Gynodioecy in Plantago lanceolata. VI. Functions of cytokinins in growth, development, and reproduction of two sex types

Abstract

Theoretical models predict that male sterile plants of gynodioecious species should show at least some compensation for their disadvantage of not reproducing as males through female component of fitness, In this study, growth, development, and reproduction of a hermaphrodite and a male sterile family of Plantago lanceolata L. were compared under controlled conditions. The male sterile plants produced more and longer spikes and had relatively longer styles. The male sterile plants achieved their final biomass sooner, by an earlier formation of side rosettes, and flowered earlier. The hypothesis was tested as to whether cytokinins in the plants are involved as a pleiotropic factor in either or both sex expression and the various plant characteristics associated with the male sterile phenotype. The roots of the male sterile plants had higher concentrations of putative zeatin riboside than the roots of the hermaphroditic plants, as quantified by an enzyme-linked immunoassy after separation of cytokinins by high performance liquid chromatography. Spraying the plants with benzyladenine did not affect internal cytokinin concentrations or sex expression. Benzyladenine spray increased the growth rate of the main rosette and stimulated floral initiation. Our results indicate that cytokinins are possibly involved in determining the morphological differences between sex types in this species.