Foliar Area Research Articles

A low-cost high-throughput phenotyping system for automatically quantifying foliar area and greenness.

With modern advances in genetic sequencing technology, plant phenotyping has become a substantial bottleneck in crop improvement programs. Traditionally, researchers have manually measured phenotypic traits to help determine genotype-phenotype relationships, but manual measurements can be time consuming and expensive. Recently, automated phenotyping systems have increased the spatial and temporal density of measurements, but most of these systems are extremely expensive and require specialized expertise. In the present paper, we develop and validate a low-cost, scalable, high-throughput phenotyping (HTP) system for automating the measurement of foliar area and greenness. During a greenhouse experiment on the effects of abiotic stress on Brassica rapa, we collected images of hundreds of plants every hour for over a month with a system that cost approximately US$1000. In comparison with manually acquired images, this HTP system was able to produce similar estimates of foliar area and greenness, developmental trends, and treatment effects. Foliar area was correlated between the two image sets, but greenness was not. These findings highlight the potential of HTP systems built from low-cost hardware and freely available software. Future work can use this system to investigate genotype-environment interactions and the genetic loci underlying morphological changes resulting from abiotic stress.

Automated Health Estimation of Capsicum annuum L. Crops by Means of Deep Learning and RGB Aerial Images

Recently, the use of small UAVs for monitoring agricultural land areas has been increasingly used by agricultural producers in order to improve crop yields. However, correctly interpreting the collected imagery data is still a challenging task. In this study, an automated pipeline for monitoring C. Annuum crops based on a deep learning model is implemented. The system is capable of performing inferences on the health status of individual plants, and to determine their locations and shapes in a georeferenced orthomosaic. Accuracy achieved on the classification task was 94.5. AP values among classes were in the range of [63,100] for plant location boxes, and in [40,80] for foliar area predictions. The methodology requires only RGB images, and so, it can be replicated for the monitoring of other types of crops by only employing consumer-grade UAVs. A comparison with random forest and large-scale mean shift segmentation methods which use predetermined features is presented. NDVI results obtained with multispectral equipment are also included.

Cutting grafting of Leucospermum ‘Tango’ on L. ‘Spider’ – effect of wounding, rooting media, and reduction of foliar area of the scion

Cutting grafting of <i>Leucospermum</i> ‘Tango’ on <i>L</i>. ‘Spider’ – effect of wounding, rooting media, and reduction of foliar area of the scion

Plantlia: free android app for measurement of foliar area and color with automated scaling

There is a plethora of apps available for different biological applications, however, mobile software for plant measurement, specifically for field conditions are limited. Additionally, there is a need to create large training datasets for machine learning applications. A free app called Plantlia, which is available to download from the Google Play Store, aims to resolve this with an intuitive interface, and a method to automatically scale images using homography. Plantlia also includes methods to share results from either direct measurements or thresholded images. This paper aims to describe some of the functions of Plantlia, as well as show scenarios that display its performance. Images from cellphones and drone pictures were used for validation on different devices. This is important, as it means that users with low-cost equipment, like drones with no GPS information, can still analyze localized field information. Similarly, researchers can do communal efforts to share and receive in-field data to create machine learning datasets.

Salinity Effect of Nutrient Solution on Maradol papaya

Papaya (Carica papaya L.) is a crop of great economic importance. It is the fourth most produced tropical fruit in the world. The most substantial problems faced during its production are pests and diseases, which is why it has been planted under greenhouse conditions. However, it is required that the plants not be of great height not to need tall greenhouses. Therefore, this research aims to evaluate to the salinity effect and identify nutritive solutions that reduce plant height. The experimental design was completely randomized with four treatments and ten replications. The treatments were four concentrations of Steiner nutrient solution (50 %, 100 %, 150 %, and 200 %) in whose composition are anions (phosphate, nitrate, and sulfate) and cations (potassium, calcium, and magnesium), thus generating electrical conductivity of 1.0, 2.0, 3.0, and 4.0 dS/m, respectively. The variables evaluated were plant height, number of leaves, stem diameter, foliar area, chlorophyll a and b concentration, proline content, and foliar nutrient concentration. The nutrients comprise nitrogen, phosphorus, potassium, calcium, and magnesium. The analysis of variance indicated significant differences in all variables except magnesium concentration. As salinity increased, plant height, number of leaves, stem diameter, leaf area, phosphorus, potassium, and calcium decreased, but chlorophyll a and b concentration, proline content, and nitrogen increased. We conclude that Steiner nutrient solution with 4.0 dS/m (200 %) can reduce plant height to grow it in greenhouses.

