Abstract
Background: the cool-season grass Achnatherum inebrians (drunken horse grass) is an important species in the northwest grasslands of China. This grass engages in a symbiotic relationship with Epichloë endophytes, which affect host plants by increasing growth, repelling herbivores, and increasing tolerance to stressful environments. Methods: in this work, we evaluated the interaction effects of the endophyte on various dormancy-breaking treatments on A. inebrians seeds from six different locations. We used both endophyte-infected plants and noninfected plants and applied four dormancy-breaking methods to test germination. Results: our results showed that the germination rate of endophytic Achnatherum inebrians seeds from the Xiahe site (with highest altitude) was significantly higher than that from other sites when water soaking was applied (p < 0.05). Endophytic seeds had a greater germination rate, and soluble sugar, indole acetic acid (IAA), and gibberellin (GA) contents, under any condition. There was a significant interaction among the method, endophyte status, and origin regarding germination (p < 0.001); particularly, the effects of warm water soaking and endophyte infection on the germination of seeds from the Xiahe site was significant (p < 0.05). Conclusions: the infection of Epichloë endophyte is able to increase the content of soluble sugar, IAA, and GA, and stimulate the seed germination of A. inebrians.
Highlights
Seed dormancy prevents seeds from germinating, which protects plants from development in an unfavorable season [1]
The current study proved that Epichloë endophyte significantly enhanced the seed germination of drunken horse grass, under either a low or high temperature, which justified the statement that endophyte increases competitive advantages [42,43]
The present study was designed to determine the effects of various seed dormancy-breaking treatments, seed origins and Epichloë endophyte infection in Achnatherum inebrians on seed germination
Summary
Seed dormancy prevents seeds from germinating, which protects plants from development in an unfavorable season [1]. Numerous studies proved that seed dormancy is caused by either seed coat hardness (physical) or embryo dormancy (physiological) [2,3]. Physical dormancy from seed drying causes the seed to remain dormant until sufficient water is available [4]. Physiological dormancy could be broken and achieved by removing the seed coat or surrounding tissues [5]. Another method to break dormancy is to add hormones, such as gibberellin (GA) and abscisic acid (ABA), which promotes germination [2,6,7,8]. Studies suggest that ABA has a positive regulating effect on seed dormancy. Fennimore and Foley [12] suggested the prerequisites of dormancy termination are the breakdown
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