Academic literature on the topic 'Photoselective nets'

Shade nets are widely used to protect floricultural crops from excessive radiation, wind, hail, and birds. Although black nets are most frequently used, growers are experimenting with colored, gray, and white dispersive netting to impact vegetative vigor, dwarfing, branching, leaf variegation, and timing of flowering. We monitored environmental data inside replicated shadehouse structures (10 × 10 × 3 m high) with full covering of red, blue, pearl, and black nets (all 50% nominal shading factor) in central Florida over 12 months. Actual photosynthetically active radiation (PAR, μmol·m−2·s−1) was reduced most by black nets (55% to 60% shading factor depending on the season) and least under red nets (41% to 51%) with blue and pearl nets intermediate. Spectral analysis revealed blue nets had distinctive peaks at the blue (450 to 495 nm) and far-red beyond 750 nm. Red nets had a minor peak ≈400 nm and major transmittance beyond 590 nm. Pearl nets transmitted more light above 400 nm compared with black nets but did not otherwise alter spectral composition in the visible range. No nets had red/far-red (R/FR) ratios (600 to 700/700 to 800 nm) significantly greater than ambient (close to 1), whereas blue nets had a consistently lowest R/FR ratio of ≈0.8. Both ultraviolet-B and ultraviolet-A (280 to 400 nm) were reduced most by pearl nets and least by red nets. We also noted elevated temperatures and wind resistance (but not relative humidity) under colored and pearl nets compared with black, probably as a result of the different net porosities. Our study documents the different environmental modifications inside structures covered with black, colored, and photoneutral translucent nets, which will help predict or interpret specific plant responses.

High temperatures, wind, and excessive sunlight can negatively impact yield and fruit quality in semi-arid apple production regions. Netting was originally designed for hail protection, but it can modify the light spectrum and affect fruit quality. Here, pearl, blue, and red photoselective netting (≈20% shading factor) was installed in 2015 over a commercial “Cameron Select® Honeycrisp” orchard. Our research objectives were to (1) describe the light quantity and quality under the colored nets compared to an uncovered control and (2) investigate the effect of Photoselective nets on “Honeycrisp” apple quality for two growing seasons. Light transmittance and scattering for each treatment were measured with a spectroradiometer, and samples for fruit quality analyses were collected at harvest. PAR (photosynthetic active radiation), UV, blue, red, and far-red light were lower underneath all netting treatments compared to an uncovered control. The scattered light was higher under the pearl net compared to other colors, while red and far-red light were lower under the blue net. For two consecutive years, trees grown under the photoselective nets intercepted more incoming light than the uncovered trees with no differences among the three colors. In both years, trees under red and blue nets had more sunburn-free (clean) apples than pearl and control. Red color development for fruit was lower when nets were used. Interestingly, bitter pit incidence was lower underneath red nets for both years. Other than red color development, “Honeycrisp” fruit quality was not appreciably affected by the use of netting. These results highlight the beneficial effect of nets in improving light quality in orchards and mitigating physiological disorders such as bitter pit in “Honeycrisp” apple.

Manipulation of microenvironments by means of photoselective nettings is widely used to improve the productivity and quality of high-value vegetables. The aim of this study was to investigate the effect of photoselective nettings on growth, productivity, and postharvest quality attributes of baby spinach. Baby spinach cv. Ohio was grown from seeds, and the trial was repeated. Plants were planted in an open field (control) and under closed nets, viz., black, pearl, yellow, and red nets. At harvest, baby spinach leaves were subjected to 4, 10, and 20 °C storage temperatures for 12 days. Crops grown under black nets and stored at 4 °C retained higher level of antioxidant activity (0.23 g·kg−1), whereas the least level of antioxidant activity was observed in baby spinach grown under red and yellow shade nets (0.01 g·kg−1). Similar trend was evident with flavonoid content where baby spinach leaves grown under black nets maintained high level of flavonoids at 4, 10, and 20 °C during storage period compared with other shade nets and the control. The study control showed a better potential in retaining antioxidant activity over red and yellow shade nets. Results showed that black shade nettings have the potential to reduce water loss, decay incidents, and maintain flavonoid content and antioxidant activity followed by pearl and yellow nets.

