Gδ-Embeddings in Hilbert space, II

AbstractIn this paper—which is a continuation of [10]—we exhibit some topological conditions on a Banach space which ensure that it contains isometric copies of infinite-dimensional conjugate spaces. This result is used to identify a large class of Banach spaces that are hereditarily separable duals. A method of defining a “Jamestree sum” of a countable number of Banach spaces is given. It is used to construct various counterexamples; for instance, there exists for each integer n a Banach space that can be mapped into Hilbert space via the composition of n but not (n − 1) Gδ-embeddings. We also continue the investigation of the global structure of some geometrically defined Banach spaces. For example, it is shown that a separable Banach space X with the Radon-Nikodym property (R.N.P.) has a subspace y with a boundedly complete finite-dimensional decomposition (F.D.D.) such that XY has an F.D.D. and the R.N.P

The effects of elevated CO_2 and tropospheric O_3 on the growth and development of hybrid poplar

SIGLEAvailable from British Library Document Supply Centre-DSC:DXN005761 / BLDSC - British Library Document Supply CentreGBUnited Kingdo

Elevated CO2 and hybrid poplar a detailed investigation of root and shoot growth and physiology of Populus euramericana, 'Primo'

Exposure of the hybrid poplar clone ‘Primo’ (Populus deltoidex × Populus nigra) to 580 ?l 1?1 carbon dioxide for just 68 days significantly (P ? 0.05) increased stem height by 13% compared with trees grown in ambient CO2 concentrations. The stem diameter was significantly (P ? 0.05) increased and both total biomass and woody stem biomass also showed higher values (38% and 31% increases respectively) in elevated CO2. Trees in elevated CO2 had more leaves and a greater total leaf area, whilst the specific leaf area was decreased in elevated CO2 on four out of five occasions and was significantly (P ? 0.05) lower after 68 days, an effect indicating that leaves were thicker and/or heavier. Rates of photosynthesis (A) measured after 49 and 67 days of exposure revealed that trees in the elevated CO2 treatment had lower values of A when measured at either 350 or 580 ?l 1?1 CO2. Sequential harvests at intervals during the study in which the root and shoot components were analysed separately allowed the construction of root:shoot ratios and allometric coefficients; there was no significant effect on the allometric coefficient and the root:shoot ratio was significantly increased on only one occasion. However, measurements of the ‘apparent’ root length suggested that root lengths were greater in the CO2 treatment. There was a significant increase in the number of fine root tips visible down the surface of specially designed rooting tubes (P ? 0.05), indicating more fine roots or an increase in fine root branching. The growth rates of individual fine or large roots over 24 h were unaffected, again suggesting that increases in biomass may be due to more root segments rather than longer individual roots. Root water relations were also examined and showed a tendency towards solute accumulation and increases in turgor pressure (P) and effective turgor (Pe) at times when root growth was stimulated, although these were not consistent. Cell wall plasticity of the tips of large roots was significantly (P ? 0.01) reduced in elevated CO2, possibly indicating a greater tendency to divert resources to the formation of root branches. The results of the study are discussed in the light of the possible consequences of changes in poplar growth and physiology for forestry practice in an increased CO2 environment

Elevated CO2 and plant-growth: cellular mechanisms and responses of whole plants

Much research has focused on the photosynthetic responses of plants to elevated CO2, with less attention given to the post-photosynthetic events which may lead to changes in the growth of tissues, organs and whole plants. The aim of this review is to identify how plant growth is altered in elevated CO2 and to determine which growth processes or cellular mechanisms are sensitive to carbon supply. For leaves, both the expansion of individual leaves and the initiation of leaf primordia are stimulated in elevated CO2. When lamina growth is promoted, this is usually associated with increased leaf cell expansion rather than increased leaf cell productio

Effects of elevated CO2 on cellular mechanisms, growth and development of trees with particular reference to hybrid poplar

Growth is often stimulated when C3 plants, including trees, are exposed to elevated CO2, although evidence from the literature suggests that the responsiveness of trees to CO2 varies, depending on species. This paper explores some of the cellular mechanisms which underlie increased growth, using both the authors' own data and information from the literature. Mechanisms include photosynthetic fixation of CO2 and the role of Rubisco, the link between carbon fixation and growth, in particular, how increased carbon is thought to influence the process of plant cell expansion and cell production and finally the consequences of cellular effects for the growth and development of whole plants. Data are presented for the growth and development of hybrid poplars in elevated CO2, following both field (open-top chambers) and laboratory experiments which suggest that this type of tree with indeterminate, rapid growth may be favoured by the CO2 concentrations of the next century