The mechanisms of pollen tube growth have been studied in a wide variety of plant species. Since the 1990s, with the explosion of molecular genetic analyses in Arabidopsis thaliana, most studies started to focus on this model plant. However, because of their particular characteristics, plant species other than Arabidopsis are still used to reveal physiological mechanisms and identify novel molecules relating to pollen tube growth, including, for example, lily, tobacco, Nicotiana alata, tomato, rice, maize, Brassica spp., corn poppy and Torenia (Table 1). Here, we designate all of these relatively common experimental plants as “biological models” for the study of pollen tube growth. These models sometimes provide a good first step in the identification of novel physiological mechanisms and molecules. As genome sequencing technologies become more advanced, the difficulty of performing molecular analyses in these biological models will decrease. Thus, a better understanding of these biological models will allow researchers to perform unique studies of pollen tube growth. In this chapter, we compare the characteristics of biological models, focusing on in vitro systems, to facilitate the use of these biological models for in vitro analyses.