Espeletia saboyana (Millerieae, Asteraceae), a New Critically Endangered Caulirosula from Cordillera Oriental, Colombia

Abstract— Espeletia saboyana, a new species from Páramo de Saboyá, Boyacá department, Colombia, is described and illustrated. It is a caulescent rosette up to 5 m tall, with whitish-cinereous appearance, sessile leaves with elliptic laminae, cymose capitulescences with aphyllous unbranched portion and 3‐5 capitula, 5‐13 phyllaries, the external ones 17.4‐26.0 mm long, 49‐92 ray florets 13.0‐18.4 mm long, and 162‐347 disc florets 8.2‐12.2 mm long. Espeletia saboyana is similar to E. incana, but with longer laminae, bigger foliar area, and fewer ray floret series. It is also similar to E. murilloi, but with longer ray tubes, ray paleae, disc corollas, disc styles, disc anther appendages, and disc paleae. In addition, E. saboyana is distributed allopatrically in regard to E. incana and E. murilloi. This species is informally proposed to be listed as IUCN Critically Endangered (CR), since it is restricted to a single population with extent of occurrence = 1.83 km2 and area of occupancy = 0.48 km2. Besides, this population is severely fragmented into 40‐50 demes, the largest one covering only 34,000 m2. Most demes are found in humid soils and wetlands submitted to continuous habitat deterioration as water is drained for use in agriculture. Espeletia saboyana is rare or absent in these newly drained areas, which are either colonized by other species that thrive on drier soils or transformed into pastures for cattle grazing. Furthermore, analyses of size class distributions show that recruitment rates of E. saboyana are significantly lower in small demes, which, if not reversed, can further reduce population size in the near future.

Biosólidos como fertilizante en el cultivo de tomate

The sludge produced in wastewater treatment plants constitutes a potential alternative to replace traditional fertilizers and reduce costs in agricultural activities. The objective of this work was to compare the fertilizing effect of the sludge produced in the wastewater treatment plant of Sotaquirá-Colombia, with the fertilizers traditionally used on the tomato crop (Solanum lycopersicum L). For this, the sludge was previously stabilized with two different treatments: dehydration and the addition of CaO. Subsequently, four treatments were applied to the tomato seedlings, 135 g.kg-1 of dehydrated biosolid, 135 g.kg-1 biosolid stabilized with CaO, 135 g.kg-1 of ABIMGRA®, 135 g.kg-1 of naturcomplet®-G, and greenhouse soil without biosolids. The height of the plant, the fresh and dry mass, foliar area, and fruits per plant, were measured at 0, 30, 60 and 90 days after sowing. In tomato fruits, the concentrations of heavy metals, coliforms, helminth eggs, somatic phages, and Salmonella sp., were determined. The dehydrated biosolids had a significant effect on the size, the fresh mass, foliar area, and the number of fruits per plant, compared to the alkaline biosolids. The dry mass of the plants (120 g. plant-1) was similar to traditional fertilizers and biosolids. Tomatoes produced with biosolids had low levels of heavy metals and an absence of pathogenic microorganisms. In conclusion, the biosolid obtained by dehydration in Sotaquirá can be used as a potential fertilizer in tomato cultivation.

