增铵对小白菜生长和叶绿素含量的影响

在营养液中添加一定量的铵态氮能提高作物生物量和叶绿素含量。为研究增铵对植物生长及叶绿素含量的影响机理,采用了6个NO3-∶NH4 浓度比为5·0∶0·0、5·0∶2·5、5·0∶5·0、5·0∶7·5、5·0∶10·0和0·0∶5·0的处理对小白菜进行培养试验。结果表明,在5mmolL-1硝态氮存在时,适当添加一定量的铵态氮(2·5mmolL-1)小白菜生物量和叶面积分别增加39·6%和16·3%,叶面积与生物量显著相关(r=0·941,p<0·01)。营养液中铵态氮浓度与叶片SPAD值、活性铁及叶绿体蛋白质含量均显著相关,相关系数r分别为0·914、0·954和0·964。适当提高铵态氮浓度增加小白菜产量的机制在于其促进了叶片扩展,提高了总光合面积,其原因可能是适当提高铵态氮浓度促进了叶片细胞分裂。进一步研究表明,提高铵态氮浓度提高叶绿素含量的原因,可能在于其促进了小白菜体内全铁的再利用,从而提高了叶片活性铁含量和叶绿体蛋白质含量。

EFFECTS OF ENHANCED AMMONIUM ON THE GROWTH AND CHLOROPHYLL CONTENT OF CHINESE CABBAGE

Chlorophyll content and biomass of plants are usually increased by the addition of certain amount of ammon-i um to the nutrient solution.In order to study the mechanisms of enhanced effects by ammonium on plant growth and chlorophyll content,Chinese cabbage was hydroponically grown in nutrient solutions with six different ratios of NO₃^-:NH₄⁺,i.e.,5.0:0.0,5.0:2.5,5.0:5.0,5.0:7.5,5.0:10.0 and 0.0:5.0.The results obtained were as follows.In the presence of 5 mmol L^-1 nitrate,addition of ammonium(2.5 mmol L^-1) to the solution promoted the biomass and leaf area of Chinese cabbage by 39.6% and 1613% compared with no ammonium addition and the leaf area was significantly correlated with biomass(r=0.941,p< 0.01).There was a significant relationships between ammonium concentration added and SPAD readings,active iron content and chloroplast protein content in the plants with the r values of 0.914,0.954 and 0.964,respectively.The mechanism of the properly enhanced ammonium on biomass was the facilitated expansion of leaf blade,and thus the increased total photosynthet ic area.The facilitated expansion of leaf blade can be attributed to leaf cell division resulting from the enhanced ammonium effect,which should be studied in future.A further study showed that the reason for enhanced ammonium to increase the chlorophyll content was related to the increased reusage of total iron in Chinese cabbage plant,thus increasing the active iron content in leaf blade and chloroplast protein content.