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Title: The effect of ethylene and carbon dioxide on root-nodule formation and nitrogen fixation in three grain legumes
Author: Rahman, Mahbubur
Awarding Body: University of Edinburgh
Current Institution: University of Edinburgh
Date of Award: 1992
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The involvement of ethylene, C2H4 (exogenous and endogenous) in the formation and persistence of legume root nodules, and its interaction with carbon dioxide, CO2 have been studied in three different legume species, namely, pea (Pisum sativum L.), bean (Phaseolus vulgaris L.) and lentil (Lens culinaris Medik.). This work was undertaken because of the possible connection between tolerance to ethylene in the root zone and tolerance to waterlogging. Two different techniques for root aeration were employed: a 'constant flow-through' system and a 'closed-vessel' (recirculatory) system. In the constant flow-through system, legume roots were exposed to an air stream containing 0, 0.11, 0.33, or 1 ppm of C2H4. In the closed-vessel system endogenous C2H4 and/or CO2 was allowed to accumulate around the roots. Exogenous C2H4 at 1 ppm significantly inhibited root nodule formation and the nitrogenase activity of existing nodules in pea and bean, but had no comparable effect on the lentil cultivar which is known to be moderately waterlogging tolerant. However, nodule biomass production in lentil was inhibited by 1 ppm of C2H4. The inhibition of root formation in pea appears to have occurred during the infection process. In bean it appeared that inhibition occurred later during nodule development. Nodule production and nitrogenase activity of pea and bean were inhibited by 0.4-0.7 ppm of endogenous C2H4. Carbon dioxide (0.6-1%) in the root atmosphere stimulated nodule biomass production and nitrogenase activity. The presence of CO2, however, could not counteract the inhibitory effects of C2H4. The effect of endogenous C2H4 appears to have been mediated through the induction of early nodule senescence. In contrast to these inhibitory effects of endogenous C2H4 in pea and bean, a significant stimulation of nodule production and nitrogenase activity by C2H4 was observed in lentil, in the initial stages of growth.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available