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

Munir, Rushna, Konnerup, Dennis, Khan, Hammad A., Siddique, Kadambot H.M., Colmer, Timothy D.
Plant, cell and environment 2019 v.42 no.1 pp. 85-97
Cicer arietinum, Vicia faba, carbon dioxide, chickpeas, death, ethylene, faba beans, flooded conditions, hypoxia, oxygen, porosity, rhizosphere, root tips, soil, sugars
During soil waterlogging, plants experience O₂ deficits, elevated ethylene, and high CO₂ in the root‐zone. The effects on chickpea (Cicer arietinum L.) and faba bean (Vicia faba L.) of ethylene (2 μL L⁻¹), CO₂ (2–20% v/v) or deoxygenated stagnant solution were evaluated. Ethylene and high CO₂ reduced root growth of both species, but O₂ deficiency had the most damaging effect and especially so for chickpea. Chickpea suffered root tip death when in deoxygenated stagnant solution. High CO₂ 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 O₂ movement was more prominent in faba bean when in an O₂‐free medium. Ethylene treatment increased the porosity of roots. The damaging effects of low O₂, such as death of root tips, resulted in poor recovery of root growth upon reaeration. In conclusion, ethylene and high CO₂ partially inhibited root extension in both species, but low O₂ in deoxygenated stagnant solution had the most damaging effect, even causing death of root tips in chickpea, which was more sensitive to the low O₂ condition than faba bean.