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Interspecific C transfer was studied in laboratory microcosms containing pairs of 6-month-old Betula papyrifera Marsh. and Pseudotsuga menziesii (Mirb.) Franco seedlings growing in individual, root-restrictive (28 μm pore size) pouches filled with field soil. Interspecific transfer was examined by reciprocal labelling of seedlings with 13CO2(gas) and 14CO2(gas). At the time of labelling, the root zones of ectomycorrhizal (EM) B. papyrifera and P. menziesii were interconnected by an extensive network of EM mycelium. Carbon transferred through EM connections was distinguished from that through soil pathways by comparing microcosms where interconnecting hyphae were left intact vs. those where they were severed immediately before labelling. Transfer was bidirectional, and represented 5% of total isotope uptake by both B. papyrifera and P. menziesii together. P. menziesii received on average 50% more 14C and 66% more 13C from paper birch than vice versa, however, differences between species were not statistically significant. Neither net nor bidirectional transfer differed between severing treatments, leaving in question the relative importance of EM hyphae versus soil transfer pathways. The tendency for P. menziesii to receive more isotope than B. papyrifera corresponded with a 10-fold greater net photosynthetic rate per seedling and two-fold greater foliar N concentration of B. papyrifera than P. menziesii. [ABSTRACT FROM AUTHOR]

• It is widely recognized that the red:far-red ratio (ζ) acts as a signal that triggers plant morphogenesis. New insights into photomorphogenesis have been gained through experiments in controlled environments. Extrapolation of such results to field conditions requires characterization of the ζ signal perceived by plant organs within canopies. This paper presents a modeling approach to characterize this signal. • A wheat ( Triticum aestivum) architectural model was coupled with a three-dimensional light model estimating the irradiances of virtual sensors. Architectural parameters and ζ values were measured on two contrasting spring wheat canopies under outdoor conditions. Light simulations were compared with measurements, and an analysis of sensitivity to measurement conditions was carried out. • The model results agreed well with measurements and previously published data. The sensitivity analysis showed that ζ strongly depends on canopy development as well as on sky conditions, sensor orientation, and sensor field of view. • This paper shows that modeling enables investigation of ζ distribution in a canopy over space and time. It also shows that the characterization of light quality strongly depends on measurement conditions, and that any discrepancies in results are likely attributable to different experimental set-ups. The usefulness of this modeling approach for crop photomorphogenesis studies is discussed. [ABSTRACT FROM AUTHOR]

The previous paper in this series argued that whole plant development is best viewed as a population-type process in which attention is focused on the production of modular plant parts. This approach is of more relevance to quantifying whole plants architecture than conventional growth analysis. The present paper describes an experiment in which the growth of two cultivars of Fuchsia was followed as a developing system of meristems. The noted features of growth and development were the changes in numbers of meristems as the plants produced flowers, the age distribution of vegetative meristems and the probabilities of transition between different modular states as the plant developed. [ABSTRACT FROM AUTHOR]

The article offers observations on a paper by Erik Lilleskov and colleagues in this issue about fruiting of mycorrhizal fungi in drought-stressed soil conditions. The results demonstrate the water-flow complexities where the soil, fungi, and plant meet. It discusses drought conditions in recent years and the lack of predictability of plant response. Mathematical modeling is conducted to make these predictions, but such predictions are difficult with unsaturated soil conditions. Tracer studies show that plants in arid areas extract water from fractured bedrock by developing deep root systems.

• A previously published model of crop nitrogen (N) status based on intercepted photosynthetically active radiation ( Ri, mol per plant) suggested that plant organic N accumulation is related to Ri by a constant ratio, defined hereafter as the radiation use efficiency for N (NRUE). The aim of this paper was to compare the effects of N nutrition and CO2 enrichment on NRUE and RUE (radiation use efficiency for biomass accumulation). • In three unrelated glasshouse experiments, tomato plants ( Solanum lycopersicum) grown in hydroponics were fed for 28 d (exponential growth) with full solutions containing constant concentrations ([ ]) ranging from 0.05 to 15 mol m−3, both under ambient or CO2-enriched (1000 µl l−1) air. • Each experiment comprised five harvests. Low [ ] (< 0.3 mol m−3) limited growth via leaf area (LA) restriction and decreased light interception. CO2 enrichment enhanced dry weight and LA. RUE was not affected by [ ], but increased under CO2-enriched air. By contrast, NRUE was not affected by [ ] or CO2 enrichment. • It is suggested that the radiation efficiency for organic N acquisition (NRUE) did not depend on C or N nutrition for young plants grown under unstressed conditions. [ABSTRACT FROM AUTHOR]

