Low-temperature storage is one of the most effective techniques to maintain the quality and durability of cut flowers. Both quality maintenance and durability are dependent on plant metabolism factors such as antioxidant system. The objective was to evaluate the effect of low-temperature on precooling and storage after harvest, on the metabolism of calla lily [Zantedeschia aethiopica (L.) K. Spreng] concerning the antioxidant system, levels of hydrogen peroxide (H₂O₂), and malondialdehyde (MDA). Therefore, different storage temperatures (4 ºC and 21 ºC) were tested as well as the effect of precooling in different periods (0 to 24 hours). It was observed that the activity of catalase (CAT) and superoxide dismutase (SOD) was increased at 4 °C, as well as inflorescence durability in the commercial standard (around 12 days). At 21 °C, the content of H₂O₂ and MDA was higher and the visual quality reduction in the inflorescence was accelerated. Low-temperature leads to a higher activity of the enzymes of the antioxidant system (CAT and SOD) and increases postharvest longevity for calla lily. Precooling did not influence the visual quality and longevity of calla lily. Long-term exposure periods at low temperatures, with 12 and 24 hours of precooling caused stress, evidenced higher MDA levels and higher CAT activity. SOD activity was related to low temperature and shorter precooling periods resulted in better antioxidant system activity and lower MDA levels.

The propagation of strelitzia plants can be carried out in vitro as an alternative to combine the aseptic conditions of the culture medium with the use of strategies to promote germination and controlled abiotic conditions. However, this technique is still limited by the prolonged time and low percentage of seed germination, which is the most viable explant source, due to dormancy. Thus, the objective of this study was to evaluate the influence of chemical and physical scarification processes of seeds combined with gibberellic acid (GA₃), as well as the effect of graphene oxide in the in vitro cultivation of strelitzia plants. Seeds were subjected to chemical scarification with sulfuric acid for different periods (10 to 60 min) and physical scarification (sandpaper), in addition to a control treatment without scarification. After disinfection, the seeds were inoculated in MS (Murashige and Skoog) medium with 30 g L⁻¹ sucrose, 0.4 g L⁻¹ PVPP (polyvinylpyrrolidone), 2.5 g L⁻¹ Phytagel^®, and GA₃ at different concentrations. Growth data and antioxidant system responses were measured from the formed seedlings. In another experiment, the seeds were cultivated in vitro in the presence of graphene oxide at different concentrations. The results showed that the highest germination was observed in seeds scarified with sulfuric acid for 30 and 40 min, regardless of the addition of GA₃. After 60 days of in vitro cultivation, physical scarification and scarification time with sulfuric acid promoted greater shoot and root length. The highest seedling survival was observed when the seeds were immersed for 30 min (86.66%) and 40 min (80%) in sulfuric acid without GA₃. The concentration of 50 mg L⁻¹ graphene oxide favored rhizome growth, while the concentration of 100 mg L⁻¹ favored shoot growth. Regarding the biochemical data, the different concentrations did not influence MDA (Malondialdehyde) levels, but caused fluctuations in antioxidant enzyme activities.

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.