Desenvolvimento do óvulo de três especies de Cassia L.

Abstract

Cassia is a tropical genus that together with Senna and Chamaecrista compose the subtribe Cassiinae.aaa However, the relationship between the members of Cassinae is still unclear, and anatomical studies have contributed to the improvement of their circumscription. Thus, we studied the ovule development of three species of Cassia to the understanding of the Cassiinae relationship. For this, ovules of C. fistula, C. grandis, and C. javanica from flowers at different stages of expansion were fixed in FAA 50 and Karnovsky, dehydrated and embedded in histological resin. The material was sectioned to about six micrometres and stained with toluidine blue. All species of Cassia present the anatropous, bitegmic, and crassinucellate ovules with zigzag micropile. They also show the outer epidermis of the outer integument containing phenolic compounds. All species had an archesporial cell that directly originates a megaspore mother cell. Some ovules of C. fistula and C. javanica present two archesporial cells originating two megaspore mother cells. All three species possess linear tetrad of megaspores. However, C. grandis and C. javanica also presented tetrad in ⊥ and C. fistula presented oblique-linear tetrad. Despite the differences in sporogenesis, all species had only one Polygonum-type megagametophyte. The embryology in Cassia was similar to that already described for Caesalpinioideae. The only feature distinguishing Cassia from the other Cassiinae was the phenolic ovule outer epidermis, which appears as a possible apomorphy for the genus