Abstract
ABSTRACT Tropical species may require higher temperatures as well as higher growth regulator concentrations for in vitro development. Since these conditions may affect plant metabolism, the objective of this study was to identify how different temperatures and gibberellin concentrations may affect the in vitro development of strelitzia embryos, analyzing the effect on ROS and cytogenetic stability. Zygotic embryos were cultivated on MS medium supplemented with 5, 10 and 20 µM GA3 under temperatures of 25 °C, 30/25 °C and 30 °C. After 60 days, higher embryonic germination rate (72%) and shoot length of plantlets (3.14 cm) were observed on medium containing 20 µM gibberellic acid (GA3). At this concentration, there was an increase in nitrate reductase activity with no change in the cytogenetic stability. The temperature influenced only shoot and root lengths, which were highest at 25 °C. At 30 °C, superoxide dismutase (SOD) and ascorbate peroxidase (APX) activities increased compared with those at 25 °C. Thus, the addition of 20 µM GA3 to the culture medium and a temperature of 25 °C in the growth room should be used for zygotic embryo culture of strelitzia.
Highlights
Embryo rescue is one of the most feasible techniques for propagation of species with propagation limitations, mainly due to seed dormancy, such as strelitzia (Strelitzia reginae Banks ex Aiton)
Enhancement of nitrate reductase activity may be beneficial, since this enzyme is responsible for the assimilation of nitrogen, an essential element found in many macromolecules and components of secondary metabolism, including proteins, nucleic acids, cell wall components, hormones, and vitamins (Krapp, 2015)
Mature seeds collected from strelitzia plants cultivated at 21° 45′ S latitude, 45° 00′ W longitude, and 920 m altitude were sterilized in a laminar flow hood by immersion for 30 seconds in 70% ethanol and in 2.5% sodium hypochlorite for 15 minutes, washed three times in distilled water and autoclaved (Paiva et al, 2004)
Summary
Embryo rescue is one of the most feasible techniques for propagation of species with propagation limitations, mainly due to seed dormancy, such as strelitzia (Strelitzia reginae Banks ex Aiton). Supplementation of the culture medium with gibberellic acid (GA3) may increase propagation efficiency. The in vitro germination of some species, such as Maclura tinctoria, Cocos nucifera, and Syagrus coronata, has been increased by supplying the medium with GA3 (Gomes et al, 2010; Medeiros et al, 2015; Montero-Cortés et al, 2011). This growth regulator could be important for cell growth and elongation, leaf expansion and photosynthetic processes, as well as for the activity of important metabolic enzymes, such as nitrate reductase (Gupta; Chakrabarty, 2013, Bezerra et al, 2019). Enhancement of nitrate reductase activity may be beneficial, since this enzyme is responsible for the assimilation of nitrogen, an essential element found in many macromolecules and components of secondary metabolism, including proteins, nucleic acids, cell wall components, hormones, and vitamins (Krapp, 2015)
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