Some observations on root-hair infection by nodule bacteria

The infection by nodule bacteria of the root hairs of Vicia hirsuta and of twelve species of Trifolium described.

The proportion of root hairs deformed by bacterial secretions varies between host species and form point to point along the root but is unaffected by bacterial strain. Infection is more frequent in regions of maximum curling. Infection threads differ in their place of origin in the hair (apical or lateral), their mode of development and detailed morphology; some of these differences are characteristic of host species. The growth of infection threads is often arrested in the root hair. Least arrested growth occurs on 2-week-old seedlings infected at about twenty sites. The proportion of lateral infections increases with seedling age.

Root-hair curling, infection-thread initiation and growth are associated with the near presence of the host cell nucleus.

The observational data support the hypothesis of formation of the infection thread by invagination of the root-hair wall.

No infections were observed in the root hairs of nodulated plants of Lotus hispida, Lotus angustissimus, and Anthyllis vulneraria.
RESP-4170