered in the Kranz cells with abundant large mitochondria, and do not show such centripetal position as is known in the “classical NAD-malic enzyme type”. The suberized lamellae occur in the mestome sheath cells internally surrounding the Kranz sheath and may contribute to maintaining high CO₂ concentration in the Kranz cells. These new structural features of the NAD-malic enzyme type found inEleocharis are added to the structural and functional relationships of the C₄ types in the Cyperaceae reported previously     

THE KRANZ SYNDROME IN THE GRAMINEAE AS INDICATED BY CARBON ISOTOPIC RATIOS

The Kranz syndrome, as indicated by relatively high ¹³C/¹²C ratios is characteristic of 16 ½ tribes and about ½ of the species of the Gramineae. Data are given for 198 species from 129 genera and 47 tribes, and from at least 6 subfamilies of grasses. This information is correlated with data from the literature on anatomical and physiological characters of both Kranz and non-Kranz grasses. All subfamilies, tribes, and genera seem to be uniformly all Kranz or non-Kranz except the subfamily Panicoideae and the genus Panicum which have both Kranz and non-Kranz species represented.     

Comparison of methods for rooting phylogenetic trees: A case study using Orcuttieae (Poaceae: Chloridoideae)

DNA sequence data (cpDNA trnL intron and nrDNA ITS1 and ITS2) were analyzed to identify relationships within Orcuttieae, a small tribe of endangered grasses endemic to vernal pools in California and Baja California. The tribe includes three genera: Orcuttia, Tuctoria, and Neostapfia. All three genera carry out C₄ photosynthesis but aquatic taxa of Orcuttia lack Kranz anatomy. The unusual habitat preference of the tribe is coupled with the atypical development of C₄ photosynthesis without Kranz anatomy. Furthermore, the tribe has no known close relatives and has been noted to be phylogenetically isolated within the subfamily Chloridoideae. In this study we examine the problem of inferring the root of the tribe in the absence of an identified outgroup, analyze the phylogenetic relationships of the constituent taxa, and evaluate the evolutionary development of C₄ photosynthesis. We compare four methods for inferring the root of the tree: (1) the outgroup method, (2) midpoint rooting, the imposition of a molecular clock for both (3) maximum likelihood (ML) and (4) Bayesian analysis. We examine the consequences of each method for the inferred phylogenetic relationships. Three of the methods (outgroup rooting and the ML and Bayesian molecular clock analyses) suggest that the root of Orcuttieae is between Neostapfia and the Tuctoria/Orcuttia lineage, while midpoint rooting gives a different root. The Bayesian method additionally provides information about probabilities associated with other possible root locations. Assuming that the true root of Orcuttieae is between Neostapfia and the Tuctoria/Orcuttia lineage, our data indicate Neostapfia and Orcuttia are both monophyletic, while Tuctoria is paraphyletic (with no synapomorphies in either dataset) and forming a grade between the other two genera and needs taxonomic revision. Our data support the hypothesis that Orcuttieae was derived from a terrestrial ancestor and evolved specializations to an aquatic environment, including C₄ photosynthesis without Kranz anatomy.     

Diversity in forms of C4 in the genus Cleome (Cleomaceae)

Background and Aims

Cleomaceae is one of 19 angiosperm families in which C₄ photosynthesis has been reported. The aim of the study was to determine the type, and diversity, of structural and functional forms of C₄ in genus Cleome.

Methods

Plants of Cleome species were grown from seeds, and leaves were subjected to carbon isotope analysis, light and scanning electron microscopy, western blot analysis of proteins, and in situ immunolocalization for ribulose bisphosphate carboxylase oxygenase (Rubisco) and phosphoenolpyruvate carboxylase (PEPC).

Key Results

Three species with C₄-type carbon isotope values occurring in separate lineages in the genus (Cleome angustifolia, C. gynandra and C. oxalidea) were shown to have features of C₄ photosynthesis in leaves and cotyledons. Immunolocalization studies show that PEPC is localized in mesophyll (M) cells and Rubisco is selectively localized in bundle sheath (BS) cells in leaves and cotyledons, characteristic of species with Kranz anatomy. Analyses of leaves for key photosynthetic enzymes show they have high expression of markers for the C₄ cycle (compared with the C₃–C₄ intermediate C. paradoxa and the C₃ species C. africana). All three are biochemically NAD-malic enzyme sub-type, with higher granal development in BS than in M chloroplasts, characteristic of this biochemical sub-type. Cleome gynandra and C. oxalidea have atriplicoid-type Kranz anatomy with multiple simple Kranz units around individual veins. However, C. angustifolia anatomy is represented by a double layer of concentric chlorenchyma forming a single compound Kranz unit by surrounding all the vascular bundles and water storage cells.