Many human activities, such as ore mining and smeltering, sewage sludge treatment and fossil fuel consumption, result in toxic soil concentrations of 'heavy metals' (Al, Cd, Co, Cr, Cu, Hg, Mn, Ni, Pb, Ti, Zn and others) (Gadd, 1993). There are also natural soils, such as serpentine, with levels of heavy metals that inhibit or preclude the growth of many plants and soil micro-organisms. However, certain plants and microorganisms do grow in these metalliferous sites. Understanding the physiology, ecology and evolution of tolerance to elevated soil metal concentrations is important in an applied setting, and is also of interest in theoretical biology. Applied importance relates to the improvement of forest health in areas subject to increasing pollution, rehabilitation of severely polluted sites by phytostabilization of metals, and metal removal using hyperaccumulating plants (Krämer, 2000; Ernst, 2000). Areas of theoretical interest include the evolution of local adaptation (Sork et al., 1993) and how it is shaped by the combined influences of natural selection, gene flow and genetic architecture, as well as metal influences on various species interactions (Pollard, 2000). A paper appears on pages 367-379 in this issue by Jan Colpaert and coworkers which adroitly combines the disparate fields of physiology, genetics and ecology to answer several outstanding questions concerning heavy metal tolerance in mycorrhizal fungi. Mycorrhizal fungi, which interact mutualistically with the majority of plant species, are well known for improving the P status of their hosts (Smith & Read, 1997). Some mycorrhizal fungi are also able to mobilize N and P from organic substrates and to provide plants with improved micronutrient and water acquisition, pathogen resistance, and a variety of other benefits (Smith & Read, 1997). One of these additional benefits is the amelioration of toxicity in metalliferous soils. [ABSTRACT FROM AUTHOR]

This paper reports the effects of nutrient magnesium (Mg) concentrations on the growth and photosynthetic physiology of clonal Pinus radiata from four female parents (families) known to differ in their tolerance to Mg deficiency and in their needle Mg concentrations. Plants were grown in flowing nutrient solutions with 2 mg l-1 (control) and 0.8 mg l-1 (low) Mg. Plant growth, needle Mg concentration, photosynthesis, chlorophyll fluorescence and carotenoid pigment content were measured. At low Mg, needle Mg concentration was about half that of control plants, height growth was reduced 15-25%, and the needles showed strong visual characteristics of Mg deficiency. Photosynthesis was also halved, and was associated with closure of the stomata under low Mg and with reductions in the residual conductance. In needles from plants grown at low Mg, photochemical yield was reduced both in the light and in the dark, and was strongly dependent on needle Mg concentrations below a threshold concentration of 0.02-0.025% (d. wt basis). The electron transport rate (ETR) at saturating photon flux density in low-Mg-grown needles was reduced to about half that of their Mg controls, but the photon efficiency of ETR was unaffected by the Mg concentration the plants were grown in. Photosynthetic quenching was markedly reduced and non-photosynthetic quenching was increased following growth in low Mg. Growth under low Mg also increased levels of zeaxanthin. Although family differences in growth and photosynthetic physiology were present, few family × Mg interactions were significant. We conclude that Mg deficiency probably affects growth through severe reductions in photosynthesis. [ABSTRACT FROM AUTHOR]

