PUMP-AND-PROBE LIDAR TECHNIQUE: NEW APPROACH 
TO ACTIVE BIOMONITORING OF SEA AND LAND 
A.M. CHEKALYUK and M.Yu. GORBUNOV* 
Moscow State University 
Dept, of Physics (*Dept. of Chemistry), Moscow 119899 (Russia) 
ABSTRACT: 
Relying on the relationship between the photosynthesis efficiency and variable 
fluorescence of in vivo chlrophyll-a, the lidar implementation of pump-and- 
probe technique can provide a way for remote monitoring of ongoing 
photosynthesis in algae and high plants. The basic idea of pump-and-probe 
technique is the use of actinic (pump) light flash to cause for a short period 
the change in functional state of photosynthetic apparatus. The prototype of 
pump-and-probe lidar-fluorosensor is described. The laboratory experiments on 
optimalization of laser excitation are discussed. The results of field 
measurements in the Mediterranean and Black sea, and in the Atlantic are 
presented. This novel lidar technique, capable for remote control over 
functional state of the object, may by classified as superactive. The problems 
of future development of pump-and-probe lidar technique are discussed. 
KEY WORDS: Lidar, Remote Sensing, Photosythesis, Chlorophyll, Fluorescence 
1. - INTRODUCTION 
Due to recent advances in remote sensing, several promising technologies for 
biomonitoring are under development at present time. Nevertheless, there is a 
demand for remote technique, capable of providing direct information about 
ongoing photosynthesis of algae, plants and terrestrial vegetation. It is 
difficult to overestimate the value of such information for global change 
studies, monitoring of biological production (including application in 
agriculture, forestry and fishery), as well as for environmental survey. Our 
recent lidar implementation of pump-and-probe technique may be a step towards 
solution of some relevant problems. 
2. - RELATIONSHIP BETWEEN IN VIVO CHLOROPHYLL FLUORESCENCE AND 
PHOTOSYNTHESIS 
Fluorescent methods for estimation of photosynthetic activity of plants and 
algae rely on the relationship between fluorescence of chlorophyll-a ( Chl-a) 
(the main pigment in photosynthetic apparatus) and the efficiency of photosyn 
thesis processes. Below we present a brief summary on biophysical backgrounds 
of Chl-a fluorescence emission (see as reviews e.g. Krause and Weis, 1991). 
In vivo Chl-a fluorescence accompanies primary stages of photosynthesis, 
which include the absorption of photons by pigments of the light-harvesting 
antenna, migration of the resulting excitons through the light-harvesting 
antenna to the reaction centers (RCs), trapping of excitons by the RCs, and 
Primary charge separation (photochemistry). The photochemical energy is used 
for fixation and conversion of inorganic C0 2 into sugars and biomass. At room 
temperature the major contribution to Chl-a fluorescence is emitted from 
photosystem II (PS II) (see e.g. Krause and Weis, 1991).