The assessment of the chlorophyll content of lichens has gained importance in large-scale and long-term monitoring programs. However, these programs require an efficient, rapid, and reliable method of pigment measurement. Non-destructive methods of measurement using portable chlorophyll meters are rarely used for lichens.

Researchers from Xishuangbanna Tropical Botanical Garden (XTBG) compared the non-destructive methods with traditional methods and evaluated their applicability in studying lichen pigment content.  

They aimed to determine the empirical relationship between chlorophyll meter readings and pigment content of thalli of different lichen species. They also wanted to determine which instrument is more accurate and, therefore, more suitable for measuring the chlorophyll content of lichens. 

The researchers collected seven epiphytic lichen species, including three chlorolichens and four cyanolichens from various habitats across the subtropical forests of the Ailao Mountains in southwest China.  

SPAD-502 (a hand-held absorbance-based dual wavelength chlorophyll meter) and CCM-300 (a lightweight hand-held device) were used to measure the pigment content of seven foliose lichen species. 

The pigment readings by SPAD-502 and CCM-300 were compared with those determined using the dimethyl sulphoxide (DMSO) extraction method. 

They observed significant correlations between SPAD/CCM values and pigments (chlorophyll and total carotenoids) extracted from chlorolichens, especially species with a smooth surface. 

They further found that the CCM-300 was more accurate in detecting the pigment content of foliose chlorolichens. However, both instruments showed certain limitations in the determination of pigment content in cyanolichens, especially gelatinous species. 

SPAD-502 was able to analyze all foliose lichen samples and produced readable values. SPAD-502 thus may be applicable for a wider range of foliose species across various habitats than CCM-300. 

The study entitled "Comparison of two noninvasive methods for measuring the pigment content in foliose macrolichens" has been published online in Photosynthesis Research.