Photosynthetic Pathway Types Research Articles

The Diversification of Downy Mildew Species Was Not Driven by the Loss of Mycorrhizal Associations or the Evolution of C4 Photosynthesis

There are approximately 700 obligate biotrophic species grouped into 20 genera (Oomycota, Peronosporaceae) that cause downy mildew diseases. In 2001, Dick hypothesized that diversification of downy mildew species was driven in part by host plant secondary metabolites. Dick further speculated that this was driven by the transition of host plants away from mycorrhizal associations or the evolution of C4 photosynthesis. Specifically, loss of mycorrhizal associations or the use of C4 photosynthesis would result in more free carbon that the plants could then use to produce more secondary metabolites. If true, then there should be more downy mildew species that infect hosts from plant lineages that lack mycorrhizal associations or use C4 photosynthesis. However, analysis of 677 downy mildew species for host plant mycorrhizal associations and host plant photosynthetic pathway type shows that this is not what occurred. Seventy percent of downy mildew species parasitize hosts that form mycorrhizal associations, and 94% of downy mildew species parasitize hosts that use C3 photosynthesis. From this, it is concluded that the diversification of downy mildew species was not driven by the loss of mycorrhizal associations or the evolution of C4 photosynthesis. However, 85% of downy mildew species that parasitize Poaceae (grasses) parasitize C4 hosts. Thus, it is possible that C4 photosynthesis plays a role in the diversification of these genera. [Formula: see text] The author(s) have dedicated the work to the public domain under the Creative Commons CC0 “No Rights Reserved” license by waiving all of his or her rights to the work worldwide under copyright law, including all related and neighboring rights, to the extent allowed by law, 2022.

Directly estimating diurnal changes in GPP for C3 and C4 crops using far-red sun-induced chlorophyll fluorescence

Accurate estimation of gross primary production (GPP) is of great importance to global change research and also food and fuel security. Previous studies have demonstrated that values of sun-induced chlorophyll fluorescence (SIF) retrieved from hyperspectral data provide a direct measure of ecosystem GPP. However, global analysis of the relationship between satellite SIF and model-based GPP indicates that the relationship between the two parameters is highly dependent on the plant functional type (PFT). The overarching goal of this study is to examine the potential of far-red SIF retrieved at 760nm (SIF760) to track the diurnal variations in GPP for C3 and C4 crops, and to investigate whether the GPP–SIF relationship is dependent on the type of photosynthesis. GPP values are estimated from flux tower records and daily SIF760 data are derived from ground-based spectral measurements. The results show that GPP and SIF760 have similar diurnal patterns and are linearly correlated for C3 and C4 crops. However, the ratio of εP to εF (the slope of the linear SIF-based GPP model, GPP=εPεF×SIF) for C3 wheat is about 46% of that for C4 maize. The findings from the diurnal variation experiments imply that theεF is weakly sensitive to the photosynthetic pathway type (PsP type) and that the large difference in εP between C3 and C4 crops leads to the difference in the slopes. Our studies confirm the capability of the remotely sensed SIF signals to act as a direct proxy for GPP and suggest that the PsP type should be considered when trying to accurately quantify the ecosystem productivity using the straightforward empirical approach.

Ecophysiological aspects in 105 plants species of saline and arid environments in Tunisia

