Mechanisms of nitrogen conservation at the leaf-level in annual and perennial desert forbs: Implications for perennial crops domestication

Abstract

Perennial plants show traits such as long-lived leaves and higher nutrient retention that provide a more efficient use of nutrients in low-resource environments when compared to annuals. These traits do not only generate yield stability but should be relevant in the provision of regulating ecosystem services for sustainability. The understanding of the mechanisms underlying nutrient use and conservation in perennial herbaceous crops might provide useful evidence to test the potential benefits of perennial crops in low-resource environments. Using annual and perennial Physaria as a working model, we tested the link between nitrogen use efficiency (NUE), plant´s life-cycle, and specific leaf area (SLA), as an indicator of C economy strategy. As expected, SLA was pivotal in determining differences in N use and conservation, except for two processes: resorption efficiency and proficiency. The maintenance of green leaf tissues through long-lived leaves in perennials may play a key role in the capacity to store carbon and nitrogen during the grain-filling phase. Perennials had 50% less leaf senescence, lost 50% less nitrogen, had higher mean residence time, and a higher nitrogen use efficiency than annuals. Photosynthetic N use efficiency and N productivity were dependent on environmental conditions: perennials which maintained a conservative strategy both years also showed a more stable biomass production. Traits relevant for the ability to minimize nitrogen losses and internal plant nitrogen turnover over multiple seasons shown by perennials may be relevant in improving both resource use efficiency and yield stability.