Variation In Leaf Area Research Articles

Plant Growth, Antioxidative Enzymes, Lipid Peroxidation and Organic Solute Contents in Mulungu Seedlings (Erythrina velutina) Under Different Field Capacities

Erythrina velutina (mulungu) is an endemic species of caatinga found in Northeast Brazil. As a result of its rapid plant growth, the species may be an alternative for the recovery of degraded areas. Thus, the present study aimed to analyze the effects of irrigation with different field capacilities (FC): 20, 50 and 80% on plant growth, antioxidative enzyme activities, membrane lipid peroxidation and organic solute contents in mulungu seedlings under greenhouse conditions. The experiment was carried out at Instituto Federal Educação, Ciência e Tecnologia do Ceará (IFCE)-Campus Maracanaú, Ceará, Brazil. Under the presented experimental conditions, E. velutina plants showed higher growth variables (dry matter yield and leaf area) when submitted to daily irrigation of 50% of FC. Irrigation at 20% of FC caused a small water deficit. However, 80% of FC watering may have resulted in an excess of water. In general, despite the reduction in plant growth in plants irrigated at 20% of FC, the activities of the antioxidant enzymes did not differ substantially between treatments. In general, the lowest organic solute contents were detected in irrigations at 20 or 80% of FC.

Leaf physiological and anatomical responses of Lantana and Ligustrum species under different water availability

Understanding the plant characteristics that support tolerance to water stress is important in choosing plants in arid or semi-arid environments, such as the Mediterranean. In particular, leaf characteristics can affect the response of plants to water stress. In order to understand how plants with different leaf features can overcome water stress, four water regimes were adopted on two species that are widespread in the Mediterranean environment, Lantana camara and Ligustrum lucidum. The four treatments were: control (C), in which the pot substrate moisture was maintained close to water container capacity (WCC), light deficit irrigation (LDI) irrigated at 75% of WCC, moderate deficit irrigation (MDI) at 50% of WCC, and severe deficit irrigation (SDI) at 25% of WCC. To better understand the action mechanisms, the trial was repeated twice (from January to May, and from May to September). Morphological, anatomical and physiological data were measured to identify the action mechanisms. Water deficit significantly decreased the biomass accumulation in both species during the experimental growth period. In Lantana, significant variations in total leaf area and leaf number were registered between C and SDI, while in Ligustrum, the differences were significant only for total leaf area. The water deficit treatments reduced the leaf thickness especially in Ligustrum. In both species, photosynthesis reduction was related to stomatal closure. Ligustrum showed a higher variability among treatments indicating a faster and more efficient response to water limitations compared to Lantana, as also demonstrated by the lower biomass reduction in the most severe water stress treatment.

Manipulating tree crown structure to promote old-growth characteristics in second-growth redwood forest canopies

In old-growth Sequoia sempervirens forests, reiterated trunks and limbs provide required habitat elements for specialized arboreal species, including an endangered seabird, Brachyramphus marmoratus. The oldest second-growth redwood forests—established after 19th century logging—lack species dependent on complex structure, presumably because redwoods maintain simple, model-conforming crowns for centuries unless damaged by wind or fire. We imposed a factorial experiment on 24 redwoods 59–75 m tall in six second-growth forests to determine if trunk reiteration and limb formation can be induced by removing treetops (topping) and branch tips (tipping) to disrupt apical control. We also increased light availability in the upper crown by pruning branches. After intensively mapping trunks and branches and imposing treatments, we re-mapped trees three years later to quantify growth increments. Topping stimulated trunk reiteration from the cut, and reiterated tops gained height more rapidly than controls. Tipping also stimulated trunk reiteration from branches, especially when combined with topping, resulting in formation of limbs (i.e., branches giving rise to reiterated trunks). Pruning had consistently negative effects on trunk and branch growth increments even after accounting for post-treatment variation in leaf area and light availability, suggesting that photosynthate was diverted to compartmentalization of wounds. Strategic injury of trees may have long-term conservation value in second-growth redwood forests if limbs can be initiated high enough in the crown to persist as trees approach maximum height. Topping and tipping treatments should be combined with silvicultural thinning of neighboring trees to increase light availability far more than can be achieved by pruning.

