## 3 Results
### Fourier Transform Infrared Spectroscopy  
The FTIR spectroscopy was performed to identify the functional groups of polysaccharide samples (Figure 3). The IR spectrum of isolated crude and purified fractions showed bands at \(\approx\)3270-3300 cm\({}^{-1}\) and 2920 cm\({}^{-1}\), indicating the presence of -OH and -CH stretching, respectively [36]. The intense band in the range of 1620-1631 cm\({}^{-1}\) might correspond to amide I, which is mostly a carbonyl (C-O) stretching. The peak at 1537 and 1541 cm\({}^{-1}\) could be attributed to the amide II (N-H) band. The signals extending from 1449 to 1377 cm\({}^{-1}\) might contribute to the amide III bands [37; 38], and absorption in the range of 1141-1216 cm\({}^{-1}\) was attributed to the sulfate ester functional groups. The strong signal at \(\approx\)1019-1022 cm\({}^{-1}\) indicated the stretching vibrations of sulphoxides (S=O). The wavenumber at 930-934 cm\({}^{-1}\) could correspond to the absorbance of galactopyranose [39]. Around 840 cm\({}^{-1}\) to 850 cm\({}^{-1}\), the signals indicate the sulfate location bonded in the axial or equatorial positions [39]. The intense band in the range of 570-594 cm\({}^{-1}\) is characteristic of the bending vibration of C-O-SO\({}_{3}\). Based on the peak intensities, the AGB and AGP fractions contained a significant content of sulfate groups, indicating that the extracts were confirmed as sulfated polysaccharides. Effect of AGB and AGP Fractions on the Induction of PAL Activity in the Roots and the Leaves of Tomato Seedlings  
AGB and AGP extracts were applied using two modes of treatment, foliar spray, and syringe infiltration of 1 g/L of elicitors. Control plants were treated with water. The PAL activity was measured in the roots and two apical leaves (n and n \(-\) 1) of 45-day-old tomato seedlings. The sulfated glycoproteins significantly induced the PAL activity in the roots and the leaves of treated plants, depending on the incubation period (_p_ < 0.05). After the injection of AGB, the PAL activity showed an upward trend in the leaves from 24 h, achieving a peak value 1.6-fold higher after 72 h. In response to AGP, the activity in the leaf tissue was induced after 24 h and 72 h (Figure 4a). In the roots, levels rose slowly after 48 h and 72 h after the treatment by both fractions (Figure 4b). Based on this, both fractions exhibited considerable induction of the PAL activity. The crude fractions (AGB) showed an elicitor capacity more effective in the leaf tissue; however, the purified polysaccharides (AGP) exhibited an efficient activity in the roots of tomato seedlings (Figure 4). \begin{table}
\begin{tabular}{c c c} \hline
**Monosaccharides** & **AGB 1** & **AGP 2** \\
**(\%olar Ratio)** & **46.07 \(\pm\) 1.46 & 51.55 \(\pm\) 2.67 \\ Glucose (Glc) & 38.78 \(\pm\) 0.24 & 24.56 \(\pm\) 1.05 \\ Arabinose (Ara) & 12.08 \(\pm\) 1 & 17.32 \(\pm\) 1.33 \\ Xylose (Xyl) & 1.70 \(\pm\) 0.23 & 3.93 \(\pm\) 0.61 \\ Rhamnose (Rha) & 1.37 \(\pm\) 0.13 & 2.63 \(\pm\) 0.15 \\ \hline \end{tabular} 1  
\end{table} 
Table 3: Monosaccharide compositions determined by GC-EI/MS of sulfated glycoproteins AGB and AGP extracted from the green seaweed _C. decorticatum_. Figure 3: ATR-FTIR spectra of sulfated glycoproteins from _C. decorticatum_, AGB **(a)**, and AGP **(b)**. The foliar spray of the AGB and AGP extracts revealed globally similar responses to PAL activity. As illustrated in Figure 5, a significant increase was observed after 72 h of treatment by both sulfated polysaccharides in the leaves and the roots. After 48 h, the elicitor activity was more important in the roots in responses to AGP treatment. In the leaves, the stimulation of the PAL was precocious after the injection of elicitors (24 h) compared to foliar spray. The sulfated glycoproteins showed fluctuations in the elicitor effect depending on the elicitation method (injection and foliar spray) (Figures 4 and 5).