影響大豆癒合組織與根瘤菌共生現象及其固氮活性因子之研究I.——碳源

Factors Effect on the Nitrogen Fixation of Rhizobia in the Symbiotic Rhizobium-Callus Tissues 1. Carbon sources

1. 碳源之不同可影響癒合組織中根瘤菌之固氮活性及固氮壽命。其中以fructose為碳源者效果最好，xylose者最差。若以有機酸為碳源者fumaric acid最佳而isocitric acid較差，在同一濃度下，若以fructose，sucrose或glucose作為碳源時癒合組織中根瘤菌固氮活性於第30天、27天或24天達到最高，並於第37天、33天或27天失去活性，此時癒合組織已老化。2. 碳源濃度以20 g/l最佳，若是給予碳濃度高於此濃度時根瘤菌固氮作用反而減低並縮短根瘤菌之固氮活性壽命。3. 癒合組織中沒有血紅素存在，癒合組織之木質化作用可能有助益於癒合組織中氧氣濃度之控制，使固氮酶活性不受氧氣所抑制。4. 癒合組織之nitrate respiration活性很低，對根瘤菌固氮作用所需之能量之供給沒有多大貢獻。

Activity and span of nitrogen fixation (acetylene reduction) of rhizobia in the symbiotic rhizobium-callus tissues changed by the carbon sources and concentrations. Hexoses were better than pentoses, and sugars were better than those organic acids, except the fumaric acid, for the rhizobial acetylene reduction in the symbiotic tissues. High concentration of sugar promoted the symbiotic tissues to senescence. No leghemoglobin was found in the symbiotic tissues. The lignification of callus tissues might have a regulatory function to prevent the nitrogenase in rhizobia of callus tissues from oxygen-denaturation. Negligible amount of N2O realeased by symbiotic system. The nitrate respiration might not provide energy to support the rhizobial acetylene reduction in symbiotic callus tissues.