Seed Germination Ecology of the Cold Desert Annual Isatis violascens (Brassicaceae): Two Levels of Physiological Dormancy and Role of the Pericarp

The occurrence of various species of Brassicaceae with indehiscent fruits in the cold deserts of NW China suggests that there are adaptive advantages of this trait. We hypothesized that the pericarp of the single-seeded silicles of Isatis violascens restricts embryo expansion and thus prevents germi...

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Bibliographic Details
Published in:	PloS one 2015-10, Vol.10 (10), p.e0140983-e0140983
Main Authors:	Zhou, Yuan M, Lu, Juan J, Tan, Dun Y, Baskin, Carol C, Baskin, Jerry M
Format:	Article
Language:	eng
Subjects:	Autumn Biology Brassicaceae Climate change Cold Desert environments Deserts Dormancy Ecology Embryos Germination Gibberellic acid Grasslands Isatis Isatis - physiology Laboratories Pericarp Phenotype Physiology Plant Dormancy Seed banks Seed germination Seeds Seeds - physiology Soil Soil moisture Soil sciences Stratification Summer Temperature
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Summary:	The occurrence of various species of Brassicaceae with indehiscent fruits in the cold deserts of NW China suggests that there are adaptive advantages of this trait. We hypothesized that the pericarp of the single-seeded silicles of Isatis violascens restricts embryo expansion and thus prevents germination for 1 or more years. Thus, our aim was to investigate the role of the pericarp in seed dormancy and germination of this species. The effects of afterripening, treatment with gibberellic acid (GA3) and cold stratification on seed dormancy-break were tested using intact silicles and isolated seeds, and germination phenology was monitored in an experimental garden. The pericarp has a role in mechanically inhibiting germination of fresh seeds and promotes germination of nondormant seeds, but it does not facilitate formation of a persistent seed bank. Seeds in silicles in watered soil began to germinate earlier in autumn and germinated to higher percentages than isolated seeds. Sixty-two percent of seeds in the buried silicles germinated by the end of the first spring, and only 3% remained nongerminated and viable. Twenty to twenty-five percent of the seeds have nondeep physiological dormancy (PD) and 75-80% intermediate PD. Seeds with nondeep PD afterripen in summer and germinate inside the silicles in autumn if the soil is moist. Afterripening during summer significantly decreased the amount of cold stratification required to break intermediate PD. The presence of both nondeep and intermediate PD in the seed cohort may be a bet-hedging strategy.
ISSN:	1932-6203 1932-6203