Understanding the temporal dimension of the red-edge spectral region for forest decline detection using high-resolution hyperspectral and Sentinel-2a imagery

The operational monitoring of forest decline requires the development of remote sensing methods that are sensitive to the spatiotemporal variations of pigment degradation and canopy defoliation. In this context, the red-edge spectral region (RESR) was proposed in the past due to its combined sensitivity to chlorophyll content and leaf area variation. In this study, the temporal dimension of the RESR was evaluated as a function of forest decline using a radiative transfer method with the PROSPECT and 3D FLIGHT models. These models were used to generate synthetic pine stands simulating decline and recovery processes over time and explore the temporal rate of change of the red-edge chlorophyll index (CI) as compared to the trajectories obtained for the structure-related Normalized Difference Vegetation Index (NDVI). The temporal trend method proposed here consisted of using synthetic spectra to calculate the theoretical boundaries of the subspace for healthy and declining pine trees in the temporal domain, defined by CItime=n/CItime=n+1 vs. NDVItime=n/NDVItime=n+1. Within these boundaries, trees undergoing decline and recovery processes showed different trajectories through this subspace. The method was then validated using three high-resolution airborne hyperspectral images acquired at 40 cm resolution and 260 spectral bands of 6.5 nm full-width half-maximum (FWHM) over a forest with widespread tree decline, along with field-based monitoring of chlorosis and defoliation (i.e., ‘decline’ status) in 663 trees between the years 2015 and 2016. The temporal rate of change of chlorophyll vs. structural indices, based on reflectance spectra extracted from the hyperspectral images, was different for trees undergoing decline, and aligned towards the decline baseline established using the radiative transfer models. By contrast, healthy trees over time aligned towards the theoretically obtained healthy baseline. The applicability of this temporal trend method to the red-edge bands of the MultiSpectral Imager (MSI) instrument on board Sentinel-2a for operational forest status monitoring was also explored by comparing the temporal rate of change of the Sentinel-2-derived CI over areas with declining and healthy trees. Results demonstrated that the Sentinel-2a red-edge region was sensitive to the temporal dimension of forest condition, as the relationships obtained for pixels in healthy condition deviated from those of pixels undergoing decline.

Relationships between leaf functional traits of Machilus pauhoi understory seedlings from different provenances and geographical environmental factors.

To understand the adaptation mechanism of Machilus pauhoi seedlings to environmental changes, leaf functional traits of M. pauhoi seedlings from nine provenances, as well as relationships between leaf traits and environmental factors were analyzed. The results showed that leaf functional traits of M. pauhoi seedlings from different provenances showed significant intraspecific variations, with the coefficient of variation ranging from 8.8% to 28.2%. Specific leaf area, leaf relative water content, leaf tissue density and leaf thickness differed significantly among seedlings from different provenances, implying high leaf morphological plasticity. Moreover, leaf tissue density was positively correlated to leaf dry matter content and leaf relative water content, but negatively correlated to specific leaf area and leaf thickness. Specific leaf area showed significantly negative correlations with leaf dry matter content and leaf area. The covariation among those traits examined here indicated that M. pauhoi seedlings could adjust and balance the combination of leaf traits in response to environmental changes. Longitude, latitude, >10 ℃ annual accumulated temperature and mean annual temperature contributed largely to the variation of leaf functional traits of M. pauhoi seedlings. Leaf thickness decreased with the increase of longitude, while leaf dry matter content and leaf relative water content increased with the increase of longitude. Leaf tissue density was positively correlated with longitude and mean annual temperature, suggesting that longitude rather than mean annual temperature had greater effects on it. Leaf area was positively correlated with >10 ℃ annual accumulated temperature and longitude, indicating that annual accumulated temperature rather than longitude had greater effects on the variation of leaf area.

