Summary and Conclusions

Cotton crops grown in future environments will be subjected to projected climatic changes for which they were not bred. Our series of studies, using SPAR, OTC and FACE experimental technologies and facilities, provided detailed insight into how cotton will respond to a changing environment. We believe that several important conclusions regarding the effects of elevated [CO2], temperature, water and nutrients on plants can be drawn from our cotton experiments. The direct physiological effects of higher [CO2] on cotton photosynthesis and transpiration will have a myriad of secondary effects. More carbon was fixed in plants grown in high [CO2] at all levels of water and nutrient deficient conditions and across a wide range of temperatures. Plants grown in high [CO2] have greater stomatal resistance. However, increased green leaf area offsets that effect, resulting in virtually no difference in canopy water use. The developmental events of cotton plants such as floral initiation, flowering, boll opening and leaf initiation are relatively insensitive to high [CO2]. Since cotton is very plastic in its growth, additional carbon available in a high [CO2] environment will favour more vegetative and reproductive growth across a wide range of conditions. This will result in more fruit and, if temperature conditions are favourable for fruit retention, higher yields. Developmental processes are very temperature dependent, because increases in temperature due to greenhouse gases or small changes in canopy temperatures due to effects induced by high [CO2] will be reflected in overall crop development. Average temperatures above 30°C caused young bolls to abscise. Doubling [CO2] did not ameliorate the adverse effects of high temperatures on cotton fruit retention. If temperature increases, farmers will likely modify their cultural practices by planting earlier. In that way, plants may escape some of the adverse effects of temperature extremes by completing flowering prior to the onset of injurious high temperatures. Also, one would expect the geographical distribution of individual crops to shift. One would expect the areas of the world that are marginally too cool to become more productive, and areas that are marginally too warm to become less productive. No difference was found in tolerance to high temperatures among the widely grown upland cotton cultivars. However, in the less tolerant Pima cotton species (K.R. Reddy et al., 1992a; Lu et al., 1998), some cultivars were found to escape the effects of high temperature by transpirational cooling. Because young fruits of all cotton cultivars are particularly vulnerable to heat, increasing crop tolerance to high temperatures and short-term heat-shock would be useful to sustain crop productivity in a warmer world. Water and nutrients are scarce resources that will be required in greater quantity to utilize high [CO2] environments fully for cotton production. Resource-rich economies will benefit more from the greater yield potential resulting from increased [CO2] because they can more adequately provide these yield-limiting variables.

Guide to Alternative Fuels

Guide to Alternative Fuels

Your Alternative Fuel Solution for Saving Money, Reducing Oil Dependency, and Helping the Planet. Ethanol is an alternative to gasoline. The use of ethanol has been demonstrated to reduce greenhouse emissions slightly as compared to gasoline. Through this ebook, you are going to learn what you will need to know why choosing an alternative fuel may benefit you and your future.

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