Novel Red, Green, Blue LED Light Source and Whole Plant Chamber Make Possible Photosynthetic Assessment of Small Plants

With increasing use of narrow-band LED lights in commercial horticulture production systems, photosynthetic responses to spectral light quality are increasingly important.   Previously, photosynthetic studies of young or small, low-stature plants have been limited because small leaves with short or no petioles are difficult to enclose within a traditional clamp-style gas exchange chamber.  Total plant CO₂ flux can be measured by enclosing entire container-grown plants within chambers.  However, the resulting net flux is the sum of the plant, growth media and container fluxes.  Isolation of only aboveground fluxes from low-stature plants is now possible with the new LI-COR 6400-17 Whole Plant Arabidopsis (WPA) Chamber. This chamber uses a novel flow path and blocking techniques to allow aboveground fluxes to be measured independent of belowground gas exchange.  Injections of 80 µg CO₂ (250 µl pure CO₂) into the growth media just below the surface were suppressed by blocking and positive pressure (not detectable at 0.3 ppm resolution).  With this chamber, fluxes can be measured from low-stature and rosette plants as small as 1.5cm² total leaf area.  The 6400-18 RGB (red, green, blue) LED light source, in conjunction with this novel chamber, facilitates rapid assessments of photosynthetic capacity.  The independently controlled red, green and blue LEDs can be used to measure photosynthetic efficiency at different wavebands and intensities.  Data will be presented demonstrating the use of the WPA and RGB to explore response of a small rosette froming species to spectral light quality. This chamber and light combination will allow growth selection based on photosynthetic response assessment of small plants or seedlings in a high throughput system.