不同形态N素对水曲柳幼苗生长的影响

在温室内用砂培的方法研究了ＮＯ＾－３－Ｎ、ＮＨ＾＋４－Ｎ及其不同配比对水曲柳（Ｆｒａｘｉｎｕｓ ｍａｎｄｓｈｕｒｉｃａ）幼苗生长的影响。结果表明，水曲柳幼苗在营养液ＮＯ＾－３－Ｎ：ＮＨ＾＋４－Ｎ为７５：２５时生长最好，营养液中ＮＨ＾＋４－Ｎ比例继续增加则生长下降。过量的ＮＨ＾＋４－Ｎ可抑制水曲柳幼苗根系生长，降低幼苗的地下／地上比。营养液中ＮＨ＾＋４－Ｎ比例增加，水曲柳幼苗的净光合速率下降，体内Ｐ

Effect of different nitrogen forms on growth of Fraxinus mandshurica seedlings

The effect of NO\ -\-3 N and NH\ \-4 N and their different supply ratios on the growth of Fraxinus mandshurica seedlings was studied by sand culture in greenhouse.The highest seedling growth was obtained at a NH\ -\-3 N/NH\ \-4 N ratio of 75/25 in nutrient solution.The growth of seedlings declined with the increasing ratio of NH\ \-4 N to NO\ -\-3 N. Excessive NH\ \-4 N inhibited root growth,and the root/shoot ratio of the seedlings significantly decreased as the NH\ \-4 N/NO\ -\-3 N ratio was over 50%.Increasing NH\ \-4 N in nutrient solution led to the decrease of net photosynthetic rate,the increase of phosphorus content in plant tissues,and the decrease of Zn and Fe contents.The pH value of cultural medium was affected markedly by nitrogen form,which was increased with increasing NO\ -\-3 N and decreased with increasing NH\ \-4 N in nutrient solution.The pH value was up to 7\^22 in the medium contained NO\ -\-3 N alone,while decreased to 4\^20 only with NH\ \-4 N.