In Tunisian arid regions, plant life forms, ecotypes, physiological types and photosynthetic pathways (C3, C4 or CAM) remain unclear. Understanding the characters of these plant species could be important for land restoration. A literature survey was conducted for 105 species from arid regions of Tunisia. These plant species belong to several ecotypes: halophytes, xerophytes, gypsophytes, psamophytes, xero-halophytes, gypso-halophytes, psamo-halophytes, psamo-xerophytes, xero-gypsophytes and hygro-halophytes. The variation of photosynthetic pathway types in the 105 studied species shows that 56.2% are C3, 41.0% are C4, 1.9% are CAM and 1.0% are C3-CAM. The C3 pathway is more abundant in the halophytes, whereas the C4 one is more common in the xerophytes, gypsophytes, gypso-halophytes and psamo-halophytes. The ratio of C3 to C4 species (C3/C4 ratio) is 0.2 in the psamo-halophytes, 0.8 in the gypso-halophytes, 1.1 in the xerophytes, 1.6 in the xero-halophytes, 1.8 in the hygrohalophytes, 2.0 in the psamophytes and 3.8 in the halophytes. The annuals are mainly C3 plants whereas most of perennials are C4 ones. The C3/C4 ratio is 1.3 in succulent species and 1.4 in non-succulent species. Thus, succulence seems not to affect the distribution of C3 and C4 pathways within the studied plants. This investigation shows high percentages of C4 plants in plants of Tunisian arid regions. However, there are significant differences in their abundance among ecotypes. Based on C3/C4 ratio, the abundance of the C4 pathway is in the following order: psamo-halophytes, gypso-halophytes, xerophytes, xero-halophytes, hygro-halophytes, psamophytes, halophytes. In Tunisian arid regions, C4 species are most abundant in xerophytes and less abundant in halophytes. In the Chenopodiaceae the number of C3 plants is 13 and the number of C4 species is 20 and in the Poaceae the number of C3 was 23 and the number of C4 was 19 species. Thus, the most C4 proportion is in the Chenopodiaceae and Poaceae species. This confirms the fact that the Chenopodiaceae and the Poaceae were the leading families that tolerate salinity and aridity.

기후변화에 따른 국내 C4식물 목록과 분포 변화:고찰

<TEX>$C_4$</TEX> 식물의 식별 및 자료구축은 식생의 계절변동이나 천이와 관련된 생태학적 연구뿐만 아니라, 최근 주목받고 있는 기후변화의 영향을 과학적으로 증명할 수 있는 지표로서 그 활용이 크게 기대된다. 따라서 본 연구에서는 국내에 생육하는 <TEX>$C_4$</TEX> 식물에 대한 전체 목록을 작성하고, 지구온난화에 따른 <TEX>$C_4$</TEX> 식물의 반응과 식물생태계에 미치는 영향에 대하여 살펴보았다. 광합성 경로 유형에 대한 자료는 1971년에서 2010년 사이에 출판된 학술논문에서 얻어졌고, 그 자료와 국내에 구축되어 있는 식물목록 자료를 기반으로 국내에 생육하는 <TEX>$C_4$</TEX> 식물의 목록을 작성하였다. 그 결과, 국내에는 약 197과 1123속 4476종의 관속식물이 생육하고 있으며, 그 중 <TEX>$C_4$</TEX> 식물(<TEX>$C_3$</TEX>-<TEX>$C_4$</TEX> 중간형 포함)은 약 21과(10.7%), 84속(7.5%), 206종(4.6%)으로 확인되었다. 국내에 생육하는 <TEX>$C_4$</TEX> 식물 중 쌍자엽식물은 53종(25.7%)이고, 단자엽식물은 153종(74.3%)으로 나타났다. 과 수준에서는 벼과가 102종(49.5%), 사초과가 45종(21.8%), 명아주과가 15종(7.3%), 비름과가 13종(6.3%), 국화과가 6종(3.0%), 석죽과, 대극과 및 메꽃과가 각각 3종(1.4%)으로 나타났다. 생활형을 살펴보면, 휴면형은 1년생식물이 95종(46.1%), 번식형에서 지하기관형은 <TEX>$R_5$</TEX>가 123종(59.7%), 산포기관형은 중력산포형(<TEX>$D_4$</TEX>)이 179종(85.9%), 생육형은 총생형(t)이 122종(59.2%)으로 높은 비율로 나타났다. 지구온난화에 따른 기온 상승은 국내에 생육하는 <TEX>$C_4$</TEX> 식물에 좋은 환경조건을 제공해 줄 것이며, 그 결과 <TEX>$C_3$</TEX> 식물과 <TEX>$C_4$</TEX> 식물간의 종간경쟁, <TEX>$C_4$</TEX> 식물의 분포, 식물계절 및 생물다양성에 영향을 미칠 것으로 사료된다. It is expected that identification and lists of <TEX>$C_4$</TEX> plants in specific regions are useful not only for the ecological researches that are related to vegetation phenology and succession but also as an index of climate change. In this review, <TEX>$C_4$</TEX> plants growing in South Korea were listed and their life forms were investigated. In addition, we discussed the influences that climatic change and the <TEX>$C_4$</TEX> plants exerted on plant ecosystem. Photosynthetic pathway types (<TEX>$C_3$</TEX> and <TEX>$C_4$</TEX>) for the plant species in South Korea were determined by reviewing the scientific literatures published between 1971 and 2010. Of the total 4476 species in 1123 genera and 197 families, 206 species (4.6%) in 84 genera (7.5%) and 21 families (10.7%) were identified as <TEX>$C_4$</TEX> plants (including <TEX>$C_3$</TEX>-<TEX>$C_4$</TEX> intermediate plants). Among the identified <TEX>$C_4$</TEX> species, 53 species (25.7%) in 26 genera and 15 families were classified as Dicotyledoneae, while 153 species (74.3%) in 58 genera and 6 families were classified as Monocotyledoneae. The majority of the <TEX>$C_4$</TEX> species belong to four families: Chenopodiaceae (15 species), Amaranthaceae (13 species), Gramineae (102 speceis) and Cyperaceae (45 species). With respect to life form composition of 206 <TEX>$C_4$</TEX> species, Th-<TEX>$R_5$</TEX>-<TEX>$D_4$</TEX>-t was most dominant: 95 species (46.1%) were included in Th, 123 species (59.7%) in <TEX>$R_5$</TEX>, 179 species (86.9%) in <TEX>$D_4$</TEX>, and 122 species (59.2%) in t. The projected increase in temperature due to climate change may provide better conditions for the growth of <TEX>$C_4$</TEX> plants. Such a result will have considerable impacts on the interspecific competition between <TEX>$C_3$</TEX> and <TEX>$C_4$</TEX> plants, the distribution of <TEX>$C_4$</TEX> plants, plant phenology, and plant diversity.

