Factors affecting dormancy of <i>Oncocyclus</i> iris seeds

Abstract

Oncocyclus irises (Iridaceae) are endangered plants in Israel, yet with high potential for cultivation as ornamental flowers. However, their high seed dormancy level prevents fast development of germplasm for horticultural reproduction. In this paper we describe in-vitro and in-vivo germination experiments with seeds of Oncocyclus irises from Israel. We examined the effects of (1) mechanical scarification and different growing media on in-vitro seed germination; and (2) soil type, covering, and water amount on in-vivo germination. Seeds showed high dormancy, as hardly any seed germinated in the first year after sowing, and only in the second growing season the germinating fraction was considerable (up to 37%), still only under high humidity conditions. We also report an effective in-vitro forced germination protocol, which employs seed scarification. Following these results for in-vivo germination, and based on the protocol developed for in-vitro germination, we recommend two methods for artificial seed germination. For fast germination, good results from a modest quantity of seeds can be obtained by an in-vitro forced germination. For mass seed propagation, when time is not a limiting factor, the in-vivo procedure can be used, using an artificial soil seed bank and treating those seeds during (at least) two seasons under shade and continuous watering.