Optical Screening as a Photoprotective Mechanism

The Pigment World

“…The singular importance of pigments to the development of life can be observed in the historical fossil record in which organic pigments are first seen to arise in the UV-C and then evolve gradually to cover the entire solar spectrum up to the red-edge (∼ 700 nm) [9]. Contemporary biology based on Darwinian principles recognizes pigments of phototrophic organisms as primary, or accessory, light collection molecules, or as photo-protective agents, of the photosynthetic system [10]. However, broadband absorption of photons over the entire spectrum (Figure 1) is not congruent with the tenants of Darwinian theory since broadband absorption, and rapid dissipation of the electronic excitation energy into vibrational energy (heat), requires numerous complex pigments and their support structures.…”

“…Although screening certain UV wavelengths may indeed be protective in contemporary photosynthetic organisms relying on weak Van der Waals bonds, pigments screening the visible part of the spectrum (e.g., the secondary carotenoids) remains enigmatic [10]. Isolated chlorophylls are susceptible to bleaching (the opening up of the tetrapyrrole ring), particularly in the UV-A at 350 nm where there is significant absorption.…”

Dynamic photosynthesis under a fluctuating environment: a modelling-based analysis

“…In a typical green leaf, chlorophyll pigments absorb mostly blue and red irradiance (and, to a small degree, also UV and infrared), carotenoids absorb blue and green irradiance, whereas phenolic compounds and extra-thylakoid carotenoids absorb from UV-B to green irradiance (Solovchenko, 2010). Absorptance of NIR is mostly due to leaf water content .…”

“…Because `a bc was estimated from measurements at the leaf level, it includes absorption by non-photosynthetic pigments (e.g., phenolic compounds and non-photosynthetic carotenoids) as well as auxiliary photosynthetic pigments (carotenoids) that transfer energy to chlorophyll pigments of PSIIac and the antenna complexes associated to PSI (Solovchenko, 2010). A detailed simulation of the optical properties of a leaf is beyond the …”

Comparison of parsimonious dynamic vegetation modelling approaches for semiarid climates

“…energy consumption by processes that do not involve CO 2 fixation) and chlorophyll fluorescence. When excessive radiation exposure is combined with other sources of stress, such as high temperatures, drought or nutrients deficiency, plants can incur more easily in photodamage (Solovchenko, 2010).…”