ESTIMATION OF GROSS PRIMARY PRODUCTION USING SATELLITE DATA AND GIS IN URBAN AREA, DENPASAR

Remote sensing data with high spatial resolution is very useful to provideinformation about Gross Primary Production (GPP) especially over spatial coverage in theurban area. Most models of ecosystem carbon exchange based on remote sensing data usedlight use efficiency (LUE) model. The aim of this research was to analyze the distributionof annual GPP urban area of Denpasar. Two main satellite data used in this study wereALOS/AVNIR-2 and Aster satellite data. Result showed that annual value of GPP usingALOS/AVNIR-2 varied from 0.130 gC m-2 yr-1 to 2586.181 gC m-2 yr-1. Meanwhile, usingAster the value varied from 0.144 gC m-2 yr-1 to 2595.264 gC m-2 yr-1. The annual value ofGPP ALOS was lower than the value of Aster, because ALOS have high spatial resolutionand smaller interval of spectral resolution compared to Aster. Different land use couldeffect the value of GPP, because the different land use has different vegetation type,distribution, and different photosynthetic pathway type. The high spatial resolution of theremote sensing data is crucial to discriminate different land cover types in urban region.With heterogeneous land cover surface, maximum value of GPP using ALOS/AVNIR-2was smaller than that of Aster, however, the annual mean of GPP value usingALOS/AVNIR-2 was higher than that of Aster.

Medium Spatial Resolution Satellite Imagery to Estimate Gross Primary Production in an Urban Area

Remote sensing data with medium spatial resolution can provide useful information about Gross Primary Production (GPP), especially on the scale of urban areas. Most models of ecosystem carbon exchange that are based on remote sensing use some form of the light use efficiency (LUE) model. The aim of this work is to analyze the distribution of annual GPP in the urban area of Denpasar, Bali. Additional analysis using two types of satellite data (ALOS/AVNIR-2 and Aster) addresses the impact of spatial resolution on the detection of various ecosystem processes in Denpasar. Annual GPP estimated using ALOS/AVNIR-2 varied from 0.13 gC m−2 yr−1 to 2,586.18 gC m−2 yr−1. Meanwhile, the Aster estimate varied from 0.14 gC m−2 yr−1 to 2,595.26 gC m−2 yr−1. GPP as measured by ALOS/AVNIR-2 was lower than that from Aster because ALOS/AVNIR-2 has medium spatial resolution and a smaller spectral range than Aster. Variations in land use may influence the measured value of GPP via differences in vegetation type, distribution, and photosynthetic pathway type. The medium spatial resolution of the remote sensing data is crucial for discriminating different land cover types in heterogeneous urban areas. Given the heterogeneity of land cover over Denpasar, ALOS/AVNIR-2 detects a smaller maximum value of GPP than Aster, but the annual mean GPP from ALOS/AVNIR-2 is higher than that from Aster. Based on comparisons with previous work, we find that ALOS/AVNIR-2 and Aster satellite data provided more accurate estimates of maximum GPP in Denpasar and in the tropical Kalimantan-Indonesia and Amazon forest than estimates derived from the MODIS GPP product (MOD17).

