ETD Collection

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    Quantifying drought strategies in C4 perennial Southern African grasses
    (2024) Marutha, Tebogo Rector
    Plants have a range of strategies for surviving drought associated with the morphological and physiological traits that govern water use and loss. Most research has been done on woody species and whether the research applies in C4 grasses whose above-ground biomass cures annually over a dry season is not clear. In this study I described and quantified drought strategies and recovery patterns of thirteen perennial C4 grass species found in savanna and grassland ecosystems in South Africa. An experiment was undertaken where the grasses were grown and then exposed to a drought for three months, after which they were watered for one week to simulate a post drought recovery. I monitored stomatal conductance, leaf water potential, osmotic adjustment, leaf senescence and post-drought resprouting to assess whether plants with restricted water availability retained varying proportions of live leaf material or whether a wasteful water strategy during drought was associated with increased leaf death and post-drought recovery. Based on the measurements of the thirteen species, a broad range of strategies emerged related to the trade-offs between being efficient or safe, whereby some grasses control water loss by closing stomata and sacrificing photosynthesis while others continue to lose water while they photosynthesise. Additionally, osmotic adjustment demonstrated in species such Digitaria eriantha and Panicum maximum demonstrated an alternative drought strategy that is not currently recognised in the literature. Grasses with low stomatal control cured faster than those with a high stomatal control, which might have implications for flammability and leaf phenology in seasonal ecosystems with annual drought.