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A method for the combined estimation of caffeine, theophylline and theobromine in plant material is presented. The method involved a chloroform-ammonia extraction, separation of the bases in the chloroform extract by thin layer or paper chromatography and finally estimation of the eluted bases by spectrophotometry. Good recoveries of all three compounds were recorded. The method was used to estimate the level of these compounds in tea, coffee beans and cocoa cotyledons. [ABSTRACT FROM AUTHOR]

Summary: Greenbeards are selfish genetic elements that make their bearers behave either altruistically towards individuals bearing similar greenbeard copies or harmfully towards individuals bearing different copies. They were first proposed by W. D. Hamilton over 50 yr ago, to illustrate that kin selection may operate at the level of single genes. Examples of greenbeards have now been reported in a wide range of taxa, but they remain undocumented in plants. In this paper, we discuss the theoretical likelihood of greenbeard existence in plants. We then question why the greenbeard concept has never been applied to plants and speculate on how hypothetical greenbeards could affect plant–plant interactions. Finally, we point to different research directions to improve our knowledge of greenbeards in plants. [ABSTRACT FROM AUTHOR]

An introduction is presented in which the editor discusses the contribution of former editor-in-chiefs (EiCs) Peter Ayres and Ian Woodward within the issue.

The influence of number of seeds per clump upon germination of Plantago coronopus L. was investigated at different salinity levels on filter paper, sand and soil. These substrates provide both artificial and semi-natural microenvironments for seed germination. On all substrates, germination was positively dependent on clump density and seeds in clumps had a higher tolerance of salinity as reflected in higher germination percentages. Final percentage germination for a given clump size and salinity level depended upon substrate, being far higher on filter paper and sand than on soil, whilst the time required to reach final germination also increased in that order. The possible ecological significance of density-dependent seed germination is discussed. [ABSTRACT FROM AUTHOR]

In a previous paper (Faiz and Weatherley, 1977), evidence was put forward for the development of steep gradients of water potential in the soil surrounding the individual roots of rapidly transpiring plants (perirhizal gradients). In this paper, similar experiments are described in which additional data on the dimensions of the root system, distribution of soil water potentials within the rooting zone and the water potentials of the roots themselves were obtained. It was found with experiments on soil that the surface area of the root system was X 60 the cross-sectional area of the pararhizal pathway (cross-sectional area of the pot) through which water moved to the root zone from the water table below. Since the volume rate of flow through the pen- and pararhizal zones was the same, the velocity of movement up to the individual root was therefore only 1/60 of that through the soil supplying the root system. Under conditions of rapid transpiration, the gradient of water potential in that part of the pararhizal pathway immediately beneath the root zone was found to be about 1 bar cm-1. Thus it would be expected that the perirhizal gradient would be 1/60 of this, i.e. it would be negligibly small. However, the actual perirhizal drop in water potential was found to be about 8 bars through a distance of 0.1 cm, i.e. the gradient was 80 bars cm1. Such a steep gradient would require the hydraulic conductivity of the soil in the perirhizal zones to be 4 orders of magnitude lower than that in the pararhizal pathway. An even greater discrepancy was found with fine sand. The soil within the rooting zone had a somewhat lower water content than that in the pararhizal zone, but it is not thought that this, and some other imponderables which are discussed, could account for this enormous discrepancy. It is concluded that in these experiments, measurable perirhizal gradients were unlikely to develop. [ABSTRACT FROM AUTHOR]

The Scholander-Hammel pressure chamber has been used in thousands of papers to measure osmotic pressure, πc, turgor pressure, Pt, and bulk modulus of elasticity, ε, of leaf cells by pressure-volume ( PV) curve analysis. PV analysis has been questioned in the past., In this paper we use micromechanical analysis of leaf cells to examine the impact on PV curve analysis of negative turgor in living cells ( Pt)., Models predict negative Pt (−0.1 to −1.8 MPa) depending on leaf cell size and shape in agreement with experimental values reported by J. J. Oertli. Modeled PV curves have linear regions even when Pt is quite negative, contrary to the arguments of M.T. Tyree. Negative Pt is totally missed by PV curve analysis and results in large errors in derived πc and Pt but smaller errors in ε., A survey of leaf cell sizes vs habitat (arid, temperate, and rainforest), suggests that the majority of published PV curves result in errors of 0.1-1.8 MPa in derived πc and Pt, whereby the error increases with decreasing cell size. We propose that small cell size in leaves is an ecological adaptation that permits plants to endure negative values of water potential with relatively little water loss. [ABSTRACT FROM AUTHOR]

Methods of growing axenic seedlings infected by vesicular arbuscular mycorrhizal fungi are described, using agar, paper or glass as a support. Two of the techniques are particularly suitable for studying the interaction between the fungus and the host plant, for example the germination of the spore inoculum, hyphal growth around the roots before the symbiosis has been initiated and the early stages of root penetration. [ABSTRACT FROM AUTHOR]