Photoselective nets have proven to be effective for aphid pest control as they limit their dispersal ability. However, little is known on the impact of such nets on natural enemies of aphids. In this work, we study the effect of UV-absorbing nets on the syrphid fly Sphaerophoria rueppellii Wiedemann (Diptera: Syrphidae), a commercially available aphid biocontrol agent in Mediterranean horticultural crops. First, we released mature syrphid adults and evaluated density and dispersal of the resulting immatures in a turnip crop grown under either UV-blocking (Bionet) or standard net. Second, we assessed, under controlled conditions, the impact of UV radiation on fitness-related parameters, and on flight behavior of S. rueppellii adults. Results showed that, while syprhid immature density was higher, their dispersion was reduced under Bionet. UV-absorbing nets are known to influence the dispersion pattern of aphids, which may have indirectly conditioned the distribution of their predator S. rueppellii. On the other hand, the type of net had no influence on the performance of adults. We conclude that the use of photoselective nets and the release of syrphid predators such S. rueppellii are compatible strategies to be used in IPM aphid-control programs.

In recent years and thanks to innovative technological advances in supplemental lighting sources and photo-selective filters, light quality manipulation (i.e. spectral composition of sunlight) have demonstrated positive effects on plant performance in ornamentals and vegetable crops. However, this aspect has been much less studied in fruit trees due to the difficulty of conditioning the light environment of orchards. The aim of the present PhD research was to study the use of different colored nets with selective light transmission in the blue (400 – 500 nm), red (600 – 700 nm) and near infrared (700 – 1100 nm) wavelengths as a tool to the light quality management and its morphological and physiological effects in field-grown apple trees. Chapter I provides a review the current status on physiological and technological advances on light quality management in fruit trees. Chapter II shows the main effect of colored nets on morpho-anatomical (stomata density, mesophyll structure and leaf mass area index) characteristics in apple leaves. Chapter III provides an analysis about the effect of micro-environmental conditions under colored nets on leaf stomatal conductance and leaf photosynthetic capacity. Chapter IV describes a study approach to evaluate the impact of colored nets on fruit growth potential in apples. Summing up results obtained in the present PhD dissertation clearly demonstrate that light quality management through photo-selective colored nets presents an interesting potential for the manipulation of plant morphological and physiological traits in apple trees. Cover orchards with colored nets might be and alternative technology to address many of the most important challenges of modern fruit growing, such as: the need for the efficient use of natural resources (water, soil and nutrients) the reduction of environmental impacts and the mitigation of possible negative effects of global climate change.

