Induction of antioxidant system in plant and calli of rice by oxidant stress

• Main Authors: Jeang, Shwu-Jiuan, 蔣淑娟
• Other Authors: Jenq-Horng Lin
• Format: Others
• Language: zh-TW
• Published: 1996
• Online Access: http://ndltd.ncl.edu.tw/handle/67949082712111334796

碩士 === 國立中興大學 === 植物學系 === 84 === The effects of high O2 on photosynthesis and antioxidant enzymes wereinvestigated in rice (Oryza sativa L.). Different potted rice varieties(KK30, TN67, NJBN, TC65, TN1, and Mars) were short-term treated withdifferent concentrations of oxygen. Rates of photosysthesis decreasedwith the increasing of oxygen concentrations in all rice varietiestested, but the degrees of inhi-bition were different. These six ricevarieties were classified into two groups according to their sensitivityof photosynthesis to high oxygen : the sensitive group (KK30, NJBN, TC65)and the less-sensitive group ( TN67, TN1, Mars). Long-term treatmentswith mixed air ( 20% O2 plus 350 ppm CO2, 40% O2 plus 700 ppm CO2, or60% O2 plus 1050 ppm CO2 ) the degrees of O2 in- hibition were differentthan those of short-term O2 treatments with highest O2 inhibitionoccurred at 60% O2 treatment in Mars variety. The degree of lipidperoxidation of membrane was also the highest in Mars among 4 ricevarieties tested. Damaged membrane structure caused by active oxygenattack would be the major contribution to the decreased rate ofphotosynthesis under high O2 stress. Activities of SOD, one of the antioxidant enzymes, were increasedafter high oxygen treatments in Mars, while treatments with TN67,NJBN, and TN1 showed no affect on SOD activities. The activitiesof GR and APX were significantly increased in the TN67 and NJBN,while the TN1 and Mars were not. Although SOD was the first committedenzyme in the antioxidant systems, accumulation of H2O2 , the productof SOD, would cause oxidative damages to the living tissues. To evaluate the effects of oxidizing reagents, different con-centrations of H2O2 and MV were applied to the suspension culturesof two rice varieties, TN67 and NJBN. Growth inhibition of culturedcell was found in both H2O2 and MV treatments . The growth of NJBNestimated by packed cell volume was signifi-cantly reduced by 5 mMH2O2. The growth of TN67 was corre-lated with the increase of APXactivity, but not with the SOD activity. The results showed thatconstitutive level of SOD in mature leaves of rice is high enoughto scavenge the superoxide evolved from high oxygen treatments.The efficient H2O2 scavenging system under oxidative stressesvia ascorbate-glutathione cycle may play a major role in theantioxidant system.