Shading Screens Research Articles

Hybrid passive cooling and heating system for Mediterranean greenhouses. Microclimate and sweet pepper crop response

The microclimate of low-tech, unheated greenhouses in Mediterranean areas, associated with the local outdoor climate, is often outside the optimal range for most horticultural crops during both the warm and cold growing season. The use of a new hybrid system of passive cooling (evaporative screens) and heating (water-filled sleeves), in combination with an internal movable shading/thermal screen, was evaluated on a representative summer transplanted sweet pepper crop grown in perlite growing bags. The experiment was carried out in two identical greenhouses at the IFAPA La Mojonera research center in Almeria (SE Spain): one greenhouse with the hybrid passive system of cooling and heating, in combination with a shading/thermal screen, and another (reference greenhouse) using common local greenhouse climate management practices. Evaporative screens, in combination with a movable shading screen, improved the greenhouse climate, in particular the air vapour pressure deficit, and increased the leaf area index in the early stages of the crop, which, in turn, increased the early production of leaf and shoot dry matter and marketable fruit, compared to the reference greenhouse crop. In addition, the combined use of water-filled sleeves and thermal screen during the cold growth period increased greenhouse air temperatures, especially at night, and substrate temperatures. Overall, by improving the greenhouse microclimate during the warm and cold growth periods, the hybrid passive cooling/heating system, in combination with the shading/thermal screen, increased the marketable yield of a summer transplanted sweet pepper crop by 25 %, reduced the irrigation water supply by 8 %, and improved the irrigation water use efficiency by 20 % (including the potential water used to humidify the evaporative screens).

Aerodynamic properties of boundary layers along the roof of a large banana screenhouse under near-neutral atmospheric stability

Cultivation under screens and in screenhouses protects the crops from insects and extreme climate conditions and allows water saving. Previous studies considered the aerodynamic properties of boundary layers along two types of screens: a small shading thermal screen covering a hedgerow citrus orchard and a large 50-mesh, insect-proof screen covering a pepper plantation. To extend the previous results, a third type of screen was analysed in this study, a large flat-roof 17-mesh white woven shading screen covering a banana plantation. Vertical profiles of wind speed, air temperature, relative humidity, and friction velocity were measured by a lifting tower, and wind profiles were analysed under near-neutral atmospheric stability. Results show that normalised friction velocity, normalised roughness length, normalised zero plane displacement height and aerodynamic resistance are closer to the previous results of the large insect-proof screenhouse than those of the small shade net.

Tecnologias para redução do uso de água no abacaxizeiro em região semiárida

ABSTRACT: In irrigated systems, the adoption of management methods like soil cover, polymers which absorb the water present in the soil and the utilization of shading screens can decrease the water consumption by the plants. This is achieved as these means protect the plant and soil against radiation and wavelengths of light undesirable for cultivation. However, for pineapple cultivation in the semi-arid climate regions, very little study has been done regarding these technologies. Hence, the present study conducted to assess the pineapple growth, production and quality when various kinds of soil cover, red shading screen and water absorption polymers are employed. To accomplish this, a field trial was performed utilizing four types of soil cover in the plots (plastic mulching; organic matter; organic matter + red shading screen 50%; plastic mulching + red shading screen 50% and the control (no cover).Two treatments were included in the subplots namely, either the absence or presence of a water-absorbing polymer in the planting hole (0.5 g per plant), arranged in subdivided plots. We adopted the Randomized Complete Block (RCB) , with three replications. The following aspects of the plants were studied: naturally flowering, stem diameter; leaf area index; D-leaf area and total leaf area; fruit weight with crown; fruit weight without crown; fruit length with crown; and fruit length without crown, as well as the traits of the post-harvest fruit, soluble solids, titratable acidity, pH and the soluble solids/titratable acidity ratio. Further, the productivity in t ha-1 and efficiency of water use (EUA) were ascertained. It was evident that the plastic mulching + 50% red shading screen favored the vegetative development and productivity of the ‘IAC Fantástico’ pineapple plants. The characteristics of the quality of the postharvest fruit were unaffected by the treatments. The shading screen reduced the percentages of natural flowering in the treatments which included organic matter + red shading screen 50% and plastic mulching + red shading screen 50%.

