Study on the Morphodifferentiation and Anther Structure in Flowers of Cardiospermum halicacabum Linn.

Flowering and stamen development in staminate and pseudo-bisexual flowers of Cardiospermum halicacabum Linn. were studied using stereomicroscopy, with semi-thin and ultra-thin sections. Results showed that:(1) At the early development of flower buds, no differences were observed between staminate and pseudo-bisexual flower buds. At the late development of flower buds, the staminate flower pistils had degenerated, but the pseudo-bisexual flower pistils were still developing. Thus, both types of flower buds could be distinguished by bud morphology. During anthesis, the staminate flower anthers were dehiscent, whereas those of the pseudo-bisexual flowers were not. (2) The anthers were tetrasporangiate in both types of flower. The wall consisted of an epidermis, endothelium, two middle layers and an uninucleate secretory tapetum. The development of the anther wall was basic. The microspore tetrads were tetrahedral. Mature anthers had the remnants of a middle layer in both types of flower. Tapetal cells of both types of flower began to degrade during microspore vacuolization; when pollen was two-celled, the tapetal cells in the pseudo-bisexual flowers degraded faster than those of the staminate flowers. (3) The fibrillar thickenings in the endothecium of the staminate flowers were well-developed. Two locules were formed by the dissolution of the septum before anther dehiscence. In the pseudo-bisexual flowers, only a few endothecium cells were thickened; mature anthers had lip cells and were not dehiscent, and the anthers had four locules due to septum indissolubility. Mature pollen grain cytoplasm was scarce, and the intine was not complete. In conclusion, at the early development stage of bisexual flowers, staminate flowers formed because the pistil stopped developing; however, at late development, pseudo-bisexual flowers formed because the anthers stopped developing.