Allometric equations to estimate the leaf area of Psychotria colorata (Willd. Ex Schult.) Müll.Arg.

Estimating leaf area using non-destructive methods from regression equations has become a more efficient, quick, and accurate way. Thus, this study aimed to propose an equation that significantly estimates the leaf area of Psychotria colorata (Rubiaceae) through linear leaf dimensions. For this purpose, 200 leaves of different shapes were collected, and length (L), width (W), product of length by width (L.W), and real leaf area (LA) of each leaf blade were determined. Then, equations were adjusted for predicting leaf area using simple linear, linear (0.0), quadratic, cubic, power, and exponential regression models. The proposed equation was selected according to the coefficient of determination (R²), Willmott's agreement index (d), Akaike's information criterion (AIC), mean absolute error (MAE), mean squared error (RMSE) and BIAS index. It was noted that the equations adjusted using L.W met the best criteria for estimating leaf area, but the equation LA = 0.59 * L.W from linear regression without intercept was the most suitable. This equation predicts that 59% of leaf area is explained by L.W. Concluding, the leaf area of P. colorata can be estimated using an allometric equation that uses linear leaf blade dimensions.

Functional–Structural Plant Modeling Highlights How Diversity in Leaf Dimensions and Tillering Capability Could Promote the Efficiency of Wheat Cultivar Mixtures

Increasing the cultivated diversity has been identified as a major leverage for the agroecological transition as it can help improve the resilience of low input cropping systems. For wheat, which is the most cultivated crop worldwide in terms of harvested area, the use of cultivar mixtures is spreading in several countries, but studies have seldom focused on establishing mixing rules based on plant architecture. Yet, the aerial architecture of plants and the overall canopy structure are critical for field performance as they greatly influence light interception, plant interactions and yield. The very high number of trait combinations in wheat mixtures makes it difficult to conduct experimentations on this issue, which is why a modeling approach appears to be an appropriate solution. In this study, we used WALTer, a functional structural plant model (FSPM), to simulate wheat cultivar mixtures and try to better understand how differences between cultivars in key traits of the aerial architecture influence mixture performance. We simulated balanced binary mixtures of cultivars differing for different critical plant traits: final height, leaf dimensions, leaf insertion angle and tillering capability. Our study highlights the impact of the leaf dimensions and the tillering capability on the performance of the simulated mixtures, which suggests that traits impacting the plants' leaf area index (LAI) have more influence on the performance of the stand than traits impacting the arrangement of the leaves. Our results show that the performance of mixtures is very variable depending on the values of the explored architectural traits. In particular, the best performances were achieved by mixing cultivars with different leaf dimensions and different tillering capability, which is in agreement with numerous studies linking the diversity of functional traits in plant communities to their productivity. However, some of the worst performances were also achieved by mixing varieties differing in their aerial architecture, which suggests that diversity is not a sufficient criterion to design efficient mixtures. Overall, these results highlight the importance of simulation-based explorations for establishing assembly rules to design efficient mixtures.

Estimation of buckwheat leaf area by leaf dimensions

The objective of this work was to model and identify the best models for estimating the leaf area, determined by digital photos, of buckwheat (Fagopyrum esculentum Moench) of the cultivars IPR91-Baili and IPR92-Altar, as a function of length (L), width (W) or length x width product (LW) of the leaf blade. Ten uniformity trials (blank experiments) were carried out, five with IPR91-Baili cultivar and five with IPR92-Altar cultivar. The trials were performed on five sowing dates. In each trial and cultivar, expanded leaves were collected at random from the lower, middle and upper segments of the plants, totaling 1,815 leaves. In these 1,815 leaves, L and W were measured and the LW of the leaf blade was calculated, which were used as independent variables in the model. The leaf area of each leaf was determined using the digital photo method (Y), which was used as a dependent variable of the model. For each sowing date, cultivar and thirds of the plant, 80% of the leaves (1,452 leaves) were randomly separated for the generation of the models and 20% of the leaves (363 leaves) for the validation of the models of leaf area estimation as a function of linear dimensions. For buckwheat, IPR91-Baili and IPR92-Altar cultivars, the quadratic model (Ŷ = 0.5217 + 0.6581LW + 0.0004LW2, R2 = 0.9590), power model (Ŷ = 0.6809LW1.0037, R2 = 0.9587), linear model (Ŷ = 0.0653 + 0.6892LW, R2 = 0.9587) and linear model without intercept (Ŷ = 0.6907LW, R2 = 0.9587) are indicated for the estimation of leaf area determined by digital photos (Y) based on the LW of the leaf blade (x), and, preferably, the linear model without intercept can be used, due to its greater simplicity.

