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hy L D hv L 0 before after transfer hy L D hv L 0 before after transfer

Fig. 6.30 Elimination of dark CO2 fixation (D) and stimulation of light CO2 fixation (L ) in a well-watered plant of Clusia minor by transfer from lower to high irradiation (hv). (Data from Schmitt et al. 1988)

Table 6.8 The highest nocturnal acid accumulation (mmol titratable H+/l) and the highest nocturnal citrate accumulation (mmol citrate/l) observed in CAM. These records were measured in epiphytes (Aechmea nudicaulis) and hemi-epiphytes (Clusia species)

Titratable acidity

Aechmea nudicaulis Field Trinidad, March 1983

625a

Clusia rosea, phytotron

1120c

Clusia minor Field, Trinidad, March 1990

1410b

Citrate

Clusia minor Field Trinidad, March 1990

125b

Clusia rosea, phytotron

200c

Data from a Smith et al. 1986b, b Borland et al. 1992, c Franco et al. 1992

Data from a Smith et al. 1986b, b Borland et al. 1992, c Franco et al. 1992

that of malic acid, and the availability of this internal CO2 could prevent photoinhibition (see Sect. 4.1.7) more effectively when light intensity is high. In fact it has been observed for four different Clusia species that the ratio of malic acid : citric acid accumulated during the dark period decreased in response to drought stress, relatively favouring carbon recycling via citrate. Since citrate accumulation does not contribute to C-acquisition, naturally it also does not help to improve water-use-efficiency (WUE). It also adds less to changes in cell-sap osmotic pressure than malate accumulation, because only one mole of citrate is formed per mole of hexose consumed. However, citrate is known to be an effective buffering sub-

Table 6.9 Comparative evaluation of the ecophysiological advantages of nocturnal accumulation of malate (a malate) and citrate (a citrate) respectively, in CAM. (Franco et al. 1992; Haag-Kerwer et al. 1992)

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Renewable Energy 101

Renewable Energy 101

Renewable energy is energy that is generated from sunlight, rain, tides, geothermal heat and wind. These sources are naturally and constantly replenished, which is why they are deemed as renewable. The usage of renewable energy sources is very important when considering the sustainability of the existing energy usage of the world. While there is currently an abundance of non-renewable energy sources, such as nuclear fuels, these energy sources are depleting. In addition to being a non-renewable supply, the non-renewable energy sources release emissions into the air, which has an adverse effect on the environment.

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