Morpho-anatomical characterization of the root nodules of some selected leguminous species
1992
Agrupis, S.C.
Root nodules of Pterocarpus indicus, Vigna sp., Centrosema pubescens, and Desmodium scorpiurus (desmodioid nodules); mucuna sp (mucunoid) and Aeschynomene aspera (aeschynomenoid) were of determinate type. They were generally characterized by their apically situated meristem, close endodermis and vascular system. A morphological characteristic specially prominent in desmodioid nodules was the presence of lenticel tissue, believed to be an adaptive mechanism for its closed endodermis. Root nodules of Acacia auriculiformis, Presopis vidaliana (Caesalpinioid) and Crotalaria incana (Crotalaria) were of indeterminate type. They were characterized by their apically situated meristem, graded or segmented infected region, open endodermis and vascular system at the tip, providing avenue for continuous growth of the nodule structure. The degree of infection of all the investigated species was strongly species specific. Vigna species had degree of infection ranging from 36-66%; Mucuna, 42%; Centrosema, 93%; Desmodium, 23%, Prosopies, 30%, and Acacia, 47%. Pterocarpus indicus and Crotalaria incana had 100% infection. The analysis of variance on the different parameters tested for the major anatomical determinants of nitrogen fixation revealed that the degree of infection (as determined by the number of infected and uninfected cells) and extent uninfected cells) and extent of the bacteroid tissue in an intact state were positively correlated with the nitrogen fixing activity of the species. Size of nodule and central bacteroid region were insignificant. Anatomically, Pterocarpus indicus, Centrosema pubescens, Vigna marina and Crotalaria incana are efficient nitrogen fixers.
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