Effect of Temperature and Exposure Time on Cambium Cell Viability In Vitro for Eucalyptus Species

Abstract

(1) Research Highlights: Thermal damage to cambium cells of Eucalyptus held in vitro was recorded at sublethal temperatures (40 °C–50 °C) when the duration of exposure extends beyond 2.5 min up to 5 min. (2) Background and Objectives: During a forest fire, heat can be transferred through tree bark potentially impacting viability of vascular cambium cells and the perennial growth of the tree. With the increased temperature of the cambium, cells are known to lose viability at temperatures exceeding 60 °C. However, it is possible that extended exposure to temperatures below 60 °C may also impair cell viability. This study aimed to identify the effect of the temperature and exposure time interaction on the cambium cell viability of Eucalyptus, a genus widely distributed in natural forests and commercial plantations globally. (3) Methods: Excised cambium-phloem tissue sections from three Eucalyptus species (Messmate–E. obliqua L’Hér., Narrow-leaf peppermint–E. radiata Sieber ex DC. and Swamp gum–E. ovata Labill.) were exposed in vitro to a series of temperature–time treatments (40 °C, 50 °C, 60 °C, 70 °C for 1 min, 2.5 min, and 5 min) and tested for cell viability using a tetrazolium reduction method. (4) Results: Cell viability of cambium cells decreased with increased temperature and exposure times for all three Eucalyptus species. Longer exposure to sublethal temperatures of 40 °C to 50 °C showed statistically similar results to shorter exposure to lethal temperatures (>50 °C). (5) Conclusions: Longer exposure to sublethal temperatures (40 °C–50 °C) caused irreversible thermal damage to cambium cells of Eucalyptus when tested in vitro, further refining our understanding of raised temperature on cell viability.

Experimental burns in an open savanna: Greater fuel loads result in hotter fires

“…Temperature and time of exposure are important factors determining fire effects on plant tissues (Dickinson & Johnson 2004; Subasinghe Achchige et al . 2021) and increased fire temperatures belowground may affect not only the plant community but also the soil microbiota and the whole ecosystem functioning (Neary et al . 1999; Fontúrbel et al .…”

“…Additionally, we found that the number of points in which temperatures belowground exceeded the lethal threshold of cell tissue (~60°C, Daniell et al 1969) increased consistently with greater firefree intervals: 25% of points in FI-1 plots, 44% in FI-2 plots, and 75% with the greatest fire-free interval (FI-4 plots). Temperature and time of exposure are important factors determining fire effects on plant tissues (Dickinson & Johnson 2004;Subasinghe Achchige et al 2021) and increased fire temperatures belowground may affect not only the plant community but also the soil microbiota and the whole ecosystem functioning (Neary et al 1999;Font urbel et al 2012). Nonetheless, only in plots with greater fire-free intervals (FI-4) did temperatures over 60°C last around two minutes, but over 100°C they lasted for barely 30s.…”