Elevated CO2 causes large changes to morphology of perennial ryegrass (Lolium perenne)
Brinkhoff, R and Porter, M and Hovenden, MJ, Elevated CO2 causes large changes to morphology of perennial ryegrass (Lolium perenne), Crop and Pasture Science ISSN 1836-0947 (In Press) [Refereed Article]
Plant morphology and architecture are essential characteristics for all plants but perhaps most importantly for agricultural species since economic traits are linked to simple features like blade length and plant height. It is likely that key morphological traits respond to CO2 concentration ([CO2]) and the degree of this response could be influenced by water availability, but this has been comparatively little studied. This study aimed to determine the impacts of [CO2] on gross morphology of the most widespread temperate pasture species, perennial ryegrass (Lolium perenne), and whether these impacts are influenced by water availability. We grew perennial ryegrass in a well-fertilised Free-Air Carbon dioxide Enrichment (FACE) experiment in southern Tasmania. Plants were exposed to one of three CO2 concentrations; ambient (∼400 Ámol mol-1), 475 Ámol mol-1 and 550 Ámol mol-1 at each of three watering treatments (adequate, limited and excess). We measured shoot dry weight, height, leaf area, leaf blade separation, leaf size, relative water content and specific leaf area. We also measured shoot density per unit area as a measure of tillering. Perennial ryegrass morphology responded dramatically to elevated [CO2], with plants being smaller, with shorter leaf blade separation lengths and smaller leaves than in ambient plots. Elevated [CO2] increased tillering but did not substantially affect relative water content or specific leaf area. Water supply did not affect any traits measured nor the response to elevated [CO2]. The impacts of elevated [CO2] on the morphology of a globally-important forage crop that we observed have profound implications for pasture productivity. The reduction in plant and leaf size were consistent across a range of soil water availability, indicating that they are likely to be uniform. Clearly, elucidating the mechanisms driving these responses will be essential in improving predictability of these changes and potentially for breeding varieties suited to future conditions.