Effect Of Leaf Size Research Articles

Lek Site Selection by Male Mediterranean Fruit Flies

The mating system of the Mediterranean fruit fly, Ceratitis capitata (Wiedemann), is based on leks. In field cage choice experiments we examined lek site selection as influenced by the presence of fruit and the presence of conspecific flies. Males were allowed to choose between artificial trees containing fruit and trees without fruit. Males showed a significant preference for the tree baited with fruit. To determine which fruit-related stimuli were important, males were allowed to choose between visual and/or olfactory fruit-derived stimuli. Males preferred to lek on trees presenting both stimuli. To determine the influence of conspecifics on lek site selection, males were allowed to choose between trees containing male and/or female conspecific flies. The presence of pheromone-emitting males was preferred. In addition, both in the field and on artificial trees, we examined the effect of leaf size on lek site selection. In the field, males preferred to lek on leaves of a particular size. Moreover, leaf integrity was important, as males tended to select undamaged leaves as lek sites. In field cage experiments, males consistently chose to lek on trees containing the largest leaves. We conclude that the choice of lek site is influenced by the presence of fruit and of other lekking males, while leaf size and integrity determine male location within a lek.

Previous Cropping and Light History Influence Early Season Vegetative Development of Grapevines

Early season vegetative development of grapevines was studied in the year after imposing three cropping levels to mature `Seyval' vines in the field or establishing two light levels to potted `DeChaunac' vines growing in the greenhouse. Heavily cropped `Seyval' vines (averaging 90 buds, 15.8 kg fruit per vine over the previous two growing seasons) had 85% fewer count buds and 31% fewer non-count (latent) buds than lightly cropped vines (averaging 25 buds, 9.7 kg fruit per vine). The rate of leaf area expansion was reduced on heavily cropped vines. Covering `DeChaunac' vines in the greenhouse with 80% shade from bloom onwards reduced the leaf area per shoot in the year after treatment by reducing both the rate of leaf appearance and the rate of leaf expansion. The leaf at node four from the base of the shoot had the greatest area on both shaded and control vines; however, the area was reduced 33% on shaded vines. Data from the greenhouse experiment were used to model the effect of leaf size at the transition from sink to source on total source leaf area per shoot. Prior to bloom the total source leaf area per shoot was increased when individual leaves became sources earlier, i.e., at a lower percent of their final size. Whether a leaf became a source at either 30%, 50%, or 80% of its final size had little effect on total source leaf area per shoot after bloom. The proportion of source to sink leaf area at bloom was greater than 90% for both slow- and rapidly growing shoots (those on shaded and control vines, respectively). Expansion of grapevine leaves was reduced by heavy cropping and low light levels in the previous year, greatly reducing the source leaf area per shoot.

QTL analysis to study the association between leaf size and abscisic acid accumulation in droughted rice leaves and comparisons across cereals.

Plants accumulate abscisic acid (ABA) under droughted conditions. Genetic variation in the accumulation of ABA in deteched and partially dehydrated leaves of rice has previously been reported, and this was found to be associated with variation in leaf size (smaller leaves made more ABA). Correlation analysis failed to distinguish clearly between a causal relationship between the two traits and close genetic between loci controlling the traits. Here we present a detailed genetic analysis of ABA accumulation in detached and partially dehydrated rice leaves. using a population of F2 plants generated from the lowland x upland cross IR20 (high-ABA) x 63-83 (low-ABA) which was mapped with RFLP and AFLP markers. Several highly significant quantitative trait loci (QTLs) for ABA accumulation and leaf weight were identified. Only one of the minor QTLs for ABA accumulation (accounting for only 4% of the phenotypic variance) was coincident with any QTLs for leaf size such that the high-ABA allele was associated with smaller leaves. This analysis, therefore, showed that the association previously found between ABA accumulation and leaf size was probably largely due to genetic linkage and not to a direct effect of leaf size on ABA accumulation or vice versa. Because of the importance of ABA accumulation in regulating responses of plants to drought stress and the effects of plant size on the rate of development of stress, QTLs for drought-induced ABA accumulation, leaf size and tiller number were compared between rice and wheat. In particular, a possible location in rice was sought for a homoeologue of the major wheat vernalization responsive gene, Vrn1, as this gene is also associated with major effects on leaf size, tiller number and ABA accumulation in wheat. The likelihood of homoeologous loci regulating ABA accumulation, leaf size and tiller number in the two crops is discussed.

