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Intraspecific variation in leaf growth of wheat (Triticum aestivum) under Australian Grain Free Air CO2 Enrichment (AGFACE): is it regulated through carbon and/or nitrogen supply?

Thilakarathne, Chamindathee L., Tausz-Posch, Sabine, Cane, Karen, Norton, Robert M., Fitzgerald, Glenn J., Tausz, Michael, Seneweera, Saman
Functional plant biology 2015 v.42 no.3 pp. 299-308
Triticum aestivum, carbon, carbon dioxide, cell division, cultivars, free air carbon dioxide enrichment, intraspecific variation, leaf area, leaf blade, nitrogen, nitrogen content, photosynthesis, spring wheat
Underlying physiological mechanisms of intraspecific variation in growth response to elevated CO2 concentration [CO2] were investigated using two spring wheat (Triticum aestivum L.) cultivars: Yitpi and H45. Leaf blade elongation rate (LER), leaf carbon (C), nitrogen (N) in the expanding leaf blade (ELB, sink) and photosynthesis (A) and C and N status in the last fully expanded leaf blade (LFELB, source) were measured. Plants were grown at ambient [CO2] (~384µmolmol-1) and elevated [CO2] (~550µmolmol-1) in the Australian Grains Free Air CO2 Enrichment facility. Elevated [CO2] increased leaf area and total dry mass production, respectively, by 42 and 53% for Yitpi compared with 2 and 13% for H45. Elevated [CO2] also stimulated the LER by 36% for Yitpi compared with 5% for H45. Yitpi showed a 99% increase in A at elevated [CO2] but no A stimulation was found for H45. There was a strong correlation (r2=0.807) between LER of the ELB and soluble carbohydrate concentration in LFELB. In ELB, the highest spatial N concentration was observed in the cell division zone, where N concentrations were 67.3 and 60.6mg g-1 for Yitpi compared with 51.1 and 39.2mg g-1 for H45 at ambient and elevated [CO2]. In contrast, C concentration increased only in the cell division and cell expansion zone of the ELB of Yitpi. These findings suggest that C supply from the source (LFELB) is cultivar dependent and well correlated with LER, leaf area expansion and whole-plant growth response to elevated [CO2].