Stem cell division increases the number of cells. Some cells differentiate into tissue cells with specific functions, and some cells maintain the ability of division to carry out self-renewal of stem cells.

2. The root rot of rice and other plants after long-term flooding is due to the toxic effect of alcohol, a product of anaerobic respiration, on cells. The reason of corn seed rot is that lactic acid produced by anaerobic respiration is toxic to cells.

3. The difference of anaerobic respiratory products is due to the different kinds of enzymes that catalyze the reaction, and the fundamental reason lies in the different genes that control enzyme synthesis.

4. Eukaryotes or organisms without mitochondria can only breathe without oxygen, such as mature red blood cells and roundworms. Mitochondria are the main places for aerobic respiration. Some prokaryotes have no mitochondria, but they breathe aerobically.

5. In the experiment of exploring the optimum temperature of enzyme, the enzyme solution and reactants need to be kept at their respective required temperatures for a period of time before mixing. If starch and amylase are selected to explore the optimum temperature of the enzyme, iodine solution should be used as the detection reagent, and Phyllin reagent should not be used. It is necessary to heat the reagent with hot water bath, and the temperature should be strictly controlled in this experiment.

6. In the experiment of exploring the optimum PH of enzyme, the enzyme must be placed under different PH conditions, such as water, sodium hydroxide, hydrochloric acid, and then the reactant. After enzyme is added to the reactant, hydrochloric acid or sodium hydroxide is not allowed to be added.

7. Gene mutation will definitely cause the change of gene structure, that is, the change of base arrangement order in the gene; Addition, deletion and substitution of base pairs in DNA are not necessarily gene mutations. Because genes are DNA fragments with genetic effects, DNA fragments without genetic effects can also have changes in base pairs, but they are not genetic mutations.

8. The factors that cause the uneven distribution of auxin in coleoptile are: unilateral illumination, gravity, cutting off the position of agar block containing auxin at the top on coleoptile, blocking the downward transport of auxin on one side with mica sheet and other substances.

9. The flowering period was hit by strong winds, which affected pollination. For eggplant crops, spraying a certain concentration of auxin can avoid yield reduction; For crops that harvest seeds, because seeds cannot be formed without fertilization, the yield will be reduced.

10: The pigment in corn mesophyll cells can be separated by paper chromatography. The places where ATP can be produced in mesophyll cells are cytoplasmic matrix, mitochondria and chloroplasts. After carbon dioxide enters mesophyll cells, it is fixed in the dark reaction stage, which can provide Pi, ADP and NADP+ for light reaction.

1 1: Gibberellin is mainly synthesized in immature seeds, young roots and buds. Gibberellin can break seed dormancy, promote seed germination, and has antagonistic effect with abscisic acid.

12: auxin is synthesized from tryptophan, so tryptophan is the precursor of auxin.