Evaporation, xylem sap flow, and tree transpiration in a New Zealand broad-leaved forest

Total evaporation ( E), forest floor evaporation ( E f ), tree xylem sap flow ( F), and environmental parameters were measured on 6 consecutive late-summer days under different weather conditions in a well-watered, temperate broad-leaved forest. Two tree species, Nothofagus fusca (Hook. f.) Oerst. (red beech) and N. menziesü (Hook. f.) Oerst. (silver beech), formed a vertically structured, complex canopy with a one-sided leaf area index of 7. The forest comprises 30–40 trees ha −1 of emergent red beech up to 36 m tall and 1.7 m diameter, above a mixed species canopy of 200 trees ha −1 about 20–30 m tall and 0.4 m average diameter, and approximately 900 trees ha −1 of sub-canopy, mostly silver beech <20 m tall and 0.1 m average diameter. Agreement of E (determined by eddy covariance) and the difference between available energy and sensible heat flux densities was generally within 10% on half-hourly and daily bases. On clear days, the Bowen ratio obtained a broad plateau of about 1–2 for most of the time with much lower and even negative values around sunrise and sunset. Variable cloudiness caused substantial variation in available energy and the Bowen ratio. After rain, daytime Bowen ratios were somewhat lower and relatively constant at about 0.8 when the tree canopy was partially wet. Lysimeter measurements indicated that E f was a significant evaporation component and accounted for 10–20% of E, with rates up to 0.5 mm day −1. Agreement between F (measured by a xylem sap flow method in a representative 337 m 2 plot of 14 trees) and tree canopy transpiration ( E − E f ) was reasonable, with an average disparity of order 10–20% or 0.3 ± 0.1 mm day −1 (standard deviation) when the tree canopy was dry. Within the plot, F typically varied by more than an order of magnitude. Tree social position, assessed by emergence of crown from the general canopy level, strongly affected an individual's contribution to plot sap flux density. About 50% of daily plot F emanated from only three emergent trees. Diurnal variation in coupling of the tree canopy to its aerial environment reflected changes in humidity and wind speed corresponding with changes in stomatal and aerodynamic conductances. Consequently, varying proportions of radiative and advective energy were involved in determining tree transpiration rate. Wet canopy evaporation rate was also examined because it significantly influences when transpiration takes place as rain falls on about 200 days of the year in the forest studied. Effects of leaf size and plant nutrition on tree transpiration and the partitioning of available energy are also discussed.

The effect of leaf size on mutual shading and cultivar differences in soybean leaf photosynthetic capacity

This study investigated the basis of the negative relationship between leaf size and photosynthetic rate per unit of area among five cultivars of soybeans. Exposure of developing mainstem leaves to light, and sizes and light saturated photosynthesis rates of those leaves at maturity were compared in cultivars grown in field plots for two years at Beltsville, Maryland, USA. Plants were grown both in stands at 2.5 cm by 1 m spacing and as isolated plants. While cultivar differences in leaf size were large and consistent in both planting arrangements, significant cultivar differences in light saturated photosynthetic rates were found only in plants grown in stands. Similarly, leaf size was significantly correlated with specific leaf weight only for plants grown in stands. The mainstem apex and developing mainstem leaves experienced more severe shading in large-leaved cultivars than in small-leaved cultivars when plants were grown in stands. Thus, cultivar differences in photosynthetic capacity were probably a consequence of differences in the exposure of developing leaves to light.

