Proximate factors influencing egg cannibalism in the land snail Arianta arbustorum (Pulmonata,Helicidae)

Summary Byttneria aculeata (Sterculiaceae), a subcanopy liane with a shrubby juvenile form has two distinct leaf color morphs in juvenile plants- a given juvenile has plain green leaves or leaves with whitish variegation. Both forms occur together in the forest and in clearings; however, the variegated morph is more common in open sites, and the plain morph predominates in the forest. Percent variegation per leaf for variegated plants increased from closed to open sites. Measurements of growth support the idea that variegation is favored in open habitats. Within a given habitat, rate of herbivory by leaf miners on a given morph increases with increasing relative frequency of that morph; however, at a given relative frequency, the variegated morph is less heavily attacked than is the plain morph when it occurs elsewhere at that same frequency.     

The effects of leaf size,leaf habit,and leaf form on leaf/stem relationships in plant twigs of temperate woody species

Question: Do thick‐twigged/large‐leaf species have an advantage in leaf display over their counterparts, and what are the effects of leaf habit and leaf form on the leaf‐stem relationship in plant twigs of temperature broadleaf woody species? Location: Gongga Mountain, southwest China. Methods: (1) We investigated stem cross‐sectional area and stem mass, leaf area and leaf/lamina mass of plant twigs (terminal branches of current‐year shoots) of 89 species belonging to 55 genera in 31 families. (2) Data were analyzed to determine leaf‐stem scaling relationships using both the Model type II regression method and the phylogenetically independent comparative (PIC) method. Results: (1) Significant, positive allometric relationships were found between twig cross‐sectional area and total leaf area supported by the twig, and between the cross‐sectional area and individual leaf area, suggesting that species with large leaves and thick twigs could support a disproportionately greater leaf area for a given twig cross‐sectional area. (2) However, the scaling relationships between twig stem mass and total leaf area and between stem mass and total lamina mass were approximately isometric, which indicates that the efficiency of deploying leaf area and lamina mass was independent of leaf size and twig size. The results of PIC were consistent with these correlations. (3) The evergreen species were usually smaller in total leaf area for a given twig stem investment in terms of both cross‐sectional area and stem mass, compared to deciduous species. Leaf mass per area (LMA) was negatively associated with the stem efficiency in deploying leaf area. (4) Compound leaf species could usually support a larger leaf area for a given twig stem mass and were usually larger in both leaf size and twig size than simple leaf species. Conclusions: Generally, thick‐twigged/large‐leaf species do not have an advantage over their counterparts in deploying photosynthetic compartments for a given twig stem investment. Leaf habit and leaf form types can modify leaf‐stem scaling relationships, possibly because of contrasting leaf properties. The leaf size‐twig size spectrum is related to the LMA‐leaf life span dimension of plant life history strategies.     

An integrating sphere leaf chamber

Abstract. A combination of an optical integrating sphere and leaf chamber is described, and some principles of its design are given. It is shown that the number of quanta absorbed by the leaf inside the sphere can be found from measurements of the quantum flux density inside the sphere with and without the leaf present, when certain constant parameters of the sphere are known. Methods for finding these are given. It is not necessary to know leaf area or absorptivity for the quantum yield for photosynthesis to be derived from additional measurement of CO₂, fixation.     

桃(Prunus persica)种质资源物候期性状遗传多样性的评价指标探讨

本试验对桃（Prunus persica）的301～480份种质资源的需冷量、始花期、大量落叶开始期、大量落叶终止期、果实生育期、营养生长期6个性状的遗传多样性进行了统计分析,根据性状在不同区问的频率分布,提出我国桃种质资源物候期性状评价系统的数值分级指标和参照品种,为我国桃种质资源描述系统的数量化、规范化奠定基础。     

The effects of different external nitrate concentrations on growth of Avena sativa cv. Amuri treated with diclofop-methyl

