Greening photosynthetic activity

CjoHsoO, Mr 426.73, mp. 215 C (anhydrous), 99 C (hydrate), [a]o +54 (CHCy. Tetracyclic triterpene alcohol with an extra cyclopropane ring. C. is isolated technically e.g. from the fruits of Artocarpus integri-folius, the poison nut (Strychnos nux-vomica), leaves of the potato plant (Solatium tuberosum), and the latex of Euphorbiaceae. It is present, at least in traces, in all green photosynthetically active plants since it is the first detectable cyclization product of 2,3-epoxysqua-lene in the course of the biosynthesis of cholesterol (and thus all other plant steroids) in plants. 

Lichtenthaler, H. K., P. Karunen, and K. H. Grumbach Determination of Prenylquinones in Green Photosynthetically Active Moss and Liver Moss Tissues. Physiol. Plant. 40, 105 (1977). 

The desirability of partial shade on tea estates has been a controversial subject. Desirable effects include temperature moderation at the leaf surface, which decreases low-humidity stress, and an increased yield of chlorophyll, amino acid, and caffeine production. The undesirable effects include decreased photosynthetic activity and competition for water and solid nutrients by the shade tree employed. In general, the trend has been toward the elimination of shade in most black-tea growing areas. Green tea products benefit from the additional chlorophyll and amino acid pro-... 

The photo synthetic aquatic biomass comprises cyanobacteria (formerly called blue-green algae), planktonic, filamentous and macrophytic algae, and vascular macrophytes. The net productivity of the floodwater depends on the level of primary production by the photosynthetic biomass versus its consumption by grazing animals, particularly cladocerans, copepods, ostracods, insect larvae and molluscs. Their role will change as the canopy develops and at a leaf area index of about 6-7 there will be no more photosynthetically active radiation available to them. 

Figure 7.51. Schematic representation of charge separation in the photosynthetic cycle a) in green plants involving photosystems PS II and PS I and b) in photosynthetic active bacteria (by permission from Rettig, 1986).

Photosynthetically active quinones include plastoquinone of green-plant photosystem II, ubiquinone and menaquinone in photosynthetic bacteria, and phylloquinone in photosystem I. Plastoquinone is present in green-plant photosystem II both as a tightly-bound and a loosely-bound electron carrier, designated Qa and Qb, respectively. Qa is photoreduced only to the semiquinone (PQ ) but Qb can accept two electrons, forming the plastohydroquinone (PQ-Hj) [see Chapters 5, 6 and 16 for further discussion]. Plastohydroquinone PQb H2 is the final reduction product of photosystem II and goes on to reduce the cytochrome bj complex as part of the electron transport and proton translocation processes [see Chapter 35 for detailed discussions]. 

Fig. 4. Light-induced absorbance changes (A) open symbols/solid line for Complex I" solid symbols/dashed line for the PP (ghotosystem-gigment) complex normalized to equal absorbance at 810 nm. (B) both traces for the RCPP (reaction center gigment grotein) complex, but on different AA scales. See text for discussion. Figures from Swarthoff and Amesz (1979) Photo-chemically active pigment-protein complexes from the green photosynthetic bacterium Prosthecochloris aestuarii. Biochim Biophys Acta. 548 p. 430, 431.

T Swarthoff and J Amesz (1979) Photochemically active pigment-protein complexes from the green photosynthetic bacterium Prosthecochloris aestuarii. Biochim Biophys Acta 548 427-432... 

Many modem organisms contain intracellular symbiotic bacteria, cyanobacteria, or algae that is, such associations are not difficult to establish. For example, a primitive freshwater animal called Chlorohydra owes its green color to endosym-biont algae. The hydra s nutrition is supplemented by the photosynthetic activity of the algae. 

Chlorophylls and photosynthetic activity in the green hairy roots... 

Even more complicated is the situation in the utilization of non-visible parts of the sun s radiation. Some plants, algae and cyanobacteria have a certain photosynthetic activity also in the upper part of the UV region, for green plants the maximum is at about 360 nm, for brown and red algae it is around 340 nm. Infrared radiation cannot be utilized by green organisms, but some brown and red algae are able to utilize the shortwave part of infrared spectrum quite well. The purple phototrophic bacteria also possess a similar ability [9, 10]. 

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