Effect of Enerplant® doses on the development and nutrient use by cacao (Theobroma cacao L.) seedlings

Objective: To evaluate the effect of the application of biostimulant doses on the development, absorption, and use efficiency of nitrogen, phosphorus, and potassium by cacao seedlings. Design/Methodology/Approach: Five doses of Enerplant® (0, 1, 2, 3, and 4 mL ha-1) were applied to cacao seedlings grown under a saran mesh. The study was carried out using a completely randomized design. The foliar area received a monthly application of the biostimulant. In order to determine the nutrient absorption, 3 plants per treatment were divided into leaves, stems, and roots; they were subsequently dried for 72 h at 65 °C. Finally, they were ground, packaged, labeled, and sent to the laboratory, where the macronutrients of each component were analyzed. Results: The cacao seedlings had a positive response to the biostimulant application. In average, the results of our two-year study were: 1 mL ha-1 doses of Enerplant® significantly increased height (24%), dry mass (30%), quality index (58%), and foliar area (56%) of the cacao seedlings. Doses higher than 1- and 2-mL ha-1 decreased plant growth. The nutrient absorption by cacao in the nursery stage followed the following pattern: K &gt; N &gt; P. Findings/Conclusions: The efficiency of nutrient use —regardless of the Enerplant® dose applied— was higher for P, followed by N and, finally, K. Applying 2 mL ha-1 doses of the biostimulant guaranteed the highest absorption and use efficiency values of macronutrients by cacao seedlings.

Control of N-NH4+ and K+ leaching in potato using a carrageenan hydrogel

Potato cultivation requires fertilizers to sustain crop yields, but a significant percentage of added nutrients is lost by leaching. The use of coating materials for fertilizers is currently being considered to reduce these losses. The objective of this study was to determine if a carrageenin based hydrogel (CBH), used to coat fertilizer, decreases NH4+ and K+ leaching from a potato crop without affecting growth, specific gravity, and tuber yield. The CBH was tested in a diploid potato crop, cultivar Criolla Colombia (Solanum tuberosum L., Phureja Group) using a randomized full block design including the treatments noncoated fertilizer (T1), CBH coated fertilizer (T2), and no fertilizer (T3). Mineral nutrients in soil leachates together with dry biomass, foliar area, chlorophyll, tuber specific gravity, and yield were quantified. The nutrient content in leachates from T2 were below those from T1. No significant differences between treatments were observed for growth factors, yield, and tuber specific gravity. This study confirms the controlling effect of the CBH, ensuring the retention of the nutrients added in the fertilizer and preventing them from easily leaching. Future field studies are worthwhile to establish the amount of fertilizer this coating could save.

RESPUESTA DE Origanum vulgare L. AL ESTRÉS POR NaCl

&lt;p&gt;&lt;strong&gt;Background&lt;/strong&gt;. One of the classic land degradation problems that man has had to face is controlling, preventing, or improving soils affected by salinity. &lt;strong&gt;Objective&lt;/strong&gt;. The objective of this study was to evaluate the physiological and morphometric response of &lt;em&gt;Origanum vulgare&lt;/em&gt; L. plants subjected to five concentrations of NaCl (0, 50, 100, 150 and 200 mM NaCl). &lt;strong&gt;Methodology&lt;/strong&gt;. The experiment was established in a completely randomized design with five treatments based on different concentrations of NaCl (0, 50, 100, 150 and 200 mM) with four replications per treatment. Each repetition consisted of 14 plants. The variables evaluated were fresh and dry weight of leaves, leaf area, fresh and dry weight of stem, stem length, fresh and dry weight, and root length, chlorophyll content a and b, relative water content and water potential. &lt;strong&gt;Results. &lt;/strong&gt;The results showed that the fresh and dry weight of leaves, stem and root, foliar area, as well as the length of stem and root showed significant differences between treatments, they decreased as NaCl concentrations increased in the culture medium, as did the chlorophyll content "a and b". It is concluded that oregano plants have the capacity to absorb Na from the culture medium in 50, 100 and 150 mM of NaCl. &lt;strong&gt;Implications.&lt;/strong&gt; The study makes the possibility to determine the tolerance of oregano to salinity, by subjecting the plants to different concentrations of NaCl and assessing whether it has the capacity to absorb Na&lt;sup&gt;+&lt;/sup&gt; from the culture medium. The study shows that it is possible to grow oregano in floating root hydroponic conditions, considering the advantages that this system offers, such as saving water and nutrients, being possible to obtain adequate yield using water of moderate salinity (50 mM NaCl) that represents an electrical conductivity of 5.8 dS m&lt;sup&gt;-1&lt;/sup&gt;. &lt;strong&gt;Conclusions.&lt;/strong&gt; All variables decreased as NaCl concentrations increased in the culture medium. Oregano showed the ability to absorb Na&lt;sup&gt;+&lt;/sup&gt; from the culture medium in 50, 100 and 150 mM NaCl.&lt;strong&gt;&lt;/strong&gt;&lt;/p&gt;

