【作者】 张帆；

【导师】 罗承德； 张健；

【作者基本信息】 四川农业大学 ， 森林培育学， 2002， 硕士

【摘要】 杉木是我国重要的人工造林树种，但近年来的集约化营林生产和人工林产区的酸沉降导致了林地土壤酸化，林分生产力下降。作为酸化土壤上最主要的植物生长限制因素的Al胁迫逐渐上升为引起杉木人工林更新困难的主要原因之一。对杉木人工林Al胁迫的研究，目前只进行过林地土壤Al毒害阈值的界定，对缓解途径的研究尚未涉及。营养调控是治理发生Al胁迫的酸化土壤和改造已受到Al胁迫的林分的有效而实际的途径之一，但目前国内外对这一内容的研究较少。本研究拟为通过营养调控缓解杉木人工林Al胁迫对策的提出提供基础和理论依据。 研究采用室内水培模拟试验，通过研究Ca、P和N素作为单一营养调控因素对Al胁迫下3月龄杉木实生苗生长的影响，分析探讨了各因素缓解Al胁迫的能力与机制，及其有效缓解Al胁迫对杉木幼苗生长抑制作用的浓度水平。研究结果表明： 1、Al浓度为1mmol·L^-1时能严重影响3月龄杉木实生苗的生长。提高培养液Ca/Al、P/Al、NH₄⁺-N/Al或NO₃^--N/Al（摩尔比），均能够不同程度缓解Al胁迫。其共同的原因在于调控因素水平的提高相应增加了培养液离子强度，使得Al活度降低，减少了幼苗对Al的吸收。 2、提高培养液Ca浓度能通过Ca与Al竞争性的拮抗作用抑制幼苗对Al的吸收。并提高培养液pH值，改变Al形态，降低环境中同浓度Al对植物的毒性。从而促进Al胁迫下幼苗的生长。本试验条件下，培养液Ca/Al≥2.8086（摩尔比）是Ca有效缓解Al胁迫的浓度水平。 3、提高培养液P/Al值主要是通过P与Al在幼苗体内的聚合作用，形成毒性较低的Al—P聚合体，并限制Al在幼苗体内的转运，减少其与Al敏感细胞器的接触，从而降低幼苗体内Al的毒性。本试验中，培养液P/Al≥4.5089（摩尔比）时，能显著缓解Al对幼苗生长的影响。 4、增加培养液NH4_<sup>+-N的量能部分缓解杉木幼苗受到的Al胁迫。本试验中，培养液NH₄⁺-N/Al≥4.7087（摩尔比）时，其对Al胁迫下杉木幼苗生长的促进作用较为显著。但NH₄⁺-N缓解Al对幼苗抗氧化系统损伤的作用及促进根系完整发育的作用不如Ca和P有效。其作用机理可能在于抑制植物对Al的吸收。 5、提高培养液NO₃^--N浓度对促进Al胁迫下杉木幼苗生长的作用较小。这种促进作用并非来自其提高环境pH的能力，很可能只是由于提高了培养液离子强度，减小了Al与幼苗根系接触几率的原因。更多还原

【Abstract】 Three-month-old seedlings of Chinese fir (Cunninghamia laceolatd) were grown in solution culture at pH 4.0 for 80 days with ImM Al to evaluate the effects of varying concentration of Ca, P, NH4+-N or NO3"-N in solution on seedlings growth. The effects on morphological indexes (including fresh weight, dry weight, shoot length, root length and relative elongation ratio), physiological indexes (including MDA content and POD activity), chemical composition of seedlings and concentrations of total and monomeric Al in solution were submitted to statistical analysis and compared. The results indicate:Extensive growth problems of varying severity occurred on Chinese fir seedlings in normal nutrient solution added ImM Al. The Al toxicity could be alleviated by increasing Ca, P, NH4+-N or NCV-N supply. Which were partially associated with the increased ionic strength caused by higher nutrient elements concentration. The main beneficial effects of each nutrient element on seedlings growth under Al stress were different.Significant positive correlations were found between seedlings weight or shoot length and solution Ca/Al molar ratio. MDA content, POD activity and tissue Al increased with the decreasing molar ratio. Tissue Al was at a low level and solution Tol-Al at a high one compared to other treatments among the experiment. The positive effect of Ca concentration on Chinese fir seedlings confirmed the existence of a protective action of Ca against Al toxicity. The protective mechanism attributed to antagonism between Ca and Al and the adverse effect of Ca on the cellular physiology in comparison with Al. In this experiment, Ca/Al ^2.8086 (molar ratio) was the critical ratio.The beneficial effect of high P/A1 molar ratio on Chinese fir seedlings growth under Al stress was similar to Ca/Al. Except a larger proportion of the Al remained in tissue and a lower solution Tol-Al concentration. The direct effect in alleviating Al toxicity of solution P was associated with the detoxification caused by the chelation between P and Al. In the experiment solution P/A1^4.5089 was the critical ratio.Growth of Chinese fir seedlings was improved by increased solution NH4+-N supply. Solution NH4+-N/A1^4. 7087 was critical molar ratio. But the beneficial effects ofNH4+-N/A1 on root morphology and POD activity were less effective compared to Ca or P. Alleviation of Al toxicity by NH4+-N was probably bound to the direct inhibition of A13+ uptake by NH4+.Solution NO3--N could mitigate some of the adverse effect of Al on Chinese fir seedlings growth. MDA content and tissue Al decreased with increasing solution NOs’-N. But there were no direct relationships between each indexes and solution NOs’-N/Al molar ratio. Higher correlated coefficients (still not significant) were found between solution ionic strength and each growth index. The amelioration could not be related to the induced solution pH increase by N(V absorption but probably solely attributable to increase in ionic strength.更多还原