Cytogenotoxic potential of Malva parviflora L. cultivated under different light conditions

For many centuries, the treatment with medicinal plants was the only means accessible to various ethnic groups, and nowadays plants are still widely used in the treatment of diseases, besides being the raw material for several drugs. However, many of these plants may present unknown genotoxic effects, making their consumption a health risk. Species such as Malva parviflora L. have been used by the general population for medicinal purposes: antifungal, anti-inflammatory, analgesic, and antioxidant. This study had the objective of analyzing the cytogenotoxic potential of aqueous extracts of this Malva species using the Allium cepa test, which serves as a bioindicator of the genotoxicity of plant extracts. Forty-four seedlings of M. parviflora were grown for 36 days between November and December 2020, in a greenhouse in two groups: half of the plants were protected with a shading screen, and the rest were not. The aqueous extracts were prepared from the aerial part and roots (fresh and dehydrated), at the concentration of 5 g L-¹. The bulbs of A. cepa were left for 24 hours in the treatments, plus the negative (distilled water) and positive (glyphosate 1.5%) treatments. The roots of the bulbs were collected, placed in the fixative for 24 hours, transferred to 70% alcohol, and stored in a refrigerator. The slides were prepared by the crushing technique, and cells in the division and with chromosome alteration were analyzed, mitotic and genotoxic index were calculated, and statistical analysis was done by the Chi-square and Scott-Knott tests. From the results obtained, it is possible to conclude that the aqueous extracts of M. parviflora at a concentration of 5 g L-¹ present antiproliferative activity, but are not genotoxic. The cultivation mode is relevant, that is, with and without shading the fresh leaves present a difference in cell proliferation, but the same does not occur with the dried leaves.

Characterization and modeling of bistable laminates for kinetic shading screens

There is an critical need in kinetic envelope design to propose sustainable solutions that can adjust to changing outdoor conditions. Bistable composite laminates are compliant systems appealing for kinetic building envelopes because they present two stable equilibrium states and transition between them with little input energy. This study characterizes the behavior of bistable laminates for kinetic screens by developing an FEA model and conducting experimental testing to validate the model and compare both data sets. The FEA model predicts the laminates’ cured states, snap-through movement, and required actuation force. The FEA model can accurately predict the cured states of the laminates. Regarding the movement of the laminate and actuation force, the simulation results mostly correlate quantitatively with the experimental data and differ qualitatively. However, the FEA model can accurately predict the critical force required to snap through the laminates, which ranges between 2.5 and 4 N.

Assessment of health hazards of greenhouse workers considering UV exposure and thermal comfort

Greenhouse (GH) indoor environments are usually manipulated to enhance plant growth and yield, but those environments might not be favorable for GH workers. This study aimed to investigate the health hazards of greenhouse workers from UV radiation exposure and analyze the heat stress and thermal comfort in air-conditioned greenhouses. Two GHs with different covering materials (glass greenhouse-GGH and polycarbonate greenhouse-PCGH) were selected for this study. The UV index of GGH varied from moderate to high (3 to 8) based on the season and deployment of the shade screen, whereas PCGH was always UV risk-free below and above the shade screen. Heat stress was evaluated in terms of wet bulb globe temperature (WBGT) and thermal comfort with the predicted mean vote (PMV) and predicted percent dissatisfied (PPD). The value of WBGT in GGH varied between 17.67 °C and 26.54 °C and between 18.25 °C and 25.97 °C in PCGH. The PMV values ranged from -2.57 to 1.15 for GGH and from -2.24 to 1.42 for PCGH, depending on airspeed, metabolic rate, and indoor conditions. The PPD values ranged between 5.0 to 94.6 % for GGH and 5.0 to 75.0 % for PCGH. As the optimal target range of the indoor environmental parameters (temperature and relative humidity) were maintained in the modern GHs throughout the year, the potential for heat stress and thermal discomfort was not severe. However, as a precaution, avoiding heavy activities around noon is recommended, even in perfectly conditioned greenhouses, which could be above the danger level in low-tech greenhouses.

Does brassinosteroid mitigate salt stress in sorghum?

