Genotypic variation of the interactive effects of elevated temperature and CO2 on leaf gas exchange and early growth of sugarcane.

Increased atmospheric CO2 and consequent increases in temperature are two prominent features of climate change, a major challenge to crops. Here, our objectives were to determine: (1) the responses of sugarcane during the first 90 days of elevated CO2 (ECO2 ) and elevated temperature (ETem), both individually and together, and (2) the genotypic variation of these responses. Eight varieties were grown both in open-top chambers in a factorial combination of ambient/ECO2 concentrations (344-351/777-779 ppm) and ambient/ETem (34.9-35.6/36.6-38.4°C) and in open fields. Significant treatment × variety interaction effects were observed on leaf net photosynthetic rate (An ), stomatal conductance (gs ), transpiration rate (El ), and instantaneous transpiration efficiency (TE ). In most varieties, ECO2 alone did not affect An, but the combination of ECO2 and ETem decreased An . ECO2 decreased gs and El while increasing TE in all varieties. These effects were amplified when ETem was combined with ECO2 . ETem alone had variable effects on An and gs depending on variety, while it increased El and did not affect TE in a majority of varieties. Germination, tillering and stem diameter were not affected by treatments and did not show varietal variation. Leaf water potential, chlorophyll (spad), leaf area, and aboveground dry weight per plant showed varietal variations but were not affected by treatments. The variable responses to ETem and the significant genotypic variation to ECO2 and elevated temperature (ETem) observed in this work, both individually and together, demonstrate a considerable scope to breed sugarcane varieties for a future high-CO2 and warmer climate.

Effects of elevated carbon dioxide on stomatal characteristics and carbon isotope ratio of Arabidopsis thaliana ecotypes originating from an altitudinal gradient.

Stomatal functioning regulates the fluxes of CO2 and water vapor between vegetation and atmosphere and thereby influences plant adaptation to their habitats. Stomatal traits are controlled by external environmental and internal cellular signaling. The objective of this study was to quantify the effects of CO2 enrichment (CE) on stomatal density (SD)-related properties, guard cell length (GCL) and carbon isotope ratio (δ13 C) of a range of Arabidopsis thaliana ecotypes originating from a wide altitudinal range [50-1260 m above sea level (asl)], and grown at 400 and 800 ppm [CO2 ], and thereby elucidate the possible adaptation and acclimation responses controlling stomatal traits and water use efficiency (WUE). There was a highly significant variation among ecotypes in the magnitude and direction of response of stomatal traits namely, SD and stomatal index (SI) and GCL, and δ13 C to CE, which represented a short-term acclimation response. A majority of ecotypes showed increased SD and SI with CE with the response not depending on the altitude of origin. Significant ecotypic variation was shown in all stomatal traits and δ13 C at each [CO2 ]. At 400 ppm, means of SD, SI and GCL for broad altitudinal ranges, i.e. low (<100 m), mid (100-400 m) and high (>400 m), increased with increasing altitude, which represented an adaptation response to decreased availability of CO2 with altitude. δ13 C was negatively correlated to SD and SI at 800 ppm but not at 400 ppm. Our results highlight the diversity in the response of key stomatal characters to CE and altitude within the germplasm of A. thaliana and the need to consider this diversity when using A. thaliana as a model plant.