Light interception efficiency

The acquisition of carbon is strongly modulated by the surface area of photosynthesizing leaves hence, understanding leaf area development is germane to efforts to increase yield. In many crops, biomass is linearly related to the amount of light intercepted (Monteith, 1977). This is certainly the case for Jerusalem artichoke, where total productivity is strongly correlated with the amount of solar radiation intercepted (Denoroy, 1996 Meijer et al., 1993). Leaf area, leaf duration, and photosynthetic efficiency of the crop canopy determine how much light is intercepted and subsequently utilized (Table 10.9). 

Light use efficiency (the efficiency of light energy conversion) is usually expressed in models as the slope of regression of the gross amount of dry matter produced upon the cumulative amount of intercepted light. Light use efficiency depends on canopy architecture, the chemical nature of dry matter produced, and other factors. 

In addition to light interception, the acquisition of minerals (e.g., nitrogen, phosphorous, and sulfur) from the environment is vital for photosynthetic processes to proceed efficiently. Chemical composition is one component of dynamic simulation modeling (Denoroy, 1996). 

For particles much larger than the wavelength of the incident light (x 1), the scattering efficiency approaches 2. That is, a targe particle removes from the beam twice the amount of light intercepted by its geometric cross-sectional area. What is the explanation for this paradox ... 

A number of models have been constructed to better understand the development physiology of Jerusalem artichoke. These models quantify the amount of solar radiation intercepted, the efficiency with which light is converted into dry matter, and the distribution of dry matter around the plant over time. Assimilated dry matter is used for structural growth or as storage reserves in different plant parts. 

Upon irradiation, redox dye photosensitizers adsorbed on the surface of wide-bandgap metal oxide semiconductors readily inject an electron in the conduction band of the solid. While charge injection has been found for numerous efficient systems to occur in the femtosecond time frame, the electron back transfer takes place much more slowly, typically in the microsecond-millisecond domain. This charge recombination process can be intercepted by reaction of a reducing mediator M with the oxidized dye (Eq. (43)). The overall efficiency of the light-induced charge separation then depends upon the kinetic competition between back electron transfer and dye regeneration processes. 

The intensity distribution within the diffraction pattern depends on the shape of the perimeter and size of the particle relative to the wavelength of the light. It is independent of the composition, refractive index, or reflective nature of the surface. The total amount of energy that appears in the diffraction pattern is equal to the energy in the beam intercepted by the geometric cross section of the particle. Hence the total efficiency factor based on the cross-sectional area is equal to 2. 

Fig. 2. The "efficiency" of conversion of intercepted light into dry matter (E. ), calculated from the moving average of dry weight over three adjacent harvests of the Z. mays crop. The mean quantum yield for leaves within the same crop is also indicated.

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