氨对紫背浮萍和稀脉浮萍超微结构的影响

选择紫背浮萍和稀脉浮萍，利用SEM和TEM分别对在对照液硝酸盐氮培养液和含有较高氨氮培养液中生长个体的超微结构进行了观察和分析．结果表明，与在硝酸盐氮培养液中生长的个体相比，在氨氮培养液中生长的2种浮萍上表皮的气孔张开程度明显地增大，下表皮细胞突起的细胞壁消失，细胞发生明显的变形；生长在含有氨氮培养液中的2种浮萍个体的叶绿体内膜结构均受到严重的损伤，叶绿体中淀粉粒明显增多，整个叶绿体处于解体状态，而生长于硝酸盐氮培养液中浮萍的叶绿体则完好无损．

Effect of ammonia on the ultrastructure of duckweed species

The changes of ultrastructure under scanning electron microscopy and transmission electron microscopy were described in two duckweed species of Lenma aequinoctialis and Spirodela polyrrihza cultivated in ammonia medium in present study,contrasted by the ones growing under nitrate medium.The result showed that outstanding cell wall in lower epidermis became crinkly and disappeared partly in fronds under ammonia medium.The stomata on the upper epidermis opened much wider far more than ones under nitrate medium.The chloroplast membrane limiting became blurred and disappeared partly in fronds under ammonia medium.The whole chloroplast of fronds under ammonia medium presented the trending of disassembly.And the internal membrane network including grana lamellae and stroma lamellae break off.In contrast to ones under nitrate medium,more starch grain appeared amongst stroma.Based on the results of observation,the toxicity mechanism of un-ionized ammonia(NH_3) and ammonium ion(NH~+_4) to duckweed were respectively discussed.