一、问题的提出当代,世界科学技术的迅猛发展,推动着经济和社会发生深刻的变化。然而,在展望未来时,不少人士也提出了人类面临的,诸如粮食危机、能源危机、环境危机、人口爆炸等尖锐矛盾。我国虽然无需采用这些耸人听闻的概念,但这种尖锐矛盾同样隐藏在发展之中,急待引起足够的重视和深入的探讨。党中央最近指出:解决食品问题,从长远来看,还必须调整国民的食物结构。这个问题如同计划生育一样,应当是一项基本决策,这是一项英明的决策。我国人多地少,人均耕 I. PROBLEM PRESENTATION The contemporary world and the rapid development of science and technology in the world have driven profound changes in economy and society. However, looking forward to the future, many people have also come up with sharp contradictions facing humankind such as the food crisis, the energy crisis, the environmental crisis and the population explosion. Although China does not need to adopt these sensational concepts, such sharp contradictions are also hidden in the development and are urgently aroused enough attention and in-depth discussions. The party Central Committee recently pointed out: To solve the food problem, in the long run, we must also readjust the food structure of the people. This issue, just like family planning, should be a basic decision. This is a wise decision. There are many people in our country who are less cultivated