This paper describes the ecology of a coastal alluvial plain at Chichiriviche in northern Venezuela. The area supports a great diversity of plant communities, ranging from mangroves on the seaward edge of the plain to non-halophytic, fresh-water communities on the landward side. Small differences on topography result in a mosaic of saline and less-saline environments . Rainfall is strongly seasonal, causing superficial flooding of the alluvial plain in the rainy season and the creation of a hypersaline substratum during the dry season. As a consequence, much of the plain is devoid on vegetation. Towards the landward side of the plain there are numerous small 'vegetation islands', fringed by halophilic succulent herbs, and made up of deciduous and semi-deciduous shrubs and trees together with non-halophytic CAM plants such as cacti and bromeliads. In subsequent papers the results of ecophysiological studies of these diverse plant species are presented. [ABSTRACT FROM AUTHOR]

The long period covered by this paper probably saw the most drastic changes wrought by man on the plant cover of these islands in the whole of postglacial history. Much of our information about vegetation changes comes from those parts of the country where peats and mires are abundant, which leaves those areas which were the cradle of successive cultural groups largely unrepresented. Sources of environmental evidence are now emerging even from this unpromising background, an important element amongst which are man's own works. The evidence of changes wrought by man may come from non-botanical as well as botanical material. Pollen, charcoal, phytoliths, seeds, mosses, and other macroscopic plant remains may be extracted, but indirect evidence may also be obtained from land snails, insects, bones (including small vertebrates), as well as from preserved soils and land surfaces. In the various environments considered a trend from forest through clearance to pastoral or arable agriculture can usually be demonstrated. These changes may ultimately result in site deterioration on a large scale, the nature of which will depend upon the ecological conditions and the practices at work. In extreme cases peat may form or soil erosion take place. On base-poor soils, soil acidification may become so intense that the land is no longer usable for traditional agriculture and is allowed to degenerate to moorland or heath. In early historic times much degraded land came into use again for hill-grazing, a process which further depauperated both the flora and the soils. [ABSTRACT FROM AUTHOR]

Reproduction was examined in one summer annual (Euphrasia pseudokerneri) and two biennials (Linum catharticum and Gentianella amarella) in chalk grassland, and three dune winter annuals (Erophila verna, Cerastium semidecandrum and Myosotic ramosissima). Gentianella was examined in 1979 to 1981 and all other species in 1980 and 1981, making a total of 13 separate datasets, Plants with one or two fruits had fewer seeds per fruit in all 13 cases. As plant size increased to six to ten fruits, seed number gradually increased. The relationship was similar in 1980 and 1981 for all six species. A 'depauperate' plant was therefore defined as one which produces significantly fewer seeds per fruit than large plants. Field populations of all species averaged less than nine fruits per plant, so that the relationship between seed number and fruit number was important in determining seeds produced per plant. Although this relationship has only been noted in three other species, I interpret five recent papers as suggesting the existence of a similar relationship between fruit number and seed number. I interpret the effect as analogous to the abortion of fruits in plants with many fruits. [ABSTRACT FROM AUTHOR]

The fruit of aonla (Emblica officinalis) remains at rest without growth for a period of 3½ months after setting and resumes growth thereafter. Studies on endogenous gibberellin activity of the fruit and exogenous applications of gibberellin to the fruit at rest suggest that the inability of the fruit to resume growth immediately after setting is not due to gibberellin deficiency. The fruit, when making rapid growth following its rest, contained six gibberellin-like factors active in the lettuce hypocotyl test. Five behaved like gibberellins A1, A3, A4, A7 and A9 in paper, thin-layer and silicic acid : celite column chromatography. [ABSTRACT FROM AUTHOR]

The content of gibberellin-like (GA-like) substances in various parts of young alder (Alnus glutinosa (L.) Gaertn.) plants was estimated by means of the lettuce hypocotyl bioassay. The highest levels of GA-like activity were found in the root nodules, of dormant plants, plants emerging from dormancy, and plants in full leaf. No major differences were found in the roots and leaves of nodulated as opposed to nonnodulated plants, although the stems of nodulated plants did contain lower levels of GA-like activity. The detection of seasonal changes in GA-like activity in root nodules from mature trees was dependent upon the method of chromatography employed. One major peak of biological activity was detected following paper chromatography and no large changes were detected in the level of this component. In contrast, three zones of GA-like activity could be detected after thin layer chromatography (TLC) and there were marked seasonal changes in activity in these three zones. This can be attributed either to changes in levels of the GA-like substances themselves and/or to variations in the amounts of impurities interfering with the response of the bioassay. A number of peaks of GA-like activity were detected by lettuce and rice bioassays following analysis of a large-scale extract on a preparative high performance liquid chromatograph (HPLC). However, both the total number and the identity of the substances responsible for this activity, remain to be determined. [ABSTRACT FROM AUTHOR]

