A limiting factor for photosynthetic organisms is their light-harvesting efficiency, that is the efficiency of their conversion of light energy to chemical energy. Small modifications or variations of chlorophylls allow photosynthetic organisms to harvest sunlight at different wavelengths. The photosynthetic spectral limit (red-edges at ~700 nm) of photosynthetic active radiation (PAR) is set by the Qy band position of Chl a at around 700 nm[1]. The chlorophylls having red-shifted absorption provide potential advantages to expand PAR region of 400 – 760 nm, which will increase the number of available photons (700-760 nm) by 19%[2]. The lesson from a natural photosynthetic community is that different photosynthetic organisms do exploit regions of the solar spectrum not harvested by those organisms that live spatially above them, such as the Chl d-containing organisms thriving in a coral bio-community[3] and Chl f-producing cyanobacteria thriving inside of stromatolite[4]. In one sense, the community can be viewed as a stacked optical series that maximizes the energy captured using different photopigments. Such a strategy of stacked optical series in a bio-community could be applied to intelligently organize a multilayered agricultural crop environment. Here, I will discuss the potential by using modified chlorophylls to extend the spectral region of light that drives photosynthetic organisms.
References:
1.Chen, M. and Scheer, H. (2013). J. Porphyrins Phthalocyanines 17:1–15;
3.Kühl, M. et al. (2005). Nature 433:820.