A MORPHOLOGICAL STUDY OF THE X-RAY INDUCED CAULIFLOWER-HEAD AND SINGLE-LEAF MUTATION IN MEDICAGO SATIVA L.

Abstract

The morphology of a spontaneous and an x-ray induced cauliflower-head and single-leaf mutation was compared with normal alfalia. Chromosome numbers were 32 in the normal and the spontaneous mutation, 31 in some, but not all, of the x-ray induced lines. The cauliflower mutant was unrelated to the trisomic tetraploid condition of the B45 line. Flower development in x-ray-induced cauliflowerhead was restricted to profusely branched floral axes that produced only meristem primordia, and under treatment with gibberellic acid, rudimentary pistils, but no stamens, petals, or sepals. Flower development in the spontaneous mutation showed sparingly branched floral axes, which produced rudimentary pistils and linear bracts homologous with sepal-petal primordia. With gibberellic acid treatment, pistil development approached normal, but no stamens, petals, or sepals were produced. Leaf development, which is triioliate in normal alfalfa, was unifoliate in both mutants. The uniioliate leaf appeared to result iron suppression of lateral leaflet primordia. The results suggest that the x-ray induced mutation, although similar, is more extreme and rudimentary, in tissue differentiation, than the spontaneous mutation. (P.C.H.)