The far-red light absorption and “Redundant chlorophyll” in plants: A waste of resource or an important booster of photosynthesis?

Abstract

Mature non-stressed plants often contain a lot more chlorophyll than they need to efficiently capture light energy in the PAR range. In this situation, some pigment molecules apparently become physiologically redundant because they remain shaded and cannot participate efficiently in light harvesting. As a result of the build-up of chlorophyll, strong absorption of these pigments extends well beyond 700 nm, the conventional border of PAR, into far red (FR) region of the spectrum (to 750 nm and beyond) contributing significantly to the budget of the absorbed light energy. It is also well known that FR light, when supplemented to conventional PAR spectrum, harmonizes energy flow in the photosynthetic apparatus, reduces risk of photodamage boosting plant productivity. We argue that a possible functional role of the “redundant chlorophyll” accumulated in plants is ensuring the capture of FR photons. The latter is among important acclimations to fluctuating light fluxes as well as to permanently low-light environments ensuring efficient operation of complex plant canopies. We discuss the opportunity to harness the “FR boost” of productivity by leveraging inherent optical properties of green plants without sophisticated approaches such as engineering of long-wave chlorophylls into the plant photosynthetic apparatus.