Photosynthesis control

Kuzyakov Y, Cheng W (2001) Photosynthesis controls of rhizosphere respiration and organic matter decomposition. Soil Biol Biochem 33 1915-1925 Kuzyakov Y, Domanski G (2000) Carbon inputs by plants into the soil. Rev J Plant Nutr Soil Sci 163 421—431... 

FIGURE 20-28 Regulation of ADP-glucose phosphorylase by 3-phosphoglycerate and Pj. This enzyme, which produces the precursor for starch synthesis, is rate-limiting in starch production. The enzyme is stimulated allosterically by 3-phosphoglycerate (3-PGA) and inhibited by P, in effect, the ratio [3-PGA]/[Pi], which rises with increasing rates of photosynthesis, controls starch synthesis at this step. 

Isoproturon or 3-(4-isopropylphenyl)-1,1-dimethylurea Phenylurea Inhibits photosynthesis Control of annual weeds in winter wheat and barley, rye 11-10... 

Atrazine or 6-chloro-N-ethyl-N -(l-methyethyl)-l,3,5-triazine-2,4-diamine s-Triazine Inhibits photosynthesis Control of annual weeds in maize, sugar cane, pineapples, nuts, and noncrop areas 11-11... 

Light Control of Photosynthesis Control of Ribulose-1.5-Bisphosphate Carboxylase... 

Considering the discussions related to photosynthesis control, it becomes obvious that the metabolic control systems of plants are extraordinarily sophisticated. Despite considerable research efforts, many aspects of controlling function in plants remain to be elucidated. This endeavor is clearly important, because greater insight into photosynthetic production is critical for improving crop yields and developing plant resources in the future. 

Pfannschmidt T. Chloroplast redox signals how photosynthesis controls its own genes. Trends Plant Sci. 2003 8 33-41. 

CgH,3BrN202. A soil-acting herbicide. White crystalline solid, m.p. 158-159" C. It is a non-selective inhibitor of photosynthesis used for weed control In citrus and cane fruit plantations. It is relatively non-toxic to animal life. 

WW Parson, Z-T Chu, A Warshel. Electrostatic control of charge separation in bacterial photosynthesis. Biochim Biophys Acta 1017 251-272, 1990. 

Physiological or biochemical changes have been observed in plants exposed to air pollutants, including alterations in net photosynthesis, stomate response, and metabolic activity. Such exposure studies have been conducted under controlled laboratory conditions. An understanding of the processes involved will help to identify the cause of reduction in yield. 

Rainwater and snowmelt water are primary factors determining the very nature of the terrestrial carbon cycle, with photosynthesis acting as the primary exchange mechanism from the atmosphere. Bicarbonate is the most prevalent ion in natural surface waters (rivers and lakes), which are extremely important in the carbon cycle, accoxmting for 90% of the carbon flux between the land surface and oceans (Holmen, Chapter 11). In addition, bicarbonate is a major component of soil water and a contributor to its natural acid-base balance. The carbonate equilibrium controls the pH of most natural waters, and high concentrations of bicarbonate provide a pH buffer in many systems. Other acid-base reactions (discussed in Chapter 16), particularly in the atmosphere, also influence pH (in both natural and polluted systems) but are generally less important than the carbonate system on a global basis. 

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. 

Osmond, C.B., Smith, S.D., Ben, G.-Y. Sharkey, T.D. (1987). Stem photosynthesis in a desert ephemeral, Eriogonum inflatum characterization of leaf and stem CO2 fixation and HjO vapour exchange under controlled conditions. Oecologia, 72, 542-49. 

Ureides (e.g., diuron, linuron) and triazines (e.g., atrazine, simazine, ametryne) all act as inhibitors of photosynthesis and are applied to soil (see Figure 14.1 for structures). They are toxic to seedling weeds, which they can absorb from the soil. Some of them (e.g., simazine) have very low water solubility and, consequently, are persistent and relatively immobile in soil (see Chapter 4, Section 4.3, which also mentions the question of depth selection when these soil-acting herbicides are used for selective weed control). 

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