ASSESSMENT OF THE IMPACT OF RISING CARBON-DIOXIDE AND OTHER POTENTIALCLIMATE CHANGES ON VEGETATION

The projected doubling of current levels of atmospheric carbon dioxide concentration ([CO2]) during the next century along with increases in other radiatively active gases have led to predictions of increases i n global air temperature and shifts in precipitation patterns. Additio nally, stratospheric ozone depletion may result in increased ultraviol et-B (UV-B) radiation incident at the Earth's surface in some areas. S ince these changes in the Earth's atmosphere may have profound effects on vegetation, the objectives of this paper are to summarize some of the recent research on plant responses to [CO2], temperature and UV-B radiation. Elevated [CO2] increases photosynthesis and usually results in increased biomass, and seed yield. The magnitude of these increase s and the specific photosynthetic response depends on the plant specie s, and are strongly influenced by other environmental factors includin g temperature, light level, and the availability of water and nutrient s. While elevated [CO2] reduces transpiration and increases photosynth etic water-use efficiency, increasing air temperature can result in gr eater water use, accelerated plant developmental rate, and shortened g rowth duration. Experiments on UV-B radiation exposure have demonstrat ed a wide range of photobiological responses among plants with decreas es in photosynthesis and plant growth among more sensitive species. Al though a few studies have addressed the interactive effects of [CO2] a nd temperature on plants, information on the effects of UV-B radiation at elevated [CO2] is scarce. Since [CO2], temperature and UV-B radiat ion may increase concurrently, more research is needed to determine pl ant responses to the interactive effects of these environmental variab les.