The objective of the present study was to assess the mitigating effect of brassinosteroid regulator plant on damages caused by salt stress in sorghum. The experiment was carried out in pots containing 5 kg of substrate, on benches in a greenhouse covered with transparent plastic film and with a 50% shade screen on the sides. A completely randomized design with four replications was used, in a 2×5 factorial arrangement consisted of application and non-application of brassinosteroids at concentration of 0.1 mg L-1 applied at the 30, 37, and 45 days after emergence (DAE) and five salinity levels of the irrigation water (electrical conductivities of 0, 2, 4, 8, and 16 dS m-1). The plants were irrigated with water from the public supplying system up to 45 DAE and, then, with brackish water up to 60 (DAE), when they were evaluated. Our results indicate that Brassinosteroids mitigated damages caused by salt stress by increasing the Ca to Na ratio. Sorghum is moderately resistant to salt stress by presenting a sodium extrusion mechanism activated by calcium. Further studies with longer exposure time to salt stress are recommended for a more thorough understanding and recommendation of the use of brackish water in sorghum crops

Physiological, growth, yield, and quality responses of hot pepper due to shade level

ABSTRACT High temperatures, high relative humidity, and frequent rainfall limit productivity and quality of red chili pepper (Capsicum annuum L) with 30,000 to 50,000 Scoville units. Growers in greenhouses use shading screens to limit incidence radiation in order to avoid the issue of too high temperatures and high radiation. A pot experiment was conducted to assess growth, physiology, yield, and quality responses of three pepper varieties under four shade levels. The combined effects of shade level and pepper variety affected days to 50% flowering, days to breaker stage, plant height, node number, internode length, branch number, relative growth rate, leaf number, leaf area, transpiration rate, photosynthesis rate, stomatal conductance, leaf temperature, fruit length, fruit weight per plant, total soluble solids, marketable fruit yield, cull fruit yield, total fresh fruit yield, and total dry fruit yield. Shade levels from 25% to 50% positively affected chlorophyll fluorescence, chlorophyll content, stomatal conductance, transpiration rate, fruit yield, and quality parameters; above this shade level, these parameters were negatively affected in all pepper varieties. Light and shade influenced growth, physiology, yield, and quality of hot peppers. The hot pepper variety Mareko Fana, grown under 25% shade, improved its productivity and pod quality.

Influence of Different Protected Environments and Reflector Material on Cultivated Oiti (Licania tomentosa[Benth.] Fritsch) Seedlings

Abstract Background Oiti (Licania tomentosa[Benth.] Fritsch) is an option for urban forestation and rural environments that require shading by plants, so studying the plant environment to obtain quality seedlings is essential. The present study aimed to evaluate oiti seedlings in different protected environments with or without reflective material on a cultivation bench. Methods The following protected environments were evaluated: an agricultural greenhouse covered with a low-density polyethylene film and a thermo-reflective screen with 42%/50% shading under the film; an agricultural screenhouse with an aluminized screen with 35% shading; an agricultural screenhouse with a black screen with 30% shading; and an agricultural screenhouse with a black screen with 18% shading. Production systems with and without photosynthetically active radiation-reflecting material (aluminized screen, Aluminet®) on the cultivation bench were assessed in each protected environment. Results There was no interaction between the environmental factors; however, the environments influenced height, stem diameter, root dry matter, and total biometric relationships and growth rates. The reflective material did not improve the quality of oiti seedlings. The ratio of shoot and root dry matter was, on average, 71% for the shoots and 29% for the roots. The photosynthetically active radiation received by oiti seedlings ranged from 600 to 1,100 μmol m−2s−1. Conclusions The greenhouse with 42%/50% shading screen under the film and the black screen with 30% shading were the best environments for the formation ofLicania tomentosaseedlings. The reflective material on the cultivation bench did not result in better quality oiti seedlings.

