Root nodules of some tropical legumes in Singapore

Summary A survey of 35 legume species comprising 25 of Papilionoideae, 7 of Mimosoideae and 3 of Caesalpinioideae was made. Nodulation was found in all the species except for 2 (Caesalpinnia pulcherrima and Cassia siamea) of Caesalpinioideae, both of which possessed dark coloured roots. Nodulation is reported for the first time for Adenanthera pavonina and Delonix regia. Nodule shapes were described and classified into different types. The isolates of rhizobia obtained belonged largely to the slow growing group (17 isolates) isolated mainly from members of Papilionoideae; some belonged to the fast growing group (14 isolates), and only 3 isolates belonged to the very slow growing group. The slow growing group isolates were confirmed to be cowpea type rhizobia on the basis of positive nodulation with cowpea plants. re]19750829