A Factor Analysis Study of the Functional Significance of Angiosperm Pollen

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Abstract
Investigations on the adaptive significance of pollen morphology were conducted on 17 variables of pollen, floral and anthecological characters in 100 spp. of angiosperms. Three close interrelationships among the characters were established by factor analysis: positive correlation between grain size, exine thickness, and aperture number; strong association of grain shapes with aperture types, i.e., the prolate grain with colpus and the spherical and the oblate shapes with a pore; and a positive correlation among the [animal] pollinator''s body size, the floral size, the style length, and the pollen grain size. Based on the above results, the following suggestions on the adaptive aspects of pollen can be made: exine thickness is important for mechanical support with respect to grain size and aperture number; larger grains require more apertures for rapid water absorption from the stigmatic surface; the association of grain shape and aperture type plays a role in accommodation of volume change when the grains absorb or lose water; and grain size is related to the capacity of stored nutrients which determine the potential length of a pollen tube.