| Abstract: | The infection by nodule bacteria of the root hairs of Viciahirsuta and of twelve species of Trifolium described. The proportion of root hairs deformed by bacterial secretionsvaries between host species and form point to point along theroot but is unaffected by bacterial strain. Infection is morefrequent in regions of maximum curling. Infection threads differin their place of origin in the hair (apical or lateral), theirmode of development and detailed morphology; some of these differencesare characteristic of host species. The growth of infectionthreads is often arrested in the root hair. Least arrested growthoccurs on 2-week-old seedlings infected at about twenty sites.The proportion of lateral infections increases with seedlingage. Root-hair curling, infection-thread initiation and growth areassociated with the near presence of the host cell nucleus. The observational data support the hypothesis of formation ofthe infection thread by invagination of the root-hair wall. No infections were observed in the root hairs of nodulated plantsof Lotus hispida, Lotus angustissimus, and Anthyllis vulneraria. |
