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Nitrogen (N) and phosphorus (P) have key roles in leaf metabolism, resulting in a strong coupling of chemical composition traits to metabolic rates in field-based studies. However, in such studies, it is difficult to disentangle the effects of nutrient supply per se on trait-trait relationships., Our study assessed how high and low N (5 mM and 0.4 mM, respectively) and P (1 mM and 2 μM, respectively) supply in 37 species from six plant functional types (PTFs) affected photosynthesis ( A) and respiration ( R) (in darkness and light) in a controlled environment., Low P supply increased scaling exponents (slopes) of area-based log-log A-N or R-N relationships when N supply was not limiting, whereas there was no P effect under low N supply. By contrast, scaling exponents of A-P and R-P relationships were altered by P and N supply. Neither R : A nor light inhibition of leaf R was affected by nutrient supply. Light inhibition was 26% across nutrient treatments; herbaceous species exhibited a lower degree of light inhibition than woody species., Because N and P supply modulates leaf trait−trait relationships, the next generation of terrestrial biosphere models may need to consider how limitations in N and P availability affect trait−trait relationships when predicting carbon exchange. [ABSTRACT FROM AUTHOR]

Two components of root architecture (topology and link lengths) were measured in a group of 13 dicotyledon and eight grass species. under both high and low nutrient supply races. Predictions were made, based on a simulation analysis, that root systems from plants grown in low nutrient conditions and those from plants characteristic of such conditions should have the more herringbone topology (branching principally on math axis) and longer links. Both these predictions were confirmed for the dicots, but data from grasses agreed with the predictions only in terms of geometry (link lengths) and not topology. The ecological character of the species was assessed on the assumption that species of low inherent relative growth rate were characteristic of infertile soils. Taxonomic patterns were also evident, indicating that some variation in root system architecture may be historical rather than adaptive. [ABSTRACT FROM AUTHOR]

One of the most dramatic effects of infection by vesicular-arbuscular mycorrhizal fungi on the physiology of the host plant is an increase in phosphorus absorption. When phosphorus is limiting, the maximum extent to which mycorrhizal infection can improve plant performance is thus predicted to be a function of the phosphorus deficit of the plant, the difference between phosphorus demand and phosphorus supply. Phosphorus demand is defined as the rate of phosphorus absorption that would result in optimum performance of the plant as measured by growth rate, reproduction or fitness. The phosphorus supply is defined as the actual rate of phosphorus absorption under the prevailing conditions. Variation among plant taxa in morphological, physiological or phenological traits which affect either phosphorus demand or phosphorus supply (and thus phosphorus deficit) is predicted to lead to variation in potential response to mycorrhizal infection. The actual response to mycorrhizal infection is predicted to be a function of the increase in phosphorus uptake due to mycorrhizal infection and the phosphorus utilization efficiency of the plant. Demonstrated variability in responsiveness to mycorrhizal infection among plant taxa suggests that mycorrhizal fungi may play an important role in determining the structure of plant communities. Mycorrhizal infection may alter the phosphorus deficit or phosphorus utilization efficiency independently from its direct effect on phosphorus uptake, making the prediction of response to mycorrhizal infection based on the traits of non-mycorrhizal plants quite difficult. For example, infection may at times increase the rate of phosphorus accumulation beyond that which can be currently utilized in growth, reducing the current phosphorus utilization efficiency. Such momentary 'luxury consumption' of phosphorus may, however, serve a storage function and be utilized subsequently, allowing mycorrhizal plants ultimately to outperform non-mycorrhizal plants. [ABSTRACT FROM AUTHOR]

