1. © 2011, 2007, 2002, 1988 Pearson Education, Inc. Pearson Prentice Hall - Upper Saddle River, NJ 07458 Practical Horticulture 5 th edition By Margaret J. McMahon, Anton M. Kofranek and Vincent E. Rubatsky tab Chapter 12 - Water Relations Plant Water - Absorption and Conduction Water is absorbed by the roots from the soil and distributed through the plant, to its highest leaves. Water enters root xylem by active & passive forces. –Upward movement of water occurs mainly in the xylem. Once in the xylem, potential or tension decreases from the root to the stem, to the leaves, to the air Minerals dissolved in the water are also carried to leaves, stems, and fruits via the xylem stream.

2. © 2011, 2007, 2002, 1988 Pearson Education, Inc. Pearson Prentice Hall - Upper Saddle River, NJ 07458 Practical Horticulture 5 th edition By Margaret J. McMahon, Anton M. Kofranek and Vincent E. Rubatsky tab Chapter 12 - Water Relations Plant Water - Transpiration. A water potential difference is created between dry mesophyll cells and the walls of adjacent moist cells. Evaporation of water from leaves is one of the most important ways a plant regulates its temperature. When there is not enough water available for plants to take in, the stomates close to conserve water.

3. © 2011, 2007, 2002, 1988 Pearson Education, Inc. Pearson Prentice Hall - Upper Saddle River, NJ 07458 Practical Horticulture 5 th edition By Margaret J. McMahon, Anton M. Kofranek and Vincent E. Rubatsky tab Chapter 12 - Water Relations Plant Water - Transpiration. Some water is part of the plant’s structures or held in the cytoplasm, some is used for biochemical processes, and some is stored in the tonoplast. The high volume water inside a cell creates turgor pressure, which gives plants rigidity. –If there is insufficient water to create turgor, plants wilt.

4. © 2011, 2007, 2002, 1988 Pearson Education, Inc. Pearson Prentice Hall - Upper Saddle River, NJ 07458 Practical Horticulture 5 th edition By Margaret J. McMahon, Anton M. Kofranek and Vincent E. Rubatsky tab Chapter 12 - Water Relations Absorption and Transport of Mineral Nutrients Minerals initially needed to start growth of a plant are normally provided by the seed or stored in the propagating tissue. –Additional nutrients must be absorbed from the soil. Plasma membranes of cells are largely impermeable to the movement of ions. –Energy is required to move ions against the concentration gradient and through the impermeable membranes. –Facilitated by special proteins in the plasma membranes.

5. © 2011, 2007, 2002, 1988 Pearson Education, Inc. Pearson Prentice Hall - Upper Saddle River, NJ 07458 Practical Horticulture 5 th edition By Margaret J. McMahon, Anton M. Kofranek and Vincent E. Rubatsky tab Chapter 12 - Water Relations Absorption and Transport of Mineral Nutrients Following release of the ion, the protein resumes its original shape or position and is able to carry another potassium ion.

6. © 2011, 2007, 2002, 1988 Pearson Education, Inc. Pearson Prentice Hall - Upper Saddle River, NJ 07458 Practical Horticulture 5 th edition By Margaret J. McMahon, Anton M. Kofranek and Vincent E. Rubatsky tab Chapter 12 - Water Relations Translocation of Sugars Sugars move throughout the plant, primarily in the phloem tissues. –Down from leaves to roots, lateral or upward from leaves to fruits or buds or other storage organs. In woody perennials, phloem tissue is just underneath the bark following development of secondary vascular tissue.

7. © 2011, 2007, 2002, 1988 Pearson Education, Inc. Pearson Prentice Hall - Upper Saddle River, NJ 07458 Practical Horticulture 5 th edition By Margaret J. McMahon, Anton M. Kofranek and Vincent E. Rubatsky tab Chapter 12 - Water Relations Translocation of Sugars Metabolites, ions, and water move through plants by the a variety of processes: –Diffusion, which transports ions and molecules slowly. –Cytoplasmic streaming, which transports molecules and ions within the cytoplasm faster than diffusion. –Multi-directional mass flow translocation of material in the phloem. –Very rapid upward movement of water and mineral nutrients through the xylem.