Root dynamics of themeda triandra forsk. In relation to water stress and defoliation at different phenological stages

Abstract

The impact of water stress on root growth for the indigenous apomectic C4-grass species Themeda triandra was determined over a growing season covering three growth stages (vegetative, pipe and reproductive), as well as for regrowth occurring to one, three and six days after defoliation. Four water treatments (T1 = 0–25%, T2 = 25–50%, T3 = 50–75% and T4 = 75–100% depletion of plant-available water) were applied to plants grown in pots under greenhouse conditions. Root length and root mass increased significantly, with a decrease in plant-available water over all the growth stages. Root lengths and root masses were significantly higher during the reproductive growth stage for all the water treatments. In addition, root lengths for the different defoliation treatments, within the same water treatment, did not differ significantly. The influence of water stress has more effect over the short term on root growth than defoliation or growth stage. These measures will be useful to resource managers and should be considered when predicting ecosystem responses to global climate change. © 2009, Taylor & Francis Group, LLC.