## 3 Results and Discussion
### Sulfated and Unsulfated Polysaccharides and Oligosaccharides in Olive Tree Leaves
However, the OASM (3 kDa) exhibited the highest levels of enzyme activities at 2 g/L. Alginate is an anionic polysaccharide isolated from brown algae. Recently, it has been widely utilized in agriculture as an inducer of the natural defenses of plants. The application of alignates extracted from _B. bifurcata_ and _F. spiralis_ triggered PAL activity and polyphenol synthesis in leaves of tomato seedlings and roots of date palm [18; 20]. Few research hasfocused on the use of LMW alignates as inducers of natural defenses. Partial hydrolysis with HCl of alignates extracted from _Lessonia vadose_ enhanced the PAL and peroxidase (POD) activities in wheat plants, higher levels were recorded after the treatment with polymannuronic enriched fraction [69]. A recent study has reported the effectiveness of oligoalginates (5.5 kDa), obtained after oxidative degradation, compared to their native polymer, showing their capacity to stimulate the PAL activity as well as the phenolic compounds in the leaves of tomato seedlings at a concentration of 1 g/L [18]. It has been conclusively shown that oligoglucuronans and oligoulvans with low DP (2-3) enhanced the activation of PAL, antioxidant-related enzymes as well as the accumulation of lignin and phenolic compounds, protecting apple fruit against _Penicillium expansum_ and _Botrytis cinerea_. These oligomers were more effective than their native polymers [22,23]. No previous study to date has examined the elicitor effects of alignates and their derivatives in leaf tissues of the olive tree. 5.2 Evaluation of Enzyme Activities and Secondary Metabolism Synthesis in the Leaf Discs of the Olive Tree in Response to Sulfated Polysaccharides AGB, AGP and FUCCM  
The sulfated polysaccharides, arabinogalactan, and fucoidan extracted from the brown and green seaweed were applied to the olive leaves at different concentrations. The results  
Figure 4: Effect of alignates extracted from CM (ALCM) and SM (ALSM) and their derivatives (OACM and OASM) on the induction of PAL (**a**) and TAL (**b**) activities in the leaves of olive tree after 24 h of treatment. The letters (a, b, c) indicate significant differences between treatments at each concentration using the Tukey-HSD test, at (\(p\) < 0.05). Treatments presented with the same letter are not significantly different. Figure 5: Effect of alignates extracted from CM (ALCM) and SM (ALSM) and their derivatives (OACM and OASM) on the induction of polyphenol (**a**) and lignin (**b**) contents in the leaves of olive tree after 24 h of treatment. The letters (a, b, c) indicate significant differences between treatments at each concentration using the Tukey-HSD test, at (\(p\) < 0.05). Treatments presented with the same letter are not significantly different. showed significant induction of the PAL and TAL activities accompanied by the synthesis of lignin and polyphenols (_p_ < 0.05). These responses depend on the nature of the polymers and their concentrations. In response to the tree fractions, the phenolic metabolism was significantly stimulated, at the low concentration (0.5 g/L). FUCCM revealed an important elicitor capacity at 0.5 g/L, showing high levels of PAL, polyphenols, and lignin compared to arabin galactan (crude and purified extracts). The TAL was less expressed than PAL after the treatment by the fucoidan, indicating a PAL/TAL ratio higher than 1. On the other hand, for the crude (AGB) and the purified (AGP) extracts, the PAL/TAL ratio was in the range of 0.45-0.75, showing high activity of the TAL enzyme. No considerable difference was observed in the elicitor effects between AGB and AGP (Figures 6 and 7). A similar conclusion was reached in the previous work, after the application of sulfated arabin galactan AGB and AGP for the first time as inducers of PAL activity, phenolic compounds, and lignin content in leaf and root tissues of tomato seedlings [27]. The application of sulfated polysaccharides from marine algae as stimulators of natural defenses of plants has been largely reported.