Photosynthetic measurements with the idea spec: An integrated diode emitter array spectrophotometer/fluorometer

Abstract

In vivo spectrophotometry, a non-invasive, nondestructive technique that relies on the leaf’s endogenous chromophores, has become an essential tool for understanding the photosynthetic response of plants to environmental stresses. Based on the pulsed-light spectrophotometer approach, and capitalizing on recent advances in optics and light emitting diode (LED) technology, we have developed an in vivo spectrophotometer capable of measuring absorbance changes of less than 3 × 10−5 absorption units and microsecond time resolution. The instrument can also simultaneously measure chlorophyll (or other) fluorescence signals with background or saturating actinic light, e.g. PAM fluorometry or induction curves, to give measurements of antenna and photosystem II efficiencies. We use a solid-state light source containing multiple LEDs for both measuring and actinic stimulation and direct the light to the leaf through non-focusing optics, allowing near-simultaneous multi-wavelength measurements useful for signal deconvolution.