Stable isotope ratios of carbon and nitrogen in pollen grains in order to characterize plant functional groups and photosynthetic pathway types

Measurements of delta(13)C, delta(15)N and C : N ratios on modern pollen grains from temperate plants, including whole grains as well as extracted sporopollenin, were analysed in order to characterize physiological plant types at the pollen level and to determine the variation of these parameters in modern pollen grains of the same climatic area. Measurements are presented for 95 batches of whole modern pollen from 58 temperate species and on the stable fraction of modern pollen grains, chemically extracted sporopollenin, for two modern species. Fourier transform infrared (FTIR) and cross-polarization and magic-angle spinning (CP/MAS) sporopollenin spectra were conducted in parallel. C(3) and C(4) plants can be separated by delta(13)C measurements based on pollen. Probabilistic assignments to plant functional groups (herbaceous, deciduous woody, evergreen woody) of C(3) plants by the means of a discriminant analysis can be made for C : N ratios and for delta(13)C. The results are related to other studies on sporopollenin in order to use this method in future work on fossil samples. Stable isotope measurements on pollen allow improved pollen diagrams, including forms that cannot be differentiated at species level, increasing the accuracy and resolution of plant physiological type distribution in quaternary and older fossil sediments.

δ&lt;sup&gt;13&lt;/sup&gt;C values, photosynthetic pathways, and plant functional types for some plants from saline meadows, Northeastern China

Based on stable carbon isotope ratio (δ13C) measurements, photosynthetic pathway types were determined for 61 species in 54 genera and 24 families of flowering plants from the saline meadows of Northeastern China. Of these total vascular plants, 18 species in 17 genera from 6 families were found to have C4 photosynthesis; 43 species in 38 genera from 20 families had C3 photosynthesis. Six dicotyledonous species exhibited C4 pathway, 12 monocotyledonous species were found with C4 photosynthesis. The dicotyledonous C4 species had relative greater mean δ13C value and less total carbon content than both monocotyledonous C4 and C3 species. Most dicotyledonous C4 species were annual forbs and halophytes. Some C4 species had been previously documented, but their δ13C values varied remarkably from those of the present study. Even though there are some fluctuations for the δ13C values of some C4 species, δ13C value was still more reliable for C3 and C4 identification than the use of the enzyme ratio method and of low CO2 compensation concentration.

Temporal and spatial variations of canopy temperature over a C3C4 mixture grassland

AbstractThis study discusses the photosynthetic pathway types involved in canopy temperature measurements on a mixed grassland consisting of C3 and C4 plants (dominant species in biomass were Solidago altissima (C3), Miscanthus sinensis (C4), and Imperata cylindrica (C4)). In the wet conditions immediately after the rainy season, the mean canopy temperature for S. altissima was the lowest among the dominant species, mainly due to its leaf conductance being twice as large as the other two species. Despite using the same C4 photosynthetic pathway, M. sinensis had a lower apparent canopy temperature than I. cylindrica due to a smaller proportion of sunlit elements in the field of view. In the dry conditions during late July, the mean canopy temperatures of the three dominant species were within 0·3 °C of one another. These results can be explained by poor water conditions for C3 species (S. altissima). The simultaneous survey of vegetation and thermal imaging can help clarify characteristics of C3 and C4 canopy temperature over complicated grassland. Copyright © 2006 John Wiley &amp; Sons, Ltd.

Photosynthetic and morphological functional types from different steppe communities in Inner Mongolia, North China

Morphological functional types and photosynthetic pathway types were identified for the forage species from steppe communities in Inner Mongolia, China, using the data of both field survey and published papers. Seven typical steppe communities were selected to investigate the morphological functional type and photosynthetic pathway type compositions and plant functional type (PFT) diversity in steppe communities at regional scale. Morphological functional types, based on plant height and leaf type combined with life span, were optimal for comparing the community differences in the region, while photosynthetic pathway types were fairly coarse for such studies. Of the seven morphological functional types in the steppe communities, perennial forbs (PEF) were the dominant type, and 60 % of species belonged to this type. Each of the high perennial grass (HPG), short perennial grass (SPG), and annual grass (ANG) types represented less than 10 % of the total, even though the grass species were dominant in the seven steppe communities. The differences of PFTs between the steppe communities were remarkable, and the PFT richness and diversity increased from the communities with moist conditions to the ones with dry environments.

