© 2011, 2007, 2002, 1988 Pearson Education, Inc. Pearson Prentice Hall - Upper Saddle River, NJ Practical Horticulture 5 th edition By Margaret J. McMahon, Anton M. Kofranek and Vincent E. Rubatsky tab Chapter 7 - Plant Growth and Development Germination and Early Seedling Growth In general, seed germination occurs in three stages: –Imbibition (water uptake). –Increase in biological activity. –Radicle (root) and shoot emergence. Figure 7-1 The seed on the left has not begun to germinate. The center seed has imbibed water. The seed on the right has the radicle & plumule emerging.

© 2011, 2007, 2002, 1988 Pearson Education, Inc. Pearson Prentice Hall - Upper Saddle River, NJ Practical Horticulture 5 th edition By Margaret J. McMahon, Anton M. Kofranek and Vincent E. Rubatsky tab Chapter 7 - Plant Growth and Development Germination and Early Seedling Growth Germination starts with the seed imibing water. –This causes cells to swell and the seed increases in size. Cells elongate and begin to divide and differentiate. Leaves start to photosynthesize & the new plant is then independent of energy reserves in the seed.

© 2011, 2007, 2002, 1988 Pearson Education, Inc. Pearson Prentice Hall - Upper Saddle River, NJ Practical Horticulture 5 th edition By Margaret J. McMahon, Anton M. Kofranek and Vincent E. Rubatsky tab Chapter 7 - Plant Growth and Development Vegetative Growth/Development - Shoots & Roots Strictly speaking, vegetative growth includes roots, shoots, and leaves, but not reproductive structures.

© 2011, 2007, 2002, 1988 Pearson Education, Inc. Pearson Prentice Hall - Upper Saddle River, NJ Practical Horticulture 5 th edition By Margaret J. McMahon, Anton M. Kofranek and Vincent E. Rubatsky tab Chapter 7 - Plant Growth and Development Vegetative Growth/Development - Shoots & Roots Four principal functions of roots in higher plants are: The roots of some plants can also function in vegetative reproduction, as in root cuttings. Once the radicle emerges & enters the soil, the root grows through the soil, bringing it in contact with water and nutrients. –Anchoring plants in the soil. –Absorbing water and mineral nutrients. –Conducting water and dissolved minerals –Storing food materials

© 2011, 2007, 2002, 1988 Pearson Education, Inc. Pearson Prentice Hall - Upper Saddle River, NJ Practical Horticulture 5 th edition By Margaret J. McMahon, Anton M. Kofranek and Vincent E. Rubatsky tab Chapter 7 - Plant Growth and Development Vegetative Growth/Development - Shoots & Roots The root system and the shoot system maintain a balance—as the top of the plant grows larger, leaf area & water loss through transpiration increases. –Increased water loss is made up by water absorption from an increasing root system. The enlarging shoot and root systems also requires greater amounts of water and mineral absorption. The spring flush of root growth results from the accumulated foods stored the previous year.

© 2011, 2007, 2002, 1988 Pearson Education, Inc. Pearson Prentice Hall - Upper Saddle River, NJ Practical Horticulture 5 th edition By Margaret J. McMahon, Anton M. Kofranek and Vincent E. Rubatsky tab Chapter 7 - Plant Growth and Development Vegetative Growth/Development - Shoots & Roots Shoot growth is determinate or indeterminate. –Determinate growth - after a period of vegetative growth, flower bud clusters form at shoot terminals so most shoot elongation stops. –Indeterminate growth plants bear flower clusters laterally along the stems in the axils of the leaves.

© 2011, 2007, 2002, 1988 Pearson Education, Inc. Pearson Prentice Hall - Upper Saddle River, NJ Practical Horticulture 5 th edition By Margaret J. McMahon, Anton M. Kofranek and Vincent E. Rubatsky tab Chapter 7 - Plant Growth and Development Vegetative Growth/Development - Shoots & Roots Stem growth is limited in the first growing season. Plants remain alive (dormant) through the winter. Figure 7-13Hollyhocks are a biennial plant. The plant on the right is two years old and flowering. The one on the left is in its first growing season and will remain vegetative.

© 2011, 2007, 2002, 1988 Pearson Education, Inc. Pearson Prentice Hall - Upper Saddle River, NJ Practical Horticulture 5 th edition By Margaret J. McMahon, Anton M. Kofranek and Vincent E. Rubatsky tab Chapter 7 - Plant Growth and Development Vegetative Growth/Development - Shoots & Roots Exposure to chilling temperatures triggers hormonal changes leading to stem elongation, flowering, fruit Most annual and biennial plants flower and fruit only once before dying. –In woody perennial plants, shoot & root systems remain alive indefinitely, growing to the ultimate size for the particular plant. –Magnitude of growth can vary considerably from season to season.

© 2011, 2007, 2002, 1988 Pearson Education, Inc. Pearson Prentice Hall - Upper Saddle River, NJ Practical Horticulture 5 th edition By Margaret J. McMahon, Anton M. Kofranek and Vincent E. Rubatsky tab Chapter 7 - Plant Growth and Development Phase Change: Juvenility, Maturation, Senescence A newly seedling undergoes a phasic development throughout life—essentially the same as in animals. –Embryonic growth; juvenility; a transition stage; maturity or adult phase; senescence; and death. The juvenile phase is characