Tropical plants, photosynthesis

The C4 Pathway of Tropical Plants Accelerates Photosynthesis by Concentrating Carbon Dioxide... 

Overall, the C4 cycle consumes two ATP equivalents to deliver a CO2 to Rubisco. During active photosynthesis, this is not a problem—plenty of ATP exists from the action of Photosystems I and II. Why, then, don t C4 plants take over the world Probably because the increased energy demands make these plants less efficient under conditions where sunlight is limited. Consistent with this idea, C4 plants are mostly confined to tropical climates, while the C3 plants predominate in more temperate regions. 

Dissolved oxygen concentration 1. Surface water (1) near the equilibrium saturation concentration with atmospheric oxygen at a given temperature [6 ppm (in the tropics) 11 ppm (in the Arctic) (2) can be supersatured due to photosynthesis by microscopic plants (up to 200%) and entrainment of air bubbles (up to 10%) 2. Variation with depth (1) tends to be under saturated due to consumption by the biochemical oxidation of organic matter (2) goes though a minimum at intermediate depths (400-2400 m)... 

Cabrera, H. M., Rada, F., Cavieres, L. 1998. Effects of temperature on photosynthesis of two morphologically contrasting plant species along an altitudinal gradient in the tropical high Andes. Oecologia 114 145-152. 

When the so-called fossil fuels such as coal and petroleum are used a large amount of carbon dioxide is released, resulting in an increase of carbon dioxide in the atmosphere. As carbon dioxide is a gas with an influence on the greenhouse effect, its increase in the atmosphere results in the raising of the temperature on the surface of Earth. Therefore the increase of carbon dioxide in the atmosphere should be curtailed. It is usually thought that most carbon dioxide in the atmosphere is consumed by plants on the land. Of course this idea is not incorrect the tropical rain forests of the Amazonian area, Kalimantan (Borneo) and some other areas consume much of the carbon dioxide in the atmosphere. However, it should be kept in mind that the consumption of the gas by algae and cyanobacteria in the ocean is also sizable. Some researchers say that 70% of carbon dioxide in the atmosphere is consumed by the photosynthesis of algae and cyanobacteria in the oceans. 

Thiele A, Krause GH and Winter K (1998) In situ study of photoinhibition of photosynthesis and xanthophyll cycle activity in plants growing in natural gaps of the tropical forest. Austr J Plant Physiol 25 189-195... 

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