The quality and quantity of light are important factors in controlling in vitro plant growth in photoautotrophic systems. The aim of this study was to evaluate the influence of light quality (fluorescent, white, red, blue, red/blue, and distant red) on microstumps of a Eucalyptus urophylla clone in an in vitro photoautotrophic system, as well as the intensity of fluorescent light (60, 85, 100, and 140 μmol m–2 s–1) in the growth and production of microcutting. The number of shoots and microcutting, the size of the largest shoot, the stomatal density, chlorophyll, and carotenoid content were analyzed. Light quality altered plant growth, and fluorescent light intensity did not affect the microstumps’ production during the evaluation period. In white light-emitting diode (LED) light, there was higher production of carotenoids, with a lower initial production of microcuttings. A smaller number of shoots were obtained in blue LED. In general, the different qualities and light intensities tested allowed for the growth of the Eucalyptus urophylla clone grown in vitro, making it possible to obtain microcuttings under photoautotrophic cultivation. Study Implications In vitro propagation is a stressful process for plants and has limitations for commercial-scale Eucalyptus production. Fluorescent lamps, closed containers, and high sucrose concentrations are traditionally used. To reduce costs and improve production, the use of efficient light sources and photoautotrophic cultivation systems become alternatives. This study investigated the influence of light on the in vitro growth of a Eucalyptus clone in a photoautotrophic system. The quality was more important than the intensity of light. Foresters will be able to indicate the use of LEDs (light-emitting diodes) as a replacement for fluorescent lamps. This approach is useful in enhancing micropropagation techniques.

El objetivo de este trabajo fue evaluar el potencial de la técnica de miniestaca para la propagación vegetativa de la especie forestal Jequitibá (Cariniana estrellensis (Raddi) Kuntze). Para esto se utilizo la metodología de miniestacas enraizadas en condiciones de invernadero utilizando los reguladores de crecimiento Acido indol butílico (AIB) y Acido naftaleno acético (ANA) en las dosis 0, 1000, 2000, 3000 y 4000 mg L-1, determinando la producción y sobrevivencia de las minicepas en las sucesivas cosechas. Se verifico la alta sobrevivencia de las minicepas (98%) y la media de producción de miniestacas por minicepas por cosecha fue de 3,9 miniestacas. El ANA presentó resultados superiores al AIB con 83,3% de enraizamiento en el tratamiento 2000 mg L-1 mientras que el AIB presento 75%. La sobrevivencia a los 90 días fue superior en las tratadas con ANA y AIB en las dosis 2000, 3000 y 4000 mg L-1, presentado diferencias significativascon el testigo. Se concluye que la técnica de miniestaca es una eficiente estrategia para la propagación vegetativa de Jequitibá.

The objective of the present study was to test the effects of explant type, auxin concentrations, culture media, and auxin concentrations on the induction and proliferation of somatic embryos of Eucalyptus grandis x E. urophylla. Seeds and cotyledons were used as explants and inoculated in culture media containing 1.13, 2.26, 3.39 and 4.52 µM dicamba or 4.14, 10.35, 20.71 and 31.06 µM picloram. Embryogenic calli induced in the picloram treatments were used as explants and inoculated in semisolid or liquid media containing 4.14, 10.35, 20.71 and 31.06 µM picloram and keeping the origin of the embryogenic callus (seeds or cotyledons) and the concentration of picloram in those who were in the induction phase. Statistical, descriptive and anatomical analyses were performed. Induction of somatic pro-embryos into the juvenile plant material of Eucalyptus grandis x E. urophylla was performed using seeds or cotyledons as the source of explants, with the addition of dicamba and picloram as growth regulators. The use of cotyledons as a source of explants and the concentration of 4.1 µM picloram added to the culture media resulted in a higher induction of somatic pro-embryos. Proliferation of secondary somatic embryos was achieved using liquid medium added with picloram.

