Photosynthetic characteristics and their defense chemicals of deciduous broadleaf trees raised under enriched CO_2 and temperature

对食草动物的抗性分为防御能力和补偿能力两种。昆虫幼虫不能吃防御能力强的叶片，或因叶片消化能力差而几乎不吃叶片。从叶片化学成分分析来看，蒙古青和金针叶中总酚化合物含量高于其他树种。白桦叶片含有较多的缩合单宁。这些物种对食草动物有更高的防御能力。另一种能力被认为是补偿。当叶片被食草动物放牧时，叶片的恢复可能与光合能力和叶片原基的形成过程密切相关。总体而言，除白桦外，自由生长型树木叶片中防御化学物质含量较低，而固定生长型树木叶片中防御化学物质含量较高。无论光照条件如何，白桦均具有较高的防御化学物质含量。这种能力可能导致在这个桦树物种广泛的分布范围。在高CO_2条件下，山柰和白桦的酚类化合物和缩合单宁含量较高，而油麻和蒙古栎只增加了总酚含量，而缩合单宁含量没有增加。这一趋势可能表明，在未来的温室环境中，绿桫椤和蒙古桫椤对食草动物的放牧敏感性更高。

Resistance against herbivores is classified into two ideas, namely the capacity of defense and compensation. Insect larva cannot eat leaves with high capacity of defense or hardly eat leaves because of low digestion in leaves. According to chemical analysis of leaves, amount of total phenolic compound in leaves of Q.mongolica and A.mono was larger than the other species. Leaves of B.platyphylla contained larger amount of condensed tannin. These species have higher capacity of defense against herbivores. The other capacity is considered to be compensation. When leaves would be grazed by herbivores, recovery of leaves may be strongly correlated with photosynthetic capacity and the process of formation of leaf primordia. In general, except for B.platyphylla, defense chemicals in leaves of trees with free growth type had lower amount of defense chemicals while these with fixed growth type had higher amount. B.platyphylla usually has high amount of defense chemicals irrespective of light condition. This ability may lead to broad distribution range in this birch species. Under high CO_2, L.Kaempferi and B.platyphylla had larger amount of phenolic compounds and condensed tannin while Fagus crenata and Q.mongolica increased only amount of total phenol but not condensed tannin. This tendency may imply that F.crenata and Q.mongolica would have higher susceptibility to grazing by herbivores in future greenhouse environment.