EFFECTS OF HEAT STRESS ON SOME BIOCHEMICAL TRAITS OF SMALL REDDISH BEAN

The effects of heat stress on malondialdehid (MDA) content, ascorbic acid (AsA), isoperoxidases, total soluble protein (TSP) and SDS-PAGE protein profiles of small reddish bean (Phaseolus vulgaris L. cv. Keklik) leaves were investigated. For this purpose, the collected leaf samples (preferably the third from the apex) were placed into pyrex tubes with caps closed and incubated in a water bath: after a 30-minutes habituation at 30ºC, to apply heat stress the leaves were subjected to 35, 40, 45, 50, 55 and 60°C with gradual increments every 30-minutes. According to the results, the MDA content increased with escalating temperatures, starting with 40°C. Although there was fluctuation, the AsA content generally decreased with high temperatures. Besides, TSP content decreased after 50°C. Moreover, three asidic and four basic isoperoxidase bands were identified. There was a marked difference at acidic isoperoxidase band intensities under 40 and 45°C heat treatment. Protein bands with molecu1ar weight of approximately 14.5-195 kDa were determined. In conclusion, especially 40°C is critical for small reddish bean plants, besides 40°C and above temperatures causes oxidative stress in small reddish bean plant. Additionally, isoperoxidases and proteins may be an effective mean on heat stress tolerance.