Arbuscular mycorrhiza infection enhances the growth response of Lolium perenne to elevated atmospheric pCO(2).

Elevated atmospheric pCO(2) increases the C-availability for plants and thus leads to a comparable increase in plant biomass production and nutrient demand. Arbuscular mycorrhizal fungi (AMF) are considered to play an important role in the nutrient uptake of plants as well as to be a significant C-sink. Therefore, an increased colonization of plant roots by AMF is expected under elevated atmospheric pCO(2). To test these hypotheses, Lolium perenne L. plants were grown from seeds in a growth chamber in pots containing a silica sand/soil mixture for 9 weeks with and without inoculation with Glomus intraradices (Schenck and Smith). The growth response of plants at two different levels of N fertilization (1.5 or 4.5 mM) combined with ambient (35 Pa) and elevated atmospheric pCO(2) (60 Pa) was compared. The inoculation with G. intraradices, the elevated atmospheric pCO(2) and the high N fertilization treatment all led to an increased plant biomass production of 16%, 20% and 49%, respectively. AMF colonization and high N fertilization increased the plant growth response to elevated atmospheric pCO(2); the plant growth response to high N fertilization was also increased by AMF colonization. The root/shoot ratio was reduced by high N fertilization or elevated atmospheric pCO(2), but was not affected by AMF colonization. The unchanged specific leaf area indicated that if AMF colonization represented an increased C-sink, this was fully covered by the plant. Elevated atmospheric pCO(2) strongly increased AMF colonization (60%) while the high N fertilization had a slightly negative effect. AMF colonization neither improved the N nor P nutrition status, but led to an improved total P uptake. The results underline the importance of AMF for the response of grassland ecosystems to elevated atmospheric pCO(2).

Differential expression of alpha- and beta-expansin genes in the elongating leaf of Festuca pratensis.

Grasses contain a number of genes encoding both alpha- and beta-expansins. These cell wall proteins are predicted to play a role in cell wall modifications, particularly during tissue elongation. We report here on the characterisation of five alpha- and three vegetative beta-expansins expressed in the leaf elongation zone (LEZ) of the forage grass, Festuca pratensis Huds. The expression of the predominant alpha-expansin (FpExp2) was localised to the vascular tissue, as was the beta-expansin FpExpB3. Expression of another beta-expansin (FpExpB2) was not localised to vascular tissue but was highly expressed in roots and initiating tillers. This is the first description of vegetative beta-expansin gene expression at the organ and tissue level and also the first evidence of differential expression between members of this gene family. In addition, an analysis of both alpha- and beta-expansin expression along the LEZ revealed no correlation with growth rate distribution, whereas we were able to identify a novel xyloglucan endotransglycosylase (FpXET1) whose expression profile closely mimicked leaf growth rate. These data suggest that alpha- and beta-expansin activities in the grass leaf are associated with tissue differentiation, that expansins involved in leaf growth may represent more minor components of the spectrum of expansin genes expressed in this tissue, and that XETs may be useful markers for the analysis of grass leaf growth.

Differential expression of XET-related genes in the leaf elongation zone of F. pratensis.

Festuca pratensis Huds. is a forage grass with the ability to withstand harsh climatic conditions. However, its potential agronomic use is limited by its poor competitive ability, which can be traced to limitations in leaf growth. In order to characterize this process and to identify genes which might function as markers for leaf growth, three XET-related genes in the leaf elongation zone (LEZ) of F. pratensis are reported. A detailed expression analysis is presented of the three genes in two F. pratensis genotypes with contrasting leaf growth characteristics grown under two nitrogen levels. By means of a detailed spatial analysis of growth and XET encoding transcript pattern along the LEZ, a specific correlation is shown between FpXET1 expression and tissue elongation that is maintained under the different growth conditions, while the two other XETs expressed in the LEZ show different transcript dynamics. Tissue localization of FpXET1 and FpXET2 transcripts indicate an accumulation throughout young tissue, which is consistent with the encoded proteins playing roles in cell wall modification processes during growth. It is proposed that FpXET1 is a potential marker for tissue elongation and leaf growth in F. pratensis.

Evidence that P deficiency induces N feedback regulation of symbiotic N2 fixation in white clover (Trifolium repens L.).