Insecticides action of neonicotinoids group in fall armyworm (Spodoptera frugiperda) control on bean leaves (Phaseolus vulgaris)

Among several factors that impact the bean culture productivity there are pest insects, which affect the plant since seeding until postharvest, causing loss in the culture yield. The fall armyworm (Spodoptera frugiperda) stands out among the main pests of common bean (Phaseolus vulgaris). The aim of this work was to evaluate the effectiveness of insecticides of the neonicotinoid group in the control of the fall armyworm in the bean crop, comparing dinotefuran, acetamiprid, thiamethoxam and imidacloprid performance. Experimental design was composed of blocks entirely randomized, with 9 treatments and 10 replicates. Three caterpillars, at the stage of second instar, were used in each experiment, focusing on the ingestion of leaves containing the treatments. Evaluations were realized in the intervals of 1, 3, 6 and 8 days after every application, counting the number of caterpillars alive in the Petri’s dish, attributing visual notes on bean leaves, according to the foliar area affected (consumed). The dinotefuran treatment with the highest dose presented superior efficiency at 80% in the first evaluation. The thiamethoxam treatment with the lowest dose, in the latest analyses, showed efficient superior at 90%. The major doses of all treatments presented efficiency higher than 80% in the last evaluations, being efficient in the S. frugiperda control.

STUDIES REGARDING WHEAT LEAVES INVESTMENTS IN RELATION WITH NITROGEN SUPPLY

The purpose of this research was to describe the behavior of some determined and calculated indices for wheat leaves samples in relation with ammonium nitrate fertilizing dose. Also, relations between these indices were done. Wheat, Triticum aestivum, Ciprian cultivar, was grown within the Didactic Station of Banat’s University of Agricultural Sciences and Veterinary Medicine “King Michael I of Romania” from Timisoara in 2018-2019 agricultural year. Here the soil can be described as cambic chernozem, partially gleized. Wheat plants were fertilized with ammonium nitrate in five experimental doses, 0, 50, 100, 150 and 200 kg ha-1, respectively. Healthy, intact, with no visible damage leaves were harvested (BBCH Code 45) and taken into a laboratory. The samples were scanned, dried in an oven, incinerated and organic matter per surface (OMPS) was determined. This index described the realized investments in organic substances in the case of leaves and had bigger values for doses between 100 and 200 kg ha-1 N. Moreover, classical gravimetric indices, LDW – leaf dry weight, LAC – leaf ash content, OM – organic matter, were determined in order to realize correlation analysis between all parameters. Also, foliar areas, perimeters and lengths were determined. Mathematical models for foliar area, leaf dry weight and organic matter determination in relation with other indices were developed. Positive correlation were noticed between the majority of the studied indices. Also, PCA and Cluster analysis were realized, resulting in two major groups of plants: those fertilized with N0 and N50, and another group formed by N100, N150 and N200 group.

Leaf Area Calculation Models for Vines Based on Foliar Descriptors.

