Sensitivity of chickpea and faba bean to root‐zone hypoxia, elevated ethylene, and carbon dioxide

During soil waterlogging, plants experience O 2 deficits, elevated ethylene, and high CO 2 in the root‐zone. The effects on chickpea ( Cicer arietinum L.) and faba bean ( Vicia faba L.) of ethylene (2 μL L −1 ), CO 2 (2–20% v/v) or deoxygenated stagnant solution were evaluated. Ethylene and high CO 2 reduced root growth of both species, but O 2 deficiency had the most damaging effect and especially so for chickpea. Chickpea suffered root tip death when in deoxygenated stagnant solution. High CO 2 inhibited root respiration and reduced growth, whereas sugars accumulated in root tips, of both species. Gas‐filled porosity of the basal portion of the primary root of faba bean (23%, v/v) was greater than for chickpea (10%), and internal O 2 movement was more prominent in faba bean when in an O 2 ‐free medium. Ethylene treatment increased the porosity of roots. The damaging effects of low O 2 , such as death of root tips, resulted in poor recovery of root growth upon reaeration. In conclusion, ethylene and high CO 2 partially inhibited root extension in both species, but low O 2 in deoxygenated stagnant solution had the most damaging effect, even causing death of root tips in chickpea, which was more sensitive to the low O 2 condition than faba bean.