Shahnaj Parvin1 2, Shihab Uddin2 3, Maryse Bourgault3 8, Glenn Fitzgerald4, James Nuttall4, Sabine Tausz-Posch3 6, Ute Roessner5, Michael Tausz1 7
1School of Ecosystem and Forest Sciences, The University of Melbourne, Creswick, VIC, Australia.
2Department of Agronomy, Bangladesh Agricultural University, Mymensingh-2202, Bangladesh.
3Faculty of Veterinary and Agricultural Sciences, The University of Melbourne, Creswick, VIC, Australia.
4Department of Economic Development, Jobs, Transport and Resources, Horsham, VIC, Australia.
5School of Bioscience, The University of Melbourne, Parkville, VIC, Australia.
6present address: School of Biosciences, University of Birmingham, UK.
7present address: Birmingham Institute of Forest Research, University of Birmingham, UK
8present address: Montana State University, USA.
The rise in atmospheric CO2 concentration from 400 to 550 ppm by 2050 will stimulate crop growth and yield and legumes may have a competitive advantage over non-legumes due to stimulation of N2 fixation under elevated CO2. However, heat stress is a major limitation to crop yield and elevated CO2 may mitigate the effects of heat shock impacts. This study evaluated whether N2 fixation and seed N yield of two lentil genotypes (PBA Ace and 05H010L-07HS3010, shortened HS3010 from here onwards) are buffered by heat waves impacts when grown under e[CO2]. Lentils were grown under ambient CO2 (a[CO2], ~400 ppm) and or elevated CO2 (e[CO2], ~ 550 ppm) in the Australian Grains Free Air CO2 Enrichment facility at Horsham, Victoria in 2015. A heat shock (40⁰C) was imposed at flat pod stage for three consecutive days using custom built heat chambers. Under e[CO2] symbiotically fixed N and total N content of both cultivars were significantly higher (11%) compared to a[CO2]. Heat stress reduced N2 fixation (19%) compared with the ambient temperature controls (CO2 pooled). More soil N was taken up in heat stress than control treatments partly offsetting lower N2 fixation. The decrease of seed N concentration by heat was more apparent under a[CO2]. Seed N content and seed yield increased under e[CO2] and the cultivar PBA had higher seed N and yield than HS3010. Heat stress reduced the seed N and yield of lentils more under a[CO2] than e[CO2]. Evidence from this study suggested that e[CO2] may mitigate the deleterious effect of heat stress on N2 fixation and yield of legumes.