Senecio vulgaris (groundsel), healthy or inoculated with rust (Puccinia lagenophorae), was grown in a nutrient-poor sand-soil mixture amended with a compound fertiliser to provide a range of nutrient regimes. The greatest number of pustules per plant occurred on unamended soil but fertiliser addition increased the sporulating area of each pustule: the leaf area occupied by by pustules was unaffected by nutrient supply. Since total leaf area increased with increasing nutrient supply, the percentage of total area that was infected declined. Plant and root dry weights increased with nutrient supply and decreased with rust infection. Infection also reduced root fresh weight and length, which were little changed by nutrient supply, but reduced leaf area only under the most nutrient-rich conditions. The ratios of root length; leaf area (R:L) and, especially, root: shoot dry weight (R:S) were reduced by infection. Root length per unit root weight was increased by infection when expressed on the basis of dry weight but not on the basis of fresh weight. Conversely, increasing nutrient supply decreased root length: weight only on basis of fresh weight. The concentrations of P and K per unit dry weight were increased in rusted leaves but that of N was unchanged. Because infection increased the dry weight: fresh weight ratio (d. wt: f. wt) of leaves, concentrations of P and K on a fresh weight basis increased by up to 3-fold over those in controls and that of N was also substantially increases. On a dry weight basis, the concentration of N and K, but not P, increased in the roots of rusted plants. However, since d. wt: f. wt of roots was decreased in infected plants, the concentrations of N and K were unchanged on a fresh weight basis and that of P was significantly reduced. Rates of uptake of N, P and K were significantly increased in rusted plants both on the basis of root dry weight and root length. This was attributed to increased 'shoot demand' on each unit of root which, in turn, reflected the decreased R:S and R: L of infected plants. [ABSTRACT FROM AUTHOR]

An experiment was set up in order to investigate semelparity and seed output of Daucus carota L., Linum catharticum L., Picris hieracioides L. and Scabiosa columbaria L. in relation to various levels of nutrient supply. Some plants of Daucus carota and Scabiosa columbaria were found to flower within one growing season, when nutrient supply was at its highest, whereas the other species did not flower. In the second growing season almost all plants receiving a maximum supply of nutrients flowered and produced seeds. In Linum catharticum flowering plants were recorded in all treatments. The reproductive plants of all species died after seed shedding, except those of Picris hieracioides and Scabiosa columbaria under high nutrient conditions which formed lateral shoots. These plants survived and were iteroparous. Seeds produced early in the fruiting period were most numerous and heaviest in the treatments with highest levels of fertilization. In Daucus and Scabiosa a positive linear relationship between seed weight and germination success was found. Thus, the plants grown under the highest nutrient supply conditions showed the highest seed output in all species, although this was less clear in Linum. The significance of these results for the field situation is discussed. [ABSTRACT FROM AUTHOR]

The author offers insights about an article that focused on the significance of transpiratory mass flow of water through soil in moving nutrients to the root surface. The two categories of embryophytes include the poikilohydric and homoiohydric. The major determinant of the fate of absorbed short-wave radiation as energy storage in net photosynthesis and energy dissipation by transpiration is stomata.

One of the most dramatic effects of infection by vesicular-arbuscular mycorrhizal fungi on the physiology of the host plant is an increase in phosphorus absorption. When phosphorus is limiting, the maximum extent to which mycorrhizal infection can improve plant performance is thus predicted to be a function of the phosphorus deficit of the plant, the difference between phosphorus demand and phosphorus supply. Phosphorus demand is defined as the rate of phosphorus absorption that would result in optimum performance of the plant as measured by growth rate, reproduction or fitness. The phosphorus supply is defined as the actual rate of phosphorus absorption under the prevailing conditions. Variation among plant taxa in morphological, physiological or phenological traits which affect either phosphorus demand or phosphorus supply (and thus phosphorus deficit) is predicted to lead to variation in potential response to mycorrhizal infection. The actual response to mycorrhizal infection is predicted to be a function of the increase in phosphorus uptake due to mycorrhizal infection and the phosphorus utilization efficiency of the plant. Demonstrated variability in responsiveness to mycorrhizal infection among plant taxa suggests that mycorrhizal fungi may play an important role in determining the structure of plant communities. Mycorrhizal infection may alter the phosphorus deficit or phosphorus utilization efficiency independently from its direct effect on phosphorus uptake, making the prediction of response to mycorrhizal infection based on the traits of non-mycorrhizal plants quite difficult. For example, infection may at times increase the rate of phosphorus accumulation beyond that which can be currently utilized in growth, reducing the current phosphorus utilization efficiency. Such momentary 'luxury consumption' of phosphorus may, however, serve a storage function and be utilized subsequently, allowing mycorrhizal plants ultimately to outperform non-mycorrhizal plants. CONTENTS Summary 365 I. Introduction 366 II. The concepts of phosphorus supply, phosphorus demand and phosphorus deficit 367 III. Factors which affect phosphorus supply 369 IV. Plant traits which affect phosphorus demand 370 V. Variation in response to mycorrhizal infection 372 VI. The effect of infection on inherent traits which influence phosphorus supply, phosphorus demand or phosphorus utilization efficiency 378 VII. Mycorrhizal effects not related to phosphorus 380 VIII. Conclusions 380 Acknowledgements 381 References 381.