【英语时差8,16】秋季落叶的奥秘-下
时间：2019-02-15 作者：英语课 分类：英语时差8，16
Because chlorophyll is the chemical responsible for making leaves green, its absence allows chemicals such as carotinoids, xanthophylls, and others to give leaves their orange, yellow, and various other colors. As trees stop producing chlorophyll, they start producing sugars and amino acids that act as a sort of antifreeze to protect plants from the winter cold. Meanwhile, nutrients 1 drain from the leaves, through the stems, and eventually into the roots, where they remain for the winter. When the nutrients have left the leaves, all that remain are cell walls and nutrient-depleted protoplasm. Since all that now holds leaves to a tree are brittle 2, dry, and easily broken veins 3, a gust 4 of wind is enough to tear leaves from the tree and send them fluttering to the ground. When dead leaves break away, they leave behind waxy 5 cells that form a small bud called a bundle scar. When warm weather returns, each scar will give rise to a newly born leaf.
- a lack of essential nutrients 基本营养的缺乏
- Nutrients are absorbed into the bloodstream. 营养素被吸收进血液。 来自《简明英汉词典》
- The pond was covered in a brittle layer of ice.池塘覆盖了一层易碎的冰。
- She gave a brittle laugh.她冷淡地笑了笑。
- The blood flows from the capillaries back into the veins. 血从毛细血管流回静脉。 来自《简明英汉词典》
- I felt a pleasant glow in all my veins from the wine. 喝过酒后我浑身的血都热烘烘的，感到很舒服。 来自《简明英汉词典》
- A gust of wind blew the front door shut.一阵大风吹来，把前门关上了。
- A gust of happiness swept through her.一股幸福的暖流流遍她的全身。