Leaf temperatures during radiation frost Part I. Observations

Temperatures attained by leaves in natural environments are significantly influenced by microhabitat and morphology of the plant. Effects of leaf size, height above ground and the type of underlying surface on leaf temperatures of Eucalyptus pauciflora and E. viminalis seedlings during nights of radiation frost were investigated. Temperatures of leaves exposed to clear skies after sunset were 1–3°C lower than those of the adjacent air at all heights except ground level. Intensity and duration of sub-freezing temperatures of leaves diminished with increasing height above ground. Temperatures at the centre of larger E. pauciflora leaves were 0.5–1.5°C lower than for smaller E. viminalis leaves, but tip temperatures of the former were similar to those at the centre of E. viminalis. Leaf temperatures of E. pauciflora were ∼ 0.5–1.5°C lower when held horizontally compared to vertical leaves at the same height. The corresponding change in E. viminalis was between 0.2 and 0.6°C. At each height, leaf temperatures above grass were lower than those above dry soil and these were lower than those above moist soil. Frequency distributions relating screen temperatures to those of leaves of isolated seedlings were determined.

Measures of disease intensity in powdery mildew (Erysiphe graminis) of winter wheat. 2. Relationships and errors of estimation of pustule number, incidence and severity

Assessments of pustule number, incidence and severity of powdery mildew on winter wheat in the Netherlands were made in commercial fields and in experimental plots. Assuming a constant leaf and pustule size, a leaf can carry at most Mm pustules. If the number of clusters, each consisting of n pustules, follows a binomial distribution, then the relation between incidence (I, proportion diseased leaves) and severity (S, proportion diseased leaf surface) is: (1−S)=(1−I)n/M m. The model explains the main effects of leaf, pustule and cluster size on incidence-severity relations and gave a good description of the measured relation. The negative binomial distribution poorly described the measured relation. The model of Nachman (1981) gave a good description of the relation between mean pustule number $$(\bar m)$$ and incidence (I). The relation found in commercial fields, irrespective of fungicide treatments, was: $$ln(\bar m) = 1.48 + 1.14ln(ln[1/(1 - I)])$$ . The effects of years, varieties, growth stages and leaf positions on this relation were not significant. Incidence assessments can be used to predict the pustule number, but this method is less efficient than the use of direct pustule counts. Estimates are given of the variance of the predicted pustule number. Het aantal puistjes meeldauw per blad en de fractie zieke bladeren werden bepaald in praktijkpercelen en veldproeven met wintertarwe. De fractie ziek bladoppervlak kon worden afgeleid uit het aantal puistjes. Het verband tussen de fractie zieke bladeren en de fractie ziek bladoppervlak werd bestudeerd. Bij aanname van een constante blad- en puistjesgrootte kan een blad maximaal Mm puistjes herbergen. Als het aantal meeldauwkolonies (elk bestaande uit n puistjes) een binomiale kansverdeling volgt, dan kan het verband tussen de fractie zieke bladeren (I) en de fractie ziek bladoppervlak (S) worden beschreven door: (1−S)=(1−I)n/M m. De overeenkomsten van dit model met andere modellen wordt besproken en schattingen van parameters worden vergeleken. Het model verklaart hoe blad-, puistjes- en koloniegrootte het verband tussen de fractie zieke bladeren en de fractie ziek bladoppervlak beinvloedt. Het model beschreef het verband tussen de metingen goed maar niet volledig. De negatieve binomiaal beschreef het verband tussen de metingen slecht. Het model van Nachman gaf een goede beschrijving van het verband tussen het gemiddeld aantal puistjes kper blad $$(\bar m)$$ en de fractie zieke bladeren (I). Voor de praktijkpercelen werd dit verband beschreven door: $$ln(\bar m) = 1,48 + 1,14ln(ln[1/(1 - I)])$$ . De invloed van jaren, rassen, gewasstadia en bladpositie op het verband was niet significant. De fractie zieke bladeren kan gebruikt worden om het gemiddeld aantal puistjes per blad te voorspellen, maar deze methode is minder efficient dan een directe telling van het aantal puistjes. Schattingsfouten van het voorspelde aantal puistjes per blad worden gegeven.

The effect of leaf size on the microwave backscattering by corn

Attema and Ulaby (1978) proposed the cloud model to predict the microwave backscattering properties of vegetation. This paper describes a modification in which the biophysical properties and microwave properties of vegetation are related at the level of the individual scatterer (e.g., the leaf or the stalk) rather than at the level of the aggregated canopy (e.g., the green leaf area index). Assuming that the extinction cross section of an average leaf was proportional to its water content, that a power law relationship existed between the backscattering cross section of an average green corn leaf and its area, and that the backscattering coefficient of the surface was a linear function of its volumetric soil moisture content, the author found that the explicit inclusion of the effects of corn leaf size in the model led to an excellent fit ( r 2 of 0.93) between the observed and predicted backscattering coefficients. Also, an excellent ( r 2 of 0.98) power law relationship existed between the backscattering cross section of a corn leaf and its area.