Trifolium repens L. was grown to test the following hypotheses: when P is deficient (i) N2 fixation decreases as a result of the plant's adaptation to the low N demand, regulated by an N feedback mechanism, and (ii) the decrease in the photosynthetic capacity of the leaves does not limit N2 fixation. Severe P deficiency prevented nodulation or stopped nodule growth when the P deficiency occurred after the plants had formed nodules. At low P, the proportion of whole-plant-N derived from symbiotic N2 fixation decreased, whereas specific N2 fixation increased and compensated partially for poor nodulation. Leaf photosynthesis was reduced under P deficiency due to low Vc,max and Jmax. Poor growth or poor performance of the nodules was not due to C limitation, because (i) the improved photosynthetic performance at elevated pCO2 had no effect on the growth and functioning of the nodules, (ii) starch accumulated in the leaves, particularly under elevated pCO2, and (iii) the concentration of WSC in the nodules was highest under P deficiency. Under severe P deficiency, the concentrations of whole-plant-N and leaf-N were the highest, indicating that the assimilation of N exceeded the amount of N required by the plant for growth. This was clearly demonstrated by a strong increase in asparagine concentrations in the roots and nodules under low P supply. This indicates that nodulation and the proportion of N derived from symbiotic N2 fixation are down-regulated by an N feedback mechanism.

Increased abundance of MTD1 and MTD2 mRNAs in nodules of decapitated Medicago truncatula.

To gain insight into the molecular processes occurring in root nodule metabolism after stress, we used a mRNA differential display (DDRT-PCR) approach to identify cDNAs corresponding to genes whose expression is enhanced in nodules of decapitated Medicago truncatula plants. Two full-length cDNAs of plant origin were isolated (MTD1 and MTD2). Sequence analysis revealed that MTD1 is identical to an EST clone (accession number AW559774) expressed in roots of M. truncatula upon infection with Phytophthora medicaginis, while MTD2 is highly homologous to an Arabidopsis thaliana gene (accession number AL133292) coding for a RNA binding-like protein. The two mRNAs started to accumulate in root nodules at 4 h after plant decapitation and reached even higher transcript levels at 24 h from the imposition of the treatment. MTD1 and MTD2 mRNAs were mainly induced in nodules, with very little induction in roots. The abundance of the two transcripts did not change in response to other perturbations known to decrease nitrogenase activity, such as nitrate and Ar/O2 treatments. Our results suggest that MTD1 and MTD2 represent transcripts that accumulate locally in nodules and may be involved in changes in nodule metabolism in response to decapitation.

Electron microscopic investigation of water occlusions in intercellular spaces in the inner cortex of lucerne nodules.

It is unclear to what extent oxygen diffusion pathways through the cortex of the nitrogen-fixing zone of indeterminate nodules are liquid filled and whether a blockage of these pathways is involved in varying nodule oxygen permeability to control nitrogenase activity. We examined the proportion of water-filled intercellular spaces of lucerne (Medicago sativa L.) nodules with cryo-scanning electron microscopy. This technique allows for direct observation of water accumulation. Thirty percent of all intercellular spaces in the inner cortex of lucerne nodules were liquid filled. Decreasing the nodule oxygen permeability by detopping of the plant or by increasing the rhizospheric oxygen partial pressure to 80 kPa had no statistically significant effect on the water distribution in the intercellular spaces. Therefore, the hypothesis of a continuous aqueous diffusion barrier in the inner cortex could not be supported. The abundance of glycoproteins in intercellular spaces of the inner cortex was investigated with immunoelectron microscopy. No alteration due to detopping or after increase of the rhizospheric oxygen partial pressure was observed. Therefore, our results do not support the hypothesis of a short-term regulation of oxygen permeability by blockage of diffusion pathways through morphological changes in the cortex region of the nitrogen-fixing zone of lucerne nodules.

Glycolytic flux is adjusted to nitrogenase activity in nodules of detopped and argon-treated alfalfa plants