Estimation and mapping of above-ground biomass of mangrove forests and their replacement land uses in the Philippines using Sentinel imagery

The recent launch of the Sentinel-1 (SAR) and Sentinel-2 (multispectral) missions offers a new opportunity for land-based biomass mapping and monitoring especially in the tropics where deforestation is highest. Yet, unlike in agriculture and inland land uses, the use of Sentinel imagery has not been evaluated for biomass retrieval in mangrove forest and the non-forest land uses that replaced mangroves. In this study, we evaluated the ability of Sentinel imagery for the retrieval and predictive mapping of above-ground biomass of mangroves and their replacement land uses. We used Sentinel SAR and multispectral imagery to develop biomass prediction models through the conventional linear regression and novel Machine Learning algorithms. We developed models each from SAR raw polarisation backscatter data, multispectral bands, vegetation indices, and canopy biophysical variables. The results show that the model based on biophysical variable Leaf Area Index (LAI) derived from Sentinel-2 was more accurate in predicting the overall above-ground biomass. In contrast, the model which utilised optical bands had the lowest accuracy. However, the SAR-based model was more accurate in predicting the biomass in the usually deficient to low vegetation cover non-forest replacement land uses such as abandoned aquaculture pond, cleared mangrove and abandoned salt pond. These models had 0.82–0.83 correlation/agreement of observed and predicted value, and root mean square error of 27.8–28.5 Mg ha−1. Among the Sentinel-2 multispectral bands, the red and red edge bands (bands 4, 5 and 7), combined with elevation data, were the best variable set combination for biomass prediction. The red edge-based Inverted Red-Edge Chlorophyll Index had the highest prediction accuracy among the vegetation indices. Overall, Sentinel-1 SAR and Sentinel-2 multispectral imagery can provide satisfactory results in the retrieval and predictive mapping of the above-ground biomass of mangroves and the replacement non-forest land uses, especially with the inclusion of elevation data. The study demonstrates encouraging results in biomass mapping of mangroves and other coastal land uses in the tropics using the freely accessible and relatively high-resolution Sentinel imagery.

Non-destructive measurement of soybean leaf thickness via X-ray computed tomography allows the study of diel leaf growth rhythms in the third dimension.

Present-day high-resolution leaf growth measurements provide exciting insights into diel (24-h) leaf growth rhythms and their control by the circadian clock, which match photosynthesis with oscillating environmental conditions. However, these methods are based on measurements of leaf area or elongation and neglect diel changes of leaf thickness. In contrast, the influence of various environmental stress factors to which leaves are exposed to during growth on the final leaf thickness has been studied extensively. Yet, these studies cannot elucidate how variation in leaf area and thickness are simultaneously regulated and influenced on smaller time scales. Only few methods are available to measure the thickness of young, growing leaves non-destructively. Therefore, we evaluated X-ray computed tomography to simultaneously and non-invasively record diel changes and growth of leaf thickness and area. Using conventional imaging and X-ray computed tomography leaf area, thickness and volume growth of young soybean leaves were simultaneously and non-destructively monitored at three cardinal time points during night and day for a period of 80h under non-stressful growth conditions. Reference thickness measurements on paperboards were in good agreement to CT measurements. Comparison of CT with leaf mass data further proved the consistency of our method. Exploratory analysis showed that measurements were accurate enough for recording and analyzing relative diel changes of leaf thickness, which were considerably different to those of leaf area. Relative growth rates of leaf area were consistently positive and highest during 'nights', while diel changes in thickness fluctuated more and were temporarily negative, particularly during 'evenings'. The method is suitable for non-invasive, accurate monitoring of diel variation in leaf volume. Moreover, our results indicate that diel rhythms of leaf area and thickness show some similarity but are not tightly coupled. These differences could be due to both intrinsic control mechanisms and different sensitivities to environmental factors.

