Water availability moderates N2 fixation benefit from elevated [CO2]: A 2‐year free‐air CO2 enrichment study on lentil (Lens culinaris MEDIK.) in a water limited agroecosystem. (16th July 2018)

• Record Type: Journal Article
• Authors: Parvin, Shahnaj; Uddin, Shihab; Bourgault, Maryse; Roessner, Ute; Tausz‐Posch, Sabine; Armstrong, Roger; O'Leary, Garry; Fitzgerald, Glenn; Tausz, Michael
• Is Part Of: Plant, cell and environment. Volume 41:Number 10(2018)
• Page Start: 2418
• Page End: 2434
• Publication Date: 2018-07-16
• Subjects: climate change -- grain protein -- legume -- N acquisition (fixation vs. uptake) -- nodule -- soil water; Plant physiology -- Periodicals; Plant cells and tissues -- Periodicals; Plant communities -- Periodicals; 581.105
• DOI: 10.1111/pce.13360
• Languages: English
• ISSNs: 0140-7791

Abstract

Abstract: Increased biomass and yield of plants grown under elevated [CO2 ] often corresponds to decreased grain N concentration ([N]), diminishing nutritional quality of crops. Legumes through their symbiotic N2 fixation may be better able to maintain biomass [N] and grain [N] under elevated [CO2 ], provided N2 fixation is stimulated by elevated [CO2 ] in line with growth and yield. In Mediterranean‐type agroecosystems, N2 fixation may be impaired by drought, and it is unclear whether elevated [CO2 ] stimulation of N2 fixation can overcome this impact in dry years. To address this question, we grew lentil under two [CO2 ] (ambient ~400 ppm and elevated ~550 ppm) levels in a free‐air CO2 enrichment facility over two growing seasons sharply contrasting in rainfall. Elevated [CO2 ] stimulated N2 fixation through greater nodule number (+27%), mass (+18%), and specific fixation activity (+17%), and this stimulation was greater in the high than in the low rainfall/dry season. Elevated [CO2 ] depressed grain [N] (−4%) in the dry season. In contrast, grain [N] increased (+3%) in the high rainfall season under elevated [CO2 ], as a consequence of greater post‐flowering N2 fixation. Our results suggest that the benefit for N2 fixation from elevated [CO2 ] is high as long as there is enough soil water to continue N2 fixation during grain filling. Abstract : Using a free‐air CO2 enrichment facility, this study found that elevated [CO2 ] stimulated N2 fixation in lentil through increasing number, mass, and specific activity of root nodules, but the effect was different between a low and high rainfall year. Only in the high rainfall year, N2 fixation continued until late in the season, and grain N concentration was maintained under elevated [CO2 ]. These findings suggest that elevated [CO2 ] stimulation of N2 fixation can optimize N supply to legume grains, but only if sufficient water maintains symbiotic fixation activity during the grain filling period.