O₃ Sensitivity in a Potential C₄ Bioenergy Crop: Sugarcane in California

Abstract

The C4 perennial grasses have many potential virtues as bioenergy crops—high productivity and water use efficiency, multiyear crop cycle that minimizes replanting costs, and wide environmental adaptation. In the productive San Joaquin Valley (SJV) of California, these species also confront high levels of ozone (O3) air pollution. It is often assumed that C4 species will exhibit tolerance to O3, relative to C3 species, based on limited crop yield‐loss data and on responses to a contrasting gaseous air pollutant, sulfur dioxide (SO2). Tolerance to O3 of high‐biomass C4 crops such as sugarcane (Saccharum spp.) has not been demonstrated. Here we tested the hypothesis that a clone of sugarcane currently grown on a small commercial scale in the O3–impacted SJV will exhibit tolerance to O3 The hypothesis was disproven. Biomass production declined by over one‐third and allocation to roots declined by over two‐thirds, over a range of O3 exposures (4, 58, and 114 ppb, 12‐h means). These responses are comparable to responses previously reported for O3–sensitive C3 crop species. Greater O3 tolerance may be required to maximize the potential viability of bioethanol production using tall tropical grasses such as sugarcane (for sucrose) or energy canes (for cellulose) in O3–impacted western valleys. In the case of the locally successful sugarcane clone examined here, the C4 photosynthetic pathway did not confer resistance to O3 exposure.

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

“…At 8 wk after planting, uniform plants with shoots emerging from the soil were transferred to one of nine cylindrical, Teflon‐walled, O 3 exposure chambers (continuously stirred tank reactors [CSTRs]) (Heck et al, 1978; Grantz et al, 2008) in the greenhouse. Plants were exposed to O 3 for 7 wk before measurements.…”

“…These conclusions were supported by later comparisons of wheat and maize (Rudorff et al, 1996) and two pairs of noncrop C 3 and C 4 grasses (Volin et al, 1998). In C 3 cotton ( Gossypium barbadense L.), carbon assimilation was 3.0‐fold more sensitive to O 3 than in C 4 yellow nutsedge ( Cyperus esculentus L.) (Grantz and Shrestha, 2006). A meta‐analysis of reproductive impacts of O 3 (Leisner and Ainsworth, 2011) found that in exposures to O 3 above 70 nmol mol −1 , fruit weight was less sensitive in maize than in C 3 plants, although most reproductive parameters were equally inhibited in C 3 and C 4 plants.…”

Global impacts of surface ozone changes on crop yields and land use

“…With respect to sugar cane, no suitable ERF was found. However, Grantz and Vu (2009) reported that sugar cane exhibits the same sensitivity to ozone as cotton at moderate levels of exposure and as tomato at high levels of exposure. Therefore, we used the ERF of cotton for sugar cane.…”

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).…”