Does Fluctuating Light Affect Crop Yield? A Focus on the Dynamic Photosynthesis of Two Soybean Varieties

How much could improving photosynthesis increase crop yields? A call for systems-level perspectives to guide engineering strategies

Global yield gaps can be reduced through breeding and improved agronomy. However, signs of yield plateaus from wheat and rice grown in intensively farmed systems indicate a need for new strategies if output is to continue to increase. Approaches to improve photosynthesis are suggested as a solution. Empirical evidence supporting this approach comes from small-scale free-CO2 air enrichment and transgenic studies. However, the likely achievable gains from improving photosynthesis are less understood. Models predict maximum increases in yield of 5.3-19.1% from genetic manipulation depending on crop, environment, and approach, but uncertainty remains in the presence of stress. This review seeks to provide context to the rationale for improving photosynthesis, highlight areas of uncertainty, and identify the steps required to create more accurate projections.

Photoacclimation of photosystem II photochemistry induced by rose Bengal and methyl viologen in Nannochloropsis oceanica

The photosynthetic apparatus is a major reactive oxygen species (ROS) proliferator, especially in high-light environments. The role of ROS in photoinhibition and photoacclimation mechanisms has been extensively explored, primarily in model plant species. However, little work has been performed on the topic in non-Archaeplastida organisms, such as the model heterokont species Nannochloropsis oceanica. To investigate the photoacclimation and damaging impact of singlet oxygen and superoxide anions on the photosynthetic apparatus of N. oceanica, we subjected cells to two doses of methyl viologen and rose bengal. Significant findings: Rose bengal (a singlet-oxygen photosensitizer) induced changes to the photosynthetic apparatus and PSII photochemistry mirroring high-light-acclimated cells, suggesting that singlet-oxygen signaling plays a role in the high-light acclimation of PSII. We further suggest that this singlet-oxygen pathway is mediated outside the plastid, given that rose bengal caused no detectable damage to the photosynthetic apparatus. Methyl viologen (a superoxide-anion sensitizer) induced an enhanced non-photochemical quenching response, similar to what occurs in high-light-acclimated cells. We propose that superoxide anions produced inside the plastid help regulate the high-light acclimation of photoprotective pathways.