PRODUCTION OF AMARYLLIS CULTIVAT ED UNDER PHOTOCONVERTER SHADING NETS

Plant growth and development are influenced by biotic and abiotic factors. Considering the abiotic factors, light intensity can be manipulated using shading screens in order to induce better plant performance. Thus, the objective of this study was to evaluate how different shading conditions affect growth and development, starting from Hippeastrum plantlets, and plant flowering, after vernalization. Seedlings produced in vitro and acclimatized were transferred and covered with different shading nets (black, red, blue and, as a control, full sun). Agronomic and physiological analyses were performed. At the end of the cycle, the bulbs were collected, sanitized and went through vernalization in a cold chamber at 13 °C for 40 days. After this period, the bulbs with diameters between 50 mm and 60 mm were planted under the same conditions of shading and full sun; agronomic and physiological parameters were also analyzed. In the initial development stage, plants grown under black and blue shading nets showed higher chlorophyll content, in addition to fresh and dry matter of bulbs and leaves. A greater accumulation of fresh and dry matter was observed in plants grown under red shading nets. After the vernalization period, similarity was observed in initial cultivation, in which leaf growth and chlorophyll content were higher in plants grown in blue shading net and flowering was stimulated in the red shading net. Thus, the use of blue shading nets stimulates Hippeastrum leaf growth. However, with the objective of flower production, it is recommended to use red shading nets to accelerate the flowering process.

Sombreamento e época de cultivo no desempenho agronômico de jambu

ABSTRACT The jambu (Acmella oleracea) production can be influenced by the growing season and light available for metabolic processes. This study aimed to assess the agronomic and physiological performance of two jambu varieties, under different shading levels, during the winter and summer of the Brazilian Amazon. Two random block experiments were conducted, in a 2 x 4 factorial scheme, consisting of two jambu varieties (yellow and purple flower) and four shading levels (0, 30, 50 and 70 %), with four replications. Physiological, growth and yield traits were assessed. There was no significant interaction between treatments and growing seasons (Amazon winter and summer) for growth or yield traits, nor between treatments for the physiological characteristics. The cultivation without shading screen can increase the shoot dry weight of both varieties; the yellow flower variety exhibited early-onset flowering regardless of the shading screen used; the “Amazon summer” growing season increased the jambu yield by 33 %, while the 70 % shading reduced the net photosynthetic rate, consequently not favoring the vegetative development of the jambu plants. As such, it is recommended that the yellow and purple flower jambu varieties be grown without shading screen in the Amazon summer.

Estabelecimento e produção de plantas de bastão-do-imperador associadas a inoculação com Fungos Micorrízicos Arbusculares

Abstract Traditionally, Torch Ginger is commercially propagated via rhizomes. Micropropagation (M) is a viable alternative that ensures the genetic and phytosanitary quality of plantlets. However, in vitro cultivation conditions can lead to morphophysiological disorders resulting in death or difficulties in the acclimatization process and establishment of seedlings/plantlets in field conditions. Thus, Arbuscular Mycorrhizal Fungi (AMF) has been used in some crops in order to mitigate the drastic effects during acclimatization and establishment of micropropagated plantlets in the field. In this sense, the objective of this study was to evaluate the implantation forms and efficacy of micropropagation and AMF inoculation on the establishment and production of Torch Ginger plants. The planting was carried in shading screens (50%) and different implantation forms were used; through rhizome (RIZ) and plantlets micropropagated with (M+AMF) and without (M-AMF) inoculation with arbuscular mycorrhizal fungi. Evaluations of growth, phenology and mycorrhizal colonization were carried out for one year. Micropropagation, independently of AMF inoculation, favoured a better development in height and number of tillers when compared to RIZ plants It is concluded that micropropagated plants of E. elatior showed earlier tiller emission, better development and initial establishment in the field. Additionally, the forms of implantation of E. elatior via rhizome and via micropropagation with or without AMF inoculation produce inflorescences with the minimum characteristics required for commercialization.

Chicória da Amazônia: cultivo a pleno sol ou sombreado?

ABSTRACT Climatic factors can decisively influence the growth and productivity of agricultural crops. For unconventional vegetables, such as the Amazon chicory, the influence of sunlight on growing cycle is unknown. The aim of this study was to evaluate the influence of shading levels on the productive performance of Amazon chicory. The authors used a randomized block design, with four treatments and five replicates. The treatments were black polypropylene screens, 30, 50 and 70% shading, and cultivation at full sunlight. Vegetative development and production traits were evaluated. Correlation and principal components analysis (PCA) were performed with the aid of the computer program R. No significant difference between the shading levels for the evaluated traits was noticed. Nevertheless, the cultivation at full sunlight allowed an increase in production, compared to the 70% shading screen. A strong positive correlation between productivity, leaf fresh mass and amount of water in the shoot area was verified, with a coefficient equal to 1. Only the leaf area characteristic was poorly correlated with other traits (angle >90º). Therefore, we suggest growing the Amazon chicory both at full sunlight and under 70% shading.

