Seeds were released in the strongest wind events and were more likely to be released in updrafts or horizontal winds rather than downdrafts. ![]() Further, there was an average seed loss of 76♴%, 72♵%, 73♹%, 65♳% and 58♸% for wind orientations of 0, 45, 90, 135 and 180°, where 0° indicates wind directed up towards the base of the hemispherical seed head (simulating an updraft), 90° indicate wind directed towards the side of the seed head (horizontal wind) and 180° indicate wind directed down towards the top of the seed head (simulating a downdraft). While seed loss increased with increasing wind speed, average loss from seed heads increased from 49♴% on the day they opened to 92♸% from seed heads open for 10 days. ![]() Seed head age at the time of harvest from the plant (0-10 days old, where day 0 is the day on which the seed head opens) and seed head orientation (in relation to the direction of air) were altered. Wind speeds of 0-70 m s -1 were used to remove the seeds from seed heads harvested directly prior to exposure to wind. ![]() The current research used Conyza bonariensis to examine seed release thresholds of seed heads at varying ages and at varying orientations (in relation to the direction of the air flow). It has been established that the timing of abscission has a major impact on the dispersal distances achieved by individual seeds, and yet there is little information available on seed release thresholds.
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