PARENT SESSION
Posters P1B Photo-oxidative stress, photoinhibition. Abstracts (394-443)

Exogenous salicylic acid application decreases the effects of chilling injury in rice plants. Hongxu Ren^*,1, Kenji Kurata¹, ¹ Department of Biological and Environmental Engineering, Tokyo, Japan

ABSTRACT- Previous studies have shown that salicylic acid (SA) is an essential component of the plant resistance to pathogens. During recent years, SA has received wide attention because of its role in modulating the plant response to several abiotic stresses, such as chilling, heat, drought, salt and ultraviolet radiation. To further define the role of SA in inducing chilling tolerance of plants, in the present study, we compared the effects of exogenous SA on inducing chilling tolerance in two rice cultivars differing in sensitivity to chilling. The results showed that exposing seedling roots to aqueous solutions of 0.5 mM salicylic acid for 24 h before chilling at 8 °C for 7 days increased chilling tolerance in roots of both rice cultivars, but not in their leaves. This observation was confirmed by triphenyl tetrazolium chloride (TTC) reduction tests and lipid peroxidation estimations. After a 7 d chilling period, both TTC reduction value and lipid peroxidation were greatly reduced in rice roots pretreated with SA compared to the control roots, but no such reductions were observed in leaves of both rice cultivars. A comparison of activity among five antioxidant enzymes [superoxide dismutase (SOD; EC 1.15.1.1), guaiacol peroxidase (GPX; EC 1.11.1.7), catalase (CAT; EC 1.11.1.6), ascorbate peroxidase (APX; EC 1.11.1.11) and glutathione reductase (GR; EC 1.6.4.2)] showed that GR activity remained higher, whereas the activities of other enzymes did not change so much in the roots of SA-treated seedlings compared with the untreated control seedlings during 7 days of chilling treatment. These results suggested that the chilling tolerance induced by SA in roots of rice plants was associated with an increase in the activity of glutathione reductase (GR).

KEY WORDS: rice, salicylic acid, chilling, antioxidant enzyme