The drought resistance gene is another good example. If it were expressed all the time, the plant would always be in drought resistance mode; to stay alive, it would remain stunted, which is no way to get a bumper crop.
又例如「抗旱基因」，該基因如果平時就表現，那麼作物會一直以為自己處於缺水狀態，為了活命，自然會限縮生長而長得矮小，反倒造成歉收。