Submitted to: Plant Physiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: September 26, 1996
Publication Date: N/A
Interpretive Summary: In order to determine the consequences of present and future global environmental changes on the security of world food production, efforts are underway to determine the growth and other physiological responses of major food crops to changing environmental factors. These global changes especially include the increasing concentration of atmospheric carbon dioxide (CO2) which is expected to double sometime during the next century. Climate modelers have predicted that the elevated CO2 will cause the earth to warm and that precipitation patterns will change. Elevated CO2 is also known to alter the growth of plants and may affect their production of antioxidants which protect the plants from ozone pollution and other oxidative stresses. This, the initial paper in a series, presents baseline results for wheat grown in the field at present levels of atmospheric CO2. It shows that antioxidant concentrations undergo large fluctuations during plant development. A subsequent paper will compare these baseline results with those from CO2 enriched conditions. Eventually this research should lead to optimum crop management strategies that will ultimately benefit all food consumers.
Water-soluble antioxidants, glycolate oxidase activity and net photosynthesis were measured, from seedling establishment to physiological maturity, in healthy, expanded, uppermost leaves collected weekly from wheat (Triticum aestivum L. cv. Yecora Rojo) plants growing under near-optimum field conditions. Most of the antioxidants fluctuated in a cyclic, non-regular manner throughout the season, the strongest oscillations being shown by glutathione and by H2O2-scavenging enzymes. Time series analysis revealed significant co-variation among the seasonal profiles of those antioxidants participating in the "ascorbate-glutathione cycle". Their seasonal changes were also synchronized with midday maximal net CO2 assimilation rate and glycolate oxidase activity. This could confirm, over the whole of plant ontogeny and in field-grown plant material, the connections among photosynthetic activity and the plant cell antioxidant network and could suggest that similar mechanisms intervene in the integrated control of active oxygen generated during photorespiration. Peaks of antioxidant levels concentrated during certain periods of the plant growing season. Since no evidence of environmental stress was concurrently observed, it is suggested that a higher antioxidant capacity could be required in order to face endogenous and transient oxidative strain associated with definite plant developmental stages, namely juvenility, floral induction, stem elongation, anthesis, and senescence.