Photosynthetic Pathway Types in Rangeland Plant Species from Inner Mongolia, North China

Photosynthetic pathway types, based on δ13C measurements, were determined for 125 species in 95 genera and 32 families growing in rangelands from Inner Mongolia. Of the total species, 4 species from 3 genera and 2 families had C4 photosynthesis (2 species in Gramineae and 2 in Chenopodiaceae) and 118 species from 90 genera and 31 families had C3 photosynthesis. The number of C4 species differed significantly among four rangeland sites, 4 species in desert, 3 species in steppe, but no C4 species were identified in meadow and dune. Six species [e.g. Agriophyllum arenarium Bieb., Bassia dasyphylla O. Kuntze, Saussurea japonica (Thunb.) DC.] earlier identified as C4 species using the enzyme ratio method were found as C3 species using the carbon isotope ratios (δ13C). Hence the enzyme ratio method for C3 and C4 identification may not always be reliable. The δ13C values of 3 species of Crassulaceae, which had been considered as CAM species, differed remarkably [−25.79 ‰ for Sedum aizoon L., −24.42 ‰ for Osostachys fimbriatus (Turcz.) Berger, and −16.97 ‰ for O. malacophyllus (Pall.) Fisch], suggesting that the use of δ13C method as a diagnosis for CAM photosynthetic pathway type may not always be reliable and supplementary measurements are needed.

Photosynthetic Pathways and Life Form Types for Native Plant Species from Hulunbeier Rangelands, Inner Mongolia, North China

Photosynthetic pathway Types (C3, C4, and CAM) and life forms of native species from Hulunbeier rangelands, north China were studied. Of the total 258 species, 216 species in 132 genera and 42 families had C3 photosynthetic pathway, including dominant herbs, e.g. Stipa baicalensis Roshev. and Leymus chinensis (Trin.) Tzvel., Filifolium sibiricum Kitam. and Arudinella hirta (Thunb.) Koidz. 38 species in 28 genera and 10 families were found with C4 photosynthesis, and 4 species in 2 genera and 1 family had CAM photosynthetic pathway. The occurrence of C4 species was common in Gramineae and Chenopodiaceae, and the two families were leading ones within C4 plants. More than 52 % of the total 258 species were in H form, 21 % in Th form, 19 % in G form; the other life form Types, e.g. Ch, M, N, and HH, formed less than 3 %. 68 % of C4 species were in Th form and 24 % in H form, indicating that these Types were the dominant life forms for C4 species in the rangeland region. The occurrence of C4 species was closely related with plant habitats, disturbed lands had the highest C4 abundance (55 % of the total C4 species), followed by grasslands and sandy soil, and forests had the lowest C4 abundance (8 %). Hence the occurrence of C4 species could be efficient indicator for rangeland dynamics in Hulunbeier rangelands.

Photosynthetic Pathway Types of Forage Species Along Grazing Gradient from the Songnen Grassland, Northeastern China

Photosynthetic pathway types (C3 and C4 species) and their dynamics along grazing gradient were determined for 42 plant species in 30 genera and 13 families from the Songnen grassland, Northeastern China. Of the total, 10 species in 9 genera and 4 families had C4 photosynthesis; 32 species in 21 genera and 12 families had C3 photosynthesis. The proportion of C4 species in total plants and C4/C3 increased with grazing intensity, and peaked in overgrazed plot. Most of the increased C4 species (6 of 10) along the grazed gradient were annual grasses and halophytes. This indicated that the C4 species had greater capacity to tolerate environmental stresses (e.g. drought and saline) caused by animal grazing in the Songnen grassland, Northeastern China.