This paper considers the extent to which differences in pollen tube growth rates can provide prezygotic reproductive isolation between Mimulus nasutus and its presumed progenitor, Mimulus guttatus, Mimulus nasutus is partially cleistogamous, but its larger chasmogamous flowers offer appreciable opportunity for outcrossing. Mimulus nasutus was found to have smaller pollen grains and shorter styles than M. gattatus. No differences were observed in heterospecific stigmas. However, pollen tube growth rates of M. nasutus were found to be much slower than those of M. guttatus in the styles of that species. Consequently, any M. nasutus pollen transferred to an M. guttatus stigma was found to be competitively disadvantaged in an M. guttatus style, By contrast, no difference in pollen tube growth rate was detected between the species when growing in M. nasutus styles, possibly because M. nasutus styles are unable to support fast pollen tube growth. We tested the prediction from the pollen tube studies that a 50:50 mix of M. guttatus and M. nasutus pollen would produce 50% hybrid seeds when M. nasutus was the maternal parent, and near to 0% hybrid seed when M. guttatus was the maternal parent. The results were found to support this prediction. We conclude that pollen-pistil interactions can effect strong reproductive isolation between these species, as M. guttatus pollen rubes have a competitive advantage over those of M. nasutus in an M. guttatus style, but not in an M. nasutus style. [ABSTRACT FROM AUTHOR]

Branch bags were used to expose branches on mature Sitka spruce trees to either ambient [CO2] (A) or elevated [CO2] (E) for 4 yr. This paper reports the effects of this treatment on the growth, development and phenology of the branches, including shoot expansion, shoot numbers, needle dimensions, needle numbers and stomatal density. The effect of elevated [CO2] on the relationship between leaf area and sapwood area was investigated Exposure to elevated [CO2] doubled photosynthetic rates in current-year shoots and, despite sonic down- regulation, 1-yr-old E shoots also had higher rates of photosynthesis than their A counterpart. Thus the amount of assimilate fixed by E branches was substantially more than that fixed by A branches: however, this increase in the local production of assimilate did not lead to an increase in non -structural carbohydrate or stimulate growth or meristematic activity within the E branches. There was a very consistent relationship between leaf area and stem cross-sectional area that was not influenced by [CO2]. However, unbagged branches had thicker stems than bagged branches, resulting in a slightly lower ratio of leaf area to cross-sectional area. The implications of the results tot the modelling of growth and allocation and the potential utility of the branch bag technique are discussed. [ABSTRACT FROM AUTHOR]

Evidence that enhanced reactive nitrogen deposition is affecting semi-natural terrestrial ecosystems comes from historic increases in plant tissue N concentrations, correlations between tissue N concentrations and present-day total atmospheric N deposition, changes in plant amino-acid composition and effects on N assimilation. The ecological significance of such changes in biomarkers is uncertain. This paper explores the ecological significance of reactive atmospheric N deposition through a review of previous experimental findings and new experimental evidence from an acidic and a calcareous grassland, both showing phosphorus limitation, and a N-limited Calluna vulgaris (L.) Hull heathland in upland Britain. Nitrogen addition in the range 0-20 g N m-2 yr-1 initially (years 0-4) increased the growth of Calluna and a decline in some subordinate species. In subsequent years, shoot extension was not stimulated, hut winter injury was observed from 1993 onwards, suggesting a strong interaction between N supply arid climatic conditions. By contrast, the grasslands showed a small decrease in the cover of higher plants in later years (6-7) of the experimental treatments (0 14 g N m-2 yr-1) and no growth stimulation. All N treatments reduced the bryophyte cover in the acidic grassland. There were marked effects on below-ground processes, including a sustained stimulation of N mineralization in the grassland soils, and an increase in the bacterial utilization of organic substrates in the heathland, as measured in BIOLOG plates. The results strongly suggest the importance of atmospheric N deposition on microbially driven processes in soils, and are discussed in relation to the scale of potential ecosystem changes and their reversibility by pollution abatement. [ABSTRACT FROM AUTHOR]