Avena sativa cv. Amuri fed either low or high nitrate was sprayed with diclofop-methyl (1 kg a.i. ha^-1) at the three leaf stage. The short term effects of the herbicide on chlorophyll concentration of leaves (laminae) and short and long term effects on d.wt of the component plant parts were determined by comparison with unsprayed plants. For unsprayed and sprayed plants, total leaf d.wt approximately doubled during the first twelve days after commencing treatments. Growth was substantially greater at high nitrate than low nitrate. For unsprayed plants, the increase in total leaf d.wt was due primarily to growth of leaf 3 but for sprayed plants it was due to growth of leaves 1 and 2. Twelve days after commencing treatments, d.wt of leaves 1 and 2 was substantially greater for sprayed plants than for unsprayed plants given similar nitrate, while chlorophyll concentration was substantially less. Leaf 3 d.wt and chlorophyll concentration were substantially greater in unsprayed plants than in sprayed plants given similar nitrate. For unsprayed plants, values were greater at high nitrate than low nitrate, for sprayed plants the converse was the case. Forty nine days after commencing treatments, unsprayed plants had a greater total plant d.wt than sprayed plants given similar nitrate. Total plant d.wt for unsprayed plants was greater at high nitrate than low nitrate, the opposite was the case for sprayed plants. Unsprayed plants at both nitrate levels and sprayed plants given low nitrate produced seed heads but sprayed plants given high nitrate did not. Diclofop-methyl at a rate of 0.3 kg a.i. ha^-' stopped seed head production at high nitrate. Retention and uptake of diclofop-methyl were not significantly different at low and high nitrate. At 1 kg a.i. ha-^l diclofop-methyl, plants switched from low to high nitrate at spraying showed damage similar to that shown by plants given high nitrate throughout. Addition of 200 μg GA into the leaf sheaths two days prior to spraying increased the efficacy of diclofop-methyl at low nitrate. It is proposed that increased efficiency of diclofop-methyl at high nitrate is due to increased leaf damage caused by a greater rate of leaf expansion.     

Individual leaf development in Arabidopsis thaliana: a stable thermal-time-based programme

In crop species, the impact of temperature on plant development is classically modelled using thermal time. We examined whether this method could be used in a non-crop species, Arabidopsis thaliana, to analyse the response to temperature of leaf initiation rate and of the development of two leaves of the rosette. The results confirmed the large plant-to-plant variability in the studied isogenic line of the Columbia ecotype: 100-fold differences in leaf area among plants sown on the same date were commonly observed at a given date. These differences disappeared in mature leaves, suggesting that they were due to a variability in plant developmental stage. The whole population could therefore be represented by any group of synchronous plants labelled at the two-leaf stage and followed during their development. Leaf initiation rate, duration of leaf expansion and maximal relative leaf expansion rate varied considerably among experiments performed at different temperatures (from 6 to 26 degrees C) but they were linearly related to temperature in the range 6-26 degrees C, with a common x-intercept of 3 degrees C. Expressing time in thermal time with a threshold temperature of 3 degrees C unified the time courses of leaf initiation and of individual leaf development for plants grown at different temperatures and experimental conditions. The two leaves studied (leaf 2 and leaf 6) had a two-phase development, with an exponential phase followed by a phase with decreasing relative elongation rate. Both phases had constant durations for a given leaf position if expressed in thermal time. Changes in temperature caused changes in both the rate of development and in the expansion rate which mutually compensated such that they had no consequence on leaf area at a given thermal time. The resulting model of leaf development was applied to ten experiments carried out in a glasshouse or in a growth chamber, with plants grown in soil or hydroponically. Because it predicts accurately the stage of development and the relative expansion rate of any leaf of the rosette, this model facilitates precise planning of sampling procedures and the comparison of treatments in growth analyses.     

Influence of Rate of Development of Leaf Water Deficits upon Photosynthesis, Leaf Conductance, Water Use Efficiency, and Osmotic Potential in Sorghum

