文冠果种子发育及油脂累积与糖类、蛋白质累积之间的关系研究

Seed Development,Lipid Accumulation and Its Relationship with Carbohydrates and Protein in Xanthoceras sorbifolia Bunge

文冠果（Xanthoceras sorbifolia Bunge）是我国北方重要的优良油料树种。本研究对文冠果种子发育过程中油脂、蛋白质和碳水化合物累积之间的关系，以及油脂累积过程中脂肪酸含量的变化进行了研究。文冠果种子发育可以分为4个时期，即I期（从开花到花后33d），II期（花后34～47d），III期（花后48—68d）和Ⅳ期（花后69d至成熟）。在花后33d的绿色种胚中首先观察到油体的存在，花后40～68d是种胚油脂累积的快速期，种胚成熟时油脂含量高达60％。油脂、蛋白质和碳水化合物累积模式的差异表明，油脂合成主要来源于叶片光合作用的可溶性糖，而非瞬时累积的淀粉；油脂和蛋白质的累积是两个独立的代谢途径。在油脂累积过程中检测到6种脂肪酸，油酸和亚油酸是两种主要的脂肪酸，在成熟种胚中分别占30．6％和41．6％，但它们表现出截然不同的累积模式。

Xanthoceras sorbifolia Bunge, belonging to the family Sapindaceae, is one of the most valuable oil trees widely distributed in northern China. We studied the lipid accumulation and its relationship with carbohydrates and protein in developing X. sorbifolia seeds. Seed development can be divided into stage I from flowering to 33 days after anthesis （ d）, stage 11 （ 34 - 47 d）, stage 111 （ 48 - 68 d） and stage IV （ 69 d to maturity） based on morphological traits combined with weight measurements. Oil bodies were first observed in the green embryo at around 33 d. Rapid lipid accumulation commenced at around 40 d and continued to 68 d. The long period of rapid lipid accumulation contributes to a high lipid level in the mature embryo （60% of dry mass）. Differences in the accumulation patterns of lipid, carbohydrates and protein indicate that the lipid synthesis is achieved largely by soluble sugar directly from the photosynthesis of source leaves rather than transiently accumulated starch, and the lipid and protein accumulation are independent processes in the developing embryo. We detected six fatty acids in the developing embryo. Among them, oleic and linoleic acid dominated the lipid composition, but they exhibited contrasting accumulation patterns.