PERENNIALISM IN ZEA

Abstract

Tetraploid perennial teosinte, Zea perennis (Hitchc.) Reeves and Mangelsd. is the only close relative of the annual Zea, including maize and 2n teosinte, that has the ability to regrow after producing seed. The other Zea, like most annuals, die during seed maturation. The tetraploid form retains totipotency in basal axillary buds and branches throughout the period when the older culms produce flowers and fruit. Not only do the lateral buds retain juvenility, but perennialism is also insured by the development of a horizontal system of stems, mostly subterranean. These rhizomes in the purest botancial sense, having scale or reduced leaves, adventitious roots, axillary buds and erect phases. In a form which otherwise perfectly shares a common karyotype with both maize and annual teosinte, it is surprising that the highly developed morpho-physiological differences conferring perennialism are uniqued and unbridged by intermediate forms. In view of the widespread use made of maize both in genetics and agronomy, much might be gained by a knowledge of the ctyogenetic and physiological basis of perennialism in an organism from which genes can be easily transferred to maize by crossing over.