Influence of leaf morphometric variations on the growth of seedlings and juveniles of woody species in a semiarid environment

Variations in leaf morphometry and in diameter and height growth of plants may occur due to changes in light and temperature conditions of the forest in order to compensate the stress in the habitat. In this study, we examine the relationship of seedling and juvenile size and leaf area of woody species in forests of different ages (>55 and 19 years) in northeastern Brazil. A total of 600 individuals of four species, seedlings and juveniles that survived a rainy season were evaluated. Seedlings and juveniles of Croton blanchetianus Baill, Poincianella pyramidalis (Tul.) L. P. Queiroz, Myracrodruon urundeuva Allemao and Commiphora leptophloeos (Mart.) J.B. Gillett were measured for height and stem diameter in the beginning of the rainy season of 2014. One leaf of each individual was collected in the beginning of the rainy season. Leaves were photographed, and leaf area was measured. Differences in height, diameter and leaf area between forests and the existence of a relationship of diameter and height to leaf area were examined. Leaf area and seedling and juvenile size of C. blanchetianus and C. leptophloeos decreased as succession progressed. However, this was not observed for seedlings of P. pyramidalis and juveniles of M. urundeuva. Leaf area explained 7–26% of the variation in size of individuals in the young forest and 11–39% of the variation in size of individuals in the mature forest. Despite variations in leaf area, significant changes in growth rate were not found with the increase in forest age for most ontogenetic stages and species.

Doses de nitrogênio no crescimento de Calceolaria x herbeohybrida em vaso

Calceolaria x herbeohybrida Voss (pocketbook plant, calceolaria) is an herbaceous perennial and floriferous species that can be grown in pots or beds. Nitrogen is usually the most required nutrient, being necessary to conduct studies in order to provide useful information for agronomic practices. Thus, this study aimed to evaluate nitrogen doses in the growth of Calceolaria x herbeohybrida in pots. Initially, assorted and pelleted calceolaria seeds were sow in multicellular trays containing a commercial substrate based on peat and kept in a floating irrigation system in a protected environment. At the greenhouse, seedlings with four true leaves were transplanted into 1 L pots containing the same substrate and a drip irrigation system. The treatments consisted of different nitrogen doses (0.0, 0.5, 1.0, 2.0 or 4.0 g of N L-1) applied weekly using ammonium nitrate as source. Fertilization with P and K was also done, and all treatments received de same dose. At the end of the experimental period, shoot length, leaf area, shoot and root dry matter, number of buds and flowers, chlorophyll a, b and total chlorophyll were evaluated. The experimental design was completely randomized with four replications and five plants per plot. The data were treated with ANOVA and the means were treated with regression analysis using the SigmaPlot 11.0 software. There was no survival of plants at the highest N dose (4.0 g L-1). Shoot length showed a quadratic behavior, with a maximum point at 1.25 g L-1, where plants reached 13.3 cm. There was a similar behavior for the variable leaf area, with the highest point at 1.24 g L-1. Shoot dry mass presented the maximum point at a dose of 1.20 g L-1, resulting in 4.21 g of dry matter. Regarding root dry matter, no equation could be adjusted. For the variable number of buds and flowers, the highest point was at a dose of 1.20 g L-1, with 35.86 buds and flowers per plant. For chlorophyll a, b and total chlorophyll, the maximum point was at 1.5 g L-1. The ideal nitrogen dose is between 1.2 and 1.5 g L-1 for most variables.

The influence of land cover on surface energy partitioning and evaporative fraction regimes in the U.S. Southern Great Plains