This study reports the effect of rate of development of leaf water deficits in soil-grown sorghum (Sorghum bicolor) on the relationship of net photosynthesis, leaf conductance, and water use efficiency to leaf water potential, and on the degree of solute accumulation (osmotic adjustment). Recovery of these processes on rewatering, and responses during a second stress cycle were also studied. The most rapid rate of stress (1.2 MPa day^?1) resulted in no solute accumulation and the lowest rate of net photosynthesis and leaf conductance for any given leaf water potential during stress. Stress at 0.7 and 0.15 MPa day^?1 led to equal solute accumulations of approximately 0.6 MPa, but net photosynthesis, leaf conductance, and water use efficiency at a given leaf water potential were lower with the faster rate of stress (0.7 MPa day^?1). Additionally, leaf conductance at a given leaf turgor potential was lowest at the 1.2 MPa day^?1 stress rate, slightly higher at the intermediate rate of stress, and clearly highest at the slowest rate of stress. Recovery of both net photosynthesis and leaf conductance upon rewatering was rapid, taking less than 3 days, but full recovery of osmotic potential took between 6 and 11 days. One slow stress cycle had no influence on relationships during a second cycle. The concept of a threshold leaf water potential for stomatal closure is discussed and the conclusion reached that stomatal closure occurs slowly over a wide range of leaf water potential (> 1.0 MPa), the range being greater for slower rates of stress.     

Factors' governing ingestion by the earthworm Lumbricus terrestris (L.), with special reference to apple leaves

Captive worms fed little on fresh apple leaves, but did so readily after the leaves had been leached in water. This was due to their being soft and easy to fragment and not to loss of unpalatable substances during the leaching process. A simple apparatus to measure leaf texture is described. Worm feeding rates were similar for leaves of similar texture but of different phenolic content. Filter paper was accepted as food. The addition of leaf leachates to filter paper disks increased feeding rates, so did added bacterial cells. The part played by leaf micro-organisms in the nutrition of worms and their effect on leaf texture is discussed. Unsoftened leaf material was readily eaten provided it was small enough to be swallowed whole. Leaves from various aromatic plants were eaten by starved worms, but rejected by well-fed ones. Starved worms given aromatic leaf material together with apple leaf preferred the latter. Various unusual materials were eaten, but polyester foam was accepted only when coated with bacterial cells. Responses to chemical as well as to tactile stimuli seem to be involved.     

Least-cost input mixtures of water and nitrogen for photosynthesis

In microeconomics, a standard framework is used for determining the optimal input mix for a two-input production process. Here we adapt this framework for understanding the way plants use water and nitrogen (N) in photosynthesis. The least-cost input mixture for generating a given output depends on the relative cost of procuring and using nitrogen versus water. This way of considering the issue integrates concepts such as water-use efficiency and photosynthetic nitrogen-use efficiency into the more inclusive objective of optimizing the input mix for a given situation. We explore the implications of deploying alternative combinations of leaf nitrogen concentration and stomatal conductance to water, focusing on comparing hypothetical species occurring in low- versus high-humidity habitats. We then present data from sites in both the United States and Australia and show that low-rainfall species operate with substantially higher leaf N concentration per unit leaf area. The extra protein reflected in higher leaf N concentration is associated with a greater drawdown of internal CO2, such that low-rainfall species achieve higher photosynthetic rates at a given stomatal conductance. This restraint of transpirational water use apparently counterbalances the multiple costs of deploying high-nitrogen leaves.     

Combined impacts of irradiance and dehydration on leaf hydraulic conductance: insights into vulnerability and stomatal control

The leaf is a hydraulic bottleneck, accounting for a large part of plant resistance. Thus, the leaf hydraulic conductance (K(leaf) ) is of key importance in determining stomatal conductance (g(s) ) and rates of gas exchange. Previous studies showed that K(leaf) is dynamic with leaf water status and irradiance. For four species, we tested the combined impacts of these factors on K(leaf) and on g(s) . We determined responses of K(leaf) and g(s) to declining leaf water potential (Ψ(leaf) ) under low and high irradiance (<6 and >900 μmol photons m(-2) s(-1) photosynthetically active radiation, respectively). We hypothesized greater K(leaf) vulnerability under high irradiance. We also hypothesized that K(leaf) and g(s) would be similar in their responses to either light or dehydration: similar light-responses of K(leaf) and g(s) would stabilize Ψ(leaf) across irradiances for leaves transpiring at a given vapour pressure deficit, and similar dehydration responses would arise from the control of stomata by Ψ(leaf) or a correlated signal. For all four species, the K(leaf) light response declined from full hydration to turgor loss point. The K(leaf) and g(s) differed strongly in their light- and dehydration responses, supporting optimization of hydraulic transport across irradiances, and semi-independent, flexible regulation of liquid and vapour phase water transport with leaf water status.     

