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A influência do uso de luz LED no crescimento e qualidade de plantas de Hydrangea macrophylla
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Resumo(s)
A Hydrangea macrophylla é uma espécie ornamental de elevada relevância económica, cuja produção em vaso depende de reguladores de crescimento para manter o seu aspeto compacto, assegurando a sua qualidade comercial. Contudo, a necessidade de diminuição de custos e minimização do impacto ambiental, impulsiona a procura por alternativas mais sustentáveis. Este estudo avaliou a viabilidade de diferentes tipos de iluminação LED como alternativa aos reguladores de crescimento de síntese química, assim como avaliar o seu impacto no crescimento, desenvolvimento e qualidade das plantas.
O ensaio decorreu durante sete semanas em estufa comercial, com plantas de H. macrophylla cv 'Hi White Sun' em fase de pré-floração, e quatro modalidades de iluminação: LED no espetro do vermelho (15 minutos de iluminação ao final do dia); LED com combinação de luz no espetro do azul e vermelho e LED no espetro do branco (18h de luz e 6h de escuridão), além do grupo controlo com luz natural. Avaliaram-se parâmetros como a altura das plantas, teor em clorofila, espessura, fluorescência, condutância estomática, saturação, tonalidade e luminosidade das folhas, além da área foliar unitária e a relação entre o peso seco e fresco. Após o desenvolvimento floral, avaliou-se o efeito dos LEDs na conservação e sobrevivência das plantas, submetidas a simulações de transporte (3 dias em câmara frigorífica a 18ºC) e de exposição em ponto de venda.
Os resultados demonstraram que a luz LED no espetro do vermelho foi a mais eficaz no controlo da altura, promovendo plantas mais compactas e com maior teor de clorofila, melhorando a sua qualidade estética. Economicamente, o custo da luz vermelha foi de 0,014 €/planta/mês, com redução de cerca 8,3% em comparação com o uso de reguladores de crescimento químicos. Embora o tipo de iluminação não ter tido impacto na avaliação de conservação pós-colheita, a posição das plantas nos carrinhos influenciou significativamente a sua longevidade.
Hydrangea macrophylla is an ornamental species of significant economic relevance, whose pot production in greenhouses traditionally relies on growth regulators to ensure the commercial quality of the plants. However, the need to reduce costs and minimise environmental impact has driven the search for more sustainable alternatives. This study evaluated the feasibility of using different types of LED lighting as a substitute for growth regulators, as well as their impact on the plants’ growth, development, and quality. The trial was conducted over 7 weeks in a commercial greenhouse, using H. macrophylla cv 'Hi White Sun' plants during the pre-flowering stage, under four lighting settings: red wavelength LED (with 15 minutes of illumination at the end of the day); LED combining wavelength blue and red wavelength light combination; and white wavelength LED (with a cycle of 18 hours of light and 6 hours of darkness), along with a control group only exposed to natural light. Parameters such as plant height, chlorophyll content, leaf thickness, fluorescence, stomatal conductance, saturation, hue, leaf brightness, individual leaf area and dry to fresh weight ratio were evaluated. After the floral development, the effect of the LEDs on plant conservation and survival was assessed, following transport simulations (3 days in cold storage at 18ºC) and sales placement exposure. The results showed that red wavelength LED light was the most effective in controlling plant height, promoting more compact plants with higher chlorophyll content and improving their aesthetic quality. Economically, the cost of red light was €0,014/plant/month, about 8,3% when compared with the usage of plant growth regulators chemical based. Although the type of lighting had no impact on the post-harvest preservation, the position of the plants on the shelves significantly influenced their longevity.
Hydrangea macrophylla is an ornamental species of significant economic relevance, whose pot production in greenhouses traditionally relies on growth regulators to ensure the commercial quality of the plants. However, the need to reduce costs and minimise environmental impact has driven the search for more sustainable alternatives. This study evaluated the feasibility of using different types of LED lighting as a substitute for growth regulators, as well as their impact on the plants’ growth, development, and quality. The trial was conducted over 7 weeks in a commercial greenhouse, using H. macrophylla cv 'Hi White Sun' plants during the pre-flowering stage, under four lighting settings: red wavelength LED (with 15 minutes of illumination at the end of the day); LED combining wavelength blue and red wavelength light combination; and white wavelength LED (with a cycle of 18 hours of light and 6 hours of darkness), along with a control group only exposed to natural light. Parameters such as plant height, chlorophyll content, leaf thickness, fluorescence, stomatal conductance, saturation, hue, leaf brightness, individual leaf area and dry to fresh weight ratio were evaluated. After the floral development, the effect of the LEDs on plant conservation and survival was assessed, following transport simulations (3 days in cold storage at 18ºC) and sales placement exposure. The results showed that red wavelength LED light was the most effective in controlling plant height, promoting more compact plants with higher chlorophyll content and improving their aesthetic quality. Economically, the cost of red light was €0,014/plant/month, about 8,3% when compared with the usage of plant growth regulators chemical based. Although the type of lighting had no impact on the post-harvest preservation, the position of the plants on the shelves significantly influenced their longevity.
Descrição
Mestrado em Engenharia Agronómica com especialização em Hortofruticultura e Viticultura / Instituto Superior de Agronomia, Universidade de Lisboa
Palavras-chave
planta envasada compacidade floração iluminação artificial qualidade comercial potted plant compactness flowering artificial lighting commercial quality
Contexto Educativo
Citação
Venâncio, A.C.R. A influência do uso de luz LED no crescimento e qualidade de plantas de Hydrangea macrophylla. Lisboa: ISA, 2024, 97 p. Dissertação de Mestrado
Editora
Instituto Superior de Agronomia, Universidade de Lisboa