AbstractLand‐atmosphere interactions are important to climate prediction, but the underlying effects of surface forcing of the atmosphere are not well understood. In the U.S. Southern Great Plains, grassland/pasture and winter wheat are the dominant land covers but have distinct growing periods that may differently influence land‐atmosphere coupling during spring and summer. Variables that influence surface flux partitioning can change seasonally, depending on the state of local vegetation. Here we use surface observations from multiple sites in the U.S. Department of Energy Atmospheric Radiation Measurement Southern Great Plains Climate Research Facility and statistical modeling at a paired grassland/agricultural site within this facility to quantify land cover influence on surface energy balance and variables controlling evaporative fraction (latent heat flux normalized by the sum of sensible and latent heat fluxes). We demonstrate that the radiative balance and evaporative fraction are closely related to green leaf area at both winter wheat and grassland/pasture sites and that the early summer harvest of winter wheat abruptly shifts the relationship between evaporative fraction and surface state variables. Prior to harvest, evaporative fraction of winter wheat is strongly influenced by leaf area and soil‐atmosphere temperature differences. After harvest, variations in soil moisture have a stronger effect on evaporative fraction. This is in contrast with grassland/pasture sites, where variation in green leaf area has a large influence on evaporative fraction throughout spring and summer, and changes in soil‐atmosphere temperature difference and soil moisture are of relatively minor importance.

Establishment and application of photosynthetic production model for double cropping rice

In this study, we developed a model for photosynthetic production in double cropping rice by integrating the advantages in current crop models (including the models of canopy structure, canopy light distribution, canopy photosynthesis and dry matter production). The canopy light distribution and dry matter accumulation were preliminarily validated with independent field experiment datasets. The distribution of direct radiation both on a level surface and on the leaf surface within canopy, the canopy daily photosynthate and its characteristics with varying leaf area index for three typical plant types (erect both upper and lower, upper erect and lower flat, and flat both upper and lower) were quantitatively analyzed by the model. The results indicated that there was a good agreement between the simulated and observed values. The root mean square error (RMSE), relative root mean square error (RRMSE) and correlation coefficient (r) of prediction of canopy light distribution in double cropping rice were 12.01 J ·m-2·s-1, 8.2% and 0.9929, respectively. Meanwhile, the RMSE, RRMSE and r of prediction of dry matter accumulation were 0.83 t·hm-2, 14.6% and 0.9772, respectively. It was indicated that the model had a performance. The upper erect and lower flat plant type had highest canopy daily photosynthate due to higher incident sun light received on the leaf surface, leaf photosynthetic efficiency and leaf area index.

Stomatal density, leaf area and plant size variation of Rhizophora mangle (Malpighiales: Rhizophoraceae) along a salinity gradient in the Mexican Caribbean

In community ecology, the knowledge of abiotic factors, that determine intraspecific variability in ecophysiological and functional traits, is important for addressing major questions, such as plant community assembly and ecosystem functioning. Mangroves have several mechanisms of resistance to salinity and most species exhibit some xeromorphic features in order to conserve water. Leaf area and stomatal density play an important role in maintaining water balance, and gas exchange is regulated by their aperture and density, two traits that vary intraspecifically in response to environmental conditions, such as water stress and salinity. In this study, we evaluated the effects of salinity on stomatal density, leaf area and plant size in R. mangle and we tested for associations among the three variables, across three sites along a natural salinity gradient in the Xel-Há Park, Quintana Roo, Mexico. We hypothesized that high salinity sites would produce smaller plants, with smaller leaves, and fewer stomata. Three sampling sites with different environmental conditions were chosen and salinities were monitored monthly. A total of 542 plants were tagged and tree heights and diameters were measured for each individual within each of the three sampling sites. Three leaves from 20 trees from each site were measured to determine leaf area. Stomatal densities were determined in each leaf using nail polish casts, examining ten 1 mm squares per leaf under an optical microscope. A principal component analysis was used to assess association between tree height, leaf area, and stomatal density for each plot. The salinity gradient was reflected in plant size, producing smaller plants at the higher salinity site. The largest leaves were found at the low salinity site (51.2 ± 24.99 cm2). Leaf length was not correlated to plant size (LL vs. tree height: r= 0.02, P= 0.8205; LL vs. trunk diameter: r= 0.03, P= 0.7336), so we concluded that leaf length is an environmentally plastic trait of red mangroves that may vary as a function of environmental conditions, such as hydric stress caused by elevated salinity. The larger leaves from the low salinity site had lower densities of stomata (65.0 stomata.mm2 SD= 12.3), and increasing salinities did not decrease stomatal density (intermediate salinity site: 73.4 stomata.mm2 SD= 13.5; high salinity site: 74.8 stomata.mm2 SD= 17.3). Our results confirm that stomatal density is inversely related to leaf area (r= -0.29, P < 0.001), especially leaf width (r= -0.31, P < 0.001), and that salinity may increase stomatal density by causing reduction of leaf size.

