Anatomy and cell wall polysaccharides of almond (Prunus dulcis D. A.!Webb) seeds

The anatomy of Prunus dulcis was analyzed by applying several differential staining techniques and light microscopy. Prunus dulcis seed has a thin and structurally complex seed coat, with lignitied cellulosic tissue. The embryo has two voluminous cotyledons. Cotyledon cells have a high number of protein and lipid bodies, some of which have phytin. The provascular tissue, located in the cotyledons, is oriented in small bundles perpendicular to the transverse embryonic axis. Prunus dulcis cell wall material is very rich in arabinose (45 mol %). Glucose (23%), uronic acids (12%), and xylose (12%) are also major sugar components. The polymers obtained from the imidazole and Na2CO3 extracts contain mainly pectic substances rich in arabinose, but the sugar content of these extracts was very low. The majority of the pectic substances (also rich in arabinose) was recovered with the KOH extracts. These extracts, with high sugar content, yielded also xyloglucans and acidic xylans. The 4 M KOH + H3BO3 extracts yielded polysaccharides rich in uronic acids and xylose and very rich in arabinose, accounting for 27% of the cell wall material.