Crescimento, desenvolvimento e qualidade do gladíolo ‘White Goddess’: época de cultivo, tela de sombreamento e cobertura do solo

ABSTRACT To reduce the risks associated with the production of gladiolus flowers in the climatic conditions of southwestern Paraná, Brazil, this study characterized the growth, development, and floral stem quality of plants cultivated under different-colored shade nets and mulching in four growing seasons. The gladiolus cultivar ‘White Goddess’ was grown in beds with and without mulching in the soil. Three shade nets individually stained black, silver and red all with 35% shading, were used in this study, and an additional treatment (control) in which plants were grown in full sun. Growth (LAI and height), development (cycle in days, and degree-days), and flower quality (size and stem damage) were evaluated in eight plants in each treatment. Plants were distributed in a randomized block design in a factorial scheme (season x mulching x shade screen). The cycle ranged from 66 to 89 days and 1732 to 1268°C day. The mean difference of the cycle between treatments was 3 days. Less floral stem damage happened under silver net and was more in full sun. The shading net associated with mulching favored the growth characteristics of the plants, and in autumn, the flowers had the highest quality standard.

Change in leaf anatomy, physiology, and essential oil of Varronia curassavica Jacq. accessions under two light conditions

The aim of this study was to evaluate the effect of light on anatomy, physiology and essential oil content and composition of Varronia curassavica. They were analysed two light conditions (full sunlight and protected environment with 50% shade screen) and five accessions (VCUR-101, VCUR-102, VCUR-201, VCUR-302, VCUR-802). V. curassavicacultivated in full sun presented a greater development of the leaf blade and palisade parenchyma thickness for all accessions. Chlorophyll levels did not differ according to the two light environments. The leaf area was larger in the protected environment. The essential oil yield of the accessions ranged from 0.26 to 0.87 mL/plant in full sun and from 0.34 to 0.53 mL/plant in the protected environment. The composition of the essential oil was influenced by the light and the accession. All accessions presented (E)-caryophyllene and α-humulene. The influence of light on the evaluated variables is genotype dependent.

Physiological responses of the beet crop under agricultural environment and saline stress

The deleterious effects of salts on plants exposed to high solar radiation tend to be more accelerated due to the increase of toxic ions in the aerial plant part. Consequently, the physiological and biochemical processes will be affected. These effects can be minimized, however, with the use of management strategies, such as the use of a shading screen and a protected environment. In this sense, the objective of this work was to evaluate the physiological responses of sugar beet cultivated in different environments and irrigated with saline water. The experiment was conducted in an experimental design entirely randomized, using the factorial scheme 3 × 2, equivalent to three environments (FS = full sun; SSOS = shading screen open on the sides and PE = protected environment) and two electrical conductivities of the irrigation water (0.5 and 6.2 dS m-1), with four repetitions. At 45 days after sowing (DAS) the following variables were analyzed: stomatal conductance, liquid photosynthesis, transpiration, internal CO2 concentration, leaf temperature, instantaneous water use efficiency, instantaneous carboxylation efficiency, intrinsic water use efficiency, and relative chlorophyll index. Irrigation with water of higher salinity negatively affected stomatal conductance, net photosynthesis, leaf temperature and instantaneous water use efficiency of sugar beet plants grown in a full sun environment. The protected environment and open shading on the sides partially mitigated the deleterious effects of salinity.
 Keywords: Beta vulgaris L., gas exchange, salinity levels.

