Genetic differentiation for physiological and morphological traits in Plantago lanceolata and Plantago major L. speciesEffects of vesicular-arbuscular mycorrhizal infection and phosphate on Plantago major ssp. pleiosperma in relation to internal cytokinin concentrationsGynodioecy in Plantago lanceolata L. VI. Functions of cytokinins in growth, development, and reproduction of two sex types