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Carbon Reserves (carbon + reserve)
Selected AbstractsCell wall hemicelluloses as mobile carbon stores in non-reproductive plant tissuesFUNCTIONAL ECOLOGY, Issue 5 2007G. HOCH Summary 1As essential compounds of plant cell walls, hemicelluloses account for about a quarter of all plant biomass worldwide. 2In seed cotyledons and endosperm of species from several plant families, hemicelluloses are used as mobile carbon reserves. Whether cell wall hemicelluloses of non-reproductive plant tissue are multifunctional molecules, which can also serve as carbon sources during periods of enhanced carbon demand, is still equivocal. 3This review summarizes the current understanding of a possible reserve function of hemicelluloses. Although several descriptive and experimental studies suggested at least partial mobility of cell wall polysaccharides in mature, non-reproductive plant tissues, there is still a need for a broad-scale, ecophysiological exploration of the actual nature of hemicelluloses beyond their structural function. 4The chemical heterogeneity of hemicelluloses may be the major problem for precise quantitative analyses on a large, comparative scale. 5Because of the abundant distribution of hemicelluloses in plants, the existence of a significant mobile carbohydrate pool in cell walls of non-reproductive organs would shed rather new light on plant carbon relations in a source-sink context. 6Consequently, a reserve function of hemicelluloses questions the conventional division of cell compounds into structural (i.e. immobile) and non-structural (i.e. mobile) compounds. [source] Variation in Crown and Root Organic Reserves Among Lucerne Genotypes of Different Morphology and Flower ColourJOURNAL OF AGRONOMY AND CROP SCIENCE, Issue 2 2003F. Fornasier Abstract Previous evidence indicates that differences in the concentration of underground organic reserves can drive the survival and growing ability of lucerne under cold and defoliation stresses. In order to provide the selection process with further information on compounds that may influence plant performance under grazing, we assessed variations in cold-season concentrations of nitrogen and carbon reserves on genotypes that had been identified for morphological features that possibly enhance grazing tolerance. The selected genotypes encompassed distinct morphological patterns (defined as ,models') and different taxa within the Medicago sativa complex, as shown by different flower colours. Crown concentrations of reserves were determined on 90 genotypes, whereas root concentrations were measured on a subsample of 15 genotypes. Wide intergenotypic variation was observed for all reserve substances. Comparisons among models and among flower colour classes highlighted the high concentrations of crown carbohydrates and root and crown-soluble proteins of the model coded as ,D1', characterized by prostrate, rhizomatous habit and long dormancy, which largely corresponded to plants with yellow or variegated flowers, typical of ssp. falcata and ×,varia, respectively. There was a strong ,flower colour × storage organ' interaction for sugar concentration, and the results suggested a preferential compartment of sugars in the roots of purple-flowered genotypes that belonged to the ssp. sativa. A rank correlation analysis indicated a positive relationship between persistence after two years under grazing of half-sib progenies deriving from 19 genotypes out of the 90 and crown concentrations of carbohydrates of the 19 mother plants. [source] Bacterial synthesis of biodegradable polyhydroxyalkanoatesJOURNAL OF APPLIED MICROBIOLOGY, Issue 6 2007R.A.J. Verlinden Summary Various bacterial species accumulate intracellular polyhydroxyalkanoates (PHAs) granules as energy and carbon reserves inside their cells. PHAs are biodegradable, environmentally friendly and biocompatible thermoplastics. Varying in toughness and flexibility, depending on their formulation, they can be used in various ways similar to many nonbiodegradable petrochemical plastics currently in use. They can be used either in pure form or as additives to oil-derived plastics such as polyethylene. However, these bioplastics are currently far more expensive than petrochemically based plastics and are therefore used mostly in applications that conventional plastics cannot perform, such as medical applications. PHAs are immunologically inert and are only slowly degraded in human tissue, which means they can be used as devices inside the body. Recent research has focused on the use of alternative substrates, novel extraction methods, genetically enhanced species and mixed cultures with a view to make PHAs more commercially attractive. [source] Soluble sugar content of white spruce (Picea glauca) seeds during and after germinationPHYSIOLOGIA PLANTARUM, Issue 1 2000Bruce Downie In white spruce (Picea glauca [Moench.] Voss.) seeds, the raffinose family oligosaccharides (RFOs) provide carbon reserves for the early stages of germination prior to radicle protrusion. Some seedlots contain seeds that are dormant, failing to complete germination under optimal conditions. Since dormancy may be imposed through a metabolic block in reserve mobilization, the goal of this project was to identify any impediment to RFO mobilization in dormant relative to nondormant seeds. Desiccated seeds contain primarily, and in order of abundance on a molar basis, sucrose and the first 3 members of the RFOs, raffinose, stachyose and verbascose. Upon radicle protrusion at 25°C, the contents of RFOs decreased to low amounts in all seed parts, regardless of prior dormancy status and sucrose was metabolized to glucose and fructose, which increased in seed parts. During moist chilling at 4°C, RFO content initially decreased before stabilizing and then increasing. In seeds that did not complete germination, the synthesis of RFOs at 4°C favored verbascose, so that at the end of 14 (nondormant) or 35 (dormant) weeks, verbascose contents in megagametophytes exceeded the amount initially present in the desiccated seed. This was also true in the embryos of the dormant seedlot. In seed parts from both seedlots after months of moist chilling, stachyose amounts exceeded raffinose amounts. Upon radicle protrusion at 4°C, RFO contents decreased to amounts most similar to those present in seeds that completed germination at 25°C. Hence, the RFOs are utilized as a source of energy, regardless of the temperature at which white spruce seeds complete germination. Based on the similarity of sugar contents in seed parts between dormant and nondormant seeds that did not complete germination, differences in sugar metabolism are probably not the basis of dormancy in white spruce seeds. [source] Does the 13C of foliage-respired CO2 and biochemical pools reflect the 13C of recently assimilated carbon?PLANT CELL & ENVIRONMENT, Issue 10 2009BEHZAD MORTAZAVI ABSTRACT Isotopic labelling experiments were conducted to assess relationships among 13C of recently assimilated carbon (,CA), foliage respiration (,CF), soluble carbohydrate (,CSC), leaf waxes (,CLW) and bulk organic matter (,COM). Slash pine, sweetgum and maize were grown under 13C depleted CO2 to label biomass and then placed under ambient conditions to monitor the loss of label. In pine and sweetgum, ,CF of labelled plants (,,44 and ,35,, respectively) rapidly approached control values but remained depleted by ,4,6, after 3,4 months. For these tree species, no or minimal label was lost from ,CSC, ,CLW and ,COM during the observation periods. ,CF and ,CSC of labelled maize plants rapidly changed and were indistinguishable from controls after 1 month, while ,CLW and ,COM more slowly approached control values and remained depleted by 2,6,. Changes in ,CF in slash pine and sweetgum fit a two-pool exponential model, with the fast turnover metabolic pool (,3,4 d half-life) constituting only 1,2% of the total. In maize, change in ,CF fits a single pool model with a half-life of 6.4 d. The 13C of foliage respiration and biochemical pools reflect temporally integrated values of ,CA, with change in isotopic composition dampened by the size of metabolic carbon reserves and turnover rates. [source] | ||||||||||