In many parts of the world soils are detrimental to plant growth owing to elevated levels of metal ions, caused either by natural processes or by the result of man's activities. Many plants have evolved ecotypes or varieties that are able to grow more-or-less normally on these soils. This paper reviews our knowledge of the genetics of this phenomenon. The nature of tolerance and the problems of its measurement are discussed. Tolerance is frequently measured by an index produced by comparing growth in a contaminated environment with growth in a control environment. It is argued that this measurement is inappropriate for many genetical studies, and that it is frequently more useful to use growth at a single critical level of metal as a measure of tolerance. Polygenic inheritance provides a null hypothesis that has to be tested in a genetical analysis. Examples of major genes for tolerance to aluminium, arsenic, boron, cadmium, copper and manganese are discussed. Even where major genes have been demonstrated, it is probable that other minor genes, 'modifiers', are present as well. Because of the nature of tolerance as a character, dominance and epistasis are likely to vary with the level of metal at which an analysis is performed. Tolerance is generally found to be dominant at some levels of the metal. Studies which have mapped tolerance genes, particularly to aluminium and salt, are discussed. The specificity of tolerance is a matter of some confusion. Some studies indicate that tolerances evolve independently to different metals, but others have suggested that tolerance to one metal may often confer a degree of tolerance to some other metals. Very little is known about the molecular genetics of tolerance, and the mechanisms of tolerance to most metals. The possible role of phytochelatins and metallothionein-like proteins in metal tolerance is discussed. [ABSTRACT FROM AUTHOR]

This paper re-examines the question of the susceptibility of plant roots to infection by vesicular-arbuscular mycorrhizal fungi, particularly near the root apex. The cumulative distributions of the observed distance between the root apex and the most apical mycorrhizal entry points are compared with expected distributions based on (i) a random distribution of successful encounters between hypha and root and (ii) an uninfectible apical region (of length Z0). Data for both Allium porrum L. (leek) and Trifolium subterraneum L. (clover) are well fitted by the expected distributions and in the majority of cases (17/31) the best fit is obtained with zero Z0, with 8 additional cases being best fitted by values of Z0 of 1 mm or less, Even where the best fits are obtained with values of Z0 greater than zero, the distribution using Z0 = 0 is still within the confidence limits for the data. These findings indicate that in neither species is there clear evidence for a subapical region that is immune to infection. The fact that there are short uninfected lengths immediately behind the apex is interpreted as representing a delay between an encounter and a detectable infection. Other consistent deviations of the data from the theoretical distributions are discussed. Fitting the distributions yields values for the frequency of infection (A). These are compared for the two host plants at different propagule densities. The values for leek are much lower than for clover. In both species there are increases in A with increases in propagule density which are consistent with earlier findings. [ABSTRACT FROM AUTHOR]

This paper reports a comparison of the effects of the same ozone exposure given at different stages of growth on a population major L., which is as sensitive to ozone as Bel-W3 tobacco. Plants were grown from seed for eight weeks in controlled environment chambers and exposed to 70 μl O3 l-1 7 h d-1 for the whole period or for 2-wk episodes during weeks 1+2, 3+4, 5+6 or 7+8. Controls had charcoal filtered air. Effects on leaf, flower, seed and dry matter production, and on relative growth rate of shot and root are given. At whatever time the ozone was given it altered relative growth rate, dry matter partitioning and seed output. The experiment supports the view that assessment of the sensitivity of a herbaceous species can be indicated by a short-term exposure of young plants, even though the nature of the response may change with development. Comparison of the effect of ozone on dry matter partitioning at different stages of growth suggested that at each stage in development, ozone relatively strengthened the currently dominant sink, therefore reducing allocation to subsidiary sinks. As a plant develops, the relative strengths of sources and sinks change so the effects of an ozone episode on allocation will depend upon the timing. It is concluded that the commonly held view that ozone tends to reduce root growth more than shoot may be an over-simplification. For native plants growing in the field, the timing of episodes in relation to development may be crucial to understanding ozone impact. On the ecosystem level we need knowledge of response and source - sink relationships at times of the year when episodes occur. [ABSTRACT FROM AUTHOR]

