Leaf Absorbtance
Both leaf absorptance and reflectance are important attributes of leaves and other photosynthetic structures, as they influence the proportion of light ultimately entering the photosystem.
A published average value for absorptance of around 84% is generally used in estimating ETR, although the actual absorptance value can vary widely between samples and species, leading to significant over- or under-estimates of ETR.
When conducting field or laboratory studies where ETR is calculated, the use of Aquation’s White-RAT will increase the accuracy of ETR estimates.
White-RAT Leaf Absorptance Meter
White-RAT Leaf Absorptance Meter with sample Hold, Mask for narrow samples and seagrass sample
White-RAT Leaf Absorptance Meter with leaf
What is Leaf Absorptance?
Leaf absorptance in its simplest terms can be defined by the equation R + T + A = 1, where R = reflectance, T = Transmittance and A = Absorptance. The proportion of the quanta (from a light source or solar radiation) absorbed within the leaf (or algal lamina), can be calculated by measuring both reflectance and transmittance and substituting these into the equation above. The reflectance and transmission spectrum of leaves is a function of both the concentration and physical state of the light-absorbing compounds such as chlorophylls, carotenoids and other cellular components, as well as the internal scattering of light within the leaf.
It is well established that the reflectance and transmission spectrum of leaves is a function of both the concentration of light absorbing compounds (chlorophylls, carotenoids, water, cellulose, lignin, starch, proteins, etc.), and the internal scattering of light that is not absorbed or absorbed less efficiently
The White-RAT Leaf Absorptance Meter measures the proportion of light absorbed by the sample. Coupled with ambient light measurements, and the measurement of the effective quantum yield of PSII energy conversion, one can now easily determine the rate of electron transport (ETR) with improved accuracy.