Conclusions

NAD-malic enzyme-type C₄ photosynthesis evolved multiple times in the family Cleomaceae, twice with atriplicoid-type anatomy in compound leaves having flat, broad leaflets in the pantropical species C. gynandra and the Australian species C. oxalidea, and once by forming a single Kranz unit in compound leaves with semi-terete leaflets in the African species C. angustifolia. The leaf morphology of C. angustifolia, which is similar to that of the sister, C₃–C₄ intermediate African species C. paradoxa, suggests adaptation of this lineage to arid environments, which is supported by biogeographical information.     

Occurrence of C3 and C4 photosynthesis in cotyledons and leaves of Salsola species (Chenopodiaceae)

Most species of the genus Salsola (Chenopodiaceae) that have been examined exhibit C₄ photosynthesis in leaves. Four Salsola species from Central Asia were investigated in this study to determine the structural and functional relationships in photosynthesis of cotyledons compared to leaves, using anatomical (Kranz versus non-Kranz anatomy, chloroplast ultrastructure) and biochemical (activities of photosynthetic enzymes of the C₃ and C₄ pathways, ¹⁴C labeling of primary photosynthesis products and ¹³C/¹²C carbon isotope fractionation) criteria. The species included S. paulsenii from section Salsola, S. richteri from section Coccosalsola, S. laricina from section Caroxylon, and S. gemmascens from section Malpigipila. The results show that all four species have a C₄ type of photosynthesis in leaves with a Salsoloid type Kranz anatomy, whereas both C₃ and C₄ types of photosynthesis were found in cotyledons. S. paulsenii and S. richteri have NADP- (NADP-ME) C₄ type biochemistry with Salsoloid Kranz anatomy in both leaves and cotyledons. In S. laricina, both cotyledons and leaves have NAD-malic enzyme (NAD-ME) C₄ type photosynthesis; however, while the leaves have Salsoloid type Kranz anatomy, cotyledons have Atriplicoid type Kranz anatomy. In S. gemmascens, cotyledons exhibit C₃ type photosynthesis, while leaves perform NAD-ME type photosynthesis. Since the four species studied belong to different Salsola sections, this suggests that differences in photosynthetic types of leaves and cotyledons may be used as a basis or studies of the origin and evolution of C₄ photosynthesis in the family Chenopodiaceae.This revised version was published online in October 2005 with corrections to the Cover Date.     

Does Bienertia cycloptera with the single-cell system of C(4) photosynthesis exhibit a seasonal pattern of delta (13)C values in nature similar to co-existing C (4) Chenopodiaceae having the dual-cell (Kranz) system?

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.     

Distribution of C3 and C4 grasses at different altitudes in a temperate arid region of Argentina

Summary The distribution of native C₃ and C₄ grasses in a temperate arid region of Mendoza, Argentina, was studied in six areas at different altitudes. C₄ species predominate at low elevations in both relative species abundance and plant cover. At high elevations C₃ species are dominant in cover and composition. At medium altitudes (1100–1600 m) grass species composition is balanced but plant cover of C₃ species is greater. Of 31 genera in the whole area, 19 were C₄. Only the genera Stipa (C₃) and Aristida (C₄) were present in all the six areas surveyed. The pattern of grass distribution shows high correlation with evapotranspiration and temperature parameters, but low correlation with rainfall. The relation between grass distribution and different climatic parameters is discussed.     

Genome‐wide transcript analysis of early maize leaf development reveals gene cohorts associated with the differentiation of C4 Kranz anatomy

Photosynthesis underpins the viability of most ecosystems, with C₄ 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 C₄ 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.     