• This paper presents an architectural model of wheat (Triticum aestivum), designed to explain effects of light conditions at the individual leaf level on tillering kinetics. Various model variables, including blade length and curvature, were parameterized for spring wheat, and compared with winter wheat and other Gramineae species.• The architectural model enables simulation of plant properties at the level of individual organs. Parameterization was based on data derived from an outdoor experiment with spring wheat cv. Minaret.• Final organ dimensions of tillers could be modelled using the concept of relative phytomer numbers. Various variables in spring wheat showed marked similarities to winter wheat and other species, suggesting possibilities for a general Gramineae architectural model.• Our descriptive model is suitable for our objective: investigating light effects on tiller behaviour. However, we plan to replace the descriptive modelling solutions by physiological, mechanistic solutions, starting with the localized production and partitioning of assimilates as affected by abiotic growth factors.New Phytologist(2005)doi: 10.1111/j.1469-8137.2005.01337.x© New Phytologist(2005) [ABSTRACT FROM AUTHOR]

• Functional–structural plant models that include detailed mechanistic representation of underlying physiological processes can be expensive to construct and the resulting models can also be extremely complicated. On the other hand, purely empirical models are not able to simulate plant adaptability and response to different conditions. In this paper, we present an intermediate approach to modelling plant function that can simulate plant response without requiring detailed knowledge of underlying physiology.• Plant function is modelled using a‘canonical’ modelling approach, which uses compartment models with flux functions of a standard mathematical form, while plant structure is modelled using L-systems.• Two modelling examples are used to demonstrate that canonical modelling can be used in conjunction with L-systems to create functional–structural plant models where function is represented either in an accurate and descriptive way, or in a more mechanistic and explanatory way.• We conclude that canonical modelling provides a useful, flexible and relatively simple approach to modelling plant function at an intermediate level of abstraction.New Phytologist(2005)doi: 10.1111/j.1469-8137.2005.01330.x© New Phytologist(2005) [ABSTRACT FROM AUTHOR]

• The emergence of a regular phyllochron from the dynamic processes of leaf initiation, leaf elongation and whorl construction suggests causal relationships between leaf elongation and leaf emergence. This paper presents a hypothesis as to how the ontogeny of the growth zone of leaves is triggered by emergence events, and implements it in a dynamic model of leaf elongation.• Two different experiments, presenting two contrasted cases of relationships between leaf emergence and kinetics of leaf elongation, were analysed and interpreted with the model in terms of the functioning of the growth zone.• Analysis of elongation kinetics revealed that the hypothesis allows for several contrasted elongation patterns that were observed, and for a regular phyllochron emerging from the variable dynamic of elongation. The model was able to simulate these patterns, and helped to identify the mechanisms underlying the key points of the analysis.• The hypothesis is not demonstrated, but its coherence and robustness are established, which should inform a renewal of the modelling of leaf elongation in architectural models.New Phytologist(2005)doi: 10.1111/j.1469-8137.2005.01371.x© New Phytologist(2005) [ABSTRACT FROM AUTHOR]

Summary The aim of this paper is to survey the general area of quantitative trait locus (QTL) mapping, and its specific impact on current understanding of plant domestication. Plant domestication is not only of historical interest, but is also of ongoing importance as changing human needs and availability of nonrenewable resources impel continuing (and perhaps even accelerated) investigation of prospective new crops. New genomic tools applied in conjunction with now-established approaches such as QTL mapping are opening new doors into searches for the ‘footprints’ of domestication, and promise to accelerate and streamline the identification of specific genes integral to domestication(s), building on early successes. Better understanding of plant domestication promises to enhance knowledge about the developmental basis of some of the more striking evolutionary events known, to guide efforts to catalog plant biodiversity, and to accelerate progress in improving existing and new crops to sustain humanity. [ABSTRACT FROM AUTHOR]

If metal tolerant plants, by virtue of their tolerance mechanism, are less efficient at the uptake, distribution or utilization of metals then essential micronutrient deficiency may occur at the low levels of metal supply found on non-mine soils. This argument forms the basis of the metal requirement hypothesis put forward to explain the lower fitness of tolerant individuals on uncontaminated soil, the so called 'cost of tolerance;. In this paper, copper balance was investigated in Mimulus guttatus Fischer ex. DC (the yellow monkey flower) for plants with or without the major tolerance gene which confers primary tolerance, and plants with few or many modifier genes which control degree of tolerance. No conclusive evidence to support an increased copper requirement in plants with the major tolerance gene, and/or may modifier genes was shown. Any differences in copper requirement found during vegetative growth were small, and were deemed insufficient to explain the apparent cost of tolerance. [ABSTRACT FROM AUTHOR]