To investigate the short-term (30-240 min) interactions among nitrogenase activity, NH4+ assimilation, and plant glycolysis, we measured the concentrations of selected C and N metabolites in alfalfa (Medicago sativa L.) root nodules after detopping and during continuous exposure of the nodulated roots to Ar:O2 (80:20, v/v). Both treatments caused an increase in the ratios of glucose-6-phosphate to fructose-1,6-bisphosphate, fructose-6-phosphate to fructose-1,6-bisphosphate, phosphoenolpyruvate (PEP) to pyruvate, and PEP to malate. This suggested that glycolytic flux was inhibited at the steps catalyzed by phosphofructokinase, pyruvate kinase, and PEP carboxylase. In the Ar:O2-treated plants the apparent inhibition of glycolytic flux was reversible, whereas in the detopped plants it was not. In both groups of plants the apparent inhibition of glycolytic flux was delayed relative to the decline in nitrogenase activity. The decline in nitrogenase activity was followed by a dramatic increase in the nodular glutamate to glutamine ratio. In the detopped plants this was coincident with the apparent inhibition of glycolytic flux, whereas in the Ar:O2-treated plants it preceded the apparent inhibition of glycolytic flux. We propose that the increase in the nodular glutamate to glutamine ratio, which occurs as a result of the decline in nitrogenase activity, may act as a signal to decrease plant glycolytic flux in legume root nodules.

Dry matter allocation and nitrogen productivity explain growth responses to photoperiod and temperature in forage grasses.

The mechanisms responsible for fluctuations in species composition of semi-natural grassland are not well understood. To identify plant traits that determine the poor competitive ability of Festuca pratensis compared to Dactylis glomerata especially during summer, the growth of both grasses was monitored over time and at different temperatures and photoperiods. Plants of both grasses were grown from seed with non-limiting nutrient supply at three day/night temperatures (11/6, 18/13 and 25/20°C) and two photoperiods (16 and 12 h). F. pratensis had a significantly lower relative growth rate than D. glomerata, mainly due to its lower specific leaf area and reduced nitrogen productivity. At high temperature, F. pratensis had a considerably lower root weight ratio than D. glomerata leading to substantially slower root growth. F. pratensis responded to a shorter photoperiod with an increase in the net assimilation rate, whereas D. glomerata responded with an increase in specific leaf area. The low competitive ability of F. pratensis compared to D. glomerata was mainly associated with its lower specific leaf area and nitrogen productivity. The stronger decline of its competitive ability during summer was probably related to the decreased allocation of dry matter to the roots at higher temperatures which leads to slower root growth compared to D. glomerata.

Long-term responsiveness to free air CO2 enrichment of functional types, species and genotypes of plants from fertile permanent grassland.

To test inter- and intraspecific variability in the responsiveness to elevated CO2, 9-14 different genotypes of each of 12 perennial species from fertile permanent grassland were grown in Lolium perenne swards under ambient (35 Pa) and elevated (60 Pa) atmospheric partial pressure of CO2 (pCO2) for 3 years in a free air carbon dioxide enrichment (FACE) experiment. The plant species were grouped according to their functional types: grasses (L. perenne, L. multiflorum, Arrhenatherum elatius, Dactylis glomerata, Festuca pratensis, Holcus lanatus, Trisetum flavescens), non-legume dicots (Rumex obtusifolius, R. acetosa, Ranunculus friesianus), and legumes (Trifolium repens, T. pratense). Yield (above a cutting height of 4.5 cm) was measured three times per year. The results were as follow. (1) There were highly significant differences in the responsiveness to elevated pCO2 between the three functional types; legumes showed the strongest and grasses the weakest yield increase at elevated pCO2. (2) There were differences in the temporal development of responsiveness to elevated pCO2 among the functional types. The responsiveness of the legumes declined from the first to the second year, while the responsiveness of the non-legume dicots increased over the 3 years. During the growing season, the grasses and the non-legume dicots showed the strongest response to elevated pCO2 during reproductive growth in the spring. (3) There were no significant genotypic differences in responsiveness to elevated pCO2. Our results suggest that, due to interspecific differences in the responsiveness to elevated pCO2, the species proportion within fertile temperate grassland may change if the increase in pCO2 continues. Due to the temporal differences in the responsiveness to elevated pCO2 among species, complex effects of elevated pCO2 on competitive interactions in mixed swards must be expected. The existence of genotypic variability in the responsiveness to elevated pCO2, on which selection could act, was not found under our experimental conditions.

Does nitrogen nutrition restrict the CO2 response of fertile grassland lacking legumes?

