Inter- and intra-specific variability in seed dormancy loss and germination requirements in the Lavatera triloba aggregate (Malvaceae)

Abstract

Background and aims – The genus Lavatera is comprised of perennial and annual species that grow in different ecosystems such as coastal cliffs, plains, endorheic lagoons and ditches. In this study, we compared the seed germination ecology of three phylogenetically related taxa: L. agrigentina, L. triloba subsp. pallescens and L. triloba subsp. triloba, all of which belong to the L. triloba aggregate (section Glandulosae) and grow on chalky plains, limestone cliffs and endorheic lagoons with clayey sediments. Methods – For each taxon, the effects of seed scarification and dry after-ripening (90 days at 25°C) on seed dormancy loss and of light and temperature (constant 5 to 25°C and alternating 25/10°C) on seed germination were evaluated. Key results – Scarification allowed water imbibition and subsequent seed germination, indicating physical dormancy (PY) for all three investigated taxa. In addition, dry after-ripening positively affected seed germination in L. agrigentina, thus, seeds of this species have combinational dormancy [physical (PY) + physiological (PD)]. Light did not affect the final germination in any of the taxa. The germination response to incubation temperatures varied among the taxa, suggesting ecological adaptations, with the highest germination in the range of 10–20°C for L. agrigentina and L. triloba and 5–15°C for L. pallescens. Interpopulation variability in final germination was detected for both L. agrigentina and L. triloba subsp. triloba and in germination rate only for L. agrigentina. Conclusions – The three Lavatera taxa differed in their germination requirements, and these could be related to the habitat/ecology of each taxon. Our results suggest that seeds of the three taxa can germinate in the field from autumn to spring, when conditions are favourable for seedling establishment in the Mediterranean climate.