TY - JOUR
T1 - Investigating seed dormancy in switchgrass (Panicum virgatum L.)
T2 - Understanding the physiology and mechanisms of coat-imposed seed dormancy
AU - Duclos, Denise V.
AU - Ray, Dennis T.
AU - Johnson, Daniel J.
AU - Taylor, Alan G.
N1 - Funding Information:
We would like to thank Dr. Brian Baldwin, Ernst Conservation Seeds, Sharp Bros. Seed Company, and Applewood Seed Company for supplying switchgrass seeds. We also thank Dr. Joost van Haren for providing guidance on setting-up the containers for the modified atmosphere experiment. We greatly appreciate Valerie Teetor and Sarah Pollicove for constant help, advice, and support. Special thanks to the Arizona Crop Improvement Association for providing guidance, equipment, and laboratory space. This research was supported by funding from the North Central Regional Sun Grant Center at South Dakota State University through a grant provided by the US Department of Energy Office of Biomass Programs under award number DE-FG36-08GO88073.
PY - 2013/2
Y1 - 2013/2
N2 - 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.
AB - 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.
KW - Embryo
KW - Germination
KW - Lemma
KW - Palea
KW - Pericarp
KW - Poaceae
KW - Seed coat
KW - Seed dormancy
KW - Switchgrass
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UR - http://www.scopus.com/inward/citedby.url?scp=84873839025&partnerID=8YFLogxK
U2 - 10.1016/j.indcrop.2013.01.005
DO - 10.1016/j.indcrop.2013.01.005
M3 - Article
AN - SCOPUS:84873839025
SN - 0926-6690
VL - 45
SP - 377
EP - 387
JO - Industrial Crops and Products
JF - Industrial Crops and Products
ER -