As cultivated tomatoes are autogamous (self-fertilizing) plants, we had cultivated commercial cherry tomato F1 cultivars ‘Orenji Kyaroru (Sakata Seed Co.), Aiko (Sakata Seed Co.) and Tyinkar Beru (Nanto Seed Co.)’ then got self-pollinated F2 seeds from the harvested fruits. We have cultivated 104, 70 and 41 F2 generation individuals respectively with 10.5 cm diameter small pots. In these F2 individuals, we observed clear genetically segregated characters of leaf colors with growth degree, flesh colors, pericarp colors. Especially in the case of ‘Orenji Kyaroru F2’, it showed three Mendel’s laws, i.e. the law of dominance, segregation and independence. We conclude that commercial cherry tomato F1 cultivars are good teaching materials for genetics because you cultivate them and can easily get F2 seeds which enable to cultivate sufficient quantity of individuals to observe genetic phenomena. In scientific course of a high school, they cultivated ‘Orenji Kyaroru F2’ and successfully observed genetic segregations. A survey by questionnaire showed that they have become more interested in genetics and understood Mendel’s laws more deeply. It is an advantage to use commercial cherry tomato F1 cultivars because you don’t need to cross or hybridize which is somewhat complicated procedure. Another advantage is that we can observe genetic segregation of leaf colors easily within two or three weeks after sowing. At the same time, it is a great disadvantage that we cannot use the parents of the F1 cultivars because they are never allowed to be taken out from the seed companies.
Glycerol of high purity is generally used in process of making transparent skeletal specimens for permeation and preservation. However, in the field of education, glycerol’s high cost could be a hindrance to its use. In this experiment, we tried to make transparent skeletal specimens using dishwashing liquid instead of glycerol. Medaka (Oryzais latipes) fixed in 10% formalin overnight at room temperature were put in five kinds of dishwashing liquids containing various concentrations of potassium hydroxide at 35°C for 2 weeks. Transparency of all fish specimens was enhanced by potassium hydroxide in dose dependent manner. We also treated the formalin-fixed fish in alizarine red S solution overnight followed by immersion in various dishwashing liquids as above. We found that two dishwashing liquids containing 1% potassium hydroxide could make skeleton transparent without decoloring of hard bone stained by alizarin red S. Dishwashing liquid is considerably inexpensive compared to glycerol of high purity, therefore this procedure will make it easy to use transparent skeletal specimens in schools.
Laboratory work for confirming whether rhizoids of bryophytes to can absorb water or not was developed using a riboflavin (vitaminB2) solution and UV light (352 nm) for science classes in lower secondary schools. After newly elongated rhizoids of bryophytes, Pogonatum inflexum, Plagiomnium acutum, Marchantia polymorpha and Conocephalum conicum, were immersed in a 0.05% riboflavin solution for several hours, both the top of stem of Pogonatum and Plagiomnium and the top of thallus of Marchantia and Conocephalum became fluorescent under UV-light. These results indicate that riboflavin solution was absorbed through their rhizoids, and reached the top of the plant body. In current science textbooks in lower secondary schools in Japan, only the function of rhizoids of bryophyte, “Adhesion to substrates”, is described, while learners can confirm by themselves another function of rhizoids, “Absorption of water”, through the simple laboratory work described in this paper.