Please note: This is a Sole Source Notification. Specifications include, but are not limited to: Our laboratory plans to use the Li-6800 to measure gas exchange (CO2 and H2O) in leaves and stems of desert plants. We will use this equipment mostly in natural systems, but we do not discard the possibility of using it in greenhouses. The company LI-COR Environmental is the oldest in the market and the only vendor that makes infrared gas analyzers as precise and accurate, and are a standard piece of equipment for research in the field of plant physiological ecology. Particularly, the piece of equipment that we want to purchase, the LI-6800 portable photosynthesis system, is the only system that has two absolute non-dispersive infrared gas analyzers inside the head of the chamber, which reduces the path that gas has to travel before it can be measured, so there is a more accurate control of CO2 and H2O at the leaf/stem level. These gas analyzers are cleanable by the user which prevents returning the instrument to the factory for cleaning. LI-COR provides a lot of videos on how to troubleshoot and give maintenance to some parts of the equipment, which is convenient during intense field seasons. Furthermore, the LI-6800 is the only system that can make fluorescence and gas measurements over the same area simultaneously, and both aspects are important for understanding the light and carbon reactions of photosynthesis. The LI-6800 is also the only system that allows for control and measurement of the pressure inside the chamber, and by keeping a delta pressure between the inside and outside of the chamber, it prevents leaks, and therefore leads to more accurate measurements. The LI-6800 is the only system with a sunlight readable touch screen and an Ethernet port to allow for data sharing over the internet and software upgrades without sending the instrument to the factory for upgrades. This is the only system that can measure up to 3100 ppm of CO2 which is important for performing CO2 response curves, especially in stems that have greater intercellular CO2 concentration than leaves. The LI-6800 is the only system with a flow rate of up to 2055 mL/min, which allows for larger chambers and leaf areas to be measured allowing for more accurate measurements. Furthermore, the leaf chambers can be easily changed to meet the demands and/or the leaf/stem area sizes of the plants being measured (2 to 36 cm2). The PAR sensor is a silicon photodiode. Finally, the leaf temperature sensor is made of a type E fine-wire thermocouple, which is more accurate than other thermocouples.
