Can improved canopy light transmission ameliorate loss of photosynthetic efficiency in the shade? An investigation of natural variation in Sorghum bicolor. (29th April 2021)

• Record Type: Journal Article
• Authors: Jaikumar, Nikhil S; Stutz, Samantha S; Fernandes, Samuel B; Leakey, Andrew D B; Bernacchi, Carl J; Brown, Patrick J; Long, Stephen P
• Editors: Lawson, Tracy
• Is Part Of: Journal of experimental botany. Volume 72:Number 13(2021)
• Page Start: 4965
• Page End: 4980
• Publication Date: 2021-04-29
• Subjects: C4 photosynthesis -- crop canopy architecture -- food security -- leaf form -- quantum efficiency -- stomata -- water use efficiency; Botany -- Periodicals; Botany, Experimental -- Periodicals; Plant physiology -- Periodicals; 580
• DOI: 10.1093/jxb/erab176
• Languages: English
• ISSNs: 0022-0957

Abstract

Abstract : In dense crop stands, the lower leaves of sorghum show a maladaptive loss of photosynthetic efficiency, lowering potential yield. Screening multiple genotypes shows selection for more upright leaves to protect against this loss. Abstract: Previous studies have found that maximum quantum yield of CO2 assimilation (Φ CO2, max, app ) declines in lower canopies of maize and miscanthus, a maladaptive response to self-shading. These observations were limited to single genotypes, leaving it unclear whether the maladaptive shade response is a general property of this C4 grass tribe, the Andropogoneae. We explored the generality of this maladaptation by testing the hypothesis that erect leaf forms (erectophiles), which allow more light into the lower canopy, suffer less of a decline in photosynthetic efficiency than drooping leaf (planophile) forms. On average, Φ CO2, max, app declined 27% in lower canopy leaves across 35 accessions, but the decline was over twice as great in planophiles than in erectophiles. The loss of photosynthetic efficiency involved a decoupling between electron transport and assimilation. This was not associated with increased bundle sheath leakage, based on 13 C measurements. In both planophiles and erectophiles, shaded leaves had greater leaf absorptivity and lower activities of key C4 enzymes than sun leaves. The erectophile form is considered more productive because it allows a more effective distribution of light through the canopy to support photosynthesis. We show that in sorghum, it provides a second benefit, maintenance of higher Φ CO2, max, app to support efficient use of that light resource.