Meristem characteristics of genetically modified pea (Pisum sativum) leaf primordia

Abstract

Meristem characteristics of normal, afila (af), acacia (tl), reduced stipule (st) and combinations of these leaf phenotypes were investigated in pea (Pisum sativum). The multiple tendrils of the afila leaf are formed from numerous secondary branches on the leaflet primordia. Adaxial and marginal meristems are absent in afila leaflets. The tendril-like morphology of the terminal and secondary branches of the afila leaflets is derived from a radial marginal meristem, which is characteristic of normal tendril development. The small terminal leaflet lamina on tendrils of the acacia leaf is produced by adaxial and marginal meristems which become apparent in the distal portion of the the tendril late in leaf ontogeny. The reduced stipules of the reduced stipule leaf result from early loss of abaxial and adaxial stipule marginal meristems. Combinations of the af, tl and st genes apparently have no modifying influences on their mutual expression with one exceptions; the aftlst mature reduced stipule is significantly wider than stipules in st, afst and tlst phenotypes. The greater final width of triple recessive stipules is attributed to the persistence of the adaxial stipular marginal meristem in this phenotype.