This paper describes the effects of the fungicides Benlate, Aliette and Ridomil on plant growth and on mycorrhizal development in onion plants. An attempt was made to distinguish effects on plants from those on the fungus by making comparisons between mycorrhizal plants in the absence of added phosphorus and non-mycorrhizal equivalent size plants. Vital staining techniques were used to analyse the effects of the fungicides on the living fungus both within the root and in the soil. Benlate had no effect on shoot dry weight or root length of onion plants whereas a reduction in plant growth was observed following the application of Aliette or Ridomil, in comparison to control plants. Benlate had negative effects on the num,bers of living internal hyphe, arbuscules, fungal plant interface and living external hyphae in the soil. Aliette had no effect on the number of living intercellular hyphae and arbuscules. However, it markedly reduced the root length and the length of infected root per plant. There length of external hyphae per gram of soil was reduced following the application of aliette, though not as severely as with Benlate. Ridomil had more complex effects on vesicular-arbuscular mycorrhizal symbiosis; treated plants showed a reduction in plant growth and also reduction in all fungal parameters, namely the number of living intercellular hyphae, arbuscules and fungal-plant interface, the length of infested root and the development of external hyphae in the soil. [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]

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]

Incompatibility is a common means of controlling breeding behaviour among plants, and has been an important factor in evolution. It acts to prevent self-fertilization, as well as to prevent sterilization of ovules by foreign pollen. Angiosperms have both inter- and intraspecific incompatibility, and these are controlled by the same S gene complex. Gymnosperms, however, have only interspecific incompatibility. Observations on incompatibility behaviour in flowering plants have suggested that interspecific incompatibility evolved first among gymnosperms or progymnosperms as a means of protecting their naked ovules from foreign pollen. Duplication and redifferentiation of this 'primary specificity' gene in angiosperm precursors subsequently gave rise to 'secondary specificity' controlling intraspecific incompatibility. Today there are three basic types of incompatibility found among the angiosperms: (i) inherently independent control--each allele independently expresses its individual specificity, shows allelic interaction in the pollen after S gene duplication; (ii) inherently complementary control--alleles of two or more incompatibility loci co-operate to produce a single specificity, shows no allelic interaction; and (iii) late complementary control--alleles of two or more incompatibility loci co-operate to produce a single specificity, shows allelic interaction. The pattern of distribution of these three types of control has given rise to a controversy over which represents the most primitive type of angiosperm incompatibility. The present paper examines the factors involved in secondary evolution of incompatibility, and concludes that independent control is in fact more primitive. Complementary control probably developed secondarily and independently several times during angiosperm evolution, the first occurrence. [ABSTRACT FROM AUTHOR]

Having the right neighbors: how tree species diversity modulates drought impacts on forests. Carbon, drought, experiments, models, plants, water Keywords: carbon; drought; experiments; models; plants; water EN carbon drought experiments models plants water 18 19 2 06/06/22 20220701 NES 220701 What inspired your interest in plant science?. [Extracted from the article]

The article discusses the views of the authors on a research paper about the phenotypic selection on floral traits. They emphasize that the results of the study will inspire others to make similar investigations with other model systems in pollination biology. They stress that the researchers use a logical framework in analyzing floral scent. They also assert that the paper can serve as a basis in understanding natural selection on floral scent traits.

Summary: Telomere length has been implicated in the organismal response to stress, but the underlying mechanisms are unknown.Here we examine the impact of telomere length changes on the responses to three contrasting abiotic environments in Arabidopsis, and measure 32 fitness, developmental, physiological and leaf‐level anatomical traits.We report that telomere length in wild‐type and short‐telomere mutants is resistant to abiotic stress, while the elongated telomeres in ku70 mutants are more plastic. We detected significant pleiotropic effects of telomere length on flowering time and key leaf physiological and anatomical traits. Furthermore, our data reveal a significant genotype by environment (G × E) interaction for reproductive fitness, with the benefits and costs to performance depending on the growth conditions.These results imply that life‐history trade‐offs between flowering time and reproductive fitness are impacted by telomere length variation. We postulate that telomere length in plants is subject to natural selection imposed by different environments. [ABSTRACT FROM AUTHOR]

Summary: Many plant species simultaneously interact with multiple symbionts, which can, but do not always, generate synergistic benefits for their host. We ask if plant life history (i.e. annual vs perennial) can play an important role in the outcomes of the tripartite symbiosis of legumes, arbuscular mycorrhizal fungi (AMF), and rhizobia.We performed a meta‐analysis of 88 studies examining outcomes of legume–AMF–rhizobia interactions on plant and microbial growth.Perennial legumes associating with AMF and rhizobia grew larger than expected based on their response to either symbiont alone (i.e. their response to co‐inoculation was synergistic). By contrast, annual legume growth with co‐inoculation did not differ from additive expectations. AMF and rhizobia differentially increased phosphorus (P) and nitrogen (N) tissue concentration. Rhizobium nodulation increased with mycorrhizal fungi inoculation, but mycorrhizal fungi colonization did not increase with rhizobium inoculation. Microbial responses to co‐infection were significantly correlated with synergisms in plant growth.Our work supports a balanced plant stoichiometry mechanism for synergistic benefits. We find that synergisms are in part driven by reinvestment in complementary symbionts, and that time‐lags in realizing benefits of reinvestment may limit synergisms in annuals. Optimization of microbiome composition to maximize synergisms may be critical to productivity, particularly for perennial legumes. [ABSTRACT FROM AUTHOR]

