Development of desiccation tolerance and longevity in seeds from detached capsules of foxglove (Digitalis purpurea L)

Developing capsules of foxglove (Digitalis purpurea L.) were detached at 4-d intervals between 12 and 28 d after flowering (DAF) and attached to canes within a natural foxglove stand such that they were experiencing field conditions identical to those experienced by normally developing, on-plant capsules. Seeds were subsequently harvested at 4-d intervals until 40 total d after flowering (tDAF). Capsule detachment resulted in the cessation of dry matter accumulation; the mean dry weight of seeds from 12, 16, 20, 24, and 28 DAF-detached capsules was 21, 32, 51, 60, and 79% respectively, of the mean dry weight of seeds during the post-abscission phase of normal, on-plant development. Nonetheless, seeds from detached capsules acquired the ability to germinate at harvest and tolerance to drying under seed conservation conditions (15% relative humidity and 15 degrees C). The capability to withstand storage also arose following capsule detachment. Seed longevity increased the longer the period of detachment but, in the earlier-detached capsules (12, 16, and 20 DAF) longevity subsequently declined. Only seeds from later detached capsules (24 and 28 DAF) acquired longevities which were comparable with seeds from on-plant capsules, however, no seeds from detached capsules were as long lived as seeds from on-plant capsules harvested at 40 DAF. (C) 1997 Annals of Botany Company.