Interactive computer-assisted position acquisition procedure designed for the analysis of organelle movement in pollen tubes.

An interactive computer-assisted video microscopy method has been developed for the acquisition of extensive data on the sequential positions of pollen tube organelles, which cannot be automatically tracked using geometric or motion patterns. The method consists of video microscopy, analog and digital contrast enhancement, digital time-lapsing of the images, and interactive selection of positions in a coordinate system corresponding to the cell shape and real size. Data on 15,000 positions acquired with this method have been used to make quantitative analyses of the movement patterns of the organelles. From these analyses and the reconstruction of 900 trajectories, it appears that movements are random in the tip of the pollen tube but become more directed in distal regions of the cell, indicating an increase in axial arrangement of the actin filaments. (All custom-made software is available from the authors on request.)