A technique for determining the stomach poison effect of insecticides used against leaf-eating insects

Methods devised for feeding individual insects with leaf areas bearing known deposits of insecticides are described, and the problems associated with incomplete consumption of the treated leaf portions are discussed. An account is given of the difficulties of applying the technique to small insects and to those with erratic feeding habits.
Experimental data are given to illustrate the effects on insect resistance of the following: (i) rearing conditions, (ii) larval age and body weight, (iii) acute and chronic poisoning, (iv) the diluting effect of the leaf tissue consumed with the poison dose.
The dosage mortality curve for stomach poisons was found to be typically sigmoid: analysis of results by the method of probits (Bliss, 1934) therefore proved satisfactory. Using lead arsenate against fifth-instar larvae of Phlogophera meticulosa the ratio of weight increase to increase in median lethal dose was found to be constant.     

STUDIES ON THE FORMATION AND SPROUTING OF AERIAL TUBERS IN BEGONIA EVANSIANA ANDR. V. ANTAGONISTIC ACTION OF LONG-DAYS TO SHORT-DAY RESPONSE

Tuberization of Begonia Evansiana Andr. in response to short-day(SD) treatment given to a leaf is inhibited by long-day (LD)treatment of another leaf, no matter whether the latter is situatedabove or below the former. In general, however, young leavesare more inhibitory than mature leaves, although the reverseis the case if the growing activity of the former is extremelylowered. LD treatment is inhibitory even when given prior toan SD treatment. In contrast with the above, the SD effect is slight in the youngerleaves. The LD inhibition may be attributable primarily to a formationin the LD leaf of some substance antagonizing the SD effect. (Received November 10, 1960; )     

Modulation of leaf economic traits and trait relationships by climate

Aim Our aim was to quantify climatic influences on key leaf traits and relationships at the global scale. This knowledge provides insight into how plants have adapted to different environmental pressures, and will lead to better calibration of future vegetation–climate models. Location The data set represents vegetation from 175 sites around the world. Methods For more than 2500 vascular plant species, we compiled data on leaf mass per area (LMA), leaf life span (LL), nitrogen concentration (N_mass) and photosynthetic capacity (A_mass). Site climate was described with several standard indices. Correlation and regression analyses were used for quantifying relationships between single leaf traits and climate. Standardized major axis (SMA) analyses were used for assessing the effect of climate on bivariate relationships between leaf traits. Principal components analysis (PCA) was used to summarize multidimensional trait variation. Results At hotter, drier and higher irradiance sites, (1) mean LMA and leaf N per area were higher; (2) average LL was shorter at a given LMA, or the increase in LL was less for a given increase in LMA (LL–LMA relationships became less positive); and (3) A_mass was lower at a given N_mass, or the increase in A_mass was less for a given increase in N_mass. Considering all traits simultaneously, 18% of variation along the principal multivariate trait axis was explained by climate. Main conclusions Trait‐shifts with climate were of sufficient magnitude to have major implications for plant dry mass and nutrient economics, and represent substantial selective pressures associated with adaptation to different climatic regimes.     

Interactive effects of soil nitrogen and water availability on leaf mass loss in a temperate steppe

Although the link between leaf mass loss and assessment of ecosystem nutrient use efficiency and plant nutrient resorption efficiency has received considerable attention in various ecosystems, there has been relatively little effort to assess plant leaf mass loss during senescence, especially for herbaceous species. We conducted experimental studies to assess leaf mass loss during senescence in five dominant herbaceous species and examined the effects of increasing nitrogen (N) and water availability on leaf mass loss of four species in a temperate steppe in northern China. We nondestructively estimated mature leaf mass based on leaf length and width. Leaf mass loss varied substantially among species, ranging from 20–50%. On average across all species, N and water addition increased leaf mass loss by 30% and 19%, respectively. N and water addition interacted to affect leaf mass loss, as water addition had a significant positive effect on leaf mass loss under enriched N conditions but showed no effect under ambient N levels. We conclude that leaf mass loss of herbaceous plants was considerable and can potentially be more pronounced with increasing N and water availability. It is notable that the responses of plant species to N and water addition were variable. We suggest that leaf mass loss during senescence should be given full consideration in assessing nutrient use and resorption efficiency in semi-arid areas.     

