Determination of Photosynthesis and Transpiration Using a Flow Through Gas Exchange Chamber.

摘要

Carbon assimilation chambers for measuring gas flux between the atmosphere and a leaf or plant have been used in various forms for many years. Gas exchange systems may be classified into three types:closed,semi-closed,and open. This discussion is limited to the open system and the modifications necessary for accurate measurements of gaseous flux in the open or flow through gas exchange system. In an open system an air stream of known and many cases preconditioned properties passes through an assimilation chamber at a constant flow rate. The air is passed first through instrumentation for measurement of the components of interest,through the assimilation chamber,and then through instrumentation to determine changes in the components as a result of environmental or plant factors. In this system there is no recirculation;all of the air incoming to the chamber is exhausted to the atmosphere after measurement. The open system is particularly useful for investigation of single leaves,parts of plants or small plants. It allows the continuous recording of small rapid fluctuations and changes in photosynthetic rate with considerable accuracy. Technically,the open gas exchange system is complex because it requires accurate measurement of flow rate. However,it has the advantage that it does not have to be completely leak proof. The design and construction of a flow-through assimilation chamber for measurement of photosynthesis and transpiration are described. (ERA citation 03:005056)