Drought timing affects switchgrass metabolism, biofuel yields

Background/Objective

Switchgrass is a promising bioenergy crop, due in part to its resilience to drought stress. There is limited information on how drought affects metabolite profiles across developmental stages, in particular the distinction between core and developmentally specific physiological and metabolic drought responses.

Approach

Switchgrass was grown from seedling stage through senescence and subjected to four watering treatments: a continuously-watered control and drought imposed at specific developmental stages — vegetative, flowering, and senescence.

Results

Vegetative, flowering, and senescence-stage drought significantly reduced CO2 assimilation and stomatal conductance without affecting biomass yield. Metabolic profiling revealed accumulation of glucose, fructose, quinic acid, shikimate, and GABA during vegetative-stage drought but limited metabolic changes during later stage drought. Treated and hydrolyzed biomass from vegetative-stage drought showed elevated lignocellulosic-derived compounds and saponins, which positively correlated with fermentation lag times. Vegetative-stage drought enhanced physiological resilience but compromised ethanol yields. Senescence-stage drought enhanced ethanol yields while lowing saponin levels in hydrolysates.

Significance/Impact

Understanding how varying drought conditions affect plant metabolism is crucial for improving biofuel production processes as droughts are expected to become more frequent and severe as the climate warms.

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