Vegetation variation within and among palustrine wetlands along an altitudinal gradient in KwaZulu-Natal, South Africa

The variation in graminoid species composition and diversity and the distribution of photosynthetic pathways among 66 wetlands in KwaZulu-Natal, South Africa, and within six of these wetlands was described and related to measured physical parameters, using multivariate and univariate techniques. Altitude, which ranged from 550 m to 2120 m, accounted for most variation among wetlands, with an almost complete turnover of species along this gradient. Landform setting was less important in explaining overall species composition, but relationships of individual species were revealed (e.g. Eleocharis dregeana showed an affinity for depressions). Within a wetland there was an almost complete turnover of species along a gradient of wetness, as described using soil morphological criteria. Most species were consistently associated with the same wetness zones across different wetland sites, e.g., Phragmites australis with the wettest zone, Pycreus macranthus with the intermediate zone, and Eragrostis plana with the least wet zone. The occurrence and abundance of different photosynthetic pathway types depended on altitude and degree of wetness. At high altitudes, C3 sedges, notably Carex acutiformis, dominated the wettest zone and C3 and C4 grasses and sedges dominated the intermediate and least wet zones. At mid altitudes, C3 and C4 sedges and C3 grasses dominated the wettest zone, C3 and C4 grasses and sedges dominated the intermediate zone and C4 grasses dominated the least wet zone. Low altitude sites showed a similar distribution of photosynthetic pathways as mid-altitude sites, but C3 species were less abundant. Species richness was positively associated with the log of wetland size and, at the level of an individual wetland, species richness and evenness were found to be consistently greater in the intermediate and least wet zone compared with the wettest zone. The management implications of the results are discussed in the light of continuing anthropogenic loss of wetlands in the study area and global climate change.

Vegetational patterns within coastal salines in southern Yemen

AbstractFor the first time, the species diversity and zonation of coastal dunes and littoral salt marshes of the extensive coastal belt of southern Arabia is analyzed by means of two transects (Aden/Madinat as‐Shab; al‐Mukalla/Feleq). The vegetation analysis results five (Aeluropus lagopoides‐, Halopeplis perfoliata‐, Halopyrum mucronatum‐, Sevada schimperi‐association, and one rest group – Aden transect) respectively seven (Anabasis ehrenbergii‐, Arthrocnemum macrostachyum‐, Cyperus conglomeratus‐, Stipagrostis paradisea‐, Urochondra setulosa‐Arthrocnemum macrostachyum‐, Urochondra setulosa‐association, and one rest group – Feleq transect) homogenous ecological groups, which form clearly defined belts following a strong edaphical gradient. While the associations in the vicinity of Aden are in good accordance with those, reported from the coasts of the Red Sea and the Arabian Gulf, three new associations, partly rich in endemics are reported from the southern coast of Hadramout (Feleq transect). Due to the plantgeographical relationships of the taxa (Eritreo‐Arabian chorotype), they are strongly related to the coasts of NE Africa. In addition, Coelachyrum piercei is reported as new to the flora of Yemen, closing herewith a gap in the distribution pattern of this Omano‐Makranian taxon.All taxa were examined with respect to their photosynthetic pathway type (Kranz syndrome, δ13C‐values) to clarify, if there is a correlation between the distribution of C3‐/C4‐plants and the ecological requirements of the halophytes. It turned out, that hygrohalophytes and oligohaline, xerix associations are dominated by C3‐plants, whereas C4‐plants are typical of xerohalophytic associations and those, showing an intermediate position with respect to soil salinity and available water.

Occurrence and ecological characteristics of C4 dicot and Cyperaceae species in the Hungarian flora

The non-graminaceous wild flora of Hungary was screened for C4 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 C4 species (native or naturalized) were found in the Amaranthaceae, Chenopodiaceae, Cyperaceae, Euphorbiaceae, Portulacaceae and Zygophyllaceae families. Together with the 26 C4 grass species (Poaceae) reported earlier (Kalapos 1991), a total of 57 wild C4 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 C4 plant growth. In Hungary, the C4 species are predominantly annuals growing in open habitats such as dry grasslands, inland saline areas, temporarily exposed riverbeds and disturbed sites. In comparison with C3 plants, the C4 species have higher temperature and light preferences, and their phenology lags behind that of the C3 plants. These differences might account for C4 plants being usually excluded from productive biotopes in Hungary, where the C3 canopy may become closed during the growing season before C4 plants can start their ontogenetic development. Ecological properties of C3 and C4 plants differ considerably in the Cyperaceae, but much less in the Chenopodianceae family. Among C4 annuals naturalized aliens are common, most of which colonized hungary in the last two centuries. Increasing preponderance of C4 plants is anticipated in the future as a consequence of possible climate changes and the ever increasing human impact on terrestrial vegetation.

