Three ways that plants avoid self-fertilization are: 1) The biochemical mechanism of killing genetically self pollen called self-incompatibility; 2) Having separate male and female plants; and 3) By having two different kinds of flowers (pin, thrum) on different plants of the same species.
Work Step by Step
This question is asking you to summarize the information found on pp. 828-829. You might also have slightly different set of answers by separating gametophytic and sporophytic self-incompatibilities as two of the three parts of your answer.