Influence of humidity on the migration of bacteria on cucumber seedlings.

Abstract

Bacteria carried by cucumber seeds did not appear to migrate to the aerial parts of seedlings under conditions of low humidity (30–40% RH), as determined by imprinting seedling parts in agar. At a high RH (> 90%), however, a yellow resident (isolate A180) added to seed, and bacteria carried naturally by the seed (control residents), migrated to all aerial parts. At an intermediate RH (70–80%), control residents were on all parts, and in addition, A180 consistently was in limited areas. A period of several days of low RH prevented further migration. Stained bacterial cells on the leaf surface were observed in depressions between epidermal cells and on the basal parts of hairs of plants from the high RH; they were sparse at the intermediate RH level and not detected at the low level.