Combined Effects of Elevated Carbon Dioxide and K and Mg Deficiencies on Wheat Plants

AbstractWe are facing climate change that is affecting world ecosystem substantially and we need to investigate its effects for the sake of protection and mitigation. According to different IPCC scenarios based on possible emission levels, atmospheric [CO2] which is currently around 400μmol mol-1 will rise to 421-936μmol mol-1 by the end of this century unless a strict greenhouse gas mitigation strategy is put forward on global scale (IPCC, 2013). While there are numerous studies on the effects of climate change and rising [CO2] to the plants, it is still not clear how exactly plants respond to this change. The plant-environment interaction consisting very complex facts is the main reason of this challenge. One of the most crucial parts of this is to understand the combined effects of nutrient availabilities and elevated CO2 levels.Durum wheat (Triticum durum, Saricanak 98) and bread wheat (Triticum aestivum, Adana 99) plants were grown with adequate Mg-K and low Mg (75 and 150μM) and low K (10 and 30μM) supply in nutrient solution and under three different CO2 conditions (ambient: 400μmol mol-1, elevated: 600 and 900μmol mol-1). When plants were twenty days old gas exchange parameters (using LI-6400 XT, LI-COR Biosciences, Inc. Lincoln, Nebraska, USA), chlorophyll content (using chlorophyll meter SPAD-502, Konica Minolta Sensing Europe B.V.) and specific weight were measured in the second oldest leaves.While shoot and root dry weight was increasing with elevating [CO2] in adequate Mg and K plants, there was a decrement or a very slight increment in Mg and K deficiency treated plants. Photosynthesis rate (μmol CO2 m-2 s-1) increased 18% and 19.6% in Sarıçanak 98 and 15.7% and %15.3 in Adana 99 plants with 600 and 900ppm CO2 treatments respectively in the adequate Mg and K treatments, whereas although there was some increment in Mg and K deficient plants with [CO2] elevation it was not important since overall photosynthesis rates were low in these plants in all three [CO2] treatments. Leaf specific weight was much higher in Mg and K deficient plants compare to adequate Mg and K plants which may correspond possible defects in carbohydrate partitioning. Especially in Sarıçanak 98, Mg and K deficient plants specific weight was increasing with the increasing [CO2]. Adana 99 plants showed the same trend although it was not as significant as in Sarıçanak 98 plants.With emphasizing adequate Mg and K nutrition requirement to maintain high photosynthetic efficiency and a balanced export of photo-assimilates to sink organs (Marschner, 1995; Cakmak and Kirkby, 2008), this study points out that this can be even more important under elevated [CO2].This study was supported by TUBITAK (Project no. 113Z129)