In the case of foliar area studies on vines, with a large number of determinations, a simple, fast, sufficiently accurate and low-cost method is very useful. The typology of leaves on the vine is complex, characterized by several descriptive parameters: median rib; secondary venations of the first and second order; angles between the median rib and the secondary venations; sinuses; length and width of the leaf. The present study aimed to evaluate models for calculating the leaf area based on descriptive parameters and KA (KA as the surface constant used to calculate the leaf area) for six vine cultivars, ‘Cabernet Sauvignon’ (CS), ‘Muscat Iantarnîi’ (MI), ‘Muscat Ottonel’ (MO), ‘Chasselas’ (Ch), ‘Victoria’ (Vi) and ‘Muscat Hamburg’ (MH). The determined KA surface constants had subunit values (0.91 to 0.97), except for the cultivars ‘Muscat Iantarnîi’ and ‘Muscat Ottonel’ where the surface constant KA2 (in relation to the second-order secondary venations) had supraunitary values (1.07 and 1.08, respectively). The determination of the leaf area was possible under different conditions of statistical accuracy (R2 = 0.477, p = 0.0119, up to R2 = 0.988, p < 0.001) in relation to the variety and parametric descriptors considered. The models obtained from the regression analysis facilitated a more reliable prediction of the leaf area based on the elements on the left side of the leaf, in relation to the median rib, compared to those on the right. The accuracy of the results was checked on the basis of minimum error (ME) and confirmed by parameters R2, p and RMSE.

Deep learning architectures for semantic segmentation and automatic estimation of severity of foliar symptoms caused by diseases or pests

Colour-thresholding digital imaging methods are generally accurate for measuring the percentage of foliar area affected by disease or pests (severity), but they perform poorly when scene illumination and background are not uniform. In this study, six convolutional neural network (CNN) architectures were trained for semantic segmentation in images of individual leaves exhibiting necrotic lesions and/or yellowing, caused by the insect pest coffee leaf miner (CLM), and two fungal diseases: soybean rust (SBR) and wheat tan spot (WTS). All images were manually annotated for three classes: leaf background (B), healthy leaf (H) and injured leaf (I). Precision, recall, and Intersection over Union (IoU) metrics in the test image set were the highest for B, followed by H and I classes, regardless of the architecture. When the pixel-level predictions were used to calculate percent severity, Feature Pyramid Network (FPN), Unet and DeepLabv3+ (Xception) performed the best among the architectures: concordance coefficients were greater than 0.95, 0.96 and 0.98 for CLM, SBR and WTS datasets, respectively, when confronting predictions with the annotated severity. The other three architectures tended to misclassify healthy pixels as injured, leading to overestimation of severity. Results highlight the value of a CNN-based automatic segmentation method to determine the severity on images of foliar diseases obtained under challenging conditions of brightness and background. The accuracy levels of the severity estimated by the FPN, Unet and DeepLabv3 + (Xception) were similar to those obtained by a standard commercial software, which requires adjustment of segmentation parameters and removal of the complex background of the images, tasks that slow down the process.

Self-Assembled Degradable Nanogels Provide Foliar Affinity and Pinning for Pesticide Delivery by Flexibility and Adhesiveness Adjustment.

At present, it is highly important to develop a simple and compatible nano delivery system for pesticides for foliar application, which can improve their insecticidal efficacy and resistance to adverse climates while reducing the environmental risks. Polyethylene glycol and 4,4-methylenediphenyl diisocyanate are used as hydrophilic soft and hydrophobic hard segments, respectively, for polymer self-assembly and polyurethane gelation in a nanoreactor. The nanocarrier synthesis and the pesticide loading are realized by a one-step integration procedure and suited well for hydrophobic active compounds. Modifying the molecular structure of the soft segment can adjust the flexibility of the nanocarriers and result in viscosity and deformation characteristics. After foliar spray application, the foliar flattening state of the nanogels increases the foliar protection area by 2.21 times and improves both pesticide exposure area and target contact efficiency. Concurrently, the flexibility and viscosity of the nanogels increase the washing resistance and the retention rate of the pesticide by approximately 80 times under continuous washing. The encapsulation of the nanogels reduces the foliar ultraviolet (UV) degradation and aquatic pesticide exposure, which increase the security of λ-cyhalothrine by 9.33 times. Moreover, the degradability of nanogels is beneficial for pesticide exposure and reducing pollution. This system has simple preparation, good properties, and environmental friendliness, making the nanocarriers promising for delivering pesticides.

