Environmental Engineering Reference
In-Depth Information
Fig. 2
The relationship
between photosynthesis
and (photo) bleeding within
the framework of the
conventional considerations
regarding photosynthesis
(
a
) and in accordance with
the concept proposed by the
author of the article (
b
).
Data
source
Komissarov (
2003
)
Singlet oxygen (
1
O
2
) and superoxide radical ion
O
2
•−
are formed from the tri-
•
−
plet state of
O
2
then reacts with an hydrogen ion (H
+
) to form the perhydroxyl radical
(
HO
2
•
)
(Eq.
3.17
). The species
O
2
•−
can also accept one more electron (e
−
) to form peroxide
ion (O
2
2
−
), which then combines with H
+
to generate hydrogen peroxide (H
2
O
2
)
(Eq.
3.18
). Further acceptance of one e
−
by
O
2
2
−
can form
O
2
3
−
, which can then
produce H
2
O and an oxene ion (O
−
) in the presence of H
+
(Eq.
3.19
). The ion radi-
cal O
−
can produce the hydroxyl radical in the presence of H
+
(Eq.
3.19
). Further
acceptance of one e
−
by O
−
can yield the oxide ion (O
2
−
), which finally gives H
2
O
in the presence of H
+
(Eq.
3.20
). This result shows that formation of water from O
2
is relatively more difficult than the process involving H
2
O
2
.
In the new hypothesis, the relationship between the fundamental biological pro-
cess and breathing is complicated because the final product in breathing is water,
which would not dissociate during photosynthesis (Fig.
2
b) (Komissarov
2003
).
This is not contemplated in the conventional view of photosynthesis, which is
illustrated in Fig.
2
a. Breathing is followed from right to left in both equations.
However, breathing is accompanied by the formation of endogenous H
2
O
2
that
is not only a source of O
2
, injected into the atmosphere, but also of hydrogen used
in the synthetic processes of growth (Komissarov
2003
).
Mass spectrometric examination of photosynthetic generation of O
2
using
H
2
O
2
, marked with heavy isotopic oxygen
3
O
2
in the presence of light (Eqs.
3.16
,
3.17
). The radical ion O
2
, suggests that H
2
O
2
is the
source of the entire amount of generated O
2
(Mano et al.
1987
). Experimental
studies using
18
O-
labeled H
2
O
2
H
2
18
O
2
added to seawater also
suggest that photoinduced oxidation can produce
18
O
2
and H
2
O
(Moffett and
Zafiriou
1990
), whereas label transfer is governed by the mass balance (Eq.
3.21
):
H
2
18
O
2
18
O
2
and O
2
−∆
H
2
18
O
2
= ∆
H
2
18
O
+ ∆
18
O
2
(3.21)
Similarly, catalytic epoxidation experiments using the
18
O
labels in an ace-
tone/water
H
2
18
O
solvent demonstrate that no
18
O coming from water
H
2
18
O
