Ion imbalance in Capsicum annum scarbrous diminutive a wilty mutant of pepper: II. Rubidium flux

Root tips of the wilty pepper mutant scarbrous diminutive accumulate less rubidium than those of the normal genotype. This phenomenon was evident in root tips excised from plants maintained for 2 d in CaSO₄ solution (low salt plants), especially in the lower external concentration range (0.1- 1.0 mM) of RbCl. The efflux rate of Rb⁺ from mutant root tips was twice as high as in normal root tips.These results indicate that the ability of the mutant roots to absorb and accumulate Rb⁺ and K⁺ is impaired. This defect could be a consequence of either an impaired Na⁺/K⁺ carrier system, or increased leakiness of mutant membranes, or both.The fact that the normal roots can accumulate Rb⁺ much faster than mutant roots supports the first alternative, i.e. that the high affinity carrier system was impaired in the mutant roots. However, the higher efflux rate of Rb⁺ from the mutant roots suggests that membrane leakiness was also affected.