STYLAR WATER POTENTIAL AND UNILATERAL INTERSPECIFIC INCOMPATIBILITY IN SOLANACEAE

Water and osmotic potentials were measured in young and mature styles of selfcompatible (SC) and selfincompatible (SI) species of Solanaceae . For mature flowers, the stylar water and osmotic potentials were con siderably lower in SI species Nicotiana alata and Petunia hybrida than in SC species N. sylvestris and N. tabacum. Stylar water content (in % fresh mass) was also significantly lower in SI species (N. alata, P. hybrida, diploid clones of potato) than in SC species (N. acuminata, N. glauca, N. paniculata, N. sylvestris, N. tabacum). For flower buds younger than 2 d before anthesis, no differences in stylar water poten tial between N. alata (SI) and N. tabacum (SC) were observed. During f urther flower bud development the stylar water potential in N. alata d ecreased more expressively than in N. tabacum. Pollen culture in media with various concentrations of sucrose or polyethylene glycol reveale d that optimal water potential for pollen tube growth was lower in N. alata than in N. tabacum. The differences were similar as for differen ces in stylar water potential. The results are considered in relation to possible involvement of stylar water potential in unilateral inters pecific incompatibility in Solanaceae.