Abstract
Summary: The pollen-tube attractant was first proposed in the late nineteenth century. Pollen tubes were observed to grow toward excised pistil tissues on the medium. Since then, for about 150 years, many plant biologists tried but failedto identify the attractant. Such difficulty also made some plant biologists to cast doubt on the existence of the attractant. In this decade, however, it was shown that the diffusible pollen-tube attractant navigated the directional growth of the pollen tube. Here we review the characteristics of the pollen-tube attractant to figure out the necessary and sufficient conditions as the true chemoattractant of the pollen tube.