Examination of Some Soluble Constituents of Sphagnum Gametophytes

Maass, W. S. G.

doi:10.1139/b64-072

Cited by 30 publications

(19 citation statements)

References 5 publications

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“…This initial large loss in mass would be mostly due to leaching (Scheffer et al 2001). A fifth of the volume of Sphagnum by dry weight can be composed of labile, water-soluble constituents such as carbohydrates (Maass & Craigie 1964). Loss of carbohydrates from Sphagnum structure explains the large loss in mass during the earliest stages of peat formation (Kracht & Gleixner 2000).…”

Section: Changes In Carbon Isotopesmentioning

confidence: 99%

Effects of the early stage of decomposition on change in carbon and nitrogen isotopes inSphagnumlitter

Asada

Warner

Aravena

2005

Journal of Plant Interactions

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Isotope and elemental composition of carbon (C) and nitrogen (N) as well as its mass loss were measured for Sphagnum fuscum litter after one and two years of incubation in three different soil zones defined by the position of water table in a pristine Sphagnum -dominated peatland on the coast of western Canada. Mass losses were greater for the first year than for the second year, and the greatest loss was found in the oxic zone closest to the peatland surface. Early stage of decomposition clearly affected isotope signatures in Sphagnum litter. Litter d13 C values significantly decreased after the first year of incubation. The depletion of 13 C content during the first year might be related to the loss of more isotopically enriched soluble constituents coupled with the large mass loss. Litter d15 N values significantly increased after the first year of incubation in spite of the large mass loss. Litters incubated in the oxic zone had the greatest mass loss and 15 N enrichment, suggesting that the enrichment was the result of interactions with soil microbes and preferential loss of lighter N. Conversely, litters incubated in the anoxic zone had smaller mass loss and the amount of N significantly increased, suggesting that the incorporation of bacterial biomass might also contribute to the 15 N enrichment. The 15 N enrichment trend continued in the second year, but the change was not significant as the first year. Increases in the d15 N values with depth in the near surface Sphagnum peat core suggests that the enrichment trend of litter 15 N abundance with age is likely to continue for much longer periods than observed over the two-year period of this study.

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Section: Changes In Carbon Isotopesmentioning

confidence: 99%

Effects of the early stage of decomposition on change in carbon and nitrogen isotopes inSphagnumlitter

Asada

Warner

Aravena

2005

Journal of Plant Interactions

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“…Sphangum species which contain fructans of DP 3 and 4 (Maas & Craigie, 1964). In both leafy liverworts and mosses, starch and reducing sugars such as glucose and fructose are present at relatively low concentration (Suleiman et al, 1979 ;Smirnoff, 1992).…”

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confidence: 99%

Carbohydrate composition and invertase activity of the leafy liverwort Porella platyphylla

1998

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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 −$ ) 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 during dark 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 undetectable in 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 4n5-5 and the K m for sucrose was 1n7 mol m −$ . Pyridoxal hydrochloride (5 mol m −$ ) 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.

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“…Sucrose and fructans (polymers of fructose) are among the most widespread alternative storage carbohydrates, fructans being found in a range of temperate, mainly perennial, monocots within the Liliflorae and GlumiRorae together with dicots of the Asterales, Campanales and Boraginaceae* (Meier & Reid, 1982;Lewis, 1984). Fructans have also been isolated from bryophytes (Maas & Craigie, 1964;Sulieman et al, 1979) and a range of fungi, bacteria and algae (Lewis, 1984 and references therein). Accumulation of fructans and starch may be observed within the same tissue (Smith, 1973), although under such conditions fructans and sucrose usually predominate (Lewis, 1984).…”

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Tansley Review No. 5 Fructans and the Metabolism of Sucrose in Vascular Plants

1986

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SUMMARY The occurrence, structure and metabolism of fructose polymers in tissues of vascular plants are discussed in relation to the metabolism of sucrose. Distinctions are made between long‐term and short‐term storage of such polymers and the regulatory mechanisms which govern accumulation are examined. The roles of various fructosyltransferases in the synthesis of the different fructan structures from sucrose are outlined. The potential selective advantages of the possession of fructan metabolism in different species are assessed with reference to possible roles as cryoprotectants, in osmotic control and as storage carbohydrates whose metabolism can continue at low temperatures (0 to 5°C). It is concluded that the complexity and variety of fructan structures and of the associated enzyme systems has resulted in an incomplete understanding of their physiology and biochemistry, but their significance as an alternative storage polysaccharide in both leaves and storage organs should not be underestimated.

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Examination of Some Soluble Constituents of Sphagnum Gametophytes

Cited by 30 publications

References 5 publications

Effects of the early stage of decomposition on change in carbon and nitrogen isotopes inSphagnumlitter

Effects of the early stage of decomposition on change in carbon and nitrogen isotopes inSphagnumlitter

Carbohydrate composition and invertase activity of the leafy liverwort Porella platyphylla

Tansley Review No. 5 Fructans and the Metabolism of Sucrose in Vascular Plants

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