Sensitivity of Wheat and Rice to Low Levels of Atmospheric Ethylene

Ethylene (C 2 H 4 ) gas is produced throughout the life cycle of plants and can accumulate in closed growth chambers to levels 100 times higher than in outside environments. Elevated atmospheric C 2 H 4 can cause a variety of abnormal responses, but the sensitivity to elevated C 2 H 4 is not well characterized. We evaluated the C 2 H 4 sensitivity of wheat ( Triticum aestivum L.) and rice ( Oryza sativa L.) in five studies. The first three studies compared the effects of continuous C 2 H 4 levels ranging from 0 to 1000 nmol mol −1 (ppb) in a growth chamber throughout the life cycle of the plants. A short‐term 1000 nmol mol −1 treatment was included in which exposure was stopped at anthesis. Yield was reduced by 36% in wheat and 63% in rice at 50 nmol mol −1 and both species were virtually sterile when continuously exposed to 1000 nmol mol −1 However, the yield reductions were much less with exposure that stopped at anthesis, suggesting the detrimental effect of C 2 H 4 on yield was greatest around the time of seed set. Two additional studies evaluated the differential sensitivity of two wheat cultivars (Super Dwarf and USU‐Apogee) to 50 nmol mol −1 C 2 H 4 at three CO 2 levels [350, 1200, 5000 μmol mol −1 (ppm)] in a greenhouse. Yield of USU‐Apogee was not significantly reduced by C 2 H 4 but the yield of Super Dwarf was reduced by 60%. Elevated CO 2 did not influence the sensitivity to C 2 H 4 A difference in the C 2 H 4 sensitivity of USU‐Apogee between greenhouse and growth chamber trials suggests that C 2 H 4 sensitivity is dependent on the environment. Collectively, the data suggest that relatively low levels of C 2 H 4 could induce anomalous plant responses by accumulation in greenhouses and growth chambers with inadequate ventilation. The data also suggest that C 2 H 4 sensitivity can be reduced by both genetic and environmental manipulations.