Legumes are different: Leaf nitrogen, photosynthesis, and water use efficiency

摘要: Using robust, pairwise comparisons and a global dataset, we show that nitrogen concentration per unit leaf mass for nitrogen-fixing plants (N2FP; mainly legumes plus some actinorhizal species) in nonagricultural ecosystems is universally greater (43–100%) than other (OP). This difference maintained across Koppen climate zones growth forms strongest the wet tropics within deciduous angiosperms. N2FP mostly similar advantage over OP area (Narea), even arid climates, despite diazotrophy being sensitive to drought. We also that, most N2FP, carbon fixation by photosynthesis (Asat) stomatal conductance (gs) are not related Narea—in distinct challenge current theories place nitrogen–Asat relationship at center of explanations plant fitness competitive ability. Among only forbs displayed an Narea–gs OP, whereas intrinsic water use efficiency (WUEi; Asat/gs) was positively Narea woody N2FP. Enhanced foliar (relative OP) contributes strongly evolutionarily advantageous attributes legumes, such as seed herbivore defense. These alternate clear differences N between have significant implications (e.g., models fluxes based on relationships Asat). Combined, WUE nitrogen—in variety forms—enhance survival genomes particularly semiarid climates.