顽拗型种子贮藏和脱水过程中碳水化合物、脂肪和蛋白质的生化变化

顽拗型种子通常不能干燥到较低含水量或贮藏较长时间而不受伤害。导致这一问题的生化机制因属不同甚至同一属中的种不同而异。笔者测定了栎属、槭属和七叶树属顽拗型种子在室温下贮藏或干燥过程中的生化变化。虽然贮藏脂肪组成的变化是不确定的，但膜脂肪和蛋白质的结构以及蔗糖含量发生了变化。用两份白橡树种子在室温下贮藏12d的实验表明，脱水样品的蔗糖含量发生很大变化，而保持水分的样品中蔗糖含量变化很小。因此，保持水分种子的蔗糖用于正常的生长和发育，而干燥种子的蔗糖则用作糖保护剂。尽管如此，蔗糖的存在也许能保护干燥橡实的细胞膜不致破裂，但蔗糖不能保持橡实的生活力。

Biochemistry of Recalcitrant Seeds: Carbohydrates, Lipids, and Proteins

While the commonality of recalcitrant seeds is that they cannot be dried to low moisture contents or stored for long periods of time without damage,the biochemical mechanisms that contribute to this problem may vary among genera and even among species within a genus.We examined recalcitrant-seeded species of Quercus,Acer,and Aesculus for biochemical changes that might occur during storage or during desiccation at room temperature.While changes in the composition of storage lipids were inconclusive,we did find structural shifts in membrane lipids and proteins,and amounts of sucrose.In one experiment using two subsets of Q.alba acorns kept at room temperature for 12 days,the subset that desiccated exhibited large shifts in sucrose content while the subset that was kept fully hydrated exhibited much smaller changes.It is our conclusion that the sucrose in the hydrated seeds is utilized for normal growth and development while sucrose in the desiccating seeds may function secondarily as a glycoprotectant.However,while the presence of sucrose may protect membranes from disruption in the drying acorns,it does not function to preserve acorn viability.