Abstract:

The morphological and anatomical changes during floral development and flowering reversion of Zigongdongdou, a late-maturing and photoperiod-sensitive soybean cultivar, were investigated to identify anatomic characteristics of floral development in soybean. The following photoperiod treatments were conducted to obtain different developmental status and morphological changes: (1) Continuous short days (SD, 12 h); (2) Continuous long days (LD, 16 h); and (3) SD for 13 days and then LD (SD13d-LD). The results showed that Zigongdongdou plants normally bloomed and podded in continuous SD. About 50% of plants in SD13d-LD treatment reversed from reproductive development to vegetative growth, and other plants in this treatment bore short terminal racemes. In continuous LD, all plants kept vegetative status. SD not only promoted reproductive development of soybean plants but increased the appearing rate of leaves as well. In SD treatment, first floral primordia were found in basal axil of plants at Day 3, and the apical meristem began to initiate raceme at Day 13. At Day 19, the terminal flower primordia were first found in apex. At Day 29, plants began to bloom. Plants in the treatment of SD13d-LD kept initiating floral primordia within the first fourteen days after transferred from SD to LD, but the initiating rate was slower and the number of floral primordia was fewer than that in continuous SD. About half of plants reversed to initiate vegetative organs after transferring to LD for 20 days (33 days after emergence). While in continuous LD, the apical meristem only produced leaves. The homology of leaves and floral organs was also discussed in this paper.

Key words: Soybean, Photoperiod, Floral development, Flowering reversion, Anatomic structure