UBC Theses and Dissertations
Carbon allocation patterns in plants and plant ecosystems Walton, Anne Barber
A study of plant carbon allocation patterns at the ecosystem and cellular levels revealed interactions between ecological and physiological processes. At the global level, ecosystem net' primary production was allocated to lignin and holocellulose synthesis in plant life-forms and plant organs. Forty-eight percent of the global net primary production (carbon) was estimated to be associated with the synthesis of lignin and holocellulose, which are the primary constituents of plant cell walls. The primary ecosystems associated with this lignin and holocellulose production were tropical forests, Northern Hemisphere forests, and savannas. Associated with the annual net production of lignin, it was estimated that 1 x 10¹⁴ moles of nitrogen are reassimilated through the prephenate-arogenate junction which links primary carbon metabolism to secondary carbon metabolism. Estimates of annual net primary production associated with plant life-forms and plant organs indicated that the two greatest contributors were herbaceous and nonvascular aquatic (non-macrophyte) plants. Estimates may provide a basis for future models of pools and fluxes of carbon in the global carbon cycle. At the cellular level, treatment of parsley (Petroselinum crispum L.) cell cultures with the Phytophthora megasperma elicitor caused an immediate increase in the rate of respiratory carbon dioxide evolution in the dark that corresponded to the activation of phosphofructokinase and glucose-6-phosphate dehydrogenase, the key enzymes in the regulation of carbohydrate flow to glycolysis and the oxidative pentose phosphate pathway, respectively. The increased rate of carbon dioxide evolution and the activation of phosphofructokinase and glucose-6-phosphate dehydrogenase are maintained for the duration of the experiments indicating long-term stimulation of respiration through both glycolysis and the oxidative pentose phosphate pathway. A 23% decrease in the C₆:C₁ ratio 60 minutes after elicitation was consistent with increased contribution of the oxidative pentose phosphate pathway to cellular respiration. Long-term activation of the oxidative pentose phosphate pathway following elicitation could serve to maintain the pools of substrates necessary during activation of the shikimic acid pathway, leading to the production of defensive compounds.
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