Clastogens, Cyperaceae, Paleozoic terrestrialisation, Poaceae, ultraviolet radiation, holocentric chromosomes, vegetation plots Keywords: clastogens; Cyperaceae; holocentric chromosomes; Paleozoic terrestrialisation; Poaceae; ultraviolet radiation; vegetation plots EN clastogens Cyperaceae holocentric chromosomes Paleozoic terrestrialisation Poaceae ultraviolet radiation vegetation plots 15 21 7 12/06/21 20220101 NES 220101 Acknowledgements We are indebted to Alois Schmalwieser who kindly provided the UV-B data from Verdebout (2004a). Assigning a UV-B dose to each vegetation plot UV-B doses were taken from the dataset of satellite-derived UV radiation climatology over Europe that was prepared to support UV-impact studies (Verdebout, 2004a,b). Therefore, to assess the effect of UV-B on the relative competitiveness of holocentric cyperids and monocentric grasses, we analysed the change in their relative cover in 291 883 vegetation plots across a fine-grained UV-B gradient spanning all of Europe (Fig. [Extracted from the article]

Summary: Plant–pollinator interactions provide a natural experiment in signal evolution. Flowers are known to have evolved colour signals that maximise their ease of detection by the visual systems of important pollinators such as bees. Whilst most angiosperms are bee pollinated, our understanding on how the second largest group of pollinating insects, flies, may influence flower colour evolution is limited to the use of categorical models of colour discrimination that do not reflect the small colour differences commonly observed between and within flower species. Here we show by comparing flower signals that occur in different environments including total absence of bees, a mixture of bee and fly pollination within one plant family (Orchidaceae) from a single community, and typical flowers from a broad taxonomic sampling of the same geographic region, that perceptually different colours, empirically measured, do evolve in response to different types of insect pollinators. We show evidence of both convergence among fly‐pollinated floral colours but also of divergence and displacement of colour signals in the absence of bee pollinators. Our findings give an insight into how both ecological and agricultural systems may be affected by changes in pollinator distributions around the world. [ABSTRACT FROM AUTHOR]

Summary: Florivory is an ancient interaction which has rarely been quantified due to a lack of standardized protocols, thus impairing biogeographical and phylogenetic comparisons. We created a global, continuously updated, open‐access database comprising 180 species and 64 families to compare floral damage between tropical and temperate plants, to examine the effects of plant traits on floral damage, and to explore the eco‐evolutionary dynamics of flower–florivore interactions. Flower damage is widespread across angiosperms, but was two‐fold higher in tropical vs temperate species, suggesting stronger fitness impacts in the tropics. Flowers were mostly damaged by chewers, but neither flower color nor symmetry explained differences in florivory. Herbivory and florivory levels were positively correlated within species, even though the richness of the florivore community does not affect florivory levels. We show that florivory impacts plant fitness via multiple pathways and that ignoring this interaction makes it more difficult to obtain a broad understanding of the ecology and evolution of angiosperms. Finally, we propose a standardized protocol for florivory measurements, and identify key research avenues that will help fill persistent knowledge gaps. Florivory is expected to be a central research topic in an epoch characterized by widespread decreases in insect populations that comprise both pollinators and florivores. [ABSTRACT FROM AUTHOR]

The plant kingdom has elaborated several conducting systems. Three are primarily for mass transport: the aerenchyma (for gas exchange in submerged parts), the phloem (for exchange of nutrients within the plant), and the xylem (largely for transport of water from soil to transpiring leaves). Two others are believed to be primarily defensive and to store under pressure aversive contents which they exude when punctured: the laticifer and the secretory duct. This review provides for the latter two systems the highlights of what is known about their general physiology and ecophysiology but not their metabolism and their molecular biology. It is argued that, given the importance of laticifers and secretory ducts to plant defense against insect herbivory, these structures are under-investigated and deserve more intensive study. [ABSTRACT FROM AUTHOR]

