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

Zhou YM, Lu JJ, Tan DY, Baskin CC, Baskin JM - PLoS ONE (2015)

Bottom Line: 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.Afterripening during summer significantly decreased the amount of cold stratification required to break intermediate PD.

View Article: PubMed Central - PubMed

Affiliation: Xinjiang Key Laboratory of Soil and Plant Ecological Processes, College of Grassland and Environment Sciences, Xinjiang Agricultural University, Urümqi, China.

ABSTRACT
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.

No MeSH data available.


Related in: MedlinePlus

Conceptual model comparing events in the seed stage of the life cycle of a typical temperate-zone disapore-monomorphic facultative winter annual with those of the cold desert facultative winter annual Isatis violascens.PD, physiological dormancy; D, dormant; ND, nondormant; CD, conditional dormancy, i.e. seeds can germinate at low but not at high tmperatures.
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pone.0140983.g007: Conceptual model comparing events in the seed stage of the life cycle of a typical temperate-zone disapore-monomorphic facultative winter annual with those of the cold desert facultative winter annual Isatis violascens.PD, physiological dormancy; D, dormant; ND, nondormant; CD, conditional dormancy, i.e. seeds can germinate at low but not at high tmperatures.

Mentions: Many species of temperate-zone facultative winter annuals with water-permeable seeds have been studied, and the seeds had only nondeep PD [6]. In these species, dormancy break occurs during summer, and seeds are nondormant in autumn (Fig 7). The number of seeds that germinates in autumn and percentage of seedling survival depend on amount and timing of rainfall. If seeds fail to germinate in autumn, they lose the ability to germinate at high but not low temperatures, i.e. they enter conditional dormancy and thus can germinate in early spring when temperatures are low. Long term persistence at a population site where the environment is temporally unpredictable may require the formation of a persistent soil seed bank [3], in which the buried seeds may undergo annual dormancy cycling [6]. On the other hand, only 3% of the buried silicles of I. violascens contained a viable seed after the spring germination season was completed (Fig 5), suggesting that formation of a seed bank is not very important for long-term survival of this species at a population site (Fig 7). The persistence of I. violascens is promoted by intermediate PD, which prevents germination of a high percentage of a seed cohort in autumn regardless of the amount and timing of rainfall. However, since intermediate PD is broken by cold stratification seeds can germinate in spring, when soil moisture is predictably favorable for seedling survival. Thus, we suggest that intermediate PD in seeds of I. violascens is playing the same ecological role, in terms of persistence at a site, as the persistent soil seed bank in typical temperate-zone facultative winter annuals.


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

Zhou YM, Lu JJ, Tan DY, Baskin CC, Baskin JM - PLoS ONE (2015)

Conceptual model comparing events in the seed stage of the life cycle of a typical temperate-zone disapore-monomorphic facultative winter annual with those of the cold desert facultative winter annual Isatis violascens.PD, physiological dormancy; D, dormant; ND, nondormant; CD, conditional dormancy, i.e. seeds can germinate at low but not at high tmperatures.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4626048&req=5

pone.0140983.g007: Conceptual model comparing events in the seed stage of the life cycle of a typical temperate-zone disapore-monomorphic facultative winter annual with those of the cold desert facultative winter annual Isatis violascens.PD, physiological dormancy; D, dormant; ND, nondormant; CD, conditional dormancy, i.e. seeds can germinate at low but not at high tmperatures.
Mentions: Many species of temperate-zone facultative winter annuals with water-permeable seeds have been studied, and the seeds had only nondeep PD [6]. In these species, dormancy break occurs during summer, and seeds are nondormant in autumn (Fig 7). The number of seeds that germinates in autumn and percentage of seedling survival depend on amount and timing of rainfall. If seeds fail to germinate in autumn, they lose the ability to germinate at high but not low temperatures, i.e. they enter conditional dormancy and thus can germinate in early spring when temperatures are low. Long term persistence at a population site where the environment is temporally unpredictable may require the formation of a persistent soil seed bank [3], in which the buried seeds may undergo annual dormancy cycling [6]. On the other hand, only 3% of the buried silicles of I. violascens contained a viable seed after the spring germination season was completed (Fig 5), suggesting that formation of a seed bank is not very important for long-term survival of this species at a population site (Fig 7). The persistence of I. violascens is promoted by intermediate PD, which prevents germination of a high percentage of a seed cohort in autumn regardless of the amount and timing of rainfall. However, since intermediate PD is broken by cold stratification seeds can germinate in spring, when soil moisture is predictably favorable for seedling survival. Thus, we suggest that intermediate PD in seeds of I. violascens is playing the same ecological role, in terms of persistence at a site, as the persistent soil seed bank in typical temperate-zone facultative winter annuals.

Bottom Line: 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.Afterripening during summer significantly decreased the amount of cold stratification required to break intermediate PD.

View Article: PubMed Central - PubMed

Affiliation: Xinjiang Key Laboratory of Soil and Plant Ecological Processes, College of Grassland and Environment Sciences, Xinjiang Agricultural University, Urümqi, China.

ABSTRACT
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.

No MeSH data available.


Related in: MedlinePlus