Abscission of seeds and pollen

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Models of seed and pollen dispersal by wind are handicapped by our almost complete lack of knowledge regarding the start of the event: abscission. Here I will test the hypotheses that (1) there is a strong bias toward abscission during the early afternoon (when wind speeds and atmosperic instability are maximized while relative humidity is minimized); (2) the abscission response to wind and relative humidity is similar for all plant species in both the tropics and mid-latitudes; (3) there is also a bias toward updrafts rather than downdrafts; (4) the probability of abscission is proportional to the drag force (and thus to the square of the wind speed); and (5) dispersal is almost entirely inland near coasts (due to the mid-day sea breeze) and upslope in the mountains (due to the mid-day anabatic winds).