272 
10000 1 
X 
„XI »XX 
X 
^1000 j 
M 
X * 
1 '* x 
C/D 100 1 
X 
C/D 
< 
X* 
X 
o 'o i 
K» 
-1—,—,—1—,—1—1—1—1—I—1—1—I—1— 
1 "1 
160 180 200 220 240 260 280 300 
JULIAN DAY 
180 200 220 240 260 
JULIAN DAY 
1,0 
0 , 8 - 
< 0 , 6 - 
0,4- 
0,2 
750 -1 
1 * 
1 
740 - 
X X 
X 
730 - 
X 
T, 720 - 
X 
710- 
X 
700- 
690- 
160 180 200 220 240 260 280 300 
JULIAN DAY 
180 200 220 240 260 
JULIAN DAY 
Figure 1. LAI, biomass, NDVI and A. re values versus the day of the year, showing their temporal evolution 
along the phenological cycle of the com. For the biomass, the logarithmic scale has been used to better show its 
evolution. 
0 1 2 3 4 5 
LAI 
Figure 2. NDVI values versus LAI values. Data corresponding to the development and period of maximum 
activity of the plants are represented by closed symbols (pre-L max data), whereas the others corresponding to the 
senescence of vegetation are shown in open symbols (post-L max data). The curves resulted from the adjustment 
of the values have also been represented (continuous and dotted lines, respectively). 
The distribution of points in the graph looks almost like an hysteresis cycle for the NDVI as a function 
of the LAI. Nevertheless, the empirical approach depends on the phenological stage of the crop (Baret et al., 
1989) and it is interesting to separate two periods: (i) pre-maximum LAI data, and (ii) post-maximum LAI data 
(Wiegand et al., 1992) to carry out the analysis. For this reason, in figure 2, data corresponding to the 
development and period of maximum activity of the plants are represented by closed symbols (pre-L max data),