Variations in the Leaf Anatomy among some C4 Panicum Species

The Dichotomiflora group of Panicum contains NAD-malic enzyme(ME) species with centrifugal chloroplasts in Kranz cells, NAD-ME(F)species as well as NAD-ME species with centripetal chloroplastsin Kranz cells, NAD-ME (P) species. Many attributes of leafanatomy of 22 C₄ Panicum species were investigated to identifydifferences among four different C₄ subtypes, i.e. NADP-ME,NAD-ME(F), NAD-ME(P) and PEP-CK species grouped by the C₄-aciddecarboxylating enzymes and chloroplast location in Kranz cellsin combination. Differences were found in the number of Kranzcells surrounding a large vein, and the number surrounding asmall vein, the interveinal distances, the proportion of leafcross sectional area occupied by epidermis plus sclerenchyma,by mesophyll cells, by Kranz cells, and by vascular bundles.There were also differences in the ratios of the area of thedifferent cell types. The number of the characters significantlydifferent between a respective pair of C₄ subtypes was the largestbetween NAD-ME(F) and NAD-ME(P) species. In principal componentanalysis applied to 11 leaf anatomical characters, the differentC₄ subtypes clustered into small groups, although the rangeof variations of PEP-CK species and those of NAD-ME(F) speciesoverlapped. The results were discussed in relation to taxonomyand ecological adaptation of Panicum species in the differentC₄ subtypes. C₄ photosynthesis, NADP-malic enzyme, NAD-malic enzyme, Phosphoenolpyruvate carboxykinase, C₄ leaf anatomy, Panicum, Kranz, Dichotomiflora group     

C4 plants in the vegetation of Mongolia: their natural occurrence and geographical distribution in relation to climate

The natural geographical occurrence, carbon assimilation, and structural and biochemical diversity of species with C₄ photosynthesis in the vegetation of Mongolia was studied. The Mongolian flora was screened for C₄ plants by using ¹³C/¹²C isotope fractionation, determining the early products of ¹⁴CO₂ fixation, microscopy of leaf mesophyll cell anatomy, and from reported literature data. Eighty C₄ species were found among eight families: Amaranthaceae, Chenopodiaceae, Euphorbiaceae, Molluginaceae, Poaceae, Polygonaceae, Portulacaceae and Zygophyllaceae. Most of the C4 species were in three families: Chenopodiceae (41 species), Poaceae (25 species) and Polygonaceae, genus Calligonum (6 species). Some new C₄ species in Chenopodiaceae, Poaceae and Polygonaceae were detected. C₄ Chenopodiaceae species make up 45% of the total chenopods and are very important ecologically in saline areas and in cold arid deserts. C₄ grasses make up about 10% of the total Poaceae species and these species naturally concentrate in steppe zones. Naturalized grasses with Kranz anatomy,of genera such as Setaria, Echinochloa, Eragrostis, Panicum and Chloris, were found in almost all the botanical-geographical regions of Mongolia, where they commonly occur in annually disturbed areas and desert oases. We analyzed the relationships between the occurrence of C₄ plants in 16 natural botanical-geographical regions of Mongolia and their major climatic influences. The proportion of C₄ species increases with decreasing geographical latitude and along the north-to-south temperature gradient; however grasses and chenopods differ in their responses to climate. The abundance of Chenopodiaceae species was closely correlated with aridity, but the distribution of the C₄ grasses was more dependent on temperature. Also, we found a unique distribution of different C₄ Chenopodiaceae structural and biochemical subtypes along the aridity gradient. NADP-malic enzyme (NADP-ME) tree-like species with a salsoloid type of Kranz anatomy, such as Haloxylon ammodendron and Iljinia regelii, plus shrubby Salsola and Anabasis species, were the plants most resistant to ecological stress and conditions in highly arid Gobian deserts with less than 100 mm of annual precipitation. Most of the annual C₄ chenopod species were halophytes, succulent, and occurred in saline and arid environments in steppe and desert regions. The relative abundance of C₃ succulent chenopod species also increased along the aridity gradient. Native C₄ grasses were mainly annual and perennial species from the Cynodonteae tribe with NAD-ME and PEP-carboxykinase (PEP-CK) photosynthetic types. They occurred across much of Mongolia, but were most common in steppe zones where they are often dominant in grazing ecosystems. Received: 17 March 1999 / Accepted: 1 November 1999     

Systematic and phylogenetic implications of the wood anatomy of six Neotropical genera of Primulaceae

Our main goals were to identify diagnostic characters at the species, genus, and subfamily levels, find anatomical features with potential for future morphological and molecular (combined) phylogenetic analyses, and to reconstruct the evolution of wood anatomical characters in two subfamilies of Primulaceae in a molecular phylogenetic framework. We investigated twenty-seven species from the woody Myrsinoideae (4 genera) and Theophrastoideae (2 genera) using scanning electron, light, and epifluorescence microscopy. Samples were prepared using standard protocols. Based on the wood anatomical characters, we were able to identify synapomorphies and to detect evolutionary trends of interest for the genera and subfamilies. Both subfamilies share the presence of diffuse porosity, simple perforation plates, septate fibres, and scanty paratracheal axial parenchyma. Theophrastoideae species have rays?>?10 cells wide and short (<?350 µm) vessel elements, and Myrsinoideae have breakdown areas in rays and longer vessel elements. Ardisia and Stylogyne have scalariform intervessel pits, Myrsine exhibit breakdown areas in rays, and two Cybianthus species from subgenus Weilgetia have distinguishing features (e.g., scalariform perforation plate in C. nemoralis and the absence of rays in C. densiflorus). Overall, when combining characters, we were able to segregate the Neotropical Primulaceae subfamilies and genera from each other and from the subfamily Maesoideae based on wood anatomy.     

