Abstract
As global interest in renewable energy intensifies, biofuels derived from resilient perennial grasses offer a promising alternative to fossil fuels, especially on low-input, non-arable lands. Switchgrass (Panicum virgatum) is a perennial C4 grass with strong potential as a sustainable biofuel feedstock, particularly for marginal lands where environmental stressors reduce the success of traditional crops. To identify trait combinations associated with superior biomass production, this study investigates physiological, morphological, and metabolic traits across ten switchgrass genotypes (seven lowland and three upland) under simulated marginal conditions, consisting of sandy growth matrix with low nutrient application. We examined photosynthetic efficiency (ΦII, qL), photoprotective capacity (qE, xanthophyll cycle engagement), root and leaf respiration, and carbon-to-nitrogen (C:N) allocation, integrating these traits through correlation analysis and principal component analysis (PCA). Results revealed that while photochemical parameters such as ΦII and qL varied across genotypes, they were not strong predictors of shoot biomass. Instead, respiratory efficiency particularly low root respiration relative to shoot mass, was more strongly associated with higher yield. Switchgrass genotypes such as DVR3 and FLT1 exhibited moderate photosynthetic performance but achieved greater biomass through reduced respiratory costs and efficient nutrient use, which suggests a more resource-conservative strategy. PCA further supported this paradigm, with principal component 1 (PC1) delineating a trade-off between carbon investment in biomass and respiratory carbon loss. Additionally, ecotypic distinctions were observed along PC1, but some upland genotypes displayed trait profiles overlapping with lowlands, blurring traditional ecological boundaries. Collectively, these findings underscore that maximal photosynthetic output is not the sole determinant of productivity under stress. Rather, metabolic efficiency, reflected in the coordination of carbon acquisition, photoprotection, and respiratory cost, appears to be a key factor influencing switchgrass performance under marginal land. These findings contribute to a deeper understanding of genotype-specific strategies and may help guide genetic improvement efforts for biofuel crops suited to low-input, marginal-quality systems.
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Claims 7
Claim · model-written summary
Photochemical parameters such as ΦII and qL varied across switchgrass genotypes.
- Taxon
- Switchgrass
Panicum virgatume0 - Material
- genotypese1
- Outcome
- photochemical parameters such as ΦII and qLe1
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Switchgrass (Panicum virgatum) is a perennial C4 grass”
e1“photochemical parameters such as ΦII and qL varied across genotypes, they were not strong predictors of shoot biomass”
Claim · model-written summary
Photochemical parameters such as ΦII and qL were not strong predictors of switchgrass shoot biomass.
- Taxon
- SwitchgrassPanicum virgatume0
- Outcome
- shoot biomasse1
- Qualifier
- not strong predictorse1
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Switchgrass (Panicum virgatum) is a perennial C4 grass”
e1“photochemical parameters such as ΦII and qL varied across genotypes, they were not strong predictors of shoot biomass”
Claim · model-written summary
Respiratory efficiency, particularly low root respiration relative to shoot mass, was more strongly associated with higher switchgrass yield.
- Taxon
- SwitchgrassPanicum virgatume0
- Organ / stage
- roote2
- Outcome
- yielde2
- Direction
- highere2
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Switchgrass (Panicum virgatum) is a perennial C4 grass”
e2“respiratory efficiency particularly low root respiration relative to shoot mass, was more strongly associated with higher yield”
Claim · model-written summary
Switchgrass genotypes DVR3 and FLT1 achieved greater biomass through reduced respiratory costs and efficient nutrient use, despite moderate photosynthetic performance.
- Taxon
- SwitchgrassPanicum virgatume3
- Material
- DVR3 and FLT1e3
- Outcome
- greater biomasse3
- Qualifier
- reduced respiratory costs and efficient nutrient usee3
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e3“Switchgrass genotypes such as DVR3 and FLT1 exhibited moderate photosynthetic performance but achieved greater biomass through reduced respiratory costs and efficient nutrient use”
Claim · model-written summary
Principal component 1 delineates a trade-off between carbon investment in switchgrass biomass and respiratory carbon loss.
- Taxon
- SwitchgrassPanicum virgatume0
- Outcome
- trade-off between carbon investment in biomass and respiratory carbon losse4
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Switchgrass (Panicum virgatum) is a perennial C4 grass”
e4“PCA further supported this paradigm, with principal component 1 (PC1) delineating a trade-off between carbon investment in biomass and respiratory carbon loss”
Claim · model-written summary
Ecotypic distinctions in switchgrass were observed along PC1.
- Taxon
- SwitchgrassPanicum virgatume0
- Outcome
- ecotypic distinctionse5
- Qualifier
- along PC1e5
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Switchgrass (Panicum virgatum) is a perennial C4 grass”
e5“ecotypic distinctions were observed along PC1”
Claim · model-written summary
Some upland switchgrass genotypes displayed trait profiles overlapping with lowland genotypes.
- Taxon
- SwitchgrassPanicum virgatume0
- Material
- upland genotypese6
- Outcome
- trait profilese6
- Comparator
- lowlandse6
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Switchgrass (Panicum virgatum) is a perennial C4 grass”
e6“some upland genotypes displayed trait profiles overlapping with lowlands”