Young sugarcane plants exhibit higher photosynthetic tolerance to acute ozone exposure than energy cane
摘要
We evaluated the impact of acute ozone (O3) on photosynthesis of energy cane and sugarcane, hypothesizing that energy cane –known for its resilience to environmental disturbances– would exhibit higher tolerance to O3 than sugarcane. Under growth chamber conditions, plants were exposed to three O3 concentrations (0, 150, and 300 ppb) for three consecutive days. Leaf CO2 assimilation declined in both crops after one day of exposure at 150 and 300 ppb O3. While sugarcane maintained similar performance at both 150 and 300 ppb O3, energy cane showed the lowest photosynthetic rates at 300 ppb O3. Such higher sensitivity of energy cane was driven by reduced photochemical efficiency (ΦPSII) at 150 ppb O3 and by low stomatal conductance and ΦPSII at 300 ppb O3. Notably, sugarcane showed significant stomatal closure after three days of exposure to 150 ppb O3, preventing further O3 influx and maintaining CO2 assimilation. However, this protective mechanism was not effective under 300 ppb O3. PEPCase and Rubisco carboxylation rates decreased in both crops after three days under O3 exposure. The rates of decline in leaf CO2 assimilation due to increasing air O3 concentration were higher in sugarcane and in energy cane, i.e., 0.2 and 0.3 mmol m⁻2 s⁻1 per 10-ppb O3 increase, respectively. Contrary to our initial hypothesis, energy cane was more sensitive to acute O3 exposure. Sugarcane exhibited greater short-term photosynthetic tolerance to O3 linked to stomatal regulation and photochemical stability.