Variability of the caryopsis transfer system in oat amphiploids and their parental species

Abstract

In grass caryopsis, the transfer system developed in the crease area plays a crucial role in endosperm development. Structural variation of the placental vascular bundle, pigment strand, nucellar projection and endosperm cavity were studied in oat amphiploids (4x, 6x, 8x) and parental species (2x, 4x, 6x). Ten characters are used to show multivariate relations between taxa in an ordination space. Two amphiploids, Avena magna × A. longiglumis and A. fatua × A. sterilis appeared to be extremes in a pooled group of oats. Hybrid types form a more compact group in a minimum spanning tree than do their parental species. Amphiploid arithmetic averages and character ranges exceed the corresponding values in parental species. Development of adjacent structures of the transfer system is more correlated than more distant structures. The number of xylem vessels is correlated with the width of the pigment strand (ps) and nucellar projection (np). Elongation growth of ps, np and the endosperm cavity towards endosperm is highly interrelated. Accumulation of starch grains within the endosperm cavity is determined by an anomalous discontinuity of the aleurone layer in this area. 1000-grain weight depends on some characters of the transfer system.