The extent of the response of plant growth to atmospheric CO2 enrichment depends on the availability of resources other than CO2. An important growth-limiting resource under field conditions is nitrogen (N). N may, therefore, influence the CO2 response of plants. The effect of elevated CO2 (60 Pa) partial pressure (pCO2) on the N nutrition of field-grown Lolium perenne swards, cultivated alone or in association with Trifolium repens, was investigated using free air carbon dioxide enrichment (FACE) technology over 3 years. The established grassland ecosystems were treated with two N fertilization levels and were defoliated at two frequencies. Under elevated pCO2, the above-ground plant material of the L. perenne monoculture showed a consistent and significant decline in N concentration which, in general, led to a lower total annual N yield. Despite the decline in the critical N concentration (minimum N concentration required for non-N-limited biomass production) under elevated pCO2, the index of N nutrition (ratio of actual N concentration and critical N concentration) was lower under elevated pCO2 than under ambient pCO2 in frequently defoliated L. perenne monocultures. Thus, we suggest that reduced N yield under elevated pCO2 was evoked indirectly by a reduction of plant-available N. For L. perenne grown in association with T. repens and exposed to elevated pCO2, there was an increase in the contribution of symbiotically fixed N to the total N yield of the grass. This can be explained by an increased apparent transfer of N from the associated N2-fixing legume species to the non-fixing grass. The total annual N yield of the mixed grass/legume swards increased under elevated pCO2. All the additional N yielded was due to symbiotically fixed N. Through the presence of an N2-fixing plant species more symbiotically fixed N was introduced into the system and consequently helped to overcome N limitation under elevated pCO2.

Branch and root formation in Trifolium repens is influenced by the light environment of unfolded leaves.

In plagiotropic plants, axillary buds on the stolon can be exposed to low red:far-red (R:FR) ratios, while the leaves may be positioned in the uppermost layer of the sward where they are exposed to a high R:FR ratio. We tested whether the light environment of unfolded leaves influences outgrowth of the axillary buds and the formation of nodal roots of Trifolium repens. Single plants were grown in a growth cabinet with high photosynthetic photon flux rate (PPFR) and a high R:FR ratio (FHRH, control), low PPFR and high R:FR (FLRH) or low PPFR and low R:FR (FLRL). In an additional treatment (SS), only stolons were shaded so that developing leaves grew into light conditions similar to the control treatment. Neutral shading (FLRH) had a minor effect on branching and did not influence root formation. A reduction in the R:FR ratio (FLRL) significantly delayed the outgrowth of axillary buds so that, compared to the control plants, the percentage of branched phytomers was reduced by 43% on the parent axis and by 75% on primary branches. Furthermore, the number of nodal roots per plant was reduced by about 30%. When only the stolons were shaded (SS), the percentage of branched and rooted phytomers was similar to that of the control plants. Extension of petioles and leaves was very variable, increasing the values in the FLRL treatment at least 2.5-fold compared with the control plants. It was concluded that the light environment of the unfolded leaves had a significant influence on the regulation of the outgrowth of axillary buds and that the high plasticity in petiole growth allows the positioning of the leaves in a light environment conducive to the stimulation of branch outgrowth.

Stimulation of Symbiotic N2 Fixation in Trifolium repens L. under Elevated Atmospheric pCO2 in a Grassland Ecosystem.

Symbiotic N2 fixation is one of the main processes that introduces N into terrestrial ecosystems. As such, it may be crucial for the sequestration of the extra C available in a world of continuously increasing atmospheric CO2 partial pressure (pCO2). The effect of elevated pCO2 (60 Pa) on symbiotic N2 fixation (15N-isotope dilution method) was investigated using Free-Air-CO2-Enrichment technology over a period of 3 years. Trifolium repens was cultivated either alone or together with Lolium perenne (a nonfixing reference crop) in mixed swards. Two different N fertilization levels and defoliation frequencies were applied. The total N yield increased consistently and the percentage of plant N derived from symbiotic N2 fixation increased significantly in T. repens under elevated pCO2. All additionally assimilated N was derived from symbiotic N2 fixation, not from the soil. In the mixtures exposed to elevated pCO2, an increased amount of symbiotically fixed N (+7.8, 8.2, and 6.2 g m-2 a-1 in 1993, 1994, and 1995, respectively) was introduced into the system. Increased N2 fixation is a competitive advantage for T. repens in mixed swards with pasture grasses and may be a crucial factor in maintaining the C:N ratio in the ecosystem as a whole.

Whole-Nodule Carbon Metabolites Are Not Involved in the Regulation of the Oxygen Permeability and Nitrogenase Activity in White Clover Nodules.