In 1988, open-top chambers (OTCs) based on the Raleigh (USA) design were used to investigate the effect of ambient pollutants on field-sown Vicia faba cv. Ticol. This paper reports an aspect of this study in which the effect of the chamber itself on crop growth and development was investigated. Non-filtered chamber (NF OTC) microclimates were typically 0.8 °C warmer, with 20% less radiation and reduced wind speeds compared with open-field sub-plots (AA treatments). These differences are sufficient to induce alterations in the growth and development of V. faba. Plant development progressed more quickly inside the chambers in response to the faster accumulation of thermal time. Chamber-grown V. faba were up to 20 cm taller and had fewer branches (0.7 compared with 1.2 per plant) than plants grown in the AA treatments. Larger leaf areas developed on the NF plants, and there were fewer stomata per unit leaf area in this treatment (34 compared with 42 mm-2, P = 0.01). Enclosure within an OTC did not alter the number of flowers per plant or the number of flowers which formed pods. However, at harvest, chamber-grown plants had a 13% higher yield than the plants grown in open-field plots. These differences in growth are described in relation to the microclimate differences between AA and NF treatments. [ABSTRACT FROM AUTHOR]

Mechanistic hypotheses to explain mycorrhizal enhancement of root hydraulic conductivity (Lp) suggest that phosphorus (P) nutrition, plant growth substances and/or altered morphology may be responsible. Such ideas are based on work with VA (vesicular-arbuscular) mycorrhizas. Since VA mycorrhizas and ectomycorrhizas differ in many respects, they may alter host plant water uptake via different mechanisms. This paper examines Lp in various ectomycorrhizal associations while considering factors which are important to the VA mycorrhizal effect on Lp. Douglas fir Pseudotsuga menziesii (Mirb.) Franco] seedlings inoculated with the ectomycorrhizal fungi Laccaria bicolor (Maire) Orton and Hebeloma crustuliniforme (Bull. ex St. Amans) Quel. and non-inoculated seedlings infected naturally with Thelephora were grown under three low levels of P fertilization (1, 10 and 100 μM P). Seedling morphology, tissue P levels, Lp and plant growth substance levels in xylem sap were measured after nine months growth. Increased tissue P and decreased root/shoot ratio correlated with increased Lp in each of the mycorrhizal treatments. When adjusted for the effect of these two factors, Lp of Laccaria and Hebeloma seedlings was still lower than the Thelephora seedlings. In a subsequent experiment, the Lp of seedlings with Hebeloma and Rhizopogon vinicolor Smith mycorrhizas was compared to the Lp of non-mycorrhizal seedlings (grown at 100 mM P) and no differences were found among treatments. The lack of an ectomycorrhizal effect on Lp, is quite different from the enhancement of host Lp, by VA mycorrhizas. Zeatin ribsoside concentrations of Thelephora- and Hebeloma-infected seedlings were similar, yet higher than with Laccaria. There was no relationship between plant growth substances and Lp in ectomycorrhizal Douglas fir, despite lower zeatin riboside concentration for Laccaria-incoculated plants. [ABSTRACT FROM AUTHOR]

Iron has many catalytic roles photosynthesis, respiration and nitrogen assimilation; molybdenum is involved in NO3 and (usually) N2 reduction. This paper concentrates on computing the efficiency of use of Fe and Mo in growth of organisms growing with different mixtures of the major resources photons, carbon and nitrogen. This computed efficiency is defined as mol C assimilated (mol catalytic metal in the organism)-1 S-1. The efficiency is computed from the known in vivo involvement of Fe- and Mo-containing enzymes, the specific reaction rate of these enzymes, the specific rate of these enzymes in vitro and the growth requirements for the products of the reactions, for organisms using different energy, carbon and nitrogen sources. The predicted Fe use efficiency is greater for chemo-organotrophic than for photolithotrophic growth with a given nitrogen source and increases in the order N2, NO3-, NH4+ for growth with different nitrogen sources in the presence of constant photon and carbon availability. The predicted changes with variations in nitrogen sources are greater than those with variations in photon and carbon source. These predicted values may be compared with observed metal use efficiencies, defined as mol C assimilated (mol total metal ion the organism)-1 S-1. Relatively few such observed values are available from the literature. Fore Fe in photolithotrophically growing microalgae the observed values can be as low as 16-17% of the predicted values, i.e. 83-84% of the Fe in the organism is not accounted for by known catalytic uses of Fe if the catalysts are operating at their maximum specific reaction rates. One possibly discordant prediction relates to the Fe and Mo cost of N2 fixation; the computations suggest that in vitro estimates of nitrogenase activity may be less than those sometimes found in vivo. [ABSTRACT FROM AUTHOR]

