The Kranz syndrome in the Eragrostideae (Chloridoideae, Poaceae) as indicated by carbon isotopic ratios*

Abstract

¹³C/¹²C ratios are generally regarded as being very reliable indicators of C₃ or C₄ photosynthesis. These relative carbon isotope ratios are expressed as a negative δ ³C and fall into two distinct groups: Kranz (or C₄) plants with δ between -9°/₀₀ no and -18°/₀₀ and non-Kranz (C₃) plants with δ between -22°/₀₀ and -28⁰/₀₀ no. In this paper, 29 taxa, representing 12 genera, of the tribe Eragrostideae were examined by mass spectrometry for their δ ¹³C in dried leaf tissue. All these taxa proved to be C₄, plants with δ¹³C values ranging between -13,6°/_oo and -10.9°/_oo. These findings confirmed published leaf anatomical observations which showed that all the studied taxa had characteristic Kranz leaf anatomy.