Sugarcane responses to elevated ozone

Ozone (O
3
) is a toxic oxidative air pollutant with significant detrimental effects on crops. This study aimed to assess 03 risk to sugarcane plants and understand the physiological responses and the mechanisms involved in O
3
detoxification to verify whether such mechanisms are genotype-dependent. Two sugarcane genotypes (IACSP94-2094 and IACSP95-5000) were subjected to a 90-day Free-Air Controlled Experiment (FACE) exposure at three levels of O
3
concentrations. Ozone exposure caused a negative impact on sugarcane growth, and its sensitivity may be related to its high gsto (~535 mmol H
2
O m
⁻²
s
⁻¹
), The flux-based index (PODy) performed well in estimating the O
3
effect on biomass losses. We recommend a y threshold of 2 nmol m
⁻²
s
⁻¹
to incorporate O
3
effects on sugarcane and, in order not to exceed 4% reduction in the above-ground biomass, we recommend the critical levels of 1.09 and 1.04 mmol m-
²
POD2 of IACSP95-5000 and IACSP94-2094, respectively. Photosynthesis of IACSP95-5000 was more sensitive to elevated O
3
as compared to IACSP942094. However, sugarcane plants have an effective antioxidant system to avoid O
3
-induced damage, in both genotypes, increases in ascorbate peroxidase activity was directly related to decreases in leaf H
2
O
2
concentration. In IACSP94-2094, nevertheless, catalase pathway was also stimulated for detoxifying H
2
O
2
. We concluded that sugarcane sensitivity to 03 is genotype-dependent and biomass loss due to 03 would correspond to thousand tons of lost yield per year worldwide.