Effects of Shoot Environment on Apparent Root Resistance to Water Flow in Whole Soybean and Cotton Plants

The response of leaf water potential to change in transpirationrate was examined in young soybean and cotton plants. Leaf waterpotential measured 1 h after transpiration became constant followinga change in humidity and was constant over a wide range of transpirationrates in both species. However, leaf water potential was notin equilibrium with flow until 3 h after transpiration becameconstant. At equilibrium an increase in transpiration alwaysresulted in a decrease in leaf water potential. It was alsofound that different responses of equilbrium leaf water potentialto transpiration rate occurred depending on whether transpirationwas altered by changing humidity, light intensity, or leaf area.Low light and decreased leaf area caused lower leaf water potentialsfor a given transpiration rate. These increases in root resistancecorrelated with lower rates of root elongation. The data indicatethat shoot-root interactions are occurring which affect apparentroot resistance to water flow, and complicate interpretationof whole plant data on leaf water potential and transpirationin terms of the flow dependence of root hydraulic characteristics.     

Isoenzyme Patterns in Developing Xanthium Leaves

The isoenzyme patterns of individual Xanthium leaves at various stages of development were determined by acrylamid electrophoresis. The Leaf Plastochron Index was used to measure leaf and plant age. The nature of the changes occurring during leaf development differed from enzyme to enzyme and from gfrom isoenzyme to isoenzyme; for instance, one of the glucose-6-phosphate dehydrogenases was peculiar to very young leaves, another to rapidly expanding leaves, and yet another to still older ones. On the other hand, the number of amylase isoenzymes merely increased with leaf age. Many of the changes in the isoenzyme patterns coincide with the cessation of cell division in the leaf or with the completion of leaf growth. The particular isoenzyme patterns of a given leaf depended on both leaf and plant age. While the isoenzyme patterns of leaves from maximum aldolase activity per unit protein and at a later stage than the leaves from the vegetative plants.     

Toward synthesis of relationships among leaf longevity, instantaneous photosynthetic rate, lifetime leaf carbon gain, and the gross primary production of forests

The assimilation of carbon by plant communities (gross primary production [GPP]) is a central concern in plant ecology as well as for our understanding of global climate change. As an alternative to traditional methods involving destructive harvests or time-consuming measurements, we present a simple, general model for GPP as the product of the lifetime carbon gain by a single leaf, the daily leaf production rate, and the length of the favorable period for photosynthesis. To test the model, we estimated leaf lifetime carbon gain for 26 species using the concept of mean labor time for leaves (the part of each day the leaf functions to full capacity), average potential photosynthetic capacity over the leaf lifetime, and functional leaf longevity (leaf longevity discounted for periods within a year wholly unfavorable for photosynthesis). We found that the lifetime carbon gain of leaves was rather constant across species. Moreover, when foliar biomass was regressed against functional leaf longevity, aseasonal and seasonal forests fell on a single line, suggesting that the leaf production rate during favorable periods is not substantially different among forests in the world. The gross production of forest ecosystems then can be predicted to a first approximation simply by the annual duration of the period favorable for photosynthetic activity in any given region.     

New Phytologist 141 (1999), 99–108

In the January 1999 issue of New Phytologist , we published the research paper entitled 'The effect of light on the growth and reproduction of Floerkea proserpinacoides ' by Margaret F. McKenna and Gilles Houle ( New Phytol . (1999) 141 , 99–108). Since its publication, the authors have identified two important errors in the text. First, values given for leaf area ratio (LAR) and specific leaf area (SLA) have been given erroneously in units of cm² g⁻¹; the correct units are cm² mg⁻¹. Second, the values for unit leaf rate (ULR) have been given incorrectly as tenfold lower than they should be; these should be multiplied by ten to give the correct values in mg m⁻² d⁻¹.
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