Innate growth potential and innate patterns of allocation to different plant parts are both subject to physiological limitations. Yet the ways in which these attributes not only vary between species but also exhibit plasticity in response to environmental change are important determinants of ecological behaviour and contribute strands to Plant Strategy Theory. In this paper, we review the evidence for innate variation in growth potential and partitioning and consider the implications of this variation for the development of high-level ecological syntheses. [ABSTRACT FROM AUTHOR]

This paper describes how plants can be studied as developing modular systems, with growth described as a population-type process defined by the rate of production of modular plant parts. A simple model of dynamics of meristems is developed and is followed by discussion of such features of growth as meristematic flux and the change from vegetative to a flowering state, the positional distribution of meristems and the probabilities of meristems undergoing transitions that result in architectural differences between plants. [ABSTRACT FROM AUTHOR]

Plant growth analysis, demographic analysis and yield component analysis are three procedures used to study relationships underlying plant growth and development. Previously, it has been shown that demographic analysis is qualitatively different from plant growth analysis. This paper demonstrates how plant growth analysis and yield component analysis can be merged into a composite procedure, sequential plant growth analysis. The composite approach treats some of the traditional indices of plant growth, including leaf area ratio, leaf area index, unit leaf rate, relative growth rate, crop growth rate and harvest index, as yield components. Regression analysis is used to assess quantitatively the contributions of individual yield components to variations in growth and yield. Fitted curves and trends in coefficients of determination are both used to follow the time course of relationships during development. A study of vegetative growth in bean plants is used to illustrate the composite procedure. [ABSTRACT FROM AUTHOR]

This paper reports the results of a study of the establishment of Plantago coronopus L. seeds in the field. Seeds were introduced at a range of densities into plots with intact vegetation, and plots from which the vegetation was removed. Seeds were also sown in a variety of clump sizes on to non-vegetated plots. The aim of this experiment was to determine whether the density-dependent germination patterns exhibited by this species in laboratory experiments could also be observed in the field. All treatments exhibited similar patterns of seedling recruitment although different conditions of planting showed quantitatively different responses. During the first 4 weeks after sowing there was rapid seedling recruitment followed by mortality which balanced this recruitment. Eight weeks after sowing, seedling densities were not significantly different from the starting densities in any of the treatments. In particular, the chance of a seed forming an established seedling was not increased when seeds were sown in clumps, thus calling into doubt the ecological benefits of density-dependent germination responses which have been proposed in previous laboratory studies of the phenomenon. Factors influencing germination and establishment were investigated by means of an autocorrelation matrix. Recruitment of seedlings into the population appears to be limited by the number of adult and seedling plants already present in the population. [ABSTRACT FROM AUTHOR]

This paper discusses a recent extension of demographic techniques into a field more conventionally dealt with by plant growth analysis. It concludes that the two approaches are complementary. [ABSTRACT FROM AUTHOR]

This paper reports results of inoculation with vesicular-arbuscular (VA) endophytes in twelve unsterile soils with and without added rock phosphate or Hyperphosphat. Stylosanthes guyanensis and in two soils also maize, were grown in pots and plant weight, P uptake, nodule weight and nitrogenase activity were measured at harvest, The introduced endophyte established well in all but one of the soils and inoculated plants with added phosphate grew best in eleven soils. Utilization of added rock phosphate was often considerably increased by inoculation but there was no evidence of increased availability. Inoculum density in the soil, rather than its phosphate status seemed to determine responses to VA inoculation, which were greatest in soils containing few indigenous endophytes. VA inoculation often stimulated nodulation by rhizobia but, in contrast to irradiated soils, there was no clear relationship between percentage plant P and nodulation. The results are discussed in relation to the possibility of field inoculation with VA endophytes. [ABSTRACT FROM AUTHOR]