Plant growth biostimulant activity of the green microalga Desmodesmus subspicatus

The plant biostimulant activity of the green microalga Desmodesmus subspicatus was investigated, focusing on its potential application to organic crops. Different concentrations of D. subspicatus biomass suspensions were applied to tomato seedlings (Solanum lycopersicum) via a foliar spray. The treatments promoted root growth and foliar area, which increased when the suspension was applied at concentrations of 1 g L−1 and 0.4 g L−1, respectively. To elucidate the major constituents responsible for this potential activity, the biomass of D. subspicatus was submitted to aqueous extraction and dialysis (1 kDa cut-off), giving rise to the non-dialyzable fraction E (12.3%). Size-exclusion chromatography performed on fraction E using a Bio-Gel P-2 column yielded six subfractions. Gas chromatography-mass spectrometry (GC–MS) and nuclear magnetic resonance (NMR) analyses of the E subfractions revealed the presence of glycosides as major constituents (approx. 81%), including one acidic glycoside, [6-sulfo-α-D-quinovopyranosyl-(1→1)-glycerol], and two neutral galactosyl glycosides, [α-D-galactopyranosyl-(1→6)-β-D-galactopyranosyl-(1→1)-glycerol] and [β-D-galactopyranosyl-(1→1)-glycerol]. Ultra-high-performance liquid chromatography-mass spectrometry (UHPLC-MS) analyses of fraction E resulted in the identification of the phytohormone zeatin (35 μg g−1). To evaluate the biostimulant potential of fraction E, different concentrations (0.5, 1.0, 1.5, and 2.0 g L−1) were tested for their effects on tomato seed germination, hypocotyl volume, and length. All tested concentrations induced increased hypocotyl lengths and volumes compared with standard treatment (water), at rates equivalent to those in response to a commercial product derived from Ascophyllum nodosum brown seaweed. These results indicated that the biomass suspension and aqueous extract of D. subspicatus showed plant growth biostimulant activity. Glycosides, together with zeatin, may play important roles in biostimulant activity.

The role of seed size in the performance of Ceiba aesculifolia seedlings subjected to foliar damage

In tropical forests, herbivore damage is one of the main causes of seedling mortality. However, along with seed size, the resources herbivores provide are an important factor in a seedling's response to selection pressure. The objective of this study was to evaluate the role of seed size and artificially-induced herbivory on the functional traits of Ceiba aesculifolia seedlings. To do this, we established four levels of foliar damage: 10%, 25%, 50%, and 75% (n = 270), and a control treatment (no damage; n = 60). Foliar damage treatments were conducted 60 days after germination. These treatments were applied to seedlings developing from seeds of three different sizes. The response variables were growth, some foliar traits, and seedling biomass. Seedlings from small seeds showed higher growth rates in terms of height (0.44 ± 0.02 cm month−1), diameter (0.24 ± 0.01 mm month−1), and foliar production (9.1 ± 0.19 leaves), as well as higher total dry weight (8.5 ± 0.03 g) and larger leaf area (49.3 ± 1.9 cm2) than those from medium and large seeds. Seedlings from large and medium seeds showed higher root:stem ratio values than seedlings from small seeds (p < 0.05). Foliar damage was found to have an effect on dry weight. The total biomass of seedlings with 75% damage was considerably smaller than that of seedlings with 10% damage. Chlorophyll content was found to be related to the interaction between seed size and foliar damage, and it was lower in seedlings from medium seeds and 50% damage than in those from small seeds with the same level of damage and large seeds with 75% damage. In short, seed size had a significant effect on growth traits. Contrary to our expectations, seedlings from small seeds showed the best performance in terms of height, biomass, number of leaves, and foliar area.

