The effect of CO_2 concentration and temperature on chlorophyll content of Quercus mongolica Fisch.under different nitrogen levels

Chlorophyll content in leaves plays an important role in light absorption,transfer and transformation in photosynthesis.In order to predict the photosynthetic capacity of the plant under different nitrogen levels with elevated CO_2 concentration and temperature in the future,we carried out the experiment about the chlorophyll content of one year old Q.mongolica seedlings exposed to double CO_2 concentration,elevated temperature and control under different nitrogen levels.The results showed that nitrogen levels significantly affected chlorophyll content.Under the three treatments of double CO_2 concentration,elevated temperature and control,the chlorophyll content of high nitrogen was obviously higher than normal nitrogen level and no nitrogen added.The effect of CO_2 concentration and temperature on chlorophyll content were also limited by nitrogen levels: under high nitrogen,CO_2 concentration accelerated the chlorophyll a component and more significantly accelerated chlorophyll b component.And elevated temperature(+4℃) could increased chlorophyll a content,but didn't affect chlorophyll b content.Under normal nitrogen level,chlorophyll a,b and total content were not affected by CO_2 concentration and temperature.Under no nitrogen added,double CO_2 concentration and elevated temperature to some extent might improve chlorophyll a content,but couldn't synthesize chlorophyll b at the same time.Elevated CO_2 concentration significantly resulted in more requirements of Q.mongolica seedlings to nitrogen,and the seedlings under elevated temperature also to some extent needed more nitrogen.