The direct effects of elevated [CO2] on photosynthesis and stomatal conductance lead to changes in crop growth, carbon allocation, biomass accumulation and ultimately seed yield. It is well established that stimulation of seed yield by elevated [CO2] is lower in magnitude than stimulation of photosynthesis and above-ground biomass, suggesting that feedbacks constrain the potential benefits of elevated [CO2] (Long et al. 2004). For example, in soybean, night-time foliar respiration is stimulated by elevated [CO2] (Leakey et al. 2009c), which reduces plant carbon balance, but may be necessary to produce energy for export of additional carbohydrate from leaves to reproductive sinks. In addition, there may be bottlenecks that limit transport of fixed carbon into economic yield that should be targets for further study (Ainsworth et al. 2008c). The following sections describe what we know about the magnitude of crop seed yield responses to elevated [CO2], the mechanisms for those changes, and how yield quality is altered by elevated [CO2].
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Renewable energy is energy that is generated from sunlight, rain, tides, geothermal heat and wind. These sources are naturally and constantly replenished, which is why they are deemed as renewable. The usage of renewable energy sources is very important when considering the sustainability of the existing energy usage of the world. While there is currently an abundance of non-renewable energy sources, such as nuclear fuels, these energy sources are depleting. In addition to being a non-renewable supply, the non-renewable energy sources release emissions into the air, which has an adverse effect on the environment.