Ethylene treatment modifies leaf ascorbic acid content

GERGOFF GUSTAVO; CHAVES ALICIA; BARTOLI CARLOS GUILLERMO

Ghent, Bélgica

Congreso; Reactive Oxygen and Nitrogen species in plants; 2007

The Society for Free Radical Research

The experiments of this programme of work were designed to study the effect of ethylene on the antioxidant defence in leaves. This hormone is involved in the leaf senescence and in the responses of plants to abiotic stress. The control of antioxidant defences may be important deciding the fate of the cell: cope with abiotic stress or trigger deteriorative processes leading to senescence. In this work the time course of antioxidant and senescence parameters were measured to unravel which one is primarily affected by exogenously added ethylene in detached leaves stored in darkness. Spinach (Spinacia oleracea L) plants were collected from a local producer during winter and brought immediately to the lab. Detached spinach leaves were immersed in a water solution containing 200 ppm ethephon with the addition of 0.1 % dimethyl sulfoxide for 20 min. Control leaves were immersed in a solution without addition of ethephon. Then leaves were carefully dried with a paper towel and stored in polyethylene bags in darkness at 23ºC. Senescence parameters and antioxidants were measured in the following 3 days. Chlorophyll content and solute leakage were determined to follow leaf senescence. Both parameters were not affected until the third day of storage when a drop in chlorophyll content and increase in solute leakage increased. On the other hand, leaf ascorbic acid content decreased between the first and second days after ethylene treatment showing a higher oxidised state comparing with control leaves. Glutathione content was not affected by exogenously addition of this hormone. These results suggest that the changes in ascorbic acid content and oxidised state is an early mechanism involved in leaf senescence syndrome triggered by exogenous ethylene.