Functional characteristics of a fruticose type of lichen, Stereocaulon foliolosum Nyl. in response to light and water stress
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Stereocaulon foliolosum a fruticose type of lichen under its natural habitat is subjected to low temperature, high light conditions and frequent moisture stress due its rocky substratum. To understand as to how this lichen copes up with these stresses, we studied the reflectance properties, light utilization capacity and the desiccation tolerance under laboratory conditions. S. foliolosum showed light saturation point for photosynthesis at 390 μmol CO2 m−2 s−1 and the light compensation point for photosynthesis at 64 μmol CO2 m−2 s−1. Our experiments show that S. foliolosum has a low absorptivity (30–35 %) towards the incident light. The maximum rates of net photosynthesis and apparent electron transport observed were 1.9 μmol CO2 m−2 s−1 and 45 μmol e− m−2 s−1, respectively. The lichen recovers immediately after photoinhibition under low light conditions. S. foliolosum on subjecting to desiccation results in the decrease of light absorptivity and the reflectance properties associated with water status of the thalli show a change. During desiccation, a simultaneous decrease in photosynthesis, dark respiration and quenching in the fluorescence properties was observed. However, all the observed changes show a rapid recovery on rewetting the lichen. Our study shows that desiccation does not have a severe or long-term impact on S. foliolosum and the lichen is also well adapted to confront high light intensities.
KeywordsChlorophyll fluorescence Desiccation tolerance Light absorptivity Light utilization capacity Stereocaulon foliolosum Water index
This work was supported by Council of Scientific and Industrial Research (CSIR), New Delhi, India, under its Eleventh Five Year Plan (Grant No. SIP 09). A Senior Research Fellowship provided to RS and SR by Council of Scientific and Industrial Research (CSIR), New Delhi, India, is gratefully acknowledged.
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