Effect of soil drying on growth, biomass allocation and leaf gas exchange of two annual grass species

Influence of short-term water stress on plant growth and leaf gas exchange was studied simultaneously in a growth chamber experiment using two annual grass species differing in photosynthetic pathway type, plant architecture and phenology:Triticum aestivum L. cv. Katya-A-1 (C3, a drought resistant wheat cultivar of erect growth) andTragus racemosus (L.) All. (C4, a prostrate weed of warm semiarid areas). At the leaf level, gas exchange rates declined with decreasing soil water potential for both species in such a way that instantaneous photosynthetic water use efficiency (PWUE, mmol CO2 assimilated per mol H2O transpired) increased. At adequate water supply, the C4 grass showed much lower stomatal conductance and higher PWUE than the C3 species, but this difference disappeared at severe water stress when leaf gas exchange rates were similarly reduced for both species. However, by using soil water more sparingly, the C4 species was able to assimilate under non-stressful conditions for a longer time than the C3 wheat did. At the whole-plant level, decreasing water availability substantially reduced the relative growth rate (RGR) ofT. aestivum, while biomass partitioning changed in favour of root growth, so that the plant could exploit the limiting water resource more efficiently. The change in partitioning preceded the overall reduction of RGR and it was associated with increased biomass allocation to roots and less to leaves, as well as with a decrease in specific leaf area. Water saving byT. racemosus sufficiently postponed water stress effects on plant growth occurring only as a moderate reduction in leaf area enlargement. For unstressed vegetative plants, relative growth rate of the C4T. racemosus was only slightly higher than that of the C3T. aestivum, though it was achieved at a much lower water cost. The lack of difference in RGR was probably due to growth conditions being relatively suboptimal for the C4 plant and also to a relatively large investment in stem tissues by the C4T. racemosus. Only 10% of the plant biomass was allocated to roots in the C4 species while this was more than 30% for the C3 wheat cultivar. These results emphasize the importance of water saving and high WUE of C4 plants in maintaining growth under moderate water stress in comparison with C3 species.

The distribution of vascular plant species and guilds in space and time along a desert gradient

Abstract. We studied distribution patterns of vascular plant species and environmental variables for three years along a permanent transect traversing a closed‐drainage watershed in the northern Chihuahuan Desert of south‐central New Mexico, USA. The transect extended for 2.7 km from a basin floor playa (1310 m elevation, fine‐textured soil), across a piedmont slope, and onto the base of a granitic mountain (1410 m elevation, coarse‐textured soil). The gradients in elevation and soils across our transect, along with variable seasonal rainfall, downslope redistribution of water and organic matter, and soil texture‐related variation in infiltration, water holding capacity, and moisture release characteristics, interact to generate a complex spatial and temporal gradient of available soil water and nitrogen. We grouped plant species into guilds according to growth form and photo synthetic pathway type. These guilds are spatially and temporally differentiated along the transect such that particular groups utilize particular seasonal phases or spatial regions of the gradient. We identified six distinct plant communities along the transect. C4 perennial grasses dominated the mesic/high nitrogen portion of the gradient, which occurred at the highest (upper piedmont grassland, dominated by Bouteloua eriopoda) and lowest (playa, dominated by Panicum obtusum) elevations along the transect. C3 shrubs were dominant in the xeric/low nitrogen portion of the gradient located near the middle of the transect (bajada shrubland, dominated by Larrea tridentata). C3 shrubs also dominated a narrow zone of vegetation located adjacent to the playa (playa fringe, dominated by Prosopisglandulosa). C4 perennial grasses, C3 subshrubs, and C3 and C4 perennial forbs and annuals were co‐dominant in the intermediate locations along the gradient, which occurred below (mixed basin slopes) and above (lower piedmont grassland) the bajada shrubland. Life‐form distribution patterns at the small scale of our study reflect some of the patterning that occurs at larger scales in response to climate gradients. The distributions of some species and guilds along the transect are apparently modified by competitive interactions.

The Distribution of Photosynthetic Pathway Types on a Mixed-grass Prairie Hillside

The Distribution of Photosynthetic Pathway Types on a Mixed-grass Prairie Hillside

Photosynthetic pathway types of evergreen rosette plants (Liliaceae) of the Chihuahuan desert

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.