Root growth responses of parthenium weed and different pasture plants under elevated atmospheric carbon dioxide

Abstract

Parthenium weed (Parthenium hysterophorus L.) is an alien invasive species reducing pasture productivity and livestock production in Australia and other countries around the world. Three C 4 pasture grasses (Setaria incrassata, Astrebla squarrosa and Bothriochloa decipiens) and one C 3 pasture legume species (Clitoria ternatea), all previously known to be suppressive of the growth of parthenium weed under ambient CO 2 (390 µmolmol-1), were re-tested under an elevated atmospheric CO 2 (550 µmolmol-1) level in a controlled environment growth chamber. When grown alone and under elevated atmospheric CO 2 level, the root dry biomass of S. incrassata and A. squarrosa did not get affected significantly, whereas that of B. decipiens, C. ternatea and P. hysterophorus significantly increased by 10, 34 and 26 %, respectively. When S. incrassata and A. squarrosa were grown together with parthenium weed under the same conditions, their root dry biomass reduced by 20 and 16 %, while that of B. decipiens and C. ternatea was increased by 7 and 28 %, respectively. The root to shoot ratio of S. incrassata and A. squarrosa decreased significantly by 24 and 16 %, while that of B. decipiens, C. ternatea and parthenium weed increased by 6, 17 and 12 %, respectively, under the same conditions. These results have important implications for the management of parthenium weed in future climate scenarios involving elevated atmospheric CO 2 levels. Our results suggest that some pasture species with the potential to suppress the growth of parthenium weed under the present climate will remain an important tool in managing pastures invaded by parthenium weed in the future.

A superweed in the making: adaptations of Parthenium hysterophorus to a changing climate. A review

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