A microfluidic device for quantitative analysis of chemoattraction in plants

To precisely quantitate the effect of chemoattractants on directional pollen tube growth, a new microdevice was developed. Torenia fournieri pollen tubes, which generally grow freely on agarose medium, were funneled through a narrow flow channel that splits into a T-shaped channel leading to two reservoirs. The main channel was thus divided in two so that pollen tubes could choose their growth in either the left or right direction. Liquid solution or plant tissues were loaded into the reservoir, and diffusible molecules from the materials gradually spread in the narrow channel, leading to a concentration gradient. When egg-cell containing ovules were placed in one reservoir, pollen tubes grew selectively in that direction, suggesting that materials secreted from the ovules attracted the pollen tubes. Furthermore, UV-irradiation of female gametophytes in ovules decreased their ability to attract pollen tube growth. These results suggest that this novel device provides a unique platform for screening materials that may attract pollen tubes and for quantitatively analyzing the chemical features of attractants.