For developing a student laboratory exercise on flower initiation (floral development) in senior high school biology, we selected the Wisconsin Fast Plants (WFPs) which are the new varieties of rape (Brassica rapa, syn. campestris) as our experimental material. We examined the effects of temperature, day length, light intensity and the plant hormone gibberellic acid (GA3) on the flower initiation of WFPs. Under continuous light, the days required for detecting the first flower bud were dependent on the growth temperature being between 15°C and 35°C; the higher the temperature was, the faster the flower bud formation was. In the temperature range examined, the first flower bud could be detected within at least nine days (at 15°C) after sowing the seeds. Flower initiation was dependent on the day length at 15°C, but not at 25°C. At 15°C, flower buds formed nine days after sowing the seeds under continuous light, while no flower bud was detected nearly two weeks after the seeds were sown under a short-day condition (L:D = 8:16). The intensity of light in a long-day treatment (L:D = 16:8), from about 10 μmol·m-2·s-1 (ca 1,500 lux) to 100 μmol·m-2·s-1 (ca 13,000 lux) at 15°C, did not affect flower bud formation. The flower initiation in the plants treated with 0.01 μg·mℓ-1 GA3 was faster than in the untreated plants. The results obtained in the present study reveal that by using the WFPs students can get clear results on the effects of photoperiod, temperature, and the plant hormone gibberellin on the flower initiation of long-day plants within a shorter period than by using any other plant. Biology teachers possibly can organize a student laboratory on the photoperiodic response of plants referring to the present report.
In Japan, inquiry activities have been introduced into science subjects for upper secondary schools since 1994. Through these inquiry activities students are expected to address issues actively, think deeply by themselves, and feel pleasure in solving problems. However, so far, these activities have not been implemented widely. In the present paper, an example of inquiry activities which relates to the morphology and growth of the onion bulb is proposed. The process of the activity is as follows: First, the teacher gives the students a question, “Which part of the onion do you eat: root, stem, leaf, flower or fruit?” Most of the students may not give the correct answer. Teachers can use the gap between the students' answers and the correct answer to foster students' curiosity. This part is easy and inexpensive, and it can be carried out within one school hour. The next part is also inexpensive, but more challenging. The teacher gives the students another question, “How does the onion bulb get bigger?” To figure out their answers and verify them, students are asked to carry out a series of group activities: making a hypothesis which is an answer to the question, designing an experiment, carrying out the experiment and collecting data, analyzing and discussing the results, and finally deciding whether the hypothesis is acceptable. Then, each student is asked to write a report or give a presentation. Through these activities, students' abilities of logical thinking, decision-making, and expression can be cultivated.
The germination of lettuce seed is known to be a phytochrome-mediating phenomenon: red light promotes it, while far-red light inhibits it. In Japan, this topic has been included in biology textbooks for senior high schools, but the phytochrome response experiments have not yet been practiced widely. In order to enable senior high school biology teachers to conduct these experiments, the authors developed an apparatus for the experiments, LED-attached box. This article attempts to explain how to set up the LED-attached box. By means of the LED-attached box, the experimental procedures written in Japanese biology textbooks and in some research articles were followed. The phytochrome responses in photoblastic lettuce seed germination mentioned in Japanese biology textbooks and in other articles were successfully confirmed by using this box. This experimental apparatus was piloted in biology laboratory classes for senior high school students in Japan and pre-service high school teacher trainees in Cambodia. The participants could obtain good results and they were interested in using this LED-attached box.