1 / 43

97% salt water 2% snow and ice (fresh water) 1% liquid fresh water

water. 97% salt water 2% snow and ice (fresh water) 1% liquid fresh water. 0.001% of total fresh water is available. for agriculture (70% ) for industry (20 %) for domestic (10%). The water shortage on a global scale. More than half of the world’s population

patricia-mills
Download Presentation

97% salt water 2% snow and ice (fresh water) 1% liquid fresh water

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. water 97% salt water 2% snow and ice (fresh water) 1% liquid fresh water 0.001% of total fresh water is available for agriculture (70% ) for industry (20 %) for domestic (10%)

  2. The water shortage on a global scale More than half of the world’s population lives in countries with varying degrees of water scarcity (FAO 2003).

  3. 2010年以来，云南遭遇三年连旱。 多地旱情严重，农作物受灾。 超过310万人饮水困难。 Water means life!

  4. Water means yields!

  5. Water means yields! Corn yield as a function of water availability

  6. Water means yields! Productivity of various ecosystems as a function of annual precipitation降水量

  7. Lecture 8 Water and Plant Cells Outline * Water properties * Water in plant life * Water potential * Water transport processes

  8. Water Properties 水是极性分子， H和O之间容易形成氢键。

  9. Water Properties 聚合态 游离态 水是普遍的极性容剂

  10. Water Properties Water has high specific heat（比热） 单位质量某物质升高1度所需要的热量。 水温不易改变， 以水为介质的生命活动可以在相对稳定环境进行。 入冬前， 冬小麦等越冬植物浇防冻水的原理？

  11. Water Properties Water has highlatent heat of vaporization (汽化热) 恒温下单位质量物质由液相变为气相所需要的热量 蒸腾时带走大量热量， 降低植物体温度。

  12. Water Properties 液体状态下同类分子间的吸引力 Cohesion 内聚力 内聚力给予水柱 相当于同样粗铜丝 的10%的抗张强度

  13. Water Properties Insect walking on the water Water has surface tension at an air-liquid interface

  14. Water Properties Water has surface tension at an air-liquid interface 表面张力： 打破气-液交界面 所需要的能量 内聚力越大，表面张力越大。

  15. Water Properties Adhesion 附着力： 水分子与固相表面分子之间的吸引力 若附着力＞内聚力， 则: 该物质表面可湿， 该液体为浸润液体。 水可浸润土壤、滤纸、木材等。

  16. Water Properties Adhesion 附着力： 若: 附着力＜内聚力， 则：该物质表面不可湿。 该液体为不浸润液体。

  17. Water Properties 毛细现象 Capillarity 液体在毛细管中 上升或下降的现象。 水浸润玻璃 水银不浸润玻璃 • 毛细管插入浸润液体中，管内液面上升； • 毛细管插入不浸润液体中，管内液体下降。

  18. Water Properties 毛细现象促进植物吸收和运输水分 • 细胞壁可湿，水可湿润细胞壁。 - 导管壁可湿，水可沿导管运输。

  19. Water Properties 毛细上升带 毛细现象促进植物吸收和运输水分 • 土壤可湿， • 土壤下层的水分可通过毛细作用上升。

  20. Lecture 8 Water and Plant Cells Outline * Water properties * Water in plant life * Water potential * Water transport processes

  21. Water in Plant Life Water Content 含水量 植物所含水分的量占鲜重的百分数 WC (%) = 【(FW-DW)/FW】×100% FW，fresh weight DW，dry weight

  22. Water in Plant Life Relative Water Content, RWC（相对含水量） 植物实际含水量占水分饱和时含水量的百分率 RWC = (FW-DW) / (TW-DW) 怎样使组织达到水分饱和？ (See Handout)

  23. Water in Plant Life Water status in plant 存在状态 Bound water 束缚水 自由水／束缚水 Free water 自由水

  24. Lecture 8 Water and Plant Cells Outline * Water properties * Water in plant life * Water potential * Water transport processes

  25. Water potential 水势 恒温恒压下，一偏摩尔体积水与纯水之间的化学势差 ψw = （µw -µw0）/ Vw,m 化学势µ” ：体系中某偏摩尔体积组分的自由能。 规定：纯水化学势 µw0 = 0 纯水 ψw = 0

  26. Water potential 溶液水势 ψw = ψs +ψp +ψg ψw= ψs = - i RTC (KPa ,千帕) R： 气体常数8.32J/(mol.K) T： 绝对温度 = ( 273+t) K（Kelvin） i：溶质的解离系数 C：溶质的浓度，mol/L 负号：溶解的溶质降低了溶液的水势

  27. Water potential 计算： 0.1 mol/L葡萄糖溶液的渗透势 ψs = -1×0.1RT 0.1 mol/L NaCl溶液的渗透势 ψs = -2×0.1RT

  28. Water potential 植物细胞水势 ψw = ψs +ψp + ψm + ψg ΨmMatric potential 衬质势： 由于亲水的衬质与水分子的相互作用 使水的自由能降低的部分。 风干种子的 ψw = ψm 成熟细胞ψm≈0 成熟植物细胞水势 ψw = ψs +ψp

  29. Water potential ψw= ψs+ψp 植物细胞水势 Ψp: 压力势 (王宝山，P11) - 吸胀的细胞ψp＞0 - 刚开始质壁分离而未分离的细胞ψp=0 - 已经质壁分离的细胞ψp＜0

  30. Water potential 水运动方向： 高水势 →低水势

  31. Water potential Pressure-Flow Model (Lecture 5) 筛管的液流 源端→库端

  32. Lecture 8 Water and Plant Cells Outline * Water properties * Water in plant life * Water potential * Water transport processes

  33. Water Transport Processes 集流 Bulk Flow in phloem in xylem in soil in river 所有水分子进行一致的全体运动。 特点： 速度快 适合长距离运输 驱动力：压力梯度

  34. Water Transport Processes 扩散 Diffusion 物质内部由于随机热运动 而导致原子或分子迁移的过程。 运动的方向： 高自由能 → 低自由能 高浓度 → 低浓度

  35. Water Transport Processes 扩散 Diffusion 驱动力：浓度梯度 速度较慢 适宜短距离运输 For a glucose molecule d=50 µm (a cell), t = 2.5s d=1m, t ≈ 32 years

  36. Water Transport Processes 渗透 Osmosis 水分的跨膜扩散 水从水势高的一侧通过选择性半透膜 扩散到水势低的一侧。 驱动力：水势差 方向： 高水势 → 低水势

  37. Water Transport Processes 水分的跨膜扩散 Simple diffusion 简单扩散 Facilitated diffusion 易化扩散

  38. Water Transport Processes Aquaporins 水孔蛋白: 跨膜蛋白形成的 选择性水通道， 允许水快速通过， 提高了水 的渗透效率。

  39. Water Transport Processes 等渗溶液 低渗溶液 高渗溶液 渗透 Osmosis 渗透溶液： 溶液ψw ＝细胞ψw 溶液ψw ＞细胞ψw 溶液ψw ＜细胞ψw

  40. Water Transport Processes 渗透 Osmosis 低渗溶液

  41. Water Transport Processes 渗透 Osmosis 高渗溶液 初始质壁分离

  42. Take-home-lesson (See handout)

  43. THANKS

More Related