Effect of Localized Nitrogen Availability to Soybean Half-Root Systems on Photosynthate Partitioning to Roots and Nodules

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Abstract
Dark anaerobic fermentation in the green algae Chlamydomonas MGA 161, Chlamydomonas reinhardtii, Chlorella pyrenoidosa, and Chlorococcum minutum was studied. Our isolate, Chlamydomonas MGA 161, was unusual in having high H2 but almost no formate. The fermentation pattern in Chlamydomonas MGA 161 was altered by changes in the NaCl or NH4Cl concentration. Glycerol formation increased at low (0.1%) and high (7%) NaCl concentrations; starch degradation, and formation of ethanol, H2, and CO2 increased with the addition of NH4Cl to above 5 millimolar in N-deficient cells. C. reinhardtii and C. pyrenoidosa exhibited a very similar anaerobic metabolism, forming formate, acetate and ethanol in a ratio of about 2:2:1. C. minutum was also unusual in forming acetate, glycerol, and CO2 as its main products, with H2, formate, and ethanol being formed in negligible amounts. In the presence of CO, ethanol formation increased twofold in Chlamydomonas MGA 161 and C. reinhardtii, but the fermentation pattern in C. minutum did not change. An experiment with hypophosphite addition showed that dark H2 evolution of the Escherichia coli type could be ruled out in Chlamydomonas MGA 161 and C. reinhardtii. Among the green algae investigated, three fermentation types were identified by the distribution pattern of the end products, which reflected the consumption mode of reducing equivalents in the cells.