Effect of heat stress and darkness on gametophyte growth.

Relative growth rate of gametophytes from the North Sea and Arctic populations of Laminaria digitata after 8 days in different treatments (15°C dark, 15°C, 20°C, 22.5°C and 25°C DHS). Box plots with median, boxes for 25th and 75th percentiles and whiskers indicating min and max values (n = 4). * indicates a significant difference between populations per treatment (p<0.05). For each population, different letters above boxplot bars (lowercase letters for the North Sea population and upper case letters for the Arctic population) indicate differences between treatments (p<0.05). See Table 2 for statistics.