Change of Potential Photosynthesis Rates in Fraxinus Mandshurica Seedlings Supplied with Different Phosphorus Levels

Phosphorus stress is often an environmental stress for forest trees.The properties in morphology and physiology of forest trees change greatly.In this paper,we used one-year old Fraxinus mandshurica seedlings as experimental material to study changes of potential photosynthesis rates of these seedlings under phosphorus stress.The results showed that the contents of chlorophyll a and b,total chlorophyll levels,and ratios of chlorophyll a to chlorophyll b reduced when these seedlings were under phosphorus stress.At the same time,total nitrogen contents and soluble protein contents in leaves of seedlings under phosphorus stress reduced.Although parameters of chlorophyll a fluorescence changed irregularly,the potential photosynthesis rates reduced as phosphorus levels supplied to the seedlings decreased.The reduce of potential photosynthesis rate is related to the partitioning of nitrogen in leaves to Rubisco.