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Titolo:
ECOPHYSIOLOGICAL STUDIES ON THE VEGETATION OF MADAGASCAR - A DELTA-C-13 AND DELTA-D SURVEY FOR INCIDENCE OF CRASSULACEAN ACID METABOLISM (CAM) AMONG ORCHIDS FROM MONTANE FORESTS AND SUCCULENTS FROM THE XEROPHYTIC THORN-BUSH
Autore:
KLUGE M; BRULFERT J; RAUH W; RAVELOMANANA D; ZIEGLER H;
Indirizzi:
TH DARMSTADT,INST BOT,SCHNITTSPAHNSTR 10 D-64287 DARMSTADT GERMANY UNIV PARIS 11,INST BIOTECHNOL PLANETS ORSAY FRANCE UNIV ANTANANARIVO,EES SCI,LAB PHYSIOL VEGETALE ANTANANARIO MALAGASY REPUBL TECH UNIV MUNICH,INST BOT W-8000 MUNICH GERMANY
Titolo Testata:
Isotopes in environmental and health studies
fascicolo: 2, volume: 31, anno: 1995,
pagine: 191 - 210
SICI:
1025-6016(1995)31:2<191:ESOTVO>2.0.ZU;2-M
Fonte:
ISI
Lingua:
ENG
Soggetto:
CARBON ISOTOPE DISCRIMINATION; VASCULAR EPIPHYTES; LIFE-FORMS; PLANTS; ASSIMILATION; PATHWAYS; HYDROGEN; VALUES; RATIOS;
Keywords:
CARBON ISOTOPE RATIO; CRASSULACEAN ACID METABOLISM (CAM); DIDIEREACEAE; EPIPHYTISM; HYDROGEN ISOTOPE RATIO; KALANCHOE; MADAGASCAR; MISTLETOES; ORCHIDACEAE;
Tipo documento:
Article
Natura:
Periodico
Settore Disciplinare:
Science Citation Index Expanded
Science Citation Index Expanded
Citazioni:
41
Recensione:
Indirizzi per estratti:
Citazione:
M. Kluge et al., "ECOPHYSIOLOGICAL STUDIES ON THE VEGETATION OF MADAGASCAR - A DELTA-C-13 AND DELTA-D SURVEY FOR INCIDENCE OF CRASSULACEAN ACID METABOLISM (CAM) AMONG ORCHIDS FROM MONTANE FORESTS AND SUCCULENTS FROM THE XEROPHYTIC THORN-BUSH", Isotopes in environmental and health studies, 31(2), 1995, pp. 191-210

Abstract

The incidence of Crassulacean acid metabolism (CAM) in plants collected at various habitats in Madagascar was investigated by survey of carbon and hydrogen isotope ratios ((delta(13)C and delta D values). In about 50% of the epiphytic orchids from evergreen higher and lower montane forests the delta(13)C values were indicative for CAM. The remainder of the species are presumably C-3 plants. In all samples of malagasy epiphytic leafless orchids comprising 9 species, the delta(13)C values suggest extreme CAM with CO2 uptake proceeding entirely during the night. All terrestrial orchids collected in the lower montane forests obviously acquire external carbon by C-3-photosynthesis, whereas Lissochilus decaryi, a terrestrial orchid from the semi-arid south of Madagascar and various other species of this genus are CAM plants. This is the first report of CAM occurrence in sympodial terrestrial orchids. Judged by the delta(13)C values, all succulents (mainly Didiereaceae, Euphorbiaceae. Crassulaceae and Asclepiadaceae) collected at the xerophytic thorn-bush of the semi-arid south perform pronounced CAM. Where it applies, our delta(13)C measurements in the thorn-bush succulents revealed values being practically identical with those found by K. Winter in samples of the same species collected at the same site nearly 10 years earlier. This shows extreme constancy over long duration of timein the mode of CAM performed by the succulents of the malagasy thorn-bush vegetation. Since the delta(13)C survey now comprises all 11 known species of the Didiereaceae, it is unequivocally clear that all members of this family are CAM plants. Most of the individuals of the species of the Didiereaceae grown in a glass-house had slightly more negative delta(13)C values compared with those grown at the natural stands suggesting some contribution of C-3-photosynthesis to carbon acquisition under the evaporatively less demanding lass-house conditions (and perhaps higher CO2 concentrations in the gas phase). Despite of the fact that the hydrogen isotope composition of meteoric waters depends to a large extent on the altitude and temperature-climate of the site where the concerned plants grow, it was found that in samples obtained inthe cooler higher evergreen montane forest as well as in the warmer lower evergreen montane forest and the lowland thorn-bush of the hot, semiarid south of Madagascar the delta values found in the organic matter (delta D-org) were in the same range (between about - 10 parts per thousand, to about - 90 parts per thousand,). This suggests that in our case the hydrogen isotope compositions of the meteoric waters were of minor importance in bringing about the delta D-org values found in the plants. The correlation between the delta(13)C and the delta D-org values of the plants proposed in the literature was found only in the case of epiphytic orchids from the higher evergreen montane forests. In the orchids from the lower montane forests and in the succulents of the thorn-bush, no clear-cut correlation of the two isotopic parameters could be detected. In both the orchids of the montane forests and the kalanchoe species, the delta(13)C values clearly became less negative with increase of leaf thickness showing the expected correlation of CAM with the degree of succulence. In the orchids, but not in the kalanchoe species, the delta D values also tended to become less negative with increase of leaf thickness suggesting that enrichment of the leafmaterial with deuterium might be related to succulence, i.e. to the water storage capacity of the leaves. In mistletoe-host couples studiedat the lower montane forest and in thorn-bush, the delta(13)C values of the hemiparasite were more negative compared with the host, whereasin two of three investigated cases the delta D values tended to be less negative in the mistletoes indicating that enrichment in deuterium took place in them.

ASDD Area Sistemi Dipartimentali e Documentali, Università di Bologna, Catalogo delle riviste ed altri periodici
Documento generato il 15/07/20 alle ore 07:23:42