The adaptations of plants to environment can take many morphological and physiological forms. The rate at which new plant material is accumulated is an integrated measure of plant response to environment and is a useful character when comparing either genetic differences between populations or effects of different environmental conditions on populations. Several approaches have been made to the study of quantitative plant growth. With frequent harvesting, regression analysis provides a powerful tool in describing the relationship of total weight with time. In this paper we have adopted procedures outlined by Draper and Smith (1966) and applied regression analysis to two sets of data from our programme on Atriplex. These demonstrate ways in which appropriate polynomial regression equations can be objectively applied to the total weight-time relationship. Implications of fitting an inappropriate regression equation and the problems of extrapolation are also discussed. [ABSTRACT FROM AUTHOR]

Worcester Pearmain apple trees on four rootstock varieties with a range of vigour were grown in pots for 3 years. The effects of fruiting, determined by comparison with deblossomed trees, were qualitatively similar on all the rootstocks. The growth of all parts, particularly the roots, was less on fruiting trees. The greatest differences occurred in trees on the very dwarfing 3426 rootstock which bore the largest crops relative to the size of the tree; their root systems were severely reduced. When differences in fruitfulness were taken into account, the quantitative effects of fruiting on the dry weight increment of the combined perennial parts, and of the roots alone, were apparently the same on all the rootstocks. Trees with low levels of fruitfulness produced less dry matter, including fruit, than deblossomed trees because of lesser shoot growth. Trees of high fruitfulness produced as much, or even more dry matter than deblossomed trees because of increased photosynthetic efficiency. Comparisons of the shoot growth and stern-to-root ratios of the deblossorned trees on each rootstock variety indicated that the hypothesis put forward in a previous paper to explain the dwarfing mechanism of M.IX may be valid for 3426 also. [ABSTRACT FROM AUTHOR]

This article discusses research on the relationship between genotype, nutrient availability and growth in poplars. Particular attention is paid to the interplay between genotype and nitrogen availability as it pertains biomass and wood quality. A hybrid poplar, wherein Populus trichocarpa and Populus deltoids were interbred, was employed for a quantitative trait locus (QTL) analysis on the effect of nitrogen fertilization on phenotypic plasticity. While poplars are used for the generation of pulp, paper and wood products, they are garnering attention as energy crops and potential sinks for geological carbon sequestration. Data analysis on the hybrid found that nitrogen fertilization increased the amount of cellulose and lignin.

The author discusses the importance of biophysical processes of plant growth and development, citing an article by M. R. Nelson and colleagues. It discusses the format of the study group that consists experimental biologists. The authors of the study predict the possibility the anther's two-dimensional geometry as dehydration function. The paper suggests that epidermal dehydration is enough to make the conversion from a closed to an open anther.

The article presents information on different papers published in the 1998 and 1999 issues of the periodical "New Phytologist." Some of them are, "Growth and Development of Mesembryanthemum Crystallinum (Aizoaceae)," by researcher Adams P. Nelson in the 1998 issue of the periodical "New Phytologist"; "Tree and Forest Functioning in an Enriched Carbon Dioxide Atmosphere," by researcher Saxe H. Ellsworth in the 1998 issue of the periodical "New Phytologist"; "Biological clocks in Arabidopsis Thaliana," by researcher A.J. Miller published in the 1999 issue of the periodical "New Phytologist."

• Tension wood formed in response to gravitational force is a striking example of the plasticity of angiosperm wood. In this study our goal was to characterize the early changes in gene expression during tension wood formation inEucalyptus.• Using cDNA array technology, transcript profiling of 231 genes preferentially expressed in differentiatingEucalyptusxylem was followed from 6 h to 1 wk of a tension time course of artificially bentEucalyptustrees.• 196 genes were differentially regulated between control and bent trees, some exhibiting distinctive expression patterns related to changes in secondary cell wall structure and composition. For instance, expression of a cellulose synthase gene was well correlated with the appearance of the G-layers. Cluster correlation analysis revealed differential regulation of lignin biosynthetic genes and may also be used to help infer the function of unknown gene products.• Eucalyptuswood transcriptome analysis during tension wood formation not only provided new clues into the transcriptional regulatory network of genes preferentially expressed in xylem, but also highlighted candidate genes responsible for the genetic and environmentally induced variation of wood quality traits.New Phytologist(2005)doi: 10.1111/j.1469-8137.2005.01396.x© New Phytologist(2005) [ABSTRACT FROM AUTHOR]