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Os objetivos deste trabalho foram investigar a influência da qualidade da luz no crescimento e no acúmulo de constituintes voláteis de Mentha spicata cultivada in vitro. Segmentos nodais de plântulas já estabelecidas foram mantidos sob lâmpadas fluorescentes e diodos emissores de luz (LEDs) com as regiões espectrais nas cores verde, amarelo, vermelho, azul e branco, e nas combinações entre vermelho e azul (1:1; 2:2 e 2:1). Após 45 dias, parâmetros de crescimento, área foliar, índices de crescimento, pigmentos fotossintéticos e análise da composição química volátil de folhas por headspace – CG/FID foram avaliados.  A combinação 1:2 proporcionou maiores biomassas seca de folhas, raiz e total. As plântulas dos tratamentos verde, amarelo, fluorescente e vermelho apresentaram características de estiolamento. Em relação à composição química volátil, os constituintes majoritários α-pineno, sabineno, β-pineno, mirceno, 1,8-cineol e carvona foram identificados. Plântulas crescidas sob LEDs verde e amarelo resultaram maior acúmulo de carvona. Assim, este estudo contribuiu para o entendimento das alterações causadas pela qualidade de luz no crescimento in vitro e na composição química volátil de hortelã. Conclui-se que a micropropagação de Mentha spicata sob LEDs na combinação entre vermelho e azul 1:2 é o mais favorável para o crescimento e teor de carvona e de 1,8-cineol.

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The development of modified hydroponic cultivation has aroused interest and its use has enabled advantages in several crops, but studies for coffee are still scarce. Thus, the objective of this research was to evaluate seedling production of three Coffea arabica cultivars (Mundo Novo IAC-376-4, Catuaí IAC-62 Amarelo and MGS Paraíso 2), in a modified hydroponic system, and to compare it with the nursery production system, using plastic polyethylene tubettes and bags. Coffee seedlings in the development phase with cotyledon leaves, were cultivated in both cultivation systems. At 90 days after the implementation of the experiment, the seedlings were analyzed for growth (height, stem diameter, total number, leaf area, root area, root and shoot dry matter weight), and physiological characteristics (chlorophyll content and stomatal conductance). For the statistical analysis, a completely randomized design (CRD) was used in a factorial scheme 3 (cultivars) x 2 (containers) x 2 (cultivation systems), with four replications of ten plants per plot. The innovative production system of coffee seedlings in modified hydroponics, in combination with the use of polyethylene bags, provided greater growth of coffee seedlings with better physiological characteristics. Among the cultivars tested, MGS Paraíso 2 stood out with higher seedling growth (number of leaves, stem diameter and root and shoot dry matter weight).

Brazilian coffee production represents an important activity in the country’s agricultural sector and, for this reason, it requires innovative technologies for the production of seedlings, which is one of the most important inputs in crop implantation. Thus, plant cloning by cutting, mineral nutrition via modified hydroponics and the use of alternative substrates appear as technological innovations for seedling production. This study evaluated the production of clonal coffee seedlings in a modified hydroponic system in comparison to the conventional climate-controlled greenhouse system, using vermiculite and phenolic foam as alternative substrates. At the end of the experiment, the seedlings were analyzed for growth (height, stem diameter, number of total leaves, leaf area, root area, shoot and root dry matter) and physiological (chlorophyll content and stomatal conductance) characteristics. For the statistical analysis, a completely randomized design was used in a factorial scheme 2 (types of substrate) x 2 (cultivation systems) with six replications and ten plants per plot. The innovative modified hydroponic system leads to a greater growth of coffee seedlings produced by cuttings in tubes with vermiculite compared to those produced in conventional systems. The substrate phenolic foam can be used alternatively in the air-conditioned greenhouse system. However, in the modified hydroponic system, it is not indicated, as it causes total seedling mortality.

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