**1. Introduction**

Light is one of the primary factors that affect in vitro plant morphogenesis [1,2]. Artificial light sources, including fluorescent lamps, high-pressure sodium lamps, metal halide lamps, and incandescent lamps, among others, have been widely used for plant tissue culture research and commercial micropropagation of several crops [3]. Cool-white fluorescent lamps remain the most used type of light source for micropropagation [4,5]. While popular, cool-white fluorescent light sources have a wide spectrum distribution (350 to 750 nm) and therefore are of low quality for promoting plant growth. In addition, energy consumption is increased, representing the second-highest cost in micropropagation after labor [6,7]. Fluorescent lights also emit heat, which can cause damage and photo-stress to plants [3]. Therefore, more efficient and cost-effective light systems that promote in vitro plant growth and development are necessary. Light-emitting diodes (LEDs) have become very popular in agriculture, particularly for the production of horticultural crops, and have been widely used in microgravity studies aiming at space life support systems [8,9]. More recently, LEDs have been incorporated into in vitro plant systems [10]. LEDs represent an alternative lighting source to regular fluorescent bulbs, increasing the quality of in vitro plantlets and minimizing the per plant production costs. LEDs provide selective light intensity and quality, are suitable for commercial micropropagation, and also allow the control of photosynthetically active radiation (PAR), providing optimal conditions for plant growth and development, including improved morphology and metabolism [11].

**Citation:** Vendrame, W.A.; Feuille, C.; Beleski, D.; Bueno, P.M.C. In Vitro Growth Responses of Ornamental Bananas (*Musa* sp.) as Affected by Light Sources. *Horticulturae* **2022**, *8*, 92. https://doi.org/10.3390/ horticulturae8020092

Academic Editor: Sergio Ruffo Roberto

Received: 21 December 2021 Accepted: 14 January 2022 Published: 20 January 2022

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Additional advantages of LEDs include the longer life and smaller size of light-emitting diodes compared to fluorescent bulbs, with very little heat generation [3]. In addition, LEDs may influence the growth and production of secondary metabolites in plants, such as those reported for *Pfaffia glomerata* [12]. The spectral distribution of the light affects plant growth mainly via photosynthesis, and it affects plant morphology. Plant morphology is also affected by photon flux density; therefore, there may be an interaction between these effects. Understanding these effects and these interactions is required to control plant growth and morphology using LEDs [13].

Because of the high sterility and polyploidy of cultivated or domesticated banana varieties and hybrids [14], asexual propagation methods are the primary means for banana production. However, many diseases, such as black sigatoka, fusarium wilt, banana bunchy top virus, burrowing nematodes, and banana weevil borer [15], are associated with traditional propagation techniques [16–18]. Therefore, micropropagation has become a common practice for the production of bananas, thus assisting with the production of clean, disease-free plant material [16,19,20]. The tissue culture of bananas also allows large-scale mass in vitro clonal propagation of elite banana varieties, free of diseases. The use of LEDs in micropropagation could provide higher-quality banana plants with the benefit of reduced energy costs. LEDs have been studied previously for banana in vitro cultures [21–23] with a focus either on specific wavelengths, LED ratios, or lower intensities (45 to 75 μmol m−<sup>2</sup> s−<sup>1</sup> PPFD).

Therefore, the main objective of this study was to evaluate the growth and development of in vitro ornamental bananas as affected by different light sources, including simple LED and traditional fluorescent lighting. In addition to the growth and development parameters of two in vitro ornamental banana varieties, relative chlorophyll content, leaf stomata, and anatomy characteristics were also evaluated.