Summary: The formation of Casparian strips (CS) and the deposition of suberin at the endodermis of plant roots are thought to limit the apoplastic transport of water and ions. We investigated the specific role of each of these apoplastic barriers in the control of hydro‐mineral transport by roots and the consequences on shoot growth.A collection of Arabidopsis thaliana mutants defective in suberin deposition and/or CS development was characterized under standard conditions using a hydroponic system and the Phenopsis platform.Mutants altered in suberin deposition had enhanced root hydraulic conductivity, indicating a restrictive role for this compound in water transport. In contrast, defective CS directly increased solute leakage and indirectly reduced root hydraulic conductivity. Defective CS also led to a reduction in rosette growth, which was partly dependent on the hydro‐mineral status of the plant. Ectopic suberin was shown to partially compensate for defective CS phenotypes.Altogether, our work shows that the functionality of the root apoplastic diffusion barriers greatly influences the plant physiology, and that their integrity is tightly surveyed. [ABSTRACT FROM AUTHOR]

The article presents the author's comments on the study "Author inflation masks global capacity for species discovery in flowering plants," by D.P. Bebber, which appears in the current issue. The author says that the study has put efforts to determine whether the pace of plant species discovery has truly accelerated, whether the number of authors associated with species descriptions has increased, and what this all may mean. Data has been taken from the International Plant Names Index (IPNI).

Summary: Learning from living organisms has emerged from a mainly curiosity‐driven examination, where helpful functions of biological structures have been copied, into systematic biomimetic approaches that transfer a targeted function and its underlying principles from the biological model to a technical product. Plant biomimetics is based on functional morphology, which combines the knowledge gained from the morphology, anatomy and mechanics of plants and makes a statement about their form–structure–function relationship. Since the functional morphology of plants has become key to biomimetic applications, we present its central role in deciphering the functional principles that can be applied to engineering solutions. We consider that the future of biomimetics will include bioinspired developments that will contribute to better sustainability than that achieved by conventional products. [ABSTRACT FROM AUTHOR]

Summary: Cell division in plants is particularly important as cells cannot rearrange. It therefore determines the arrangement of cells (topology) and their size and shape (geometry). Cell division reduces mechanical stress locally by producing smaller cells and alters mechanical properties by reinforcing the mechanical wall network, both of which can alter overall tissue morphology. Division orientation is often regarded as following geometric rules, however recent work has suggested that divisions align with the direction of maximal tensile stress. Mechanical stress has already been shown to feed into many processes of development including those that alter mechanical properties. Such an alignment may enable cell division to selectively reinforce the cell wall network in the direction of maximal tensile stress. Therefore there exists potential feedback between cell division, mechanical stress and growth. Improving our understanding of this topic will help to shed light on the debated role of cell division in organ scale growth. [ABSTRACT FROM AUTHOR]

A recent re-analysis of the data of Salisbury (1974) claims his data do not support the hypothesis that seeds of species from shaded habitats are heavier than those from unshaded habitats, partly because the original analysis was inappropriate and partly because of bias in the dataset. We show first that the re-analysis itself contains errors, and second that the charge of bias is based largely on a misunderstanding. We also show that analysis of a larger dataset, drawn from Salisbury (1942) and from Salisbury (1974), provides convincing support for the hypothesis and suggests that the relationship is independent of life history. [ABSTRACT FROM AUTHOR]

When isolated maize (Zea mays L.) roots were incubated for 3 h in a fully hydrated state in air, ABA content was found to increase by around 100% in all the different root tissues examined -- i.e. mature primary root sections, young and growing primary root sections, secondary roots and primary root tips - from both well watered plants and previously droughted plants. This ABA increase was not turgor-related, as usually is the case in droughted plants, and was not quantitatively related to the injury on the cutting surface. A time sequence of ABA accumulation showed a peak accumulation at about 2-3 h after initial incubation. Oxygen was essential for this increase in ABA accumulation because when roots were incubated in pure nitrogen, no such increase was found. Evidence suggests that this increase was derived from xanthophylls, the common precursors for stress-induced ABA. Maize leaves did not show such an accumulation when incubated under the same conditions. When half the root system was severed, ABA content in the remaining half rout system increased by 100-200% in 3 h. We suggest that there is a systemic effect on the ABA biosynthesis in the root system following the shock of root severing, and that roots may supply substantial amounts of ABA to the shoots even at time when there is no apparent dehydration. [ABSTRACT FROM AUTHOR]

N and P, especially when added together, significantly enhanced CO2 assimilation rate in four moss specie from a range of habitats on sub-Antarctic Marion Island. NO3- always caused a greater increase in assimilation rate than did NH4+, but this might have been due to Cl- added with the NH4+. Possibly for the same reason, K+ addition (as KCl) in some cases depressed CO2 assimilation rate compared with the controls (tapwater addition), as did K + N or K + P compared with N or P alone. The degree to which the mosses were apparently sensitive to Cl- was related to their tissue water content and to the soil water content in the habitats in which they occur. The results are discussed in the context of extremely low levels of available soil nutrients in, and small precipitation inputs of nutrients to, plant communities predominated by bryophytes on the island. [ABSTRACT FROM AUTHOR]

