Flooding-induced soil and plant ethylene accumulation and water status response of field-grown tobacco

Abstract

Ethylene (C2H4) accumulation in flooded soil was related to oxygen (O2), redox potential (Eh), and flooding rate. The water status response of tobacco (Nicotiana, tabacum L.) to these conditions was evaluated from stem diameter, relative water content, leaf water potential, and C2H4 content of leaf tissue. Treatments were: flooded with either 0,5, or 15 cm of water per day for 6 days. By the third day, O2 in the soil decreased to less than 9% in treatments flooded with 5 or 15 cm of water. When O2 in the soil air was less than 9% and redox potential (Eh) was less than +150 mv, most of the soil air samples contained some C2H4 and 16% contained more than 6 ppm. Very little C2H4 was present in soil air when O2 exceeded 9%. Tobacco leaf C2H4 peaked 3 days after flooding and then declined to the preflooding level a day later, one day ahead of the rapid increase in soil C2H4. Wilting developed progressively beginning with the rise of C2H4 in the soil; leaf water potential, stem diameter, and relative leaf water content all were decreased. Soil-and plant-produced C2H4 are suggested as factors in reducing root permeability and increasing resistance to water uptake by tobacco.