A scanning electron microscopic study on the influence of temperature on the expression of cytoplasmic male sterility in Brassica napus

Abstract

The stamens of the ogu CMS line of B. napus L. exhibited different patterns of differentiation in response to temperature but were not fertile under any conditions. Three types of CMS stamens were recognized. Type 1 stamens had a distinct anther and filament and, in some cases, microspores were observed. These stamens were found most frequently under a high temperature regime (28:23 °C, light:dark). Type 2 stamens bore features of both stamens and carpels and were most common under intermediate temperature conditions (23:18 °C, light:dark). Type 3 stamens were carpelloid bearing a stigmatic surface and external ovules, lacked a filament, and were predominant under low temperature conditions (18:15 °C, light:dark). Normal stamens retained the same morphology under all temperature conditions. The sizes of the floral organs of normal and CMS flowers were also influenced by temperatures. Sepals, petals, and stamens were longer under low temperature conditions than intermediate and under intermediate temperature conditions than high temperature conditions. The floral organs of normal plants were generally larger than those of the CMS line.