Fresh seed derived from a Mediterranean population of non-radiate Senecio vulgaris L. showed strong innate dormancy over a wide temperature range. In contrast, fresh seed of British S. vulgaris exhibited > 80% germination at 20 °C. Dormancy in Mediterranean seed was overcome by: prolonged storage at 15 °C and above; a short stratification treatment (2 wk at 4 °C); prolonged leaching with water; treatment with gibberellic acid (GA3) alone (and with kinetin); and to a lesser extent, by wounding (i.e. removal of a small portion of the fruit and seed coat). A petroleum ether extract from fresh Mediterranean seed strongly inhibited the germination of previously non-dormant seed (of British origin). This implies that dormancy may be caused by an inhibitor present in the embryo or seed coat which might act by preventing the synthesis or liberation of gibberellins required for germination. The innate dormancy exhibited by seed of non-radiate Mediterranean S. vulgaris, enables the species to adopt a winter annual life cycle which is typical of Mediterranean ephemerals. [ABSTRACT FROM AUTHOR]

The response of two populations of Bromus sterilis L. seed to light at 15°C was studied over 12 months when seeds were stored at different temperatures. White and red light inhibited the germination of both collections of seed, inhibition persisting for longer periods at low (4°C) than at high (23 °C) temperatures. The two populations of seed behaved similarly in their response to all light treatments. [ABSTRACT FROM AUTHOR]

Light and electron microscopy have been used to study the changes that accompany germination in the spores of Gigaspora margarita. Regular germination is achieved following surface sterilization of the spores and the possible role played by sodium hypochlorite in spore activation is discussed. Following spore activation there is considerable redistribution of cytoplasm with a subsequent accumulation of cytoplasmic and wall material in the region of the bulbous-shaped attachment. Germ-tube development occurs in this region without the production of peripheral compartments that have been described for other spore types. The possible significance of this feature and the mode of germ-tube wall development are discussed. [ABSTRACT FROM AUTHOR]

Analysis of root nodules of Alnus glutinosa sampled in a natural alder vegetation revealed two types, one containing clumps of endophytic spores and one without spores. The distribution pattern of both types, but especially the latter, showed considerable clustering. Both types of nodule sometimes occurred on the same tree, and some information on the dynamics of the distribution pattern was obtained from age analysis of nodules of both types. Since cross-inoculation experiments showed a genetic basis for the presence or absence of spores in root nodules, the existence of two endophytic strains differing in their ability to produce spores seems likely, Different concentrations of ammonium and nitrate incorporated into the nutrient solution of nodulated test plants had only a slight influence on spore-clump abundance in root nodules, and complete inversion of the spore type was not observed. Attempts to find additional strain differences led to the comparison of isomers of diamino-pimelic acid (DAP) from the cell wall of both types of endophyte, DAP isomer analysis of genetically more distinct `Alnus-type' root nodules, i.e. those of Myrica gale and Hippophae rhamnoides, were used as reference. No additional taxonomic differences were found between the nodule types in Alnus glutinosa, but spore-free nodules of Hippophae rhamnoides and Myrica gale differed with respect to the DAP isomer composition. Test plants of Alnus glutinosa provided artificially with either spore-rich or spore-free nodules did not differ significantly in acetylene reduction rate. [ABSTRACT FROM AUTHOR]

The number of roots induced by indolebutyric acid (IBA) in cuttings of light-grown seedlings of Phaseolus aureus Roxb. is greatly inhibited by high levels of ethanol. When supplied alone to cuttings of dark-grown seedlings increasing concentrations of ethanol progressively reduce the number of roots. The ethanol is glycosylated, at least in part, to ethyl-β-glucoside which reaches concentrations several-fold greater in cuttings of light-grown seedlings compared to those of dark-grown seedlings. In the hypocotyl of cuttings from light-grown seedlings the glucoside constitutes 26% of the extracted sugar and 1100 μg/g fresh weight after a treatment of 18 h with 2 ml/l ethanol. [ABSTRACT FROM AUTHOR]

Thalli of four saxicolous lichens on slate rock fragments were transplanted from rock surfaces to horizontal boards and then to south-east-facing and north-west-facing rock surfaces. The radial growth rate of Physcia orbicularis and Parmelia conspersa thalli declined after transplantation to north-west-facing rock surfaces and was unchanged after transplantation to south-east-facing rock surfaces compared with growth rate on the boards. The radial growth rate of P. glabratula ssp. fuliginosa thalli declined after transplantation to south-east-facing rock surfaces and was unchanged after transplantation to north-west-facing rock surfaces compared with growth rate on the boards. The radial growth rate of P. saxatilis thalli was similar on the horizontal boards, south-east-facing and north-west-facing rock surfaces. Those results are discussed in relation to the aspect distributions of the four lichens in South Gwynedd, Wales. [ABSTRACT FROM AUTHOR]

