## 4 Discussion  
The induction of the natural defenses of plants in response to polysaccharides from marine seaweed is one of the new promising alternative strategies in crop protection. Fucans, fucoidans [7], alginates [40], and laminarins [41] from the Phaeophyceae, Ulvans, and glucuronan [5] from the Chlorophyceaeae, and carrageenan [42] from the Rhodophyceaeae are the principal carbohydrates studied for their elicitor activities to control plant disease. A recent review has discussed the application of polysaccharides derived from macroalgae in crop protection [43]. The present work shows for the first time the ability of sulfated glycoproteins extracted from the Moroccan green seaweed _C. decorticatum_ to enhance the natural defense mechanisms of tomato seedlings. The crude and purified polysaccharides AGB and AGP were extracted from _C. decorticatum_ with deionized water. The purification was carried out by ultrafiltration using 100 kDa molecular weight cut-off membranes. The yield of AGB and AGP fractions was about 11% and 5% (\(w/w\)). The chemical and structural analysis revealed the presence of a significant rate of proteins and sulfates (Table 1) and the presence of galactose, arabinose, and glucose as the principal constitutive monosaccharides with a minor amount of xylose and rhamnose (Table 3). The sulfated glycoproteins extracts were characterized by a high molecular weight (M\({}_{w}\)) (>of 2000 kDa) (Table 2). Additionally, the FTIR spectroscopy has confirmed the presence of sulfates and proteins in both extracts by a strong signal extending from 1000 to 1600 cm\({}^{-1}\). Basically, the proteins are known by the presence of bands between 1720 and 1600 cm\({}^{-1}\) (intense peaks at 1627 cm\({}^{-1}\) for AGB and 1631 cm\({}^{-1}\) for AGP) corresponding to the amide I, amide II band, ranging from 1600 and 1500 cm\({}^{-1}\) (peaks at 1537 and 1541 cm\({}^{-1}\) for AGB and AGP, respectively), and the amide III band between 1450 and 1200 cm\({}^{-1}\) (peaks extending from 1449 cm\({}^{-1}\) to 1377 cm\({}^{-1}\) for both AGB and AGP) [37; 38]. This result ties approximately with previous work reported by [PERSON] et al., wherein the quality of AGPs extracted from green tea were studied [38]. Based on these, the AGB and AGP fractions seem to be a sulfated arabinocaltan-rich protein in the cell wall of the green seaweed _C. decorticatum_. One of the features that distinguishes seaweed from other resources is its large content of sulfated polysaccharides (SPs). In contrast to brown and red seaweed, green algae are still insufficiently explored as a source of SPs. The Ulvans derived from _Ulvu_ sp. are the most studied SPs because of their widespread application in agriculture, human health, and biomaterials [10]. Recently, attention has been devoted to the investigation of the SPs derived from the _Codium_ genus of the order Bryospidales to hunt for different SPs present in green seaweed. The chemical and structural analysis of the cell wall polysaccharides from _Codium_ sp. has shown the presence of three different types of SPs, sulfated galactans, sulfated arabinans, and sulfated mannans, as well as hydroxyproline-rich glycoproteins (HRGPs), also known as AGPs [11]. [PERSON] and [PERSON] (1964) have explored for the first time the cell wall polysaccharides of _C. fragile_, and they have found that the cold and hot water extracts contained galactose and arabinose as major sugars with minor amounts of glucose, mannose, xylose, and rhamnose [44]. The yield of different fractions was in the range of 0.6-5%. In addition, the extract, which was considered sulfated arabinocaltans, contained 22% of sulfates and 25% of proteins [44]. These chemical and structural features are approximately similar to those provided in the present study. It was reported in another work that the polysaccharides extracted with water at room temperature from _C.