To test the hypothesis of an indirect or direct involvement of carbon metabolites in the short-term regulation of nitrogenase activity, nodule O2 permeability was manipulated either by defoliation or by varying rhizosphere O2 partial pressure. In contrast to defoliation, a 50% reduction of the nodule O2 permeability, due to adapting nodules to 40 kPa O2, had no effect on nodule sucrose concentration. Likewise, total concentrations of other carbon metabolites such as fructose, starch, L-malate, and succinate tended to be differentially affected by the two treatments. Upon defoliation, carbon metabolites in roots responded in a manner similar to those in nodules. Sucrose concentration in nodules decreased significantly after the removal of 40% of the leaf area, which is known to have no effect on nitrogenase activity and O2 permeability. During regrowth after a 100% defoliation, nitrogenase activity could be increased at any time by elevating rhizospheric O2 partial pressure. Thus, during the entire growing cycle nitrogenase activity seems primarily oxygen limited. Changes in whole nodule sucrose pools after defoliation have to be viewed as secondary effects not necessarily linked to nodule activity. Whole-nodule carbon metabolites appear not to be determinants of nodule activity, either through direct metabolic involvement or through indirect effects such as triggering O2 permeability.

Current Nitrogen Fixation Is Involved in the Regulation of Nitrogenase Activity in White Clover (Trifolium repens L.).

Previous studies have shown that nitrogenase activity decreases dramatically after defoliation, presumably because of an increase in the O2 diffusion resistance in the infected nodules. It is not known how this O2 diffusion resistance is regulated. The aim of this study was to test the hypothesis that current N2 fixation (ongoing flux of N2 through nitrogenase) is involved in the regulation of nitrogenase activity in white clover (Trifolium repens L. cv Ladino) nodules. We compared the nitrogenase activity of plants that were prevented from fixing N2 (by continuous exposure of their nodulated root system to an Ar:O2 [80:20] atmosphere) with that of plants allowed to fix N2 (those exposed to N2:O2, 80:20). Nitrogenase activity was determined as the amount of H2 evolved under Ar:O2. An open flow system was used. In experiment I, 6 h after complete defoliation and the continuous prevention of N2 fixation, nitrogenase activity was higher by a factor of 2 compared with that in plants allowed to fix N2 after leaf removal. This higher nitrogenase activity was associated with a lower O2 limitation (measured as the partial pressure of O2 required for highest nitrogenase activity). In experiment II, the nitrogenase activity of plants prevented from fixing N2 for 2 h before leaf removal showed no response to defoliation. The extent to which nitrogenase activity responded to defoliation was different in plants allowed to fix N2 and those that were prevented from doing so in both experiments. This leads to the conclusion that current N2 fixation is directly involved in the regulation of nitrogenase activity. It is suggested that an N feedback mechanism triggers such a response as a result of the loss of the plant's N sink strength after defoliation. This concept offers an alternative to other hypotheses (e.g. interruption of current photosynthesis, carbohydrate deprivation) that have been proposed to explain the immediate decrease in nitrogenase activity after defoliation.

Purification and some properties of fructan: fructan fructosyl transferase from dandelion (Taraxacum officinale Weber).

A fructan: fructan fructosyl transferase (FFT, EC 2.4.1.100) was purified 61-4-fold from roots of Taraxacum officinale Weber. The enzyme is a glycoprotein with an apparent molecular weight of 49000 as determined by SDS-polyacrylamide gel electrophoresis. FFT activity was detected by 1-kestose-dependent nystose production. The enzyme was most active at pH 6·5 and was stable at 30°C (1 h). Separation by preparative iso-electric focusing yielded four different forms with iso-electric points around pH 4·8. The purified enzyme was active on different oligofructans of the inulin series, but not on melezitose, 6-kestose, neokestose, maltopentaose or sucrose as the sole substrate.

Bicarbonate inhibits ribulose-1,5-bisphosphate carboxylase.

Ribulose-1,5-bisphosphate carboxylase/oxygenase (RuBPCO) rapidly extracted from leaves of wheat (Triticum aestivum) and purified activated RuBPCO were incubated in the presence and absence of 20 millimolar HCO(3) (-) and changes in activation state were followed. Rapid inactivation occurred in the presence, but not in the absence, of HCO(3) (-). Effects of CO(2) concentration and pH during preincubation before assay on activation state of RuBPCO were investigated in equilibrium studies. Twenty percent inactivation occurred at high CO(2) concentration if pH was high, but not if it was low, suggesting that RuBPCO was inactivated by HCO(3) (-). The inactivation by HCO(3) (-) was more rapid than the dissociation of activating CO(2) in CO(2)-free buffer (both in the presence of 20 millimolar MgCl(2)), suggesting that HCO(3) (-) was bound to the active enzyme complex. The dissociation of inactivating HCO(3) (-) from the enzyme was slow enough that inhibition could be demonstrated in experiments with HCO(3) (-) treatments during preincubation and constant conditions during assay. Inorganic phosphate did not seem to interfere with the binding of HCO(3) (-).

