Investigating photosynthetic and chlorophyll fluorescence responses to light in peanut acclimated to elevated CO2 and temperature.

Abstract

In plants, the photo-inhibitory effects of incident lights on the light-harvesting complexes are balanced by photoprotective mechanisms to maintain photosynthesis. With increasing air CO₂ concentrations and temperatures, the balance can tilt either way, with unpredictable consequences for biomass assimilated through photosynthesis. As such, it is critical to assess the photosynthetic responses of crop plants growing in future climates to light for developing strategies for sustaining food production. This study evaluated changes in photosynthetic and chlorophyll fluorescence responses to light intensities in peanuts (Arachis hypogaea L) acclimated to projected future climates by Global Circulation Models (GCM). The plants were grown in plant growth chambers under three climate conditions (CC): (1) ambient air [CO₂] and ambient temperature [Ta] (CC1), (2) [CO₂] at 570 ppm and Ta + 3⁰ C (CC2 climate possible in 2050), and (3) [CO₂] at 780 ppm and Ta + 5⁰C (CC3, climate possible in 2080). Plants growing under all three climates enhanced photosynthetic rates (A) with light intensities from 0 to 1500 µ mol m^- 2 s^- 1 but decreased afterward. Compared to CC1, plants growing under CC2 and CC3 reduced electron transport rates (ETR), A, and transpiration (Tr) between 48 and 190%, 52 and 65%, and 22 and 24%, respectively. Concurrently, the quantum efficiency of photosystem II (ФPS2) was reduced by 88-200% and photochemical quenching (qP) by 55-170%. Non-photochemical quenching increased with increasing light levels from 200 to 1500 µmol m⁻² s⁻¹ and decreased afterward. Results indicated the possibility of reduced photosynthetic efficiencies under CC2 and CC3, which would significantly reduce biomass production in future climates. Gaining insight into these impacts can help understand plant's ability to adapt and assist in developing adaptive strategies for sustainable peanut farming.