Investigating seed dormancy in switchgrass (Panicum virgatum L.): Understanding the physiology and mechanisms of coat-imposed seed dormancy

Denise V. Duclos, Dennis T Ray, Daniel J. Johnson, Alan G. Taylor

Research output: Contribution to journalArticle

19 Citations (Scopus)

Abstract

Switchgrass (Panicum virgatum L.), a perennial warm-season grass established by seed has been recommended by the US Department of Energy as a model herbaceous biofuel crop. Neoteric seeds may be dormant resulting in delayed and sporadic germination and emergence, jeopardizing establishment of a good plant stand. Switchgrass dormancy may be alleviated by mechanical or chemical scarification, stratification, and after-ripening, suggesting physical and/or physiological dormancy. The underlying mechanisms and physiology of dormancy in these seeds; however, are not well understood. This work investigates the physiology of switchgrass seed dormancy; first by identifying the contribution of the different switchgrass structures (glumes, lemma, palea, pericarp/testa, endosperm) on regulating germination, and then by testing specific mechanisms of coat-imposed dormancy. We sequentially removed structures of freshly harvested seeds of two upland (Cave-in-Rock, Trailblazer) and two lowland (Alamo, Kanlow) cultivars. The main structure inhibiting germination was the pericarp/testa, with the lemma and palea (bracts) having a secondary effect that differed by genotype. Seeds with glumes and bracts removed, and pericarp/testa cut with endosperm either attached or removed just above the embryo, resulted in high germination percentages and rate, indicating no morphological dormancy, and no effect of the endosperm on germination. The lemma, palea, and pericarp/testa were neither a barrier for water uptake nor contained inhibitory compounds. By adjusting the oxygen concentration of the environment and the physical integrity of the covering structures, we found the enclosing structures acted as barriers to oxygen. Puncturing the pericarp/testa of seeds with glumes and bracts removed, enhanced germination at 1, 10, 21 or 100% oxygen. Combined results showed that the structural integrity of the pericarp/testa (primary) and lemma/palea (secondary) influenced germination, suggesting an important mechanical effect of these layers as barriers for radicle protrusion. Therefore, a combination of seed-coat mechanisms regulates germination in switchgrass seeds.

Original languageEnglish (US)
Pages (from-to)377-387
Number of pages11
JournalIndustrial Crops and Products
Volume45
DOIs
StatePublished - Feb 2013

Fingerprint

Panicum virgatum
seed dormancy
physiology
pericarp
testa
germination
dormancy
bracts
seeds
endosperm
oxygen
root radicle
warm season grasses
after-ripening
seed stratification
energy crops
caves
embryo (plant)
water uptake
eclosion

Keywords

  • Embryo
  • Germination
  • Lemma
  • Palea
  • Pericarp
  • Poaceae
  • Seed coat
  • Seed dormancy
  • Switchgrass

ASJC Scopus subject areas

  • Agronomy and Crop Science

Cite this

Investigating seed dormancy in switchgrass (Panicum virgatum L.) : Understanding the physiology and mechanisms of coat-imposed seed dormancy. / Duclos, Denise V.; Ray, Dennis T; Johnson, Daniel J.; Taylor, Alan G.

In: Industrial Crops and Products, Vol. 45, 02.2013, p. 377-387.

Research output: Contribution to journalArticle

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abstract = "Switchgrass (Panicum virgatum L.), a perennial warm-season grass established by seed has been recommended by the US Department of Energy as a model herbaceous biofuel crop. Neoteric seeds may be dormant resulting in delayed and sporadic germination and emergence, jeopardizing establishment of a good plant stand. Switchgrass dormancy may be alleviated by mechanical or chemical scarification, stratification, and after-ripening, suggesting physical and/or physiological dormancy. The underlying mechanisms and physiology of dormancy in these seeds; however, are not well understood. This work investigates the physiology of switchgrass seed dormancy; first by identifying the contribution of the different switchgrass structures (glumes, lemma, palea, pericarp/testa, endosperm) on regulating germination, and then by testing specific mechanisms of coat-imposed dormancy. We sequentially removed structures of freshly harvested seeds of two upland (Cave-in-Rock, Trailblazer) and two lowland (Alamo, Kanlow) cultivars. The main structure inhibiting germination was the pericarp/testa, with the lemma and palea (bracts) having a secondary effect that differed by genotype. Seeds with glumes and bracts removed, and pericarp/testa cut with endosperm either attached or removed just above the embryo, resulted in high germination percentages and rate, indicating no morphological dormancy, and no effect of the endosperm on germination. The lemma, palea, and pericarp/testa were neither a barrier for water uptake nor contained inhibitory compounds. By adjusting the oxygen concentration of the environment and the physical integrity of the covering structures, we found the enclosing structures acted as barriers to oxygen. Puncturing the pericarp/testa of seeds with glumes and bracts removed, enhanced germination at 1, 10, 21 or 100{\%} oxygen. Combined results showed that the structural integrity of the pericarp/testa (primary) and lemma/palea (secondary) influenced germination, suggesting an important mechanical effect of these layers as barriers for radicle protrusion. Therefore, a combination of seed-coat mechanisms regulates germination in switchgrass seeds.",
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