Effects of nitrogen source and water availability on stem carbohydrates and cellulosic bioethanol traits of alfalfa plants.
Symbiotic association of legumes with rhizobia frequently results in higher photosynthesis and soluble carbohydrates in comparison with nitrate-fed plants, which might improve its potential for biomass conversion into bioethanol. A greenhouse experiment was conducted to examine the effects of nitrogen source and water availability on stem characteristics and on relationships between carbohydrates, phenolic metabolism activity and cell wall composition in alfalfa (Medicago sativa L. cv. Aragón). The experiment included three treatments: (1) plants fed with ammonium nitrate (AN); (2) plants inoculated with rhizobia (R); and (3) plants inoculated with rhizobia and amended with sewage sludge (RS). Two levels of irrigation were imposed: (1) well-watered and (2) drought stress. Under well-watered conditions, nitrogen-fixing plants have increased photosynthesis and stem fermentable carbohydrate concentrations, which result in higher potential for biomass conversion to bioethanol than in AN plants. The latter had higher lignin due to enhanced activities of phenolic metabolism-related enzymes. Under drought conditions, the potential for bioethanol conversion decreased to a similar level in all treatments. Drought-stressed nitrogen-fixing plants have high concentrations of fermentable carbohydrates and cell wall cellulose, but ammonium nitrate-fed plants produced higher plant and stem biomass, which might compensate the decreasing stem carbohydrates and cellulose concentrations.
Dpto. Biología Vegetal, Sección Biología Vegetal, Unidad Asociada al CSIC-EEAD, Zaragoza, ICVV, Logroño, Facultades de Ciencias y Farmacia, Universidad de Navarra, C/Irunlarrea 1, 31008 Pamplona, Spain.
M Laura
ML
Fiasconaro
Yolanda
Y
Gogorcena
Fernando
F
Muñoz
Donato
D
Andueza
Manuel
M
Sánchez-Díaz
M Carmen
MC
Antolín
D056804:Biofuels / Q000032:analysis; D050260:Carbohydrate Metabolism / Q000187:drug effects*; D002473:Cell Wall / Q000187:drug effects / Q000378:metabolism; D002482:Cellulose / Q000378:metabolism*; D000431:Ethanol / Q000378:metabolism*; D005740:Gases / Q000378:metabolism; D008031:Lignin / Q000378:metabolism; D000455:Medicago sativa / Q000187:drug effects / Q000254:growth & development / Q000378:metabolism*; D019216:Metals, Heavy / Q000633:toxicity; D009566:Nitrates / Q000494:pharmacology; D009584:Nitrogen / Q000494:pharmacology*; D009586:Nitrogen Fixation / Q000187:drug effects; D010636:Phenols / Q000378:metabolism; D018547:Plant Stems / Q000187:drug effects / Q000201:enzymology / Q000378:metabolism*; D019655:Quantitative Trait, Heritable; D012722:Sewage / Q000737:chemistry; D012995:Solubility / Q000187:drug effects; D014867:Water / Q000494:pharmacology*
D056804:Biofuels; D005740:Gases; D019216:Metals, Heavy; D009566:Nitrates; D010636:Phenols; D012722:Sewage; D014867:Water; D000431:Ethanol; D002482:Cellulose; D008031:Lignin; D009584:Nitrogen; C006568:ammonium nitrate