The Effect of Cold Stress on the Morphologic and Physiologic Characters of Two Rice Varieties in Seedling Stage

The rice crop is cold sensitive plant that under cold stress is more decreasing yield.Therefore, knowing defense mechanism of rice crop and low temperature is necessary.In order to, the effects of cold on some morphological and physiological characters oftwo rice (Oryza sativa L.) varieties (Onda and Domsiah) were studied under controltreatment (day/night 28o/25o) and were treated after two weeks with cold stress(day/night 15o/13o). The results showed that dry weight, length of shoot and rootdecreased in both varieties significantly, but the Domsiah variety was more decreased.The amount of chlorophyll a, b and starch content was decreased under stress in twovarieties. However, the amount of decreasing was about 48, 54 and 38 percentagesrelated to control treatment in leaves of the Domsiah variety, respectively. The contentof proline, MDA, soluble sugars were increased in the Domsiah variety in which theamount of increasing of proline and MDA were 62 and 70 percentages respectivelyFructose content in Onda variety was observed about 74% as to control. Results showedthat Onda variety was tolerant than Domsiah variety and as a results was more toleranceto cold stress.