Status of water in plants bound water free water √ Cytoplasm Protein =60% Hydrophilic Hydrophobic OO OD
Status of water in plants ➢ bound water ➢ free water ✓ Cytoplasm Protein = 60% • Hydrophilic • Hydrophobic
How Does water move? Passive processes Diffusion -down a concentration gradient Bulk Flow-down a pressure-driven gradient Osmosis -down both a concentration pressure driven gradient water potential) Across a selectively semi-permeable membrane
How Does Water Move? – Passive Processes ➢ Diffusion - down a concentration gradient. ➢ Bulk Flow - down a pressure-driven gradient. ➢ Osmosis - down both a concentration & pressure driven gradient (= water potential). • Across a selectively semi-permeable membrane
Diffusio Diffusion-directed movement- high to low concentration(higher to lower free energy) Random thermal motion Significant role in short-distance movement
Diffusion ➢ Diffusion - directed movement - high to low concentration (higher to lower free energy). ➢ Random thermal motion. ➢ Significant role in: • short-distance movement
Bulk Flow E Mass Flow The concerted movement of groups of molecules by mass, most often in response to a pressure gradient Examples Water moving through the xylem Ariver flowing, rain falling Controled by Aquaporin(水孔蛋白)
Bulk Flow = Mass Flow ➢ The concerted movement of groups of molecules by mass, most often in response to a pressure gradient. ➢ Examples: • Water moving through the xylem. • A river flowing, rain falling. ➢ Controled by : • Aquaporin (水孔蛋白）
细胞外 水分子 水分子选择性孔 X 膜双分子层 088 细胞质 6882 图3.6水分子可以穿过植物体膜,通过单个水分子的扩散作用穿过 膜双分子层,如左部分所示,微量的水分子流通过由完整膜 蛋白如水孔蛋白形成的水分子选择性孔道进入植物体膜内