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Titolo:
CARBOHYDRATE-COMPOSITION AND INVERTASE ACTIVITY OF THE LEAFY LIVERWORT PORELLA-PLATYPHYLLA
Autore:
MARSCHALL M; PROCTOR MCF; SMIRNOFF N;
Indirizzi:
UNIV EXETER,DEPT BIOL SCI,HATHERLY LABS,PRINCE WALES RD EXETER EX4 4PS DEVON ENGLAND UNIV EXETER,DEPT BIOL SCI,HATHERLY LABS EXETER EX4 4PS DEVON ENGLAND
Titolo Testata:
New phytologist
fascicolo: 2, volume: 138, anno: 1998,
pagine: 343 - 353
SICI:
0028-646X(1998)138:2<343:CAIAOT>2.0.ZU;2-E
Fonte:
ISI
Lingua:
ENG
Soggetto:
LOLIUM-TEMULENTUM L; SOLUBLE ACID INVERTASE; DESICCATION TOLERANCE; FRUCTAN BIOSYNTHESIS; EXCISED LEAVES; CICHORIUM-INTYBUS; SUCROSE; PURIFICATION; METABOLISM; ACCUMULATION;
Keywords:
BRYOPHYTES; DESICCATION; FRUCTAN; INVERTASE; 1-KESTOSE; SUCROSE; WATER STRESS;
Tipo documento:
Article
Natura:
Periodico
Settore Disciplinare:
Science Citation Index Expanded
Citazioni:
49
Recensione:
Indirizzi per estratti:
Citazione:
M. Marschall et al., "CARBOHYDRATE-COMPOSITION AND INVERTASE ACTIVITY OF THE LEAFY LIVERWORT PORELLA-PLATYPHYLLA", New phytologist, 138(2), 1998, pp. 343-353

Abstract

The major soluble carbohydrates in the desiccation-tolerant leafy liverwort Porella platyphylla (L. ) Lindb. are sucrose and a homologous series of fructans including the trisaccharide 1-kestose. Exogenous glucose and fructose (10 mol m(-3)) did not affect the composition of the soluble carbohydrate pool. Sucrose caused an increase in the fructan pool. Sucrose also inhibited photosynthetic oxygen evolution and respiration. The fructan pool was maintained in preference to sucrose duringdark starvation. Low temperature and low water potential increased the fructan pool whereas desiccation increased the proportion of high molecular weight fructan. Acid invertase activity was detected in a taxonomically diverse range of liverworts but was very low or undetectablein a range of mosses. The invertase activity from P. platyphylla was partially purified by ammonium sulphate precipitation. The reaction products of the partially purified enzyme were equimolar glucose and fructose. Kestose and higher DP fructans were not detected suggesting that, at least under the assay conditions used, the enzyme does not have sucrose:sucrose fructosyl transferase activity. The pH optimum was 4.5-5 and the K-m for sucrose was 1.7 mol m(-3) Pyridoxal hydrochloride (5 mol m(-3)) caused 50 % inhibition. The coexistence of sucrose and invertase suggests that either the invertase is inactive in vivo or is in a different subcellular compartment from sucrose. The pH response shows that it would have very low activity at cytosolic pH. A large acidic vacuole was detected in P. platyphylla leaf cells by neutral-red staining in which either invertase or sucrose could be sequestered. Rehydrating desiccated P. platyphylla for 10 min resulted in a 60 % loss of extractable invertase activity. By contrast, extractable malate dehydrogenase activity increased during rehydration. Rehydrating desiccated leaves caused an increase in glucose and fructose suggesting that the sucrose pool was susceptible to invertase at this time. It is suggested that the partial inactivation of invertase during rehydration minimizes sucrose hydrolysis while membrane structure and subcellular compartmentation are re-established.

ASDD Area Sistemi Dipartimentali e Documentali, Università di Bologna, Catalogo delle riviste ed altri periodici
Documento generato il 04/12/20 alle ore 19:50:25