Extended light exposure increases stem digestibility and biomass production of switchgrass

Switchgrass is a photoperiod-sensitive energy grass suitable for growing in the marginal lands of China. We explored the effects of extended photoperiods of low-irradiance light (7 μmol·m-2·s-1, no effective photosynthesis) on the growth, the biomass dry weight, the biomass allocation, and, especial...

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Bibliographic Details
Published in:PloS one 2017-11, Vol.12 (11), p.e0188349-e0188349
Main Authors: Zhao, Chunqiao, Fan, Xifeng, Hou, Xincun, Zhu, Yi, Yue, Yuesen, Wu, Juying
Format: Article
Language:English
Subjects:
Acids
Agricultural production
Agriculture
Ammonium
Ammonium content
Arabinose
Biology and Life Sciences
Biomass
Carbohydrates
Cell Wall - metabolism
Cell Wall - radiation effects
Cell walls
Cellulose
Cellulose - analysis
Corn
Crops
Cultivars
Cultivation
Day length
Digestibility
Dry matter
Ecology and Environmental Sciences
Ethanol
Exposure
Gene expression
Genetic aspects
Genetic modification
Grasses
Growth
Hexoses
Hydrolysis
Irradiance
Irradiated
Laboratories
Light
Lignin
Lignin - analysis
Lignocellulose
Miscanthus
Nitrogen
Organ Specificity - radiation effects
Organs
Oxalic acid
Panicum - growth & development
Panicum - physiology
Panicum - radiation effects
Panicum virgatum
Phase transitions
Photoperiod
Photoperiodism
Photoperiods
Photosynthesis
Physical Sciences
Physiological aspects
Plant Stems - physiology
Plant Stems - radiation effects
R&D
Radiation
Research & development
Signal transduction
Stems
Transcription factors
Urban farming
Xylan
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Summary:Switchgrass is a photoperiod-sensitive energy grass suitable for growing in the marginal lands of China. We explored the effects of extended photoperiods of low-irradiance light (7 μmol·m-2·s-1, no effective photosynthesis) on the growth, the biomass dry weight, the biomass allocation, and, especially, the stem digestibility and cell wall characteristics of switchgrass. Two extended photoperiods (i.e., 18 and 24 h) were applied over Alamo. Extended light exposure (18 and 24 h) resulted in delayed heading and higher dry weights of vegetative organs (by 32.87 and 35.94%, respectively) at the expense of reducing the amount of sexual organs (by 40.05 and 50.87%, respectively). Compared to the control group (i.e., natural photoperiod), the yield of hexoses (% dry matter) in the stems after a direct enzymatic hydrolysis (DEH) treatment significantly increased (by 44.02 and 46.10%) for those groups irradiated during 18 and 24 h, respectively. Moreover, the yield of hexoses obtained via enzymatic hydrolysis increased after both basic (1% NaOH) and acid (1% H2SO4) pretreatments for the groups irradiated during 18 and 24 h. Additionally, low-irradiance light extension (LILE) significantly increased the content of non-structural carbohydrates (NSCs) while notably reducing the lignin content and the syringyl to guaiacyl (S/G) ratio. These structural changes were in part responsible for the observed improved stem digestibility. Remarkably, LILE significantly decreased the cellulose crystallinity index (CrI) of switchgrass by significantly increasing both the arabinose substitution degree in xylan and the content of ammonium oxalate-extractable uronic acids, both favoring cellulose digestibility. Despite this LILE technology is not applied to the cultivation of switchgrass on a large scale yet, we believe that the present work is important in that it reveals important relationships between extended day length irradiations and biomass production and quality. Additionally, this study paves the way for improving biomass production and digestibility via genetic modification of day length sensitive transcription factors or key structural genes in switchgrass leaves.
ISSN:1932-6203
1932-6203
DOI:10.1371/journal.pone.0188349