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Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPES
Photoselective screens are a recent approach in protected cultivation, which can promote benefits in addition of the protective functions of nettings. These nets not only scatter but spectrally-modify the transmitted light, in order to promote desired physiological responses and improve the penetration of the light into the inner plant canopy. Tomato is the second most important horticulture crop in the world. Traditionally, tomato is cultivated in the open field, but recently there has been an increase of the protect cultivation area aiming to protect plants from climate adversities. This study aimed to investigate whether a combination of growth regulator, increased plant density and the effect of red screen-shade net could improve tomato yield, quality and promote desired vegetative development. The experiment was conducted from May 21st to November 1st, 2014, in Goiânia, Brazil (16º35´47´´S, 49°16´47´´W, 730 m). The hybrid Ivete from Sakata Seeds® were cultivated in 16x12x 2.2 m3, 40% red shading screenhouse and field plots as control. Leaf area index, trusses height, and total height were measured. The total number, total weight, diameter and number of lost fruits were totaled. Nutritional analyses were also performed: physical (Fresh mass, total solid soluble - TSS, titritable acidity - TA, SST/AT ratio and pH) and nutritional parameters (vitamin C and lycopene) in two moments of collecting of fruits (98 and 129 days after transplantation). All the measures were carried by official methods. Results showed that highest yields were obtained using 3 plants per m2 in both environments. The highest total fruit production occurred in open field conditions. However, the total fruit lost in the open field conditions was greater. Fruits produced in an open field were more acidic and had greater titratable acidity (0.37% citric acid) compared to fruits from screenhouse (0.33 % citric acid) at 3 plant per square meter. In addition, fruits grown in the field had greater TSS content (6.6 °Brix) than tomatoes grown in a protected environment (5.4 °Brix). Fruits produced in the open field had greater TSS:TA ratios than those produced in a protected environment. Significantly higher lycopene content was observed in plastic-house tomatoes integrated with red shade netting technologies (47.0 μg g−1) using 2.3 plants per m² than in open field-grown tomatoes (29.6 μg g−1). The results provide useful data for detecting differences among environment variation in tomato composition and red colour shade nets. In addition, the photoselective red screen combined with the density of 3 plants per m² promoted higher yield of commercial fruits.
O uso de telas fotosseletivas tem sido uma abordagem recente no cultivo protegido. Pode promover benefícios, além das funções de proteção das malhas de plástico. Estas telas não só agem na dispersão da luz, como agem também na modificação do espectro da luz transmitida, de modo a promover respostas fisiológicas desejadas na planta, além de melhorar a penetração da luz no interior de sua parte aérea. No Brasil, o tomate é a olerícola mais importante e tradicionalmente cultivada em campo aberto. Recentemente o uso de telas plásticas com sombreamento colorido tem sido estudado para proteger as plantas de adversidades climáticas. Este estudo teve como objetivo investigar se a combinação do adensamento de plantas, o uso de reguladores de crescimento e o efeito da malha fotosseletiva vermelha poderiam melhorar a produtividade e a qualidade dos frutos de tomateiro e promover desenvolvimento vegetativo desejado. O experimento foi realizado no período de 21 maio a 1° novembro 2014, em Goiânia, Brasil (16º35'47''S, 49 ° 16'47''W, 730 m). O híbrido Ivete da Sakata Seeds® foi cultivado sob telado vermelho e campo aberto. Índice de área foliar, altura final da planta e altura dos cachos foram medidas. O número total, peso total, diâmetro e número de frutos não comerciais foram totalizados. Foram, também, realizadas medidas físicas (massa fresca, sólidos solúveis totais (SST em °Brix), acidez titulável (AT), razão SST / AT e pH) e variáveis nutricionais (vitamina C e licopeno) em dois momentos de coleta dos frutos (98 e 129 dias após transplantio). Todas as medidas foram realizadas por métodos oficiais de análise. Frutos produzidas em campo aberto foram mais ácidos e tiveram maior acidez total titulável (0,37%) em relação aos frutos produzidos sob telado plástico (0,33%) com 0,3 m de espaçamento entre plantas. Além disso, frutos cultivadas no campo apresentaram maior teor de SST (6,6 °Brix) do que aqueles cultivados em ambiente protegido (5,4 °Brix). Além disso, as frutos produzidas no campo aberto tiveram maior Ratio (SST/ AT) do que as produzidas em um ambiente protegido. Observou-se significativamente maiores teores de licopeno em frutos cultivados sob telado vermelho (47,0 mg g-1) em 0,4 m de espaçamento do que em tomates cultivados em campo aberto (29,6 mg g-1). Os resultados mostraram que maior produtividade foi obtidos com densidade de 3 plantas por m2 em ambos os ambientes. A maior produção total de frutos ocorreu em condições de campo aberto (12,87 kg.m-2). O total de frutos perdido nas condições de campo aberto foi maior. Os resultados do presente estudo fornecem informações úteis para a detecção e compreensão de diferenças entre variações ambiente e formas de cultivo nas características agronômicas, nutricionais e fisico-químicas dos frutos de tomate.