LI-6400 portable photosynthesis system

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The portable gas exchange system from LI-COR allows one to measure both the photosynthetic rate of leaves under light conditions and the respiratory rate of leaves and other organs in the dark. It also allows the measurement of transpiration rates, which are of primary importance when studying the response of plants to drought. Many chambers are available, depending on the type of measures and the type of plants under study. We will use this equipment to determine to which extent the annual growth of a spring ephemeral, the trout lily, is limited by the growth capacity of its bulb. To do so, we need to measure the capacity of the leaves to fix carbon and estimate the capacity of the bulb to use this carbon for its own growth or to stock it as starch. Although growth of many plants of economical use is limited by their capacity to fix carbon, many wild species exhibit some limits to use the carbon fixed by their foliage. It is important to better characterise this limitation because it has major impact on the capacity of the plants to take advantage of the atmospheric CO2 increase associated with global warming. These studies could also allow growth models to be developed for such type of plants. The equipment will also be used to measure and compare rates of photosynthesis and nitrogen use efficiency among boreal species in the understory (shrubs and trees) of black spruce stands, as part of a study evaluating physiological acclimation following clearcut or partial harvest. The estimation of nutrient and water use efficiency of the different species may contribute to our understanding of the competitive relationships between species after disturbance by harvest. This competition ultimately influences the stand dynamics and the commercial revolution of black spruce.