Changes in carbohydrate and protein content and composition of developing almond seeds

Water-soluble sugars, sugar alcohols, cell wall constituents, protein, total amino acids, and free amino acids were determined in developing almond kernels (Prunus amygdalus) at 3-week intervals from March until harvest. A sharp drop of sugars (from 60 to 5-6% dry weight) was observed in a first stage. Reducing sugars decreased from initial high percentages to a final trace level. Changes in hemicellulose, cellulose, and lignin were also studied; the results suggest that these constituents are employed as a carbohydrate source during a period. Protein content increased steadily up to harvest, more markedly during a 20-day period. Significant variations of amino acid content were detected. The content of free amino acids is considerable in developing almonds, while ripe kernels contain insignificant amounts.