The Interactive Effect of CO2, Temperature, and Water on Growth and Flowering of Petunia ×hybrida

Changes in climate, such as increases in CO₂, temperature, and variable precipitation have been observed and are expected to have a substantial impact on agriculture including the horticultural industry. Climate change could present a serious challenge to U.S. agriculture because of the sensitivity of agricul­tural systems to climate. Light, CO₂, temperature, nutrients, and water availability are important abiotic factors for plant growth and development. Among those factors increasing temperature due to the elevated atmospheric CO₂ concentration and the availability of water may have a direct impact on growth and flowering under the predicted future climate. The objectives of this research were to investigate the interactive effects of CO₂, temperature, and water availability on the growth and flowering of petunia (Petunia ×hybrida), and to examine the expression pattern of major genes involved in plant growth and flowering pathways. Petunias were exposed to two levels of CO₂ (400 and 800 µmol·m^-2·s^-1), two levels of temperature (21/18 and 28/25 °C), and two water regimes (0.12 and 0.43 m³·m^-3). To quantify the impact of three abiotic factors, growth index, gas exchange, time to anthesis, flower size, flower longevity and the number of flowers were measured. For the gene expression study, major genes in photosynthesis, respiration, hormone biosynthetic pathways, autonomous and photoperiod flowering pathways were selected and their expression patterns were determined using semi qRT-PCR. Preliminary results showed flowering was inhibited under elevated temperature with ambient CO₂, but recovered when elevated temperature was paired with elevated CO₂. At the completion of this project, we will have a fundamental understanding of the interactive effects of CO₂, temperature, and water availability on plant growth and development.