Photosynthesis nutrients assimilation

During photosynthesis nutrients, including nitrogen, are assimilated into organic matter and molecular oxygen is produced, depicted schematically by... 

The possible effects of increased atmospheric CO2 on photosynthesis are reviewed by Goud-riaan and Ajtay (1979) and Rosenberg (1981). Increasing CO2 in a controlled environment (i.e., greenhouse) increases the assimilation rate of some plants, however, the anthropogenic fertilization of the atmosphere with CO2 is probably unable to induce much of this effect since most plants in natural ecosystems are growth limited by other environmental factors, notably light, temperature, water, and nutrients. 

Photosynthesis is the process that provides energy to all anabolic and catabolic processes in ecosystems. The rate at which plants assimilate CO2 in the field may be quite different from optimal conditions in the test tube or in growth cabinets. The rate depends on the environmental conditions of the habitat which determine to what extent the genetic capability of a plant can actually be used for photosynthesis. The main factor restricting photosynthesis in the field is the availability of light. But, other factors my become just as rate 1imitating, such as atmospheric carbon dioxide concentration, air humidity and temperature, and water or nutrient supply from the soil. Time is an additional important factor which influences the carbon balance via plant age but also by deterimining the dose of stress. 

Atmospheric CO2 dififiises through leaf stomata and is assimilated, in the presence of sunlight, phosphate, nitrate, and other nutrients, into organic compounds via photosynthesis. The photosynthetic reaction can be summarized as follows ... 

Any change in enviromnental conditions such as light, temperature, water and nutrient availability may modulate the photochemical reactions of photosynthesis to a different extent than the biochemical reactions involved in carbon reduction cycle, photorespiration, and nitrogen and sulphur assimilation. Consequently, these environmental changes will modulate excitation pressure. Excitation pressure reflects an imbalance between energy absorbed through photochemistry and energy utilized... 

Hawksworth and Rose, 1970). Ahmadjian (1966) summarized the sparse early work which indicated that due to seasonal low rates of photosynthesis, the organic nutrient requirements of the thallus are quite unable to be met by the phycobiont, and suggested that the deficiency had to be met by direct absorption from the substratum or from liquids in contact with the thallus surface. While this may well be true in many instances, recent work by Lange, Schulze, and Koch (1970) has shown that Ramalina maciformis can achieve a net annual gain in assimilated carbon sufficient for a thallus growth of 5-10%. 

Nitrogen (N) is the major limiting nutrient for most plant species (Heichel, 1987). Acquisition and assimilation of nitrogen is second in importance only to photosynthesis for plant growth and development. Production of high-quality, protein-rich foods in amounts to feed an increasing world population is depen-... 

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