A semi-herbaceous. pioneer plant Chryzanihtmoidts moniiifera was grown under varying environmental condition; in order to assess whether altering environmental variables would affect its hydraulic conductance and photo synthetic rates The plants were grown under sun and shade conditions, subjected to low and high watering treatments and to two different nutrient regimes. Steady-state gaseous exchange parameters, and whole-plant and leaf hydraulic conductance were measured on plants from each treatment. A key aspect of this study was to investigate how the following leaf components - petiole. major veins, minor veins and extravascular tissue - contributed to die overall resistance to water flow in the leaf (Ricaf). Vein orders were cut in specific sequences to interrupt water flow which then allowed the partitioning of leaf hydraulic resistances. The results showed that die maximum pbotosynthetic rate, under light saturating CO;. (A,^ was significantly affected by both nutrient and light treatments Environmental conditions (light, water and nutrient treatments) did not. however, affect the CO.- compensation point, or dark respiration of the measured A:C, curves for C. moniaftra. In terms of whole-plant hydraulic conductance, the shoot, stem and root were not significantly affected by environmental treatments. When investigating R«„. only the light treatments significantly affected the resistance of the petiole, extra vascular tissue, and minor vans Rf<trfc was found to be positively correlated with and contributed between 34-59 % of the total leaf resistance When considering the resistance of the leaf it was observed that the vascular tissue of the leaf contained up to 90 % of the total leaf resistance. The results from this study show that the hydraulic conductance of C. moniijfera was found to be significantly affected by light treatment; only. Water and nutrient treatments did not have a substantial impact upon the water flow of the plant. Leaf hydraulic resistance was partitioned differently to that of results from ocher studies, in that the petiole and major veins contained the majority of the leaf resistance In retrospect this study would have been more effective if C. monilitfera treatments were more severe, in terms of water and nutrients Further studies should focus on a comparison of leaf hydraulic resistance partitioning of other species, across a range of plant types.

Thesis (M.Sc.)-University of KwaZulu-Natal, Westville, 2008.