PROTECTED ENVIRONMENTS AND REFLECTIVE MATERIAL IN THE PRODUCTION OF Hymenaea courbaril SEEDLINGS

Most seedling production is carried out in protected environments influencing plant growth and development. The present study aimed to evaluate types of the cover of protected environments and reflective material in the production of seedlings of Hymenaea courbaril. The experiments were carried out in four protected environments: (A1) agricultural greenhouse covered with low-density polyethylene (LDPE) film with 42% - 50% shading screen under the film; (A2) agricultural screen with an aluminized screen with 35% shading; (A3) agricultural screen with a black screen of 30% of shading, and (A4) agricultural screen with a black screen of 18% of shading. Production systems were tested with and without reflective material on the cultivation bench in each protected environment. The photosynthetically active radiation reflecting material used was the aluminized screen (Aluminet®). As there were no repetitions of the protected environments, each environment was considered an experiment. In each environment, the experimental design used was completely randomized, with four replications and five plants per plot. Among the variables analyzed, it was observed that the agricultural screen with a black screen (18% of shading) presented better quality seedlings. The system with reflective material presented higher values of the number of leaves and stem diameter.

How Shading and Container Type Influence Ilex paraguariensis A.St.-Hil. Seedling Production

Abstract This study aimed to evaluate the influence of containers and shading on Ilex paraguariensis A.St.-Hil (yerba mate) seedling growth. We used a completely randomized design with a 3 × 2 factorial arrangement (containers × shading). We used PlantPaper®, Ellepot® (both biodegradable containers composed of cellulose fibers), and polypropylene tube containers and shaded (75% shading screen) and unshaded (without shading screen) greenhouse environments. We measured height and stem diameter every 30 days and shoot and root dry biomass 210 days after sowing. With these data, we calculated the total dry biomass, Dickson quality index, and height/diameter ratio. The unshaded environment increased yerba mate seedlings growth in height and stem diameter. In unshaded environments, seedlings produced in biodegradable containers had greater growth than those produced in polypropylene tubes. In the shaded environment, however, seedlings produced in polypropylene tubes had better growth. Despite the differences observed between treatments, all seedlings presented adequate growth during the nursery phase. We suggest the use of biodegradable containers to produce yerba mate seedlings in unshaded environments.

Sowing depth and light intensity in the emergence and development of monocotyledonous weeds

This study aimed to evaluate the effects of different sowing depths and light intensities on the emergence and development of the monocot weed species, Urochloa decumbens and Cenchrus echinatus, under field conditions. Each species constituted an experiment, and the experimental design was completely randomized with four replicates. The treatments were arranged in a 6 x 4 factorial scheme, with six sowing depths (0.5, 1.0, 2.0, 4.0, 8.0, and 12.0 cm) associated with four solar radiation intensities (100%, 70%, 50%, and 30%) obtained through the use of shading screens. Seedling emergence capacity was evaluated daily to obtain the emergence percentage and speed index. Plant height, floral induction time, and plant dry matter at flowering were measured. Even when subjected to different solar radiation intensities, U. decumbens and C. echinatus seedlings emerged at all the sowing depths. Sowing between 2.0- and 4.0-cm depths favored the emergence of seedlings of U. decumbens and C. echinatus. However, sowing at 12-cm depth reduced the emergence of both species regardless of the solar radiation intensity. Urichloa decumbens plants grown under conditions of greater shading showed the lowest values of height and dry matter accumulation during flowering. High levels of shading facilitated only the etiolation of C. echinatus plants. Increased shading flowering time in both species compared to full sunlight.

Salt stress and ambience in the culture of yellow passion-fruit

Salt stress negatively affects the emergence and initial growth of crops. However, the use of protected environments emerges as an alternative to enhance these parameters. In this sense, the objective was to evaluate the effect of different environments and the salinity of the irrigation water on the emergence and development of yellow passion-fruit seedlings. The experiment was conducted at the University for International Integration of the Afro-Brazilian Lusophony, in the city of Redenção, Ceará. The experimental design was entirely randomized in a subdivided plot scheme, with four cultivation environments under different shading screens (black screen; white screen; red screen; all with 50% shading; and full sun), and two electrical conductivities of irrigation water: 0.3 dS m-1 and 3.0 dS m-1, with five repetitions of 25 seeds. The protected environment with 50% black roofing stood out from the others providing a better percentage of emergence, seedling height, stem diameter, number of leaves and radicle length in yellow passion-fruit. The deleterious effects of salts on the rate of emergence and shoot dry matter were reduced when the 50% black shade cloth was used. Irrigation with water of higher conductivity caused reductions and retardation in the emergence of passion-fruit. Besides negatively affecting seedling height, stem diameter and shoot dry matter.