1. Compared with germinated seeds, the experimental results are easy for students to misunderstand that germinated seeds can breathe, but germinated seeds can't. Although the textbook shows that germinated seeds can breathe, they are very weak and difficult to observe, but through comparative experiments, students' intuitive impression is very profound. For this reason, we changed the ungerminated seeds in bottle B into soaked and boiled seeds as a comparison, which made the conclusion more clear. 2. An experiment can be added before the experiment of releasing carbon dioxide when seeds breathe. Put the clear limewater into the test tube, and let the students blow into the glass tube to let them know that the CO2 exhaled by people makes the clear limewater turbid. Then demonstrate the experiment that CO2 released by germinated seeds makes limewater turbid, which is more illustrative. 3. Demonstrate the respiratory function of leaves Take a transparent plastic bag, put a proper amount of Chinese cabbage leaves or other fresh leaves, insert a glass elbow with a rubber tube above the bag, tie the bag tightly, insert one end of the glass tube into a test tube filled with clarified limewater, and squeeze the bag to keep the limewater unchanged; After refilling, tie the bag tightly, clamp the rubber tube, leave it in the dark for 10 ~ 15 min, then take it out, insert the glass tube into the clear limewater, open the clamp and squeeze the bag. You can see that the lime water has become turbid. This shows that leaves can also breathe and release carbon dioxide. In the above experiment, the leaves of Chinese cabbage are placed in the dark. The following experiment needs to be supplemented to avoid students' one-sided understanding that breathing is only available in the dark (or at night). 4. Plants also breathe during the day. Before class, yellow seedlings (wheat seedlings or leeks) are cultivated in wide-mouth bottles, packed in transparent plastic bags, tied tightly in the bags and clamped by rubber pipes connected to the bags, and the other end of the rubber pipes is sleeved on the glass tubes. One hour before the experiment, take the experimental device to outdoor lighting. During the experiment, the glass tube was moved indoors, and the glass tube was put into the clarified limewater, and the clamp was loosened and the bag was squeezed to make the clarified limewater turbid. Let the students know that breathing can be done with or without light.

Photosynthesis and respiration coexist in plants, each exercising its biological function and mission, and cooperating with each other. Obviously photosynthesis releases oxygen and absorbs carbon dioxide; Breathing releases carbon dioxide and absorbs oxygen. The intensity of photosynthesis determines the amount of oxygen released by plants, but it does not mean that photosynthesis can determine respiration, and there is no absolute dependence between them. The main controlling factor of photosynthesis is light, while the main controlling factor of respiration is temperature. The respiration of plants always exists, including day and night. The temperature during the day is higher than that at night, so the respiration during the day is stronger than that at night.