外源钙、磷、氮对铝胁迫下杉木幼苗生长影响的调控研究

为缓解Al胁迫对杉木人工林更新的影响，本文采用水培模拟Al胁迫，引入Ca、P、NH₄⁺-N、NO₃^--N营养调控因子，探讨Al胁迫对杉木幼苗根茎生长的影响.结果表明，增加Ca或P浓度，能促进根、茎的正常生长发育，根系的形态特征明显变化，降低组织内MDA含量和POD活性.增加NH₄⁺-N浓度只能促进茎的生长，对根系发育影响不明显.增加NO₃^--N浓度对根茎生长均无明显的规律性影响.增加NH₄⁺-N和NO₃^--N浓度，能抑制MDA含量增加，并在一定范围内降低POD活性，但效果不及Ca或P明显.经回归方程拟合，得出本试验条件下营养因子有效缓解Al胁迫的阈值是：Ca/Al≥2.8，P/Al≥4.4，NH₄⁺-N/Al≥4.5（摩尔比）.

Alleviation effect of exogenous Ca,P and N on the growth of Chinese fir seedlings under Al stress

In this study, three month-old seedlings of Chinese fir (Cunninghamia laceolata) were grown in solution culture with 1 mmol x 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 > or = 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 > or = 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 > or = 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.