Effect Of Environmental Factors On The Growth And Camptothecin Concentration Of Camptotheca Acuminata Seedlings

The effect of environmental factors such as soil moisture,natural soil drought,PEG drought,soil quality,light intensity and light quality on the growth,photosynthesis,camptothecin (CRT) concentration and yield of one-year-old Camptotheca acuminata seedlings were investigated. The CPT distribution in relation to the leaf,stem and root,and response to the environmental factors were analyzed. On the basis of them,we discussed and summarized the cultivation and harvest methods of seedlings with high CPT yield.The biomass of seedlings growing on the soil drought condition are obviously decreased. The net photosynthetic rate (Pn) and the stomatal conductance of seedlings growing on drought soil are lower than the normal at all stages,even appears midday depression of Pn. The order of the biomass and photosynthesis of seedlings is:the normal > the slight drought > the heavy drought. But soil drought stress increases CPT concentration in the leaves,stems and roots of the seedlings. The order of the average CPT concentration in the seedlings is:heavy drought > slight drought > the normal. But CPT yields of seedlings with highest CPT concentration are not the highest,because their biomass are restricted by soil drought stress. The results of PEG drought stress and natural soil drought stress show that the water contents of leaf are lower,and the membrane electrolyte leakage of leaf are higher than the normal. As the drought stress time delay,the damage increases gradually. The CPT concentration in leaves is increased at the early period of young seedlings,and lower than the normal at the later period.Slight shading is helpful to the growth of seedlings at the early period,but restricts the growth at the later period. The biomass and photosynthesis of the seedlings under shading are obviously lower than the normal. Shading increases CPT concentration in leaves,stems and roots of seedlings. The order of the average CPT concentration in seedlings is:heavy shading > slight shading >the normal. But CPT yields of the seedlings with highest CPT concentration are not the highest,because their biomass are restricted by heavy shading. The growth of seedlings under shading with blue and red films are not better,but the CPT concentrations in their leaves are increased gradually. The CPT concentration in leaves of seedlings under shading with yellow film is slightly higher than the normal,but it doesn't correlate with the treatment of time.The CPT concentration of seedlings under the shading and drought stress is obviously higher than the normal,but the biomass,photosynthesis and CPT yield are lower.The growth of seedlings is also influenced by soil quality. The biomass,photosynthesis and CPT concentration in leaves of seedlings growing on sand (soil:sand=l:2) are lower than that growing on soil.The relationship between CPT concentration in leaf and its position can be described by formula y=aebx. And the relationship between CPT concentration in leaf and its age can be described by formula y=kx+b. High correlation in CPT concentration was found between roots and stems,whereas low correlation between stems and leaves,roots and leaves was observed. The correlation is certainly influenced by the environmental factors.To sum up,the soil nutrition plays a great role in the growth of seedlings and higher CPT yield. In the practice of cultivating seedlings,it is a efficient method to gain high CPT yield that seedlings grow under moderately and termly shading and drought stress.