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Caryopsis Development Following Matings between Diploid and Tetraploid Strains of Zea Mays

D. C. Cooper
American Journal of Botany
Vol. 38, No. 9 (Nov., 1951), pp. 702-708
Stable URL: http://www.jstor.org/stable/2437917
Page Count: 7
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Caryopsis Development Following Matings between Diploid and Tetraploid Strains of Zea Mays
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Abstract

The study is concerned with the course of caryopsis development following crosses between diploid and tetraploid strains of maize. Most of the hybrid kernels collapse at various stages prior to maturity. A small fraction attain a germinable condition. The developmental behavior is compared with normal caryopsis formation following pollinations within the diploid and tetraploid strain. Double fertilization occurs between 18 and 24 hours following each type of mating. The early post-fertilization stages are comparable prior to 4 days following pollination. Thereafter development following the reciprocal matings 2n x 4n and 4n x 2n proceeds in a different manner from that occurring in normal caryopses. In 2n x 4n crosses, the endosperm becomes abnormally meristematic in the region of the embryo. This results in the embryo becoming deeply embedded in the endosperm. The cells on the basal surface of the endosperm fail, for the most part, to differentiate into an absorbing tissue. The central portion of the endosperm undergoes disintegration. The adjacent endosperm becomes irregularly meristematic and forms lobes which push into the central region of broken down tissue. Similar outgrowths are formed on that surface of the endosperm which lies opposite the abgerminal face of the kernel. Later the apical portion of the endosperm becomes packed with starch. Most embryos disintegrate during the course of this aberrant endosperm growth. In 4n x 2n crosses, both embryo and endosperm develop normally until 6 days after pollination. Thereafter starch is laid down throughout the endosperm. It becomes packed with storage material by 16 days and further growth ceases. The embryo continues to grow and differentiates in a normal manner but no reserve foods are stored therein at later stages of development. The failure of most caryopses to reach a germinable stage is due to the aberrant type of endosperm development and the complete lack of reserve nutrients within the embryo.

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