硝酸盐对毛萼田菁茎瘤固氮的影响

ＫＮＯ３对毛萼田菁（Ｓｅｓｂａｎｉａｒｏｓｔｒａｔａ）茎瘤和根瘤固氮的抑制作用与瘤中积累，碳水化合物减少（特别是蔗糖）以及豆血红蛋白（ｌｇｈｅｍｏｇｌｏｂｉｎ，Ｌｂ）浓度减少和功能受阻相关．经ＫＮＯ３处理的植株的茎瘤类菌体的呼吸作用和固氮活性明显下降．从ＫＮＯ３处理的植株茎瘤中提取的类菌体悬液加上未经ＫＮＯ３处理的正常Ｌｂ可提高固氮活性和耐ｐＯ２；加５ｍｍｏｌ／ＬＫＮＯ２于正常的茎瘤类菌体悬液和Ｌｂ反应体系，引起固氮活性和耐ｐＯ２都降低，证明是Ｌｂ功能受阻的重要因素．施ＫＮＯ３可能还导致茎瘤Ｏ２扩散的阻力增加．

EFFECTS OF NITRATE ON NITROGEN FIXATION OF SESBANIA ROSTRATA STEM NODULES

The inhibition effects of nitrate on nitrogen fixation of Sesbania rostrata nodules had a direct relation with the nodule nitrite accumulation , carbohydrate (especially sucrose)decrease, leghemoglobin (Lb)concentration reduction and Lb function repression. The respiration and nitrosen fixation activities (ARA)of stem nodule bacteroids isolated from the KNO3 treated plant decreased obviously compared with those from control plants. The ARA and optimal pO2 of the bacteroids isolated from the KNO3 treated plant with the same nodule Lb were lower than those with the control nodule Lb. The ARA and optimal pO2 of the bacteroids and Lb suspensions both from control nodules were reduced by adding 5 mmol/L NO This demonstrated the Lb function was repressed by NO2. KNO3 supply could abc cause an increase of the oxygen diffusion resistance in stem nodule cortex.