Effect of elevated [CO2] on cell structure and function in seed plants

Abstract

Unprecedented increase in atmospheric carbon dioxide concentration [CO2] is regarded as one of the key factors responsible for global climate change. Evidence from palaeo-records indicates a close relationship between variation in atmospheric [CO2] and corresponding structural adaptations in plants. Exposure to elevated [CO2] alters plant structure by inducing changes in rate of cell division, cell expansion and cell cycling. Alterations in plant structure under elevated [CO2] at organ level is possibly a result of metabolic changes induced at cellular level. Chloroplast, the light-harvesting organelle, has been shown to be most seriously affected by high [CO2]. Prolonged exposure to elevated [CO2] induces accumulation of starch grains within chloroplasts leading to distortion of thylakoids. Higher rate of photosynthesis in plants grown at high [CO2] is accompanied by increased number of mitochondria to meet high cellular energy demand. These ultrastructural observations are corroborated by studies on nuclear genome that have revealed up as well as down-regulation of several genes involved in photosynthetic and respiratory pathways. In some species, exposure to elevated [CO2] results in accumulation of tannin-like vacuolar deposition, suggesting activation of phenylpropanoid pathway. Ultrastructural alterations in peroxisomes, endoplasmic reticulum, Golgi apparatus and cytoskeleton due to CO2 enrichment have received less attention. It is imperative to understand cellular changes occurring with elevated [CO2]so as to correlate these with the physiological alterations at plant level. A thorough insight into ultrastructural changes in response to increased carbon dioxide will provide a better, generalized understanding of plant response to rising atmospheric [CO2] in future. Disruption of cell organelle structure and function may also indicate a wider impact of climate change across plant (and animal) groups.