Amplification of frog calls by leaf substrates: implications for terrestrial and arboreal species

Signal detection is a minimum requirement for any communicative interaction. Acoustic signals, however, often experience amplitude losses during their transmission through the environment, reducing their detection range. Displaying from sites that increase the amplitude of the sound produced, such as cavities or some reflective surfaces, can improve the detectability of signals by distant receivers. Understanding how display sites influence sound production is, however, far from understood. We measured the effect of leaf calling sites on the calls of an arboreal (Hyalinobatrachium fleischmanni) and a leaf-litter specialist (Silverstoneia flotator) frog species. We collected the leaves where males of both species were observed calling, and conducted playback experiments to measure their effect on the amplitude of frog calls. Overall, the leaves used by H. fleischmanni and S. flotator were of similar dimensions, and amplified the calls of each species by about 5.0 and 2.5 dB, respectively. The degree of call amplification was unrelated to leaf dimensions or the position of the frogs on the leaves, but explained by the different frequency content of the calls of each species. Depending on the spatial location of intended and unintended receivers, we suggest that amplification of frog calls by leaves could represent either a benefit or impose costs for arboreal and terrestrial species. We argue that the microhabitat of the substrate from which animals display needs to be considered when addressing signal evolution.Lay summaryAnimals produce signals from specific locations in the environment, yet we know surprisingly little about the effects of the small-scale habitat on animal communication. Here we show that the calls of a terrestrial and an arboreal frog species are amplified by the leaves they use as calling sites. We argue that the consequences of this enhancement need to be considered in relation to the spatial location of intended (males and females) and unintended receivers (predators and parasites).

Relationship between Leaf and Fibre Characteristics of Agave sisalana

With decrease in wood from the forest, non-wood fibres have attracted interest in the production of pulp and paper products in recent times due to their short growth cycles, moderate irrigation and fertilizer requirements as well as their low lignin content. The use of these plants will aid sustainable development in the pulp and paper industry. This study investigated leaf dimensions and fibre characteristics of Agave sisalana and how the leaf dimensions relates to its fibre characteristics. Leaves were collected from three sisal plant stands in Oyo State, Nigeria. The plant whorl was divided systematically into bottom, middle and top from which five leaves were randomly collected from each whorl position. The fibres of the leaves were extracted from which 2cm of fibres were taken from three positions on the leaf (top, middle and base). Extracted fibres were macerated and 3375 fibres were measured. The result shows that Agave sisalana leaves collected at the top had the longest length and was also widest at the base and middle. The average fibre length was 1.69 mm, while the fibre diameter, lumen width and cell wall thickness of Agave sisalana were 16.98 µm, 12.33 µm and 2.32 µm respectively. The slenderness ratio averaged 99.4 while the coefficient of flexibility averaged 72.61. The highest value of the runkel ratio of Agave sisalana was 0.42. There was significant negative correlation between leaf characteristics and fibre characteristics. Young sisal (Agave sisalana) leaves produced the best fibre characteristics suitable for the production of high quality paper.