Erinea in the 'Ansonica' grapevine cultivar: trichome complement, histological effects and analysis of chlorophyll fluorescence in affected leaves

Grapevine leaves are usually characterized by trichomes, specialized epidermal cells. They are interesting in ampelography and also important for the plant ecological responses in biotic and abiotic interactions. In nature, the trichome development is a genetic trait but it can be modified by pests as eriophyid mites. Colomerus vitis is quite common and its economic value is sometime substantial. Here, we studied the leaf erineum induced by C. vitis on 'Ansonica' ('Inzolia'), an important grapevine cultivar characterized by a low level of leaf trichome coating. To date, the interaction between C. vitis and grape has been investigated in few pedo-climatic conditions and no data are reported in 'Ansonica'. Therefore, our objectives were: (1) the analysis, in a Tuscan environment, of the morphology and histology of trichomes in 'Ansonica' leaves unaffected or affected by C. vitis; (2) evaluation, in mature leaves, of the effects of the mite both on pigment content and chlorophyll a fluorescence parameters. 'Ansonica' was devoid of glandular trichomes but it has been established the presence of few simple trichomes strictly associated with the veins. In the erineal sectors, a dense proliferation of simple trichomes in the abaxial epidermis and the development of hyperplasia in the adaxial surface were observed. Moreover, the leaf sections in the erineal regions were thicker due to an abnormal development of the lacunar parenchyma, and trichome proliferation was also extended to interveinal regions. Leaves with erinea showed a deficient content of carotenoids, in comparison to unaffected leaves. In 'Ansonica' leaves, C. vitis induced a decrease in the steady-state operational efficiency of photosystem II associated to a reduction in photochemical quenching and an increase in non-photochemical quenching values. In leaves with erinea, the reduction of photosystem II efficiency was extended to foliar areas not directly affected by galls. The collected results highlight that 'Ansonica' is susceptible to attacks by C. vitis and in the case of widespread leaf attacks the productive damage should not be underestimated.

The anniversary conference "Structural Components of Forest Ecosystems: ecology, conservation and management" held in honour of Prof. Nicolae Donita

The anniversary conference "Structural Components of Forest Ecosystems: ecology, conservation and management" held in honour of Prof. Nicolae Donita

Growth of Alfavaca-Cravo in Response to Different Levels of Shade and Tiririca Density

The species Ocimum gratissimum L. is widely utilized in food, cosmetics, and folk medicine, and is also an important source of essential oils. Understanding its behavior in response to environmental conditions is of paramount importance to improving crop management methods. In this context, the following study aimed to evaluate the effects of shade, and of competition with weeds (Cyperus rotundus L.), on the growth of Ocimum gratissimum L. The experimental design adopted was randomized blocks, in a 5 &amp;times; 5 factorial scheme, with 5 levels of shading (48%, 75%, 77%, 83% and 90%) and 5 densities of Cyperus rotundus L. (0, 5, 10, 15 and 20 per pot), with 4 repetitions. The variables analyzed were main stem height (MSH), diameter of stem base (DSB), number of leaves on the principal branch (NL), number of ramifications (NR), chlorophyll index of leaves (CIL), foliar area (FA), dry mass of the aerial part of the medicinal species (DMAPm), dry mass of the aerial part of the weed species (DMAPw) and essential oil content (EOC). The results demonstrate that the Ocimum gratissimum L. plants presented compatible tolerance responses to up to 70% shading, and that competition with Cyperus rotundus L. was detrimental in a density above 13 plants per pot in interaction with shading. The highest dry mass production and, consequently, the highest oil yield, were obtained from the 48% shading treatment.