Abstract: In this study,three month-old seedlings of Chinese fir (Cunninghamia laceolata ) were grown in solution culture with 1mmol·L^-1 Al at pH 4.0 for 80 days to evaluate the effects of varying concentrations of Ca,P,and NH₄⁺-N or NO₃^--N in solution on their growth.The morphological indexes (fresh weight, dry weight,shoot length,root length and relative elongation ratio) and physiological indexes (MDA content and POD activity) were submitted to statistical analysis and compared.The results indicated that the seedlings weight or shoot length had a significantly positive correlation with the molar ratio of solution Ca/Al.The MDA content and POD activity decreased with the increasing molar ratio of Ca/Al,and Ca/Al≥2.8 was the critical ratio.Similar to Ca/Al,high P/Al molar ratio also had an obvious effect on the growth of Chinese fir seedlings under Al stress,and P/Al≥4.5 was the critical ratio.The growth of Chinese fir seedlings was improved by increased NH₄⁺-N supply, but the effect was less obvious than Ca and P.Solution NH₄⁺-N/Al≥4.7 was the critical molar ratio.Solution NO₃^--N could mitigate some adverse effects of Al on Chinese fir seedlings growth,but no regular effects were found with the change of solution NO₃^--N/Al molar ratio.

Key words: Plutella xylostella, Pesticide, Life table