The influence of high temperature on cell damage and shoot survival rates of Plagiomnium acutum

Cell damage and shoot survival rates of Plagiomnium acutum under high temperatures were studied by immersing the moss in hot water in the light (wet) and in dark incubators in air (dry) at various constant temperatures for up to 8 h. At 35-40°C no moss cells were damaged (indicated by expansion, contraction, or breach of chloroplasts, total loss of green colour in cells, or protoplast of cell disintegrating), and all moss shoots survived. At 45°C, damage to both wet and dry moss cells, and death of moss shoots increased with exposure time. No samples survived prolonged exposure at temperatures of 50°C and higher, indicating that the lethal high temperature of Plagiomnium acutum is about 45°C. Mosses in air in a dark constant-temperature chamber required a longer time to exhibit cell damage and death, reaching 100% only at 50°C and above. Age of tissue, exemplified by position on stem, had no apparent effect on these responses