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Month: February 2011

Measuring Photorespiration with the LI-6400/XT System

Measuring Photorespiration with the LI-6400/XT System

Introduction

Oxygen is a competitive substrate for ribulose 1,5-bisphosphate carboxylase/oxygenase (Rubisco), resulting in an inhibitory effect on net photosynthesis.  Higher CO2 to O2 ratios inside the leaf decrease the Rubisco-catalyzed reactions with O2, resulting in less carbon-wasteful reactions in the light (photorespiration). Photorespiration increases on hot, dry days when evaporative stress can cause stomata to close, lowering the intercellular CO2:O2 as CO2 is assimilated. When Rubisco was evolved by plants, earth’s atmosphere had much higher concentrations of CO2 and relatively…

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Recovering from a bad zero or span; how to undo your doings.

Recovering from a bad zero or span; how to undo your doings.

The LI-7700 is an inherently stable laser-based analyzer that requires minimal user calibration during normal use. User calibrations can still be performed to validate instrument performance, and are required when changing the instrument from its warm to cold temperature operating range. The possibility does exist, however, to perform an incorrect user calibration, which will have undesirable effects on instrument performance.  The instrument software provides multiple ways to help prevent, and even undo, a bad user calibration to ensure high quality…

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