Although plant distribution patterns are well documented, our understanding of the ecophysiological mechanisms that control the geographical ranges of plant species remains poor. Using a largely ignored method, the performance of the male gametophyte in vitro, Rosbakh and Poschlod assessed whether the thermal range of pollen germination and tube growth control species distribution ranges along an elevational gradient.
They found a strong and positive relationship between temperature conditions at collection sites and the minimum temperature for both pollen germination and pollen tube growth. In addition, a significant correlation between maximum temperature of pollen tube growth and temperature of flowering month was apparent.
Sergey Rosbakh, Peter Poschlod, 2016, 'Minimal temperature of pollen germination controls species distribution along a temperature gradient', Annals of Botany, vol. 117, no. 7, pp. 1111-1120 http://dx.doi.org/10.1093/aob/mcw041