Seed-setting by alpine gentian (Gentiana nivalis L.)

Summary The seed content of individual capsules of alpine gentian (Gentiana nivalis L.), a rare annual of Scottish mountains, was compared amongst (a) single- and multi-flowered plants and (b) the years 1987–92 inclusive. Capsules contained two types of seeds, ‘live’ seeds that were terete and apparently viable, and ‘aborted’ seeds that were shrunken and clearly dead. The topmost capsule on plants with two-five flowers contained two-three times the number of live seeds found in capsules from plants with a single flower. The mean annual production of live seeds per plant ranged from 176 in single-flowered plants through 445, 580, 983 and 1145 in plants with two, three, four and five flowers respectively. The mean live seed content of capsules varied annually, depending on the numbers of seeds that aborted. Annual variation in the proportion of aborted seeds was negatively correlated with mean maximum temperature during July, when the plants began flowering. It is suggested that cold temperatures in July possibly inhibited the activity of pollinating insects and the growth of pollen tubes. The results are discussed in the context of possible future changes in the Scottish climate.