Seed germination process of cereal plants is one of the topics included in biology curriculum of high school. The rice seed consists of three major parts, embryo, endosperm and aleurone layer. Two teaching materials were developed to support the understanding of the close interaction among these parts in germination and initial seedling growth. (1) Spatial distribution of amylase activity within a seed at the germination and post-germination stages: Using a series of slice piece of a germinating seed, amylase induction within the seed was initiated from proximal region with an embryo, followed by gradual expansion towards distal region during germination and subsequent seedling growth. (2) Detection of amylase activity in three parts separated by fractionation: Amylase activities were detected in isolated embryos and isolated aleurone layers. Amylase induction occurred in embryoless seeds which were treated with gibberellin. These experimental data enabled us to confirm that the amylase produced in embryos plays a role in the germination, whereas the amylase produced in aleurone layers is involved in seedling establishment through the digestion of starch deposited in endosperm.

I developed an experiment to study the function of protease from the tissue of an organism. Fruits containing proteolytic enzymes were used as a material because it is difficult to prepare animal digestive juice. For observing protease activity, SDS-PAGE was used, which enables viewing at the molecular level. Using milk as the substrate combined with fruit juice, it was observed that the protein molecular weight reduction progressed with time. In particular, pineapple and kiwi showed remarkable protease activity. This experiment may serve as a teaching material to understand enzyme activity and it can also be used for inquiry activities in “biology” lessons.

The observation of pollen germination and pollen-tube growth is often carried out in high school biology classes to learn the process of fertilization in angiosperms. If living sperm cells are visible in the growing pollen-tubes, students’ understanding of the role of pollen in the fertilization will be improved. Yellow-flag iris (Iris pseudacorus) has colored generative cells which are visible under an optical microscope without dyeing the cells, however, divisions of the generative cells and resultant sperm cells have not been observed in in vitro pollen-tubes in this species. We cultured the pollen grains of this species using polyethylene glycol based medium with adding ammonium chloride (NH₄Cl) in the present study. Then, we found that the generative cell divisions occurred and colored sperm cells emerged about 7 hours 20 minutes after the culture initiation. We also investigated the possibility of frozen storage of the pollen grains. After 4 months’ frozen storage, the rate of pollen germination and generative cell division were 50–60% and 10–15%, respectively. By utilizing the frozen storage, we can use the pollen grains of this species as a teaching material for observing the living sperm cells over a long period from spring to autumn.