Biological limits on nitrogen use for plant photosynthesis: a quantitative revision comparing cultivated and wild species

Abstract

The relationship between leaf photosynthesis and nitrogen is a critical production function for ecosystem functioning. Cultivated species have been studied in terms of this relationship, focusing on improving nitrogen (N) use, while wild species have been studied to evaluate leaf evolutionary patterns. A comprehensive comparison of cultivated vs wild species for this relevant function is currently lacking. We hypothesize that cultivated species show increased carbon assimilation per unit leaf N area compared with wild species as associated with artificial selection for resource-acquisition traits. We compiled published data on light-saturated photosynthesis (A ) and leaf nitrogen (LN ) for cultivated and wild species. The relationship between A and LN was evaluated using a frontier analysis (90 percentile) to benchmark the biological limit of nitrogen use for photosynthesis. Carbon assimilation in relation to leaf N was not consistently higher in cultivated species; out of 14 cultivated species, only wheat, rice, maize and sorghum showed higher ability to use N for photosynthesis compared with wild species. Results indicate that cultivated species have not surpassed the biological limit on nitrogen use observed for wild species. Future increases in photosynthesis based on natural variation need to be assisted by bioengineering of key enzymes to increase crop productivity.

Photorespiration in the context of Rubisco biochemistry, CO2 diffusion and metabolism

“…Due to higher CO 2 concentrations around Rubisco C 4 plants have much lower rates of oxygenation; this allows them to compromise their Rubisco’s S c/o for a higher . Thus, their nitrogen investment in Rubisco (and other enzymes in the photorespiratory pathway) is much lower than that of C 3 plants, increasing their PNUE (Rotundo and Cipriotti, ). It has been shown that an efficient use of nitrogen in C 4 photosynthesis lessens nitrogen cost constraints on molecular sequence evolution (Kelly, ).…”

Crops, Nitrogen, Water: Are Legumes Friend, Foe, or Misunderstood Ally?

“…A recent trait study compared wild and cultivated species for photosynthesis and leaf N [53] and concluded that cultivated species have not yet surpassed the biological limit on N use (for photosynthesis) established by wild species. In physiological terms, WUE can be defined as the ratio of the net rate of carbon fixation (A), to the stomatal conductance to water vapor (g s ; a function of stomatal aperture and density [54]).…”

“…Using an approach similar to those used in other meta-analyses (e.g., [53]), we synthesized leaf trait data for annual grain legume and non-legume crops using meta-analysis of the existing literature . We used a parsimonious approach, only accepting data that met key criteria (Box 1).…”

The amount of nitrogen used for photosynthesis governs molecular evolution in plants

“…Photosynthetic nitrogen use efficiency (PNUE) is the amount of carbon that can be fixed per unit of nitrogen invested by the plant. Multiple disparate anatomical, physiological and molecular factors contribute to variation in PNUE such that there is a large variation between different plant species 7 .…”