607
Photosynthesis in Nature: A New Look
At highly elevated WT (approximately >25–50 °C), photoinduced and microbial degradation of DOM and POM is extremely enhanced, with extremely high
generation of H 2 O 2 , CO 2 and DIC. It has been shown that [CO 2 ] aq is significantly
higher (~10–120 M) at 25 °C than at 15 °C (~5–110 M) or at 9 °C (~5–50 M) in
marine waters (Hinga et al. 1994). This effect can cause extremely high photosynthesis and high primary production. This can be supported by the synergistic
effect of high H 2 O 2 , combined with high seawater temperature, which can cause
a 134 % increase in respiration rates. Such an increase surpassed the effect of
either H 2 O 2 or high seawater temperature alone (Higuchi et al. 2009). High temperature, driven by strong solar intensity, is responsible for high production of
H 2 O 2 (see also chapter “Photoinduced and Microbial Generation of Hydrogen
Peroxide and Organic Peroxides in Natural Waters”) (Mostofa and Sakugawa
2009), which is directly linked with photosynthesis. Simultaneously, this process can also generate a high amount of ROS such as O 2
•− , 1 O 2 , H 2 O 2 , and HO
•
.
The latter is a strong oxidizing agent, produced either from H 2 O 2 (via direct
photo-dissociation by sunlight or photo-Fenton reaction) or other sources, such
as the direct photolysis of NO 2
− and NO 3
− (see the chapters “Photoinduced and
Microbial Generation of Hydrogen Peroxide and Organic Peroxides in Natural
Waters”, “Photoinduced Generation of Hydroxyl Radical in Natural Waters”
and “Photoinduced and Microbial Degradation of Dissolved Organic Matter in
Natural Waters”). This effect can significantly degrade algal or phytoplankton
cells, thereby decreasing the photosynthetic efficiency. All these processes should
be able to significantly promote the photosynthetic efficiency in waters with high
contents of DOM and POM.
Temperature Effects on Higher Plants
Plants need an optimum temperature for photosynthesis. The stress represented by
extremely high- or low-temperature has a significantly negative effect on the growth
and productivity of plants (Allen and Ort 2001; Adams et al. 2002; Adams Iii et al.
2004; Öquist and Huner 2003; Yang et al. 2009). It has been shown that suboptimal and
above-optimal temperatures can promote photoinhibition, caused by an over-excitation
of photosystems (Powles 1984; Öquist et al. 1993; Huner et al. 1998). Effects of temperature on the photosynthesis of plants have been discussed as follows: First, low temperature stress or chilling stress (generally at 0–12 °C) can highly inhibit growth and
development of most plants, and in particular of those coming from tropical and subtropical regions (Allen and Ort 2001; Yang et al. 2009; D’Ambrosio et al. 2006).
The chilling stress or lower temperatures can affect several physiological functions and induce water deficiency. Commonly observed effects are decrease of leaf
water potential, of electron transport rate, of total Chl contents, of CO 2 uptake and
of the carotenoid content; stomatal closure; inhibition of thylakoid electron transport and photophosphorylation; Rubisco inactivation; inhibition of carbohydrate
metabolism; and finally, a significant decrease of the maximum quantum efficiency of PSI and PSII primary photochemistry (Allen and Ort 2001; Yang et al.
2009; D’Ambrosio et al. 2006; Berry and Bjorkman 1980; Eamus 1986; Sage and
Photosynthesis in Nature: A New Look
At highly elevated WT (approximately >25–50 °C), photoinduced and microbial degradation of DOM and POM is extremely enhanced, with extremely high
generation of H 2 O 2 , CO 2 and DIC. It has been shown that [CO 2 ] aq is significantly
higher (~10–120 M) at 25 °C than at 15 °C (~5–110 M) or at 9 °C (~5–50 M) in
marine waters (Hinga et al. 1994). This effect can cause extremely high photosynthesis and high primary production. This can be supported by the synergistic
effect of high H 2 O 2 , combined with high seawater temperature, which can cause
a 134 % increase in respiration rates. Such an increase surpassed the effect of
either H 2 O 2 or high seawater temperature alone (Higuchi et al. 2009). High temperature, driven by strong solar intensity, is responsible for high production of
H 2 O 2 (see also chapter “Photoinduced and Microbial Generation of Hydrogen
Peroxide and Organic Peroxides in Natural Waters”) (Mostofa and Sakugawa
2009), which is directly linked with photosynthesis. Simultaneously, this process can also generate a high amount of ROS such as O 2
•− , 1 O 2 , H 2 O 2 , and HO
•
.
The latter is a strong oxidizing agent, produced either from H 2 O 2 (via direct
photo-dissociation by sunlight or photo-Fenton reaction) or other sources, such
as the direct photolysis of NO 2
− and NO 3
− (see the chapters “Photoinduced and
Microbial Generation of Hydrogen Peroxide and Organic Peroxides in Natural
Waters”, “Photoinduced Generation of Hydroxyl Radical in Natural Waters”
and “Photoinduced and Microbial Degradation of Dissolved Organic Matter in
Natural Waters”). This effect can significantly degrade algal or phytoplankton
cells, thereby decreasing the photosynthetic efficiency. All these processes should
be able to significantly promote the photosynthetic efficiency in waters with high
contents of DOM and POM.
Temperature Effects on Higher Plants
Plants need an optimum temperature for photosynthesis. The stress represented by
extremely high- or low-temperature has a significantly negative effect on the growth
and productivity of plants (Allen and Ort 2001; Adams et al. 2002; Adams Iii et al.
2004; Öquist and Huner 2003; Yang et al. 2009). It has been shown that suboptimal and
above-optimal temperatures can promote photoinhibition, caused by an over-excitation
of photosystems (Powles 1984; Öquist et al. 1993; Huner et al. 1998). Effects of temperature on the photosynthesis of plants have been discussed as follows: First, low temperature stress or chilling stress (generally at 0–12 °C) can highly inhibit growth and
development of most plants, and in particular of those coming from tropical and subtropical regions (Allen and Ort 2001; Yang et al. 2009; D’Ambrosio et al. 2006).
The chilling stress or lower temperatures can affect several physiological functions and induce water deficiency. Commonly observed effects are decrease of leaf
water potential, of electron transport rate, of total Chl contents, of CO 2 uptake and
of the carotenoid content; stomatal closure; inhibition of thylakoid electron transport and photophosphorylation; Rubisco inactivation; inhibition of carbohydrate
metabolism; and finally, a significant decrease of the maximum quantum efficiency of PSI and PSII primary photochemistry (Allen and Ort 2001; Yang et al.
2009; D’Ambrosio et al. 2006; Berry and Bjorkman 1980; Eamus 1986; Sage and