Regulation of photosynthesis in nitrogen deficient wheat seedlings.

Nitrogen effects on the regulation of photosynthesis in wheat (Triticum aestivum L., cv Remia) seedlings were examined. Ribulose 1,5-bisphosphate carboxylase/oxygenase was rapidly extracted and tested for initial activity and for activity after incubation in presence of CO(2) and Mg(2+). Freeze clamped leaf segments were extracted for determinations of foliar steady state levels of ribulose 1,5-bisphosphate, triose phosphate, 3-phosphoglycerate, ATP, and ADP. Nitrogen deficient leaves showed increased ATP/ADP and triose phosphate/3-phosphoglycerate ratios suggesting increased assimilatory power. Ribulose 1,5-bisphosphate levels were decreased due to reduced pentose phosphate reductive cycle activity. Nevertheless, photosynthesis appeared to be limited by ribulose 1,5-bisphosphate carboxylase/oxygenase, independent of nitrogen nutrition. Its degree of activation was increased in nitrogen deficient plants and provided for maximum photosynthesis at decreased enzyme protein levels. It is suggested that ribulose 1,5-bisphosphate carboxylase/oxygenase activity is regulated according to the amount of assimilatory power.

Is Transfer of CO(2) to C(3)-Plants Purely by Diffusion?

The dependence of the CO(2) compensation concentration on O(2) partial pressure and the dependence of differential uptake of (14)CO(2) and (12)CO(2) on CO(2) and O(2) partial pressures are analyzed in illuminated white clover (Trifolium repens L.) leaves. The data show a deviation of the photosynthetic gas exchange from ribulose bisphosphate carboxylase oxygenase kinetics at 10 degrees C but not at 30 degrees C. This deviation is due to an effect of CO(2) partial pressure on the ratio of photosynthesis to photorespiration which can be explained if active inorganic carbon transport is assumed.

The adaptation to temperature of photorespiration and of the photosynthetic carbon metabolism of altitudinal ecotypes of Trifolium repens L.

In altitudinal ecotypes of Trifolium repens L. the oxygen inhibition of photosynthesis, the CO2 compensation point and the sugar content were examined. Excised leaves were exposed to 14CO2 for 20 s and 60 min periods and the radioactivity in different photosynthetic products was studied. In all experiments the temperature during growth and measurement was varied.To some extent, the differences between the ecotypes and the differences between the plants grown under different temperature conditions are similar. These ecotypic differences appear to reflect long-term adaptation to the general temperature conditions at each site. Alpine ecotypes and plants grown at low temperatures show an increased photorespiration. The 14C-labeling of certain photosynthetic products also changes with the ecotypes and the temperatures during growth. Other differences between the ecotypes are interpreted as adaptations to the partial pressure of Co2 and to the length of the growing season, both of which change with altitude.The metabolism of photosynthesis depends greatly on temperature. The 14C-experiments and the study of photorespiration suggest that, to a certain degree, adaptation can compensate for this dependence on temperature.

Effect of light intensity and temperature on apparent photosynthesis of altitudinal ecotypes of Trifolium repens L.

The dependence on light and temperature of the apparent photosynthetic rate was studied on ecotypes of Trifolium repens from different altitudes in the alps (600-2040 m above sea level). Due to the altitude, the natural habitats have different temperature conditions. At the higher altitudes the light conditions for the growing plants vary due to grazing or cutting management of these meadows. Accordingly, for this study the plants were grown at different temperatures and light intensities in growth cabinets.High altitude plants had higher photosynthetic rates, especially when measured at low temperatures. According to the light conditions, dependent on management, in the alpine habitats the ecotypes differed in their photosynthetic properties like sun and shade plants. It is stated, that the photosynthetic performance as well as the acclimation capacity to the growth conditions is related to the altitude of the habitats and probably also to the agricultural management.