Effect of plant spacing and fertility level on leaf area variation at different phenological stages of cape gooseberry (Physalisperuviana L.) grown in sodic soil

Vegetative and reproductive growth in cape gooseberry (Physalisperuviana L.) proceed concomitantly during the greater part of the life cycle thereby foliar traits (e.g. leaf area) become important in photosynthetic action of the plant. In present study, the leaf area variation in cape gooseberry was studied at five phenological stages i.e. pre-flowering (30 DAT), start of flowering (60 DAT), early fruiting (120 DAT), peak fruiting (180 DAT) and late fruiting (240 DAT), grown at three spacings (60 × 75, 75 × 75 and 75 × 90 cm) and four NPK levels (control, 60:40:40, 80:60:60 and 100:80:80 kg ha-1). Leaf area increased from per-flowering (73.51 cm2) to start of flowering (82.26 cm2) and thereafter, it was decreased gradually at later stages i.e. early fruiting (79.17 cm2), peak fruiting (73.15 cm2) and late fruiting (60.21 cm2). Spacing had no significant effect on leaf area at pre-flowering and start of the flowering, but at later stages, widest spacing (75 × 90 cm) exhibited significantly maximum leaf area at early fruiting (82.44 cm2), peak fruiting (78.22 cm2) and late and fruiting (65.31 cm2). Leaf area increased due to increased NPK levels with maximum values under 100:80:80 kg NPK ha-1 at all the phenological stages: pre-flowering (78.99 cm2), start of flowering (90.97 cm2), early fruiting (88.47 cm2), peak fruiting (80.74 cm2) and late fruiting (67.22 cm2). Spacing × NPK Interactions was significant only at peak fruiting and late fruiting stages with maximum leaf area (75.22 and 71.02 cm2, respectively) at 75 × 90 cm + NPK @ 100:80:80 kg ha-1. These findings can be further helpful in leaf sclerophylly studies in cape gooseberry.

Leaf area increases with species richness in young experimental stands of subtropical trees

Aims: Most biodiversity–ecosystem functioning research has been carried out in grassland ecosystems, and little is known about whether forest ecosystems, in particular outside the temperate zone, respond similarly. Here, we tested whether productivity, assessed as leaf area index (LAI), increases with species richness in young experimental stands of subtropical trees, whether this response is similar for early-season leaf area (which is dominated by evergreens) and seasonal leaf area increase (which is dominated by deciduous species), and whether responses saturate at high species richness. Methods: We used a planted tree biodiversity experiment in south-east China to test our hypotheses. LAI was determined three times by digital hemispheric photography in 144 plots that had been planted with 400 trees each, forming communities with 1, 2, 4, 8 or 16 tree species. Important Findings: LAI increased significantly with tree species richness in the fifth year of stand establishment. Similar, but weaker, statistically non-significant trends were observed 1 year before. We did not observe leaf area overyielding and the presence of particularly productive and unproductive species explained large amounts of variation in leaf area, suggesting that selection-type effects contributed substantially to the biodiversity effects we found in this early phase of stand establishment. Effects sizes were moderate to large and comparable in magnitude to the ones reported for grassland ecosystems. Subtropical (and tropical) forests harbor substantial parts of global net primary production and are critical for the Earth’s carbon and hydrological cycle, and our results suggest that tree diversity critically supports these ecosystem services.

Influencia del área foliar en el enraizamiento de genotipos superiores de Gmelina arborea Roxb.

