Sensitivity of Gas Exchange Parameters to Ozone in Diverse C₄ Sugarcane Hybrids

Abstract

In early studies, C^ species exhibited greater tolerance to O3 than C3 species. But a CŜ accharum spp. hybrid (sugarcane, cv. Elephant Cane) exhibited high sensitivity to O3. To investigate whether Saccharum is uniquely sensitive to O3 we exposed a morphologically diverse set of congeners to a range of O3. Here we test the null hypothesis that these diverse genotypes do not differ In baseline responses of carbon assimilation to intercellular CO^ or in the sensitivity of these responses to elevated O3 (4, 58, and 114 nmol moh\ 12 h means). Elephant Cane was most sensitive but all exhibited declines in net carbon assimilation (A^) and in capacities of phosphoenolpyruvate carboxylase (PEPCase) and rubisco. Phosphoenolpyruvate carboxylase was more sensitive than rubisco. The clones were distinguished by morphological traits and by estimated fraction of Saccharum spontaneum L. in their lineages. Baseline values of photosynthetic parameters were not consistently related to pedigree while morphology and sensitivity to O3 exhibited strong relationships. These results are not consistent with a generalized resistance of Cp lants to O3. This single C^ genus exhibited a wide range of sensitivities. The results suggest that sufficient variation may exist among Saccharum genotypes to allow selection for resistance to O3 and that introgression of S. spontaneum germplasm may confer resistance to O3 along with resistance to other abiotic stresses. Reduced sensitivity to O3 in dedicated biofuel feedstocks may facilitate development of production systems in novel production areas.

Elevated Ozone Concentration Reduces Photosynthetic Carbon Gain but Does Not Alter Leaf Structural Traits, Nutrient Composition or Biomass in Switchgrass

“…Here, we studied the effects of elevated O 3 on leaf photosynthetic and structural traits using a promising C 4 bioenergy crop, switchgrass, which was grown under season-long elevated O 3 in the field with FACE technology. We found that elevated O 3 significantly reduced midday A and g s (Figure 2), consistent with past observations in maize [50,51,52,53,54] and sugarcane [56,57]. Additionally, maximum photosynthetic capacity ( V max ) was lower in elevated O 3 (Figure 3), also consistent with previous observations in maize [53].…”

“…It is well established that elevated O 3 negatively impacts plant growth, development and production in C 3 species, but fewer studies have been conducted to understand the overall effects of elevated O 3 on C 4 species. Previous studies have shown that elevated O 3 significantly reduce photosynthesis and biomass in maize ( Zea mays L.) [50,51,52,53,54] and sugarcane [55,56,57]. In particular, O 3 caused yield loss are greater in dry and hot conditions than that in wet and optimal temperature conditions, implying that the yield response of O 3 can be modulated by precipitation in future climate [31,53].…”

Ozone vegetation damage effects on gross primary productivity in the United States

“…S1 in the Supplement). The YIBs simulated O 3 vegetation damage effects for C4 plants are in good agreement with field measurements from Taylor et al (2002) and Grantz et al (2012). In the case of C3 grass and C3 crop, the model simulates consistent GPP reduction percentages with observations from Feng et al (2008) for wheat, Foot et al (1996) for colluna vulgaris, and Mulchi et al (1992) for soybean.…”

“…The simulation overestimates the O 3 level by ∼ 4 ppbv (12 %) in the east and ∼ 1 ppbv (3 %) in the west. The CASTNET sites are located in rural sites, which usually have lower [O 3 ] than that in urban areas, except for some megacities where the excessive NO x emissions result in lower O 3 level (Gregg et al, 2003). .…”

Perchlorate content of plant foliage reflects a wide range of species-dependent accumulation but not ozone-induced biosynthesis

“…4662, Pioneer Seed Co., Johnston IA), sugarcane (Saccharum oficinarum  S. spontaneum hybrid cv. Elephant; Grantz and Vu, 2009;Grantz et al, 2012), and maize (Zea mays cv. Golden Cross Bantam (hybrid); Ferry Morse Seed Co., Fulton KY).…”