(修正) Seed germination Definition of seed germination Germination speed and quality are closely related to the yield of definition, germination commences when the quiescent dry seed begins to take up water(imbibitions) and is completed when the embryonic axis elongates. The visible sign that germination is completed is usually the penetration by the radical of structures surrounding the embryo. Subsequent events, including the mobilization of the major storage reserves, are associated with growth of the seedling 种子萌发过程的生理生化变化 成熟的干种子吸水可分为三个阶段,急剧地吸水(阶段Ⅰ),迟缓吸水(阶段 I),胚根伸出后重新迅速吸水(阶段Ⅲ),第三阶段属于萌发完成后的过程。种 子吸水后的变化之一是恢复呼吸活力,这种变化在种子吸水后几分钟就可以检测 到。在萌发初期氧气的消耗急剧上升,然后下降直到胚根开始延伸。这时, 急剧的呼吸上升再一次出现。种子吸水后,编码种子成熟和干燥过程必需蛋白质 的 mRNAs很可能迅速降解,而编码萌发过程必需蛋白质的 mRNAs开始合成 蛋白质的合成在种子吸水后也很快恢复,因为在成熟的干种子中含有新蛋白质合 成所需要的所有成分。胚根从包裹胚的结构中伸出标志着种子萌发过程的结束和 种苗发育过程的开始。这里需要强调的是:储藏物质的降解和转化是属于萌发后 事件,在种苗发育过程十分重要,但不属于萌发过程的事件。 Cellular events during germination Uptake of water by a mature dry seed is triphasic(Figure D); with a rapid initial uptake(phase I)followed by a plateau phase(phase II). A further increase in water uptake occurs only after germination is completed, as the embryonic axes elongate One of the first changes upon imbibition is the resumption of respiratory activity which can be detected within minutes. After a steep initial increase in oxygen consumption, the rate declines until the radicle penetrates the surrounding structures At this time, another burst of respiratory activity occurs. rapidly upon imbibiti messages encoding proteins that are important during seed maturation and drying are ikely to be degraded. Conversely, new transcripts encoding proteins required during early germination are synthesized, Resumption of protein synthesis take place soon after imbibition, for all of the components necessary for protein synthesis are present within the cells of mature dry seeds. Radicle extension through the structures surrounding the embryo is the event that terminates germination and marks the commencement of seedling growth. It is cautioned here that mobilization and conversion of the major stored reserves are postgerminative events that are important during seedling growth, but they are unrelated to germination 种子萌发需要的环境条件 种子萌发需要合适的环境条件:包括足够的水分,充足的氧气和适当的温度 种子吸水是完成萌发过程关键的第一步。因为很多种子有厚和硬的种皮。吸水后 种皮才会软化,氧气得以穿过种皮进入,种子的有氧呼吸增强。同时,种子吸水 后,胶状的细胞质变成流动状,分子可以在细胞内自由运动,生化反应才可能进 行。种子吸水后,细胞内的酶由非水合状态变为水合状态,恢复活力参与生化反（修正） Seed germination Definition of seed germination Germination speed and quality are closely related to the yield of crops. By definition, germination commences when the quiescent dry seed begins to take up water (imbibitions) and is completed when the embryonic axis elongates. The visible sign that germination is completed is usually the penetration by the radical of structures surrounding the embryo. Subsequent events, including the mobilization of the major storage reserves, are associated with growth of the seedling. 种子萌发过程的生理生化变化 成熟的干种子吸水可分为三个阶段，急剧地吸水（阶段 I），迟缓吸水 (阶段 II)，胚根伸出后重新迅速吸水（阶段 III）,第三阶段属于萌发完成后的过程。种 子吸水后的变化之一是恢复呼吸活力，这种变化在种子吸水后几分钟就可以检测 到。 在萌发初期氧气的消耗急剧上升， 然后下降直到胚根开始延伸。 这时， 急剧的呼吸上升再一次出现。种子吸水后，编码种子成熟和干燥过程必需蛋白质 的 mRNAs 很可能迅速降解，而编码萌发过程必需蛋白质的 mRNAs 开始合成。 蛋白质的合成在种子吸水后也很快恢复，因为在成熟的干种子中含有新蛋白质合 成所需要的所有成分。胚根从包裹胚的结构中伸出标志着种子萌发过程的结束和 种苗发育过程的开始。这里需要强调的是：储藏物质的降解和转化是属于萌发后 事件，在种苗发育过程十分重要，但不属于萌发过程的事件。 Cellular events during germination Uptake of water by a mature dry seed is triphasic (Figure I); with a rapid initial uptake (phase I) followed by a plateau phase (phase II). A further increase in water uptake occurs only after germination is completed, as the embryonic axes elongate. One of the first changes upon imbibition is the resumption of respiratory activity, which can be detected within minutes. After a steep initial increase in oxygen consumption, the rate declines until the radicle penetrates the surrounding structures. At this time, another burst of respiratory activity occurs. Rapidly upon imbibition, messages encoding proteins that are important during seed maturation and drying are likely to be degraded. Conversely, new transcripts encoding proteins required during early germination are synthesized, Resumption of protein synthesis take place soon after imbibition, for all of the components necessary for protein synthesis are present within the cells of mature dry seeds. Radicle extension through the structures surrounding the embryo is the event that terminates germination and marks the commencement of seedling growth. It is cautioned here that mobilization and conversion of the major stored reserves are postgerminative events that are important during seedling growth, but they are unrelated to germination. 种子萌发需要的环境条件 种子萌发需要合适的环境条件：包括足够的水分，充足的氧气和适当的温度。 种子吸水是完成萌发过程关键的第一步。因为很多种子有厚和硬的种皮。吸水后 种皮才会软化，氧气得以穿过种皮进入，种子的有氧呼吸增强。同时，种子吸水 后，胶状的细胞质变成流动状，分子可以在细胞内自由运动，生化反应才可能进 行。种子吸水后，细胞内的酶由非水合状态变为水合状态，恢复活力参与生化反