Instituto de Biologia, Universidade Federal de Uberlândia, Uberlândia, 38405-320, Brazil.
Sci Rep. 2020 Jul 22;10(1):12194. doi: 10.1038/s41598-020-69215-4.
Cassia is a diverse legume genus widespread in the (sub-)tropical zone of the world. Several studies have been done on this genus; however, significant changes have occurred at the taxonomic level over the years. This has led to inaccurate information about seed dormancy in Cassia since many species are no longer included in the genus. Thus, our work aims to investigate and update the information about the kind of dormancy that occurs in seeds of Cassia species and also look into two notorious species in this group (C. fistula and C. javanica) to compare myxospermous vs. non-myxospermous seeds regarding dormancy and germination traits. Seed dormancy reports were found for 53 Cassia species, and the only kind of seed dormancy found for these species was physical dormancy (PY). Non-dormancy was not found, and all seeds had a blockage to water uptake during the dormant state, that is, all have PY. Of these 53 species, only 18 are currently included in the genus Cassia. C. fistula and C. javanica have fully developed embryos, and dormancy is only conferred by the (water-impermeable) seed coat. The lens in the seed coat is the only structure that creates a water pathway to break PY in C. fistula. Myxospermous seeds came out of dormancy faster than non-myxospermous ones. PY seems to be the only kind of seed dormancy that has evolved in Cassia. The extent of this kind of dormancy in all subtribe Cassiinae is also discussed.
决明属是一个广泛分布于世界（亚热带）地区的豆科多样化属。已经有许多关于这个属的研究；然而，多年来，分类学水平上发生了重大变化。这导致关于决明属种子休眠的信息不准确，因为许多物种不再包含在该属中。因此，我们的工作旨在调查和更新关于决明属种子休眠类型的信息，同时研究该属中的两个著名物种（C. fistula 和 C. javanica），比较粘液种子和非粘液种子在休眠和萌发特性方面的差异。我们发现了 53 种决明属植物的种子休眠报告，这些物种唯一的种子休眠类型是物理休眠（PY）。没有发现非休眠类型，所有种子在休眠状态下都阻止水分吸收，也就是说，所有种子都具有 PY。在这 53 种物种中，只有 18 种目前被包含在决明属中。C. fistula 和 C. javanica 具有完全发育的胚胎，休眠仅由（不透水的）种皮赋予。种皮中的透镜是唯一能够打破 C. fistula 中 PY 的结构。粘液种子比非粘液种子更快地摆脱休眠。PY 似乎是决明属中唯一进化而来的种子休眠类型。还讨论了所有 Cassiinae 亚科中这种休眠的程度。
