Figure 3.

Effects of environmental signals on Physcomitrella spore germination. (a) A pulse of far‐red (FR) light inhibits spore germination and this cannot be rescued by norflurazon or GA₉‐methyl ester (GA, gibberellin). Spores plated on control medium or GA₉‐methyl ester (GA₉‐ME) or norflurazon were treated ± FR light (‘No FR’ and ‘FR’, respectively) and immediately placed in the dark for 7 d. The spores’ germination percentage was measured 7 d after treatment. All spores were then moved to white light for a further 7 d (‘No FR > White’ and ‘FR > White’, under which conditions all spores germinated to completion, showing that the effect of FR light is completely reversible. A Kruskal–Wallis test indicates differences between FR and white light‐treated samples, P < 0.05. Error bars, ± SEM. (b) A temperature of 35°C inhibits spore germination and this is completely reversible when spores are returned to 22°C. (c) High‐temperature inhibition of spore germination cannot be rescued by norflurazon, GA₉‐methyl ester or the synthetic strigolactone analogue GR24 (‘strigolactone’ on the graph). Spores were germinated for 7 d at either 22°C or 35°C. The 35°C‐treated spores were then transferred to 22°C for another 7 d (‘35°C > 22°C’). A Kruskal–Wallis test indicated differences between 35°C and 22°C spores, P < 0.05. Error bars, ± SEM.