Origin and evolution of C4 photosynthesis in the tribe Salsoleae (Chenopodiaceae) based on anatomical and biochemical types in leaves and cotyledons

 The Chenopodiaceae genus Salsola contains a large number of species with C₄ photosynthesis. Along with derivative genera they have a prominent position among the desert vegetation of Asia and Africa. About 130 species from Asia and Africa were investigated to determine the occurrence of C₃ versus C₄ syndrome in leaves and cotyledons, and to study specific anatomical and biochemical features of photosynthesis in both photosynthetic organs. The species studied belong to all six previously identified sections of the tribe Salsoleae based on morphological characters. Types of photosynthesis were identified using carbon ¹³C/¹²C isotope fractionation. The representatives of all systematic groups were investigated for mesophyll anatomy and biochemical subtypes by determination of enzyme activity (RUBPC, PEPC, NAD- and NADP-ME and AAT) and primary photosynthetic products. Two photosynthetic types (C₃ and C₄) and two biochemical subtypes (NAD- and NADP-ME) were identified in both leaves and cotyledons. Both Kranz and non-Kranz type anatomy were found in leaves and cotyledons, but cotyledons had more diversity in anatomical structure. Strong relationships between anatomical types and biochemical subtypes in leaves and cotyledons were shown. We found convincing evidence for a similar pattern of structural and biochemical features of photosynthesis in leaves and cotyledons within systematic groups, and evaluated their relevance at the evolutionary level. We identified six groups in tribe Salsoleae with respect to photosynthetic types and mesophyll structure in leaves and cotyledons. Two separate lineages of biochemical and anatomical evolution within Salsoleae were demonstrated based on studies of leaves and cotyledons. The sections Caroxylon, Malpighipila, Cardiandra and Belanthera have no C₃ species and only the NAD-ME C₄ subtype has been found in leaves. We suggest the C₄ species in the NADP-ME lineage evolved in Coccosalsola and Salsola sections, and originated in the subsection Arbuscula. Coccosalsola contains many species with C₃ and/or C₃-C₄ intermediate photosynthesis. Within these main evolutionary lineages, species of different taxonomic groups (sections and subsections) had differences in anatomical or/and biochemical features in leaves and cotyledons. We conclude that structural and biochemical changes in the photosynthetic apparatus in species of the tribe Salsoleae were a key factor in their evolution and broad distribution in extreme desert environments. Received January 25, 2001 Accepted July 17, 2001     

C4 photosynthetic modifications in the evolutionary transition from land to water in aquatic grasses

Cladistic analysis supports the conclusion that the Orcuttieae tribe of C₄ grasses reflect evolution from a terrestrial ancestry into seasonal pools. All nine species in the tribe exhibit adaptations to the aquatic environment, evident in the structural characteristics of the juvenile foliage, which persist submerged for 1–3 months prior to metamorphosis to the terrestrial foliage. Aquatic leaves of the least derived or basal genus Neostapfia have few morphological and anatomical characteristics specialized to the aquatic environment and have retained full expression of the C₄ pathway, including Kranz anatomy. Orcuttia species have many derived characteristics and are more specialized to the aquatic environment. These latter species germinate earlier in the season and persist in the submerged stage longer than Neostapfia and evidence from the literature indicates length of submergence is positively correlated with fitness components. Aquatic leaves of Orcuttia species lack Kranz or PCR bundle sheath anatomy, yet ¹⁴C-pulse chase studies indicate >95% malate + aspartate as the initial products of photosynthesis and these products turn over rapidly to phosphorylated sugars, indicating a tight coupling of the C₄ and C₃ cycles. Presence of the C₄ pathway is further supported by enzymological data. Contemporary dogma that Kranz anatomy is a sine qua non for operation of the C₄ pathway is contradicted by the patterns in Orcuttia; however, it is unknown whether the pathway acts as a CO₂ concentrating mechanism in these aquatic plants. Received: 12 June 1997 / Accepted: 10 February 1997