Evaluation of new mathematical models for estimation of single olive leaves area

The study was conducted on “Khoderi” olive cultivar planted in Jableh Region-Latakia province, Syria in 2017 in order to evaluate some mathematical models adapted for olive single leaf area estimation. Leaf samples were taken from the middle of one-year branches. Actual areas of the leaves were measured using Adobe Photoshop CS5. Leaf dimensions (length and width) were measured accurately. Coefficients of determination were estimated for the relation between leaf dimensions and the actual area. The best coefficient of determination was between the natural logarithm of the product (leaf length × leaf width) and the natural logarithm of leaf area (R2= 0.962). Linear regression equation of the mentioned relation was fitted and evaluated. The accuracy of the new model (A=e0.9509ln LW – 0.2867) was compared to other models commonly used for olive single leaf area estimation. The comparison showed no significant differences between leaf area obtained by the new model and the actual leaf area values (p=0.01), whereas significant differences were found for the other models. The new model showed the lowest Root Mean Square Error (RMSE) and high efficiency in estimating olive leaf area of “Khoderi” cultivar in two different environments; the same results were obtained for olive cultivar “Picholine” the French. We recommend the new model for olive single leaf area estimation.

The use of numerical methods in the design of a formula that returns the surface of the leaves of Phragmites australis (Cav.) Trin. Ex Steud.

The paper presents the results of calculations and a verification of numerical models developed for estimating the surface of leaves of the common reed (Phragmites australis (Cav.) Trin. Ex Steud.). The research sample consisted of 137 leaves collected from the rush zone of Lake Raduńskie Górne in 2018. The total area of leaves obtained for testing was 1932.3 cm2. To derive a formula that returns the surface of common reed foliage regression models were used – MLR (Multiple Linear Regression) and SLR (Stepwise Linear Regression). It has been shown that the measurement of basic leaf dimensions (i.e. length – L, mid-width – WM and maximum width – WX) makes it possible to define an empirical formula which, with an average accuracy of 99.9%, allows the real surface of leaves to be estimated. The modelling results were compared with formulas currently used in practice, and the measurement errors were determined using these formulas. It has been shown that the formulas used to date are subject to RMSE to the value of 1.19-2.52. The application of the developed formula (A = 0.4486 – 0.046 L + 7.9267 WM – 5.8121 WX + 0.5853 L • WX) will significantly reduce errors in leaf surface estimation (RMSE = 0.86) and thus the amount of reed transpiration and evapotranspiration, especially in the case of handling small samples (number of leaves and measurements).

Effects of foliar application of chemical agents and shading levels on growth and physiological aspects of "malagueta" pepper plants

Foliar application of chemical agents and cultivation in different levels of shading can modify pepper plants. The objective of this study was to evaluate the effect of the application of chemical agents in the growth, partition of photoassimilates and photosynthetic pigments of malagueta pepper in different growing environments. The treatments were arranged in a randomized design with a 2x5 factorial scheme under two cultivation environments [eucalyptus structures measuring 5.0 x 5.0 x 2.5 m (length x width x height), coated with type coverage screens (Sombrite®) with 18% and 35% shading], and five treatments with chemical agents [1 - C - without application; 2 - PBZ (50 mg L-1) + Nut. (1%); 3 - Gib. (50 mg L-1) + Nut. (1%); 4 - Amin. (50 mg L-1) + Ant. (50 mg L-1) and 5 - Gib. (50 mg L-1) + A (50 mg L-1) + Amin. (50 mg L-1) + Ant. (50 mg L-1)] in four replications. We evaluated the stem diameter, the plant height, number of leaves, leaf dimensions, leaf area, accumulation and dry matter partition and chlorophyll contents. The cultivation of pepper plants in environment with 18% of shading provides plants with a higher number of leaves and dry matter, as environment protects plants against climatic agents by controlling temperature, humidity and solar radiation. The application of the Paclobutrazol + Nitrogen promotes shoot growth and increases the green pigmentation in pepper plants.