Submitted to: Crop Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/2/2005
Publication Date: 9/23/2005
Citation: Mahan, J.R., Mauget, S.A. 2005. Antioxidant metabolism in cotton seedlings exposed to temperature stress in the field. Crop Science. 45:2337-2345. Interpretive Summary: During periods of temperature stress plants produce harmful chemicals that can negatively affect their subsequent growth and development. Some of these chemicals, oxidants, can damage cells through a process called oxidation. Plants have a variety of mechanisms that help reduce damage caused by oxidation and thus improve the plant's ability to thrive in unfavorable environments. It has been previously proposed that these antioxidant systems of plants are not always effective and as a consequence plants are damaged by oxidants. Efforts to analyze limitations in antioxidant systems have not clearly defined the limitations in antioxidant systems under agricultural conditions. In order to determine the best approaches to enhancing antioxidant metabolism in plants grown under agricultural conditions it is necessary to know when and to what extent antioxidant systems may be limiting. In this study we have monitored the status of the antioxidant system in cotton seedlings in the field in an effort to observe and define limitations due to unfavorable temperatures. Cotton seedlings experienced temperatures that were above and below optimal. Leaves were sampled at various times and indicators of oxidative metabolism were measured. While the indicators of oxidative stress varied over the sampling period, the changes were not related to the occurrence of low or high temperatures. These findings suggest that cotton seedlings were not experiencing temperature-related oxidative stresses that were severe enough to induce changes in antioxidant metabolism. These findings suggest that improvement in plant stress resistance by altering antioxidant metabolism may not be as straightforward as desired.
Technical Abstract: Early season temperature stress adversely affects the growth and development of cotton seedlings. Oxidative damage resulting from temperature extremes is thought to be a cause of diminished seedling performance. Cotton was planted in Lubbock, TX in 2003 and 2004 to investigate the effect of low and high temperatures on oxidative stress and antioxidant metabolism in seedlings exposed to normal thermal variation. Early and late plantings in 2003 provided seedlings of different ages for comparisons. Malondialdehyde was slightly increased in response to low temperatures indicating some oxidative damage in the seedlings. The activities of ascorbate peroxidase and glutathione reductase were not altered in response to low or high temperatures. The glutathione pool was predominately reduced in all plantings in both years indicating sufficient reduced glutathione. It is concluded that the indicators of antioxidant metabolism varied in the seedlings but not in response to temperature variation. It is proposed that antioxidant metabolism in the seedlings was sufficient to mitigate oxidative damage with only minor alterations.