Leaf bilateral asymmetry, an important indicator of leaves that tend to be affected by the above-ground architectural structure of plants and their environments (especially light), has been poorly studied. Taylor's power law (TPL) describes a power-law relationship between the mean and variance of a non-negative random variable, and its exponent has been demonstrated to reflect the degree of heterogeneity of the branch spatial arrangement of plants. In this study, we checked whether the mean-variance relationship of the absolute difference in area between the left and right sides of 11396 leaves from 35 species of plants within four families followed TPL. TPL was found to hold true for each species investigated here, and the estimated TPL exponents fell within a range of 1.5 to 2.0. At the family level, there were no any significant differences in the estimated exponents of TPL among the pooled data of Lauraceae, Oleaceae, and Bambusoideae, but those exponent values were significantly smaller than that of Magnoliaceae. We also pooled the data from the four families, and we found that there was a general rule for the mean-variance relationship for the bilateral asymmetry among the studied broad-leaved plants. Given the variety of leaf bilateral asymmetry among species, our results highlight the importance of plant aboveground architecture and the heterogeneity of leaves on different positions to a better understanding of leaf development mechanism and how it responds to the surrounding environment.
Premise The nondestructive measurement of leaf area is important for expediting data acquisition in the field. The Montgomery equation (ME) assumes that leaf area ( A ) is a proportional function of the product of leaf length ( L ) and width ( W ), i.e., A = cLW , where c is called the Montgomery parameter. The ME has been successfully applied to calculate the surface area of many broad‐leaved species with simple leaf shapes. However, whether this equation is valid for more complex leaf shapes has not been verified. Methods Leaf A , L , and W were measured directly for each of 5601 leaves of 15 vine species, and ME and three other models were used to fit the data. All four models were compared based on their root mean square errors (RMSEs) to determine whether ME provided the best fit. Results The ME was a reliable method for estimating the A of all 15 species. In addition, the numerical values of 13 of the 15 values of c fell within a previously predicted numerical range (i.e., between 1/2 and π/4). The data show that the numerical values of c are largely affected by the value of W/L , the concavity of the leaf base, and the number of lobes on the lamina. Conclusions The Montgomery parameter can reflect the influence of leaf shape on leaf‐area calculations and can serve as an important tool for nondestructive measurements of leaf area for many broad‐leaved species and for the investigation of leaf morphology.
Lamina dry mass (LDM) per unit area is an important plant functional trait. However, it is time-consuming to dry leaves in practice. Previous studies have demonstrated that lamina fresh mass (LFM) is approximately proportional to LDM for some broad-leaved plants. However, those studies largely overlooked the influence of leaf age on the proportional relationship, and leaves were sampled without distinguishing age. In the present study, we used eight leaf-age groups of Photinia serratifolia to test whether LDM is proportional to LFM. And we also compared the two linear equations ( y = a + bx , and y = a + x , where x = ln LFM, y = ln LDM, a and b are constants to be estimated) to test whether the introduction of parameter b is worthwhile based on the percent error of the goodness-of-fit between the two equations. There were four of eight leaf-age groups whose 95% confidence intervals (CIs) for b included unity, and for the other four leaf-age groups the difference between the lower limit of the 95% CI and unity was smaller than 0.03, supporting the validity of the LDM vs. LFM proportional relationship. Additionally, the percent errors between the two equations for the eight leaf-age groups were all smaller than 5%, which further supports the hypothesis of a proportional relationship at the individual leaf-age group level. However, the LDM/LFM ratio exhibited a non-linear (quadratic) function of time, which indicates that the intercept, a , depends upon leaf age.
Functional plant traits include a plant’s phenotypic morphology, nutrient element characteristics, and physiological and biochemical features, reflecting the survival strategies of plants in response to environmental changes [...]
The developmental times of poikilotherms at different stages are significantly affected by temperature. Most mathematical models describing the temperature-dependent developmental rates of poikilotherms are built according to the experimental data at various constant temperatures. However, these models can also be applied to the developmental rates at variable temperatures. It is more meaningful to use models to predict the occurrence times of pest insects that actually represent the completion for a particular developmental stage (e.g., hatching, pupation, eclosion) under a natural thermal environment. For some developmental stages, insects might experience a period of high temperatures. In this case, skewed bell-shaped nonlinear models are more reasonable than the linear and exponential models because in the high-temperature region the developmental rate decreases with temperature increasing. We used the accumulated developmental progress method that combines three representative nonlinear models to compare the model validity in predicting the egg's earliest hatching date of bamboo locust in different years. We found that for the springtime phenological event the simple Arrhenius' equation obtains the best goodness of fit. This study also provides a general R function that permits users to employ nonlinear parametric models to predict the occurrence times of insect phenology. In fact, if the investigation data cannot reflect the temperature-based phenological models proposed here, we have to consider whether the data set is reliable or whether the temperature is the crucial factor that determines the occurrence time of interest. The present study is valuable for the integrated management of pest insects because the biological or chemical control timing relies on the prediction on the occurrence time of phenological events.
Temperature can notably affect development rate and intrinsic rate of increase of the diamondback moth, Plutella xylostella L. The intrinsic rate of increase is usually regarded as a good measure of fitness in insects, and the constant temperature at which the intrinsic rate of increase reaches its maximum is defined as the “optimal” temperature for an insect species to survive. The estimates of optimal temperature for some insects and mites are ≍30°C. However, the Sharpe-Schoolfield-Ikemoto model provides an estimate about the intrinsic optimum temperature at which the probability of an enzyme being in the active state is maximal. The intrinsic optimum temperature is considered to be the most suitable temperature for an insect species to survive. The estimates of intrinsic optimum temperature for some insects and mites are ≍20°C. The optimal temperature and the intrinsic optimum temperature of the diamondback moth were estimated in the current study. The former estimate is 28.4 (95% CI: 26.2-28.8°C), whereas the latter estimate is 19.4°C (95% CI: 17.9-20.5°C). Considering the daily average air temperatures during the peaks of the diamondback moth in China, the intrinsic optimum temperature of 19.4°C might represent the most suitable temperature for this insect to survive. We also discussed whether it is sounded to use the intrinsic rate of increase as the fitness. Because the intrinsic rate of increase cannot reflect the density-dependence of population and the trade-off between individual body mass and population size, it is inappropriate to equate these two concepts.
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