The net carbon balance in relation to growth and biomass accumulation of grapevines (Vitis vinifera cv. Semillon) grown in a controlled environment

Assessing the impacts of environmental stresses on plant growth and productivity requires an understanding of the growth processes and the carbon economy that underpins this growth. Potted grapevines of the Vitis vinifera L. cv. Semillon were grown in a controlled environment and canopy growth; leaf, bunch and stem extension and net photosynthesis were routinely measured from budbreak to harvest. Allometric relationships enabled dry matter to be determined and, with net photosynthesis, used to determine the shoot carbon economy. Stems, leaves and bunches all followed a sigmoid growth pattern with leaves and stems allocated similar amounts of biomass and carbon while bunches had twice as much. Rates of carbon sequestered as biomass exceeded rates of carbon acquisition through net photosynthesis for over 25 days after budbreak. Despite the high demand for biomass in bunch growth, rates of carbon sequestration actually declined and overall, the vines maintained a positive carbon balance throughout the period of bunch growth. The Semillon shoots relied on carbon reserves to commence growth then produced a 53% carbon surplus after leaf (9%), stem (10%) and bunch (28%) growth demands were satisfied. This suggests these vines also allocated carbon to reserves to sustain the next season's growth.