The pattern of distribution of labelled assimilate, and the amounts exported from a source leaf, have been investigated in eleven species of plants growing in a potassium-deficient mediums Comparison with the same parameters for plants growing with full nutrient complement showed no detectable differences in either the pattern or quantity of photosynthate that was translocated. [ABSTRACT FROM AUTHOR]

A method for the collection and analysis of free amino acids in very small quantities of nectar is described. By dansylation and three-system polyamide chromatography individual amino acids may be detected at concentrations as low as 10 pmoles per μl. This has been used for the identification of constellations of acids present in floral nectar from species and hybrids of Aloë, Oxalis, Silene, Cercidium and Armeria. Almost without exception, nectars of F[SUB1] hybrids contain all of the amino acids found in the nectars of both parents combined. The usefulness of this 'additiveness' in tracing the phylogeny of groups of species in which allopolyploidy and auto-polyploidy may have played a role is illustrated by analyses of nectars from species of Geranium (section Ruberta). Also the value of nectar amino acid analyses in the investigation of introgressive hybridization is illustrated by studies of Aquilegia and Penstemon in the Sierra Nevada of California. The constancy of the amino acid patterns in parental species contrasts with the recombination patterns in the hybrid swarms. Finally, it is suggested that nectar amino acid patterns are as useful chemotaxonomically as other groups of plant chemicals and should be utilized accordingly. [ABSTRACT FROM AUTHOR]

The growth rates of thalli of foliose saxicolous lichens before and after the linear phase of growth were measured in 1973. Changes in the radial growth rate (measured as mm/year) with thallus size in the prelinear phase (thalli less than approximately 1.5 cm in diameter) were consistent with the hypothesis that early growth of these lichens is logarithmic. When growth in the prelinear phase was measured as a relative growth rate (measured as cm[SUP2]/cm[SUP2]/year) there was a rapid rise in growth rate until about 3 mm thallus diameter and then a decline in growth rate. The radial growth rate of non-fragmenting thalli when compared with fragmenting thalli at different stages of fragmentation suggested that the radial growth rate does not significantly decline after fragmentation of the thallus. This result is not consistent with a postlinear phase in the radial growth of a lichen thallus. [ABSTRACT FROM AUTHOR]

The effect of phosphorus deficiency on the transpiration of Arctium minus was investigated. The transpiration rate of the phosphorus-deficient plants was lower than that of the controls. This situation was reversed after wilting which depressed the transpiration rate of the control plants. The ratio of light to dark transpiration was higher in the control plants, and covering the abaxial surface of their leaves with petroleum jelly caused a proportionately greater reduction in their rate of transpiration. The leaves of the deficient plants were composed of smaller cells than those of the controls. An examination of leaf surfaces showed that those of the deficient plants were covered by a much denser layer of hairs. It was concluded that the difference in the rate of transpiration was probably connected with stomatal functioning. [ABSTRACT FROM AUTHOR]

The ultrastructure of mature guard cells of Phaseolus vulgaris L. grown under continuous light régime showed remarkable stability, remaining constant in appearance under a wide range of conditions of nutrient deficiency. The ultrastructure was quite unlike that of leaf parenchyma cells of normal plants, but had certain characteristics similar to those found in palisade parenchyma cells suffering from magnesium and potassium deficiency. [ABSTRACT FROM AUTHOR]

Young plants of the wilty tomato mutant, flacea, in which the stomata resist closure, were sprayed with abscisic acid eight times over a period of 24 hours in light and darkness. The hormone induced closure of stomata similarly in leaves treated either in light or in darkness. Abscisic add does not appear to induce stomatal closure in darkness by increasing the internal CO2 concentration in the leaf, since this concentration should already be very high in darkness. A considerable and rapid decrease of CO2 assimilation and increase of CO2 evolution were demonstrated in mutant as well as in normal plants transferred from light to darkness. [ABSTRACT FROM AUTHOR]

Most of the requirements of roots for oxygen were met by oxygen from the air entering the leaves and travelling through the plants to the roots in oxygen-free media. The amount of oxygen supplied in this way decreased proportionately with rise in oxygen partial pressure at the root surface. Although roots offered a considerable barrier to the passage of oxygen out of them, experiments in which transport from the aerial parts was prevented indicated that the roots could obtain almost all the oxygen they required from the surrounding media provided the oxygen partial pressure at the root surface exceeded the low value of 0.05 atmospheres. These results were obtained by means of a new experimental technique which enabled the effect of oxygen partial pressure at the root surfaces on oxygen uptake and root elongation to be studied. It was based on circulating a small volume of nutrient solution around roots in a gas-free enclosed system sufficiently rapidly for the partial pressure in the solution to be almost the same as at the root surfaces. [ABSTRACT FROM AUTHOR]

Discusses issues tackled in a conference on impact of soil microbes on plant population dynamics and productivity at Helsinki, Finland in June 2002. Usefulness and safety of genetic modification of plants and microorganisms; Issues on mutualistic symbioses; Nutrient turnover and acquisition in plants.