919 
pump and probe 
scattered optical 
aiding mirror is 
spectral analysis 
by 50 ns pulses 
;nsitive both to 
iduced by pump 
us measurements 
ire the variable 
lyuk, 1994a). 
■probe technique 
?reen plants. As 
1994), we will 
;ation of laser 
delay between 
lyuk, 1994a). 
ed the by weak 
g .2 for various 
Fig.3 represents 
( F690 ) and 735 
;he maize 
intensities 
s at 690 nm 
he intensity 
r RCs closed by 
ise (Fig.2,3) in 
The remarkable 
ce spectra with 
srence between 
nm (about 2.5 
(Gorbunov and 
This and similar series of experiments using maize, wheat and oak leaves 
have shown that the pump pulse photon flux density I on the leaf surface must 
23-2-1 ^ 
be more than 5*10 cm s to meet the requirement (1). This value appears to 
be an order of magnitude higher than that determined for algae ( 1 ^ = 10 23 
quanta*cm" 2 s’ 1 ; Chekalyuk and Gorbunov, 1994). 
The dependence of intensity of Chl-a fluorescence induced by probe pulse 
on the delay between pump and probe pulses (see in Gorbunov and Chekalyuk, 
1994a) has appeared to be similar to those obtained using lamp (Falkowski and 
Kiefer, 1985) and laser excitation (Chekalyuk and Gorbunov, 1994) of algae 
using pump-and-probe technique. The optimal delay between the pump and probe 
pulses has been found to be 30-50 ps in the case of both algae and plant 
leaves. 
The most interesting results have been obtained during measuring of the 
dependence of Chl-a fluorescence emission on the intensity of probe pulse I, 
varying in the range of 5*10 22 to 10 24 quanta*cm‘ 2 sec _1 . The saturation of 
both maximal 4> and original 4> fluorescence were observed (see Gorbunov and 
m o 
Chekalyuk, 1994b), but the characters of those functions were different. The 
origin of this phenomenon is discussed in (Chekalyuk and Gorbunov, 1994; 
Gorbunov and Chekalyuk, 1994b). The resulting value of n = ($ -4> )/$ appeared 
mo in 
to be also the function of I in this range. To avoid the distortions in laser 
measurements of r), the photon flux density of the probe pulse on the leaf 
surface must not exceed (2-3)*10 22 cm’ 2 s _1 according to our experiments. 
6 . - FIELD APPLICATIONS OF LIDAR PUMP-AND-PROBE TECHNIQUE 
Since the adaptation of lidar pump-and-probe technique to vegetation monitor 
ing is still under development, we will focus below on its oceanographic 
applications. 
6 . 1 . Along-track profiling 
The example of along-track high-resolution lidar monitoring of photosyn 
thesis efficiency (rj = A4>/4> ) and Chl-a fluorescence is presented in Fig.4. 
One can see near-zero variations of rj in the noon, caused by excessive solar 
illumination in nearsurface water layer, as well as recovery of rj high levels 
in the evening. Relying on night measurements, it is possible to evaluate the 
BUCK SEA. April 1991 
Figure 4. Along-track Lidar Monitoring of the Efficiency of Photosyn 
thesis (r] = M>/4>m) and Chlorophyll-a Fluorescence (actual level $)•