Researchers have identified a way to manipulate photosynthesis in plants to increase both their light-harvesting ability and biomass production. As the world population faces an immense increase in the demand for food over the next decades, this advancement, which takes advantage of deficiencies in photosynthesis, could lead to better crop yields. Due to wind-tossed canopies and moving clouds, plants must adapt to rapidly varying levels of light and shade. Under an unfiltered noon sun for example, plants protect themselves from excess sunlight by dissipating some of that light energy as heat. But while this protection mechanism jumps speedily into action during sun exposure, it is slower to "relax" back to a natural state, resulting in suboptimal photosynthetic efficiency when a passing cloud shades the plant. Here, Johannes Kromdijk and colleagues suspected that manipulating the relaxation mechanism could result in better plant productivity. In tobacco plants, they induced the expression of three genes related to two energy dissipation mechanisms suspected to play a role, Photosystem II subunit S (PsbS) and the xanthophyll cycle. Under steady light conditions, the modified plants performed similarly to controls; however, under fluctuating light conditions, the modified plants were 11 and 14% better, respectively, at carbon dioxide fixation and photosynthesis. As well, the modified plants exhibited greater leaf area and plant height, with an overall dry weight that was 14 to 20% greater than that of control plants. Similar results were found when the modified plants were grown under greenhouse and field conditions, the authors report. Importantly, they note that both PsbS and the xanthophyll cycle are common to all vascular plants, meaning that this type of efficiency-boosting manipulation could theoretically be applied to all major crops.
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