The Evolutionary Origin of C4 photosynthesis in the Grass Subtribe Neurachninae

摘要: The Australian grass subtribe Neurachninae contains closely related species that use C3, C4, and C2 photosynthesis. To gain insight into the evolution of C4 photosynthesis in grasses, we examined leaf gas exchange, anatomy ultrastructure, tissue localization Gly decarboxylase subunit P (GLDP) nine species. We identified previously unrecognized variation structure physiology within Neurachne represents varying degrees C3–C4 intermediacy Neurachninae. These include inverse correlations between apparent photosynthetic carbon dioxide (CO2) compensation point absence day respiration (C*) chloroplast mitochondrial investment mestome sheath (MS), where CO2 is concentrated C4Neurachne species; width MS cells; frequency plasmodesmata cell walls adjoining parenchymatous bundle sheath; proportion GLDP invested tissue. Less than 12% was allocated to completely C3 with C* values 56–61 μmol mol−1, whereas two-thirds lanigera, which exhibits a newly-identified, partial phenotype 44 mol−1. Increased attributed more mitochondria less mesophyll mitochondria. results are consistent model initially occurred via an increase organelle content cells, generated sink for photorespired tissues.