||P.1887 left column 2nd paragraph: "To support the latter point, [investigators] begin with an estimation of the critical oxygen concentration below which a cell could survive without the need for special protection mechanisms, assuming that the major source of photodamage in the
photosynthetic bacteria is singlet oxygen produced by unquenched
(B)Chl triplet states. Under full sunlight, monomeric (B)Chls are excited at a rate of ~10/sec. Due to efficient intersystem crossing, up to about half of the excited monomeric (B)Chls end up in triplet excited states (ref 8)."