Beware of your neighbour : the effects of intraspecific interactions and CO2-level on the plant growth of two Barley cultivars

Sammanfattning: Plants have evolved several ways to sense what is going on around them. They can detect possible competitors by picking up on airborne Volatile Compounds emitted from neighbouring plants. The cues can induce growth responses that enhances the competitive ability of the receiver. Typically, plants are bred for the purpose of growing in pure stands at high densities with only the same cultivar. However, recent research has shown that some cultivars benefit from growing in a cultivar mixture. It is important to raise the knowledge about how specific cultivars respond to different kinds of competition since it can help growers to better customize the cropping system to fit the needs of the cultivar in question. Another aspect of this study concerns CO2. With a changing climate, the level of atmospheric CO2 will increase. Elevated levels of CO2 have been shown to increase the rate of photosynthesis in C3 plants resulting in increased plant growth. But there is currently a lack of knowledge regarding how elevated levels of CO2 effects the interactions between plants. The aim of this study was to examine how two cultivars of Barley change their growth pattern when they are exposed to different forms of intraspecific competition and if changing levels of CO2 will influence the responses. In chambers with controlled conditions, some plants grew in a cultivar mixture, whilst other grew in pure stands. Two different treatments of CO2 were used to see how elevated levels of CO2 would impact the intraspecific interactions. No difference was found between the two forms of competition on the plant growth of barley and since no difference was found between the groups no conclusions could be drawn regarding the effects of elevated levels of CO2 beyond that it induced overall plant growth. However, the data indicated that different cultivars exhibit unique growth rates and responses when exposed to different forms of intraspecific competition. There was also an indication that elevated levels of CO2 effect the competitive ability of different cultivars to varying degrees.