This study aims to evaluate the microcuttings production in the micropropagation system via clumps of axillary buds in a clone of Eucalyptus grandis x E. urophylla, subjected to different types of containers and substrates. Clumps with six to eight differentiated buds of Eucalyptus grandis x E. urophylla established in vitro were used to test containers (polypropylene pot -500 ml, glass flask -250 ml; acrylic flask with gas exchange (AFGE) -250 ml; and test-tube -55 ml capacity) in a semisolid medium specific for Eucalyptus in a period of 35 days. For the substrates test, acrylic flask with gas exchange (AFGE) were used with different substrates (agar, average particle size vermiculite, and vermiculite: cellulose fiber in a 2:1 ratio) in a period of 35 days. The tests were installed in a completely randomized design (CRD). We evaluated the number of shoots larger than 0.5 cm per clump of bud, the number of microcuttings produced larger than 2 cm, the length of the longest microcutting (cm) and shoot vigor. Based on the obtained results, it was possible to observe that the best container to produce microcuttings larger than 2 cm was the polypropylene pot (500 ml). Glass flask (250 ml) was more advantageous to achieve greater production of microcuttings per square meter due to its capacity of better densification. The best substrates to produce microcutting larger than 2 cm using acrylic flask with gas exchange (AFGE) containers were agar or vermiculite. Keywords:In vitro propagation; plant tissue culture; vegetative propagation. Abbreviations: AFGE_acrylic flask with gas exchange, APDM_aerial part dry mass, APFM_aerial part fresh mass, BAP_6-benzylaminopurine, BIOAGRO_Institute of Biotechnology Applied to Agriculture, CO 2 _carbon dioxide, CRD_completely randomized design, JADS_culture medium specific for Eucalyptus (Correia et al., 1995), HCl_chloridric acid, IBA_indole-3-butyric acid, LMC_length of the largest microcutting (cm), NAA_naphthaleneacetic, NaOH_ sodium hydroxide, NMC > 2 cm_number of microcuttings larger than 2 cm, NMC > 2 cm m -2 _number of microcuttings larger than 2 cm m -2 , NS > 0.5 cm_shoots larger than 0.5 cm, NS> 2 cm m -2 _number of shoots larger than 0.5 cm m -2 , PVP-30_polyvinylpyrrolidone, RDM _root dry mass, RFM_root fresh mass, RT%_root percentage.

RESUMENCon el fin de conocer el requerimiento hídrico de Melina en la etapa de vivero, se realizó un ensayo con cuatro coeficientes de consumo (Kc: 0,6, 0,8, 1,2, 1,4. Estos tratamientos se transformaron en láminas de riego de 2,4 mm.día -1 , 3,2 mm.día -1 , 4,8 mm.día -1 y 5,6 mm.día -1 respectivamente, debido a que la evapotranspiración de referencia (ETO) de la zona fue de 4 mm.día -1 . Se observó que a medida que se aumentaba la lámina de riego, disminuía el crecimiento de las plantas. Los valores más altos de altura de planta, área foliar, masa seca de hoja, masa seca del tallo y masa seca de raíz se obtuvieron con la lámina de 2,4 mm.día -1 . Por otro lado, los índices de crecimiento (TAC, TRC, AFE, RAF) muestran la misma tendencia. Con base en estos resultados se determinó que el Kc para esta especie en la etapa de vivero es de 0,6.Palabras clave: láminas de riego, coeficiente de cultivo (Kc), crecimiento. Water Requirement of Gmelina arborea on Nursery StageUnder Controlled Conditions ABSTRACTIn order to recognize the Melina water requirement in the nursery stage, we performed a test with four crop coefficient (Kc: 0,6, 0,8, 1,2, 1,4). These treatments included irrigation blades of 2,4 mm.day -1 , 3,2 mm.day -1 , 4,8 mm.day -1 and 5.6 mm.day -1 respectively, due to the area reference evapotranspiration at 4mm.day -1 . It was observed a decrease of plant growth as the raising of the irrigation blade. The highest values of plant height, leaf area, leaf dry weight, dry weight of stem and root dry weight were obtained with the blade of 2,4 mm.day -1 . On the other hand, the growth rates studied have shown the same trend. Based on these results we determined that the Kc for this species in the pond stage is 0,6.