A procedural approach for studying the radiation regime of infinite and truncated foliage spaces. Part III. Effect of leaf size and inclination distribution on nonparallel beam radiation penetration and canopy photosynthesis

The procedural approach was used to study the effect of leaf size and inclination distribution on nonparallel beam radiation penetration and canopy photosynthesis. Horizontally infinite stands at two leaf sizes (leaf area = 0.0051 and 0.0813 m 2), were generated in the computer. Five model leaf-inclination distributions were chosen; uniform, planophile, erectophile and distributions in which the leaf angle is either 0 or 90° at the top of the canopy (Models III and IV, respectively) and changes to the other extreme towards the bottom in relation to cumulative leaf area index. Erect-leaved canopies were found not only to allow relatively more radiation to reach the lower layers but also markedly affect its distribution, primarily by having a higher proportion of penumbral solar irradiance. Model IV canopy has the highest photosynthetic rate compared with other canopies; in this type of canopy (smaller leaf size), the effect of leaf inclination distribution on momentary photosynthetic rates is as high as 86%. A quantitative evaluation of the degree of discrepancy between parallel and nonparallel radiation penetration and consequently canopy photosynthesis in relation to stand architecture is given.

Effects of Leaf Size and Decay Rate on Colonization by Aquatic Hyphomycetes

Oak and maple leaf squares of graded sizes were exposed in a Black Forest stream. Their colonization by aquatic hyphomycetes was studied in summer and in autumn, and in the presence or absence of leaf-eating invertebrates. The cumulative number of fungal species was significantly correlated with the initial size of the substrate. However, the goodness of fit of the regression equation was considerably improved when integrated decay curves instead of initial areas or weights of the squares were used. Spore production of a leaf square was directly proportional to its integrated decay curve. All fungal communities on the various squares showed close agreement with a logseries species distribution. Time of arrival of a fungal species was significantly correlated with its overall reproductive output.

Resistance to Cereal Leaf Beetle in Wheat: Density and Length of Leaf‐surface Pubescence in Four Wheat Lines1

Measurements of leaf hair length and quantity of leaf hairs were made from seedlings of four wheat (Triticum aestivum L. em. Thell.) cultivars to develop bench marks for certain genotypes and to determine the effect of leaf size on hair density. Length was measured from photographs of cleared leaf material; density was determined directly from cleared material with the aid of a compound microscope. The superior resistance of Cl 9321 to oviposition of Oulema melanopus (L.), compared with that of ‘Selkirk,’ occurred because of the greater hair density of Cl 9321. The hair length of Selkirk was probably the main factor responsible for the greater resistance of this cultivar compared with that of ‘Chris.’ The importance of choosing leaves of similar growth stages for pubescence studies was demonstrated.

Kinetics of C-14 Translocation in Soybean

Based largely on data from soybean, some mathematical models are derived to describe the transport kinetics of (14)C-photosynthate. The effects of leaf size, leaf shape, and translocation velocity on the rate of tracer efflux from the leaf are considered, and it is shown that the duration of these effects will approximate the time required for tracer to reach the petiole from the farthest point of the leaf. This duration is designated as the "kinetic size" of the leaf. Although its effect will be slight in the case of soybean (about 2 to 3 minutes), a considerable effect of the kinetic size will be found in the case of large leaves, or when the translocation velocity is low.Source pool kinetics in soybean are described by a two-compartment model, one compartment representing a photosynthetic compartment and the second (the source pool) a nonphotosynthetic compartment next to the veins. The kinetics in the petiole are approximated by a two-compartment model representing the translocation stream and tissues outside the translocation stream. A combination of the models predicts fairly accurately the translocation kinetics observed in soybean.The models are compared with others in the literature. Although the assumptions are in substantial agreement with those made by Evans, Ebert, and Moorby, they are inconsistent with the model based on the movement of transcellular strands presented by Canny and Phillips.