Se determinó el área foliar adecuada para el enraizamiento y mejor desarrollo de esquejes de Gmelina arborea dentro de túneles de enraizamiento. Se utilizaron esquejes apicales de clones de melina número 5, 6 y 9, y se colocaron en túneles de enraizamiento.<br />Los tratamientos aplicados consistieron en reducción del área foliar (8, 12, 16 y 20 cm²), la cual fue medida a partir de moldes de hojas de plástico cuadriculadas. A las tres semanas se evaluaron las variables: porcentaje<br />de enraizamiento, altura final, área foliar final y biomasa total de las plantas. Se realizó análisis de varianza, pruebas de medias Tukey (a= 0,05) y coeficiente de correlación de Pearson, con el software estadístico Info Stat; se aplicaron modelos de regresión logística mediante el software estadístico “R”. Se reportó un enraizamiento promedio de 75,8 %, influenciado por el diámetro y biomasa verde, los cuales reportaron 78 %<br />de correlación. Los tratamientos de 16 cm² y 20 cm² presentaron mejores resultados en el porcentaje de enraizamiento y altura de las plantas. Se reportaron diferencias significativas entre los tratamientos, en las variables área foliar final y biomasa total, siendo el tratamiento de 20 cm² el que presentó mayor valor para ambas variables. EL clon 5 arrojó mejores resultados en área foliar y biomasa total. El área foliar de 20 cm² mostró resultados satisfactorios para mejorar la calidad del proceso de enraizamiento.

Methods to estimate daily evapotranspiration from hourly evapotranspiration

Remote sensing provides an effective way for the estimation of regional evapotranspiration, therefore, a reliable scaling-up method from instantaneous evapotranspiration (ET) to daily ET is of great importance. In this paper, five commonly used scaling-up methods estimating daily ET from hourly latent heat measurements were compared under different energy and crop growing conditions. Field data collected during the whole growing season at 1.0 h intervals by eddy covariance system in North China were used. Evaporative fraction (EF), reference evaporative fraction (Kc), crop coefficient (modified-Kc) and surface resistance (rc) varied slightly during the daytime, which gave a solid theoretical basis for the scaling-up methods based on the constant value of these parameters. In most cases, the EF and Kc methods performed better than the others, the relative bias from 9:00–16:00 for the two methods ranged from −11.2% to 5.9% and −6.6% to 4.8%, respectively. The EF method was applicable when surface energy was limited, when Rn was less than 50 W m−2; the average modified coefficient of efficiency of EF method during the daytime from 9 am to 5 pm was 0.68, which is around twice that of the second best method. The Kc and the modified-Kc methods were applicable when surface energy was relatively large. The performance of the five methods didn't seem sensitive to variation of leaf area. Overall, the Kc and EF methods performed better, especially between 11:00 and 15:00. The results of this paper could be useful for optimisation of ET models.

Comprehensive national database of tree effects on air quality and human health in the United States

Trees remove air pollutants through dry deposition processes depending upon forest structure, meteorology, and air quality that vary across space and time. Employing nationally available forest, weather, air pollution and human population data for 2010, computer simulations were performed for deciduous and evergreen trees with varying leaf area index for rural and urban areas in every county in the conterminous United States. The results populated a national database of annual air pollutant removal, concentration changes, and reductions in adverse health incidences and costs for NO2, O3, PM2.5 and SO2. The developed database enabled a first order approximation of air quality and associated human health benefits provided by trees with any forest configurations anywhere in the conterminous United States over time.Comprehensive national database of tree effects on air quality and human health in the United States was developed.

Specific leaf area variations drive acclimation of Cistus salvifolius in different light environments

Cistus salvifolius L. is the most widely spread Cistus species around the Mediterranean basin. It colonizes a wide range of habitats growing from sea level to 1,800 m a.s.l., on silicolous and calcicolous soils, in sun areas as well as in the understory of wooded areas. Nevertheless, this species has been mainly investigated in term of its responsiveness to drought. Our aim was to understand which leaf traits allow C. salvifolius to cope with low-light environments. We questioned if biochemical and physiological leaf trait variations in response to a reduced photosynthetic photon flux density were related to leaf morphological plasticity, expressed by variations of specific leaf area (SLA) and its anatomical components (leaf tissue density and thickness). C. salvifolius shrubs growing along the Latium coast (41°43'N,12°18'E, 14 m a.s.l., Italy) in the open and in the understory of a Pinus pinea forest, were selected and the relationships between anatomical, gas exchange, chlorophyll (Chl) fluorescence, and biochemical parameters with SLA and PPFD variations were tested. The obtained results suggested long-term acclimation of the selected shrubs to contrasting light environments. In high-light conditions, leaf nitrogen and Chl contents per leaf area unit, leaf thickness, and Chl a/b ratio increased, thus maximizing net photosynthesis, while in shade photosynthesis, it was downregulated by a significant reduction in the electron transport rate. Nevertheless, the increased pigment-protein complexes and the decreased Chl a/b in shade drove to an increased light-harvesting capacity (i.e. higher actual quantum efficiency of PSII). Moreover, the measured vitality index highlighted the photosynthetic acclimation of C. salvifolius to contrasting light environments. Overall, our results demonstrated the morphological, anatomical, and physiological acclimation of C. salvifolius to a reduced light environment.

Non–destructive leaf area determination in African eggplant (<i>Solanum macrocarpon</i>)

Leaf area models are simple, accurate and non-destructive. They are important in many experimental comparisons where leaf area meters are not available. No such model exists for African eggplant (Solanum macrocarpon). This study was, therefore, conducted to develop a leaf area model for S. macrocarpon using linear measurements. A total of 80 fully opened leaves of different sizes were randomly selected. The maximum Lamina length (L) and width (W) of leaf samples were measured. Each leaf margin was traced on standard graph paper. Leaf area was subsequently estimated from the number of squares within each tracing. While the linear functions of length or width measurements, and their squares or products explained 79-92% of variations in leaf area, the linear functions of the inverse of length or width measurements, and their squares or products explained about 40-68% of the variations. Regression analysis of leaf area obtained from graph tracing as dependent variable, L and W as independent variables revealed several models that can be used for estimating the area of individual leaf. While models involving L, W, L2, W2, L×W, and L2×W2 explained 78-91% of the variations in leaf area, models with inverse parameters (1/L, 1/W, 1/L2, 1/W2,and 1/LW), explained 39-67% of the variations. Relative to all parameters evaluated, the model involving L2 had the highest r2, and explained 91% of the variation in leaf area. Since only a single linear measurement is required, the model: Leaf area = 1.06+0.4731L2, is recommended for predicting leaf area in S. macrocarpon.Keywords: Eggplant, Solanum macrocarpon, Leaf area, Leaf area meter, Leaf area model

Response of Bell Pepper Crop Fertigated with Nitrogen and Potassium Doses in Protected Environment

Bell pepper is among the ten most economically important vegetables in the country. The proper management of water and fertilizers coupled with protected environment allows to obtain a quality agricultural production. This study aimed to evaluate the response of nitrogen and potassium doses applied through fertigation on the growth and yield of bell pepper crop, Magali R hybrid. A completely randomized design was used, with 16 treatments in a factorial scheme 4×4, with four replications. The treatments resulted from the combination of four doses of nitrogen (0; 73.4; 146.8 and 293.6 kg ha-1) and potassium (0, 53.3; 106.7 and 213.4 kg ha-1). The experimental plot consisted of a 25 L pot with a bell pepper plant. Seven harvests were made throughout the experiment, and fresh fruit number and mass were evaluated. Leaf area (LA) and total matter accumulation were evaluated as growth components. Regardless of the applied potassium doses, the variables LA and total dry matter showed higher results for N ranging from 155 to 194 kg ha-1. The maximum fresh fruit matter (FFM) (1882 g plant-1) occurred at the dose of 155 kg N ha-1 and 106.7 kg K ha-1 and the maximum number of fruits (NF) (16.3 fruits plant-1) was obtained at the dose of 147 kg N ha-1 and 106.7 kg K ha-1.