Post Doc Research Associate University of Nebraska–Lincoln Lincoln, Nebraska
Body of Abstract: Crops grow in intense and frequent changes in sun light, and acclimate to photosynthetic efficiency by dissipate the excess absorbed light energy as heat via non-photochemical quenching of chlorophyll fluorescence (NPQ). Here, we analyzed natural variations in photosynthetic traits modelled to kinetics of NPQ in a diverse population of ~230 accessions from the association panel in 2019 under standard nitrogen (N) and low N field conditions. A subset of 15 accessions with increased and no changes in NPQ were chosen and verified under same N conditions in field in 2020. We describe extensive variations in Zea mays for rate, range, and steady-state response of NPQ during induction in light and relaxation in dark, suggesting the diverse adaptation of NPQ in a large number of genotypes under low N condition at early-vegetative, late-vegetative, and post-flowering stages. A detailed study of photosynthesis on four accessions in growth-chamber conditions showed that MS153 and Mo1W (non-stiff stalk with relative high NPQ) were strongly affected to low N more than NC312 and H100 (stiff stalk with relative no-change NPQ) for steady-state and dynamic-light induced net photosynthetic assimilation, ETR, NPQ, ɸPSII, chlorophyll content, PSI redox state along with growth related traits. High increase in NPQ kinetics, ɸNPQ, and transient NPQ (NPQ(T)) resulted from a high pmf level (ECSt) leading to reduction in the activity of ATP synthase (gH+) (25-30%), indicated less tolerance of MS153 and Mo1W to low N. Whereas, NC312 and H100 responded by not changing much in chlorophyll content, NPQ, ɸPSII, gH+ including other parameters, indicated better tolerance to low N. The response of NPQ was found stable across environmental conditions (years), growth stages, and treatments in both field and growth chamber conditions, suggested the conserved nature of NPQ.