Density and Distribution of Erect Glandular Hairs on Annual Medicago Species

Abstract

Erect glandular hairs on several annual Medicago species are associated with mechanisms that defend the plants against certain destructive insects. To aid in elucidating the resistance mechanism, we investigated the density and distribution of erect glandular hairs on four annual Medicago species: two tetraploids (2n = 4x = 32), M. scutellata (L.) Mill. and M. rugosa Desr., and two diploids (2n = 2x = 16), M. disciformis DC. and M. blancheana Boiss. Erect capitate glandular hairs were present on all vegetative and floral parts of the four species except cotyledons and flower petals. Density was not affected by ploidy level but showed differences, depending on whether the plants had been grown in the field or greenhouse. Both diploids and tetraploids had glandular hairs on margins of leaflets. The glandular hairs were distributed over the entire abaxial leaf surface of tetraploids, and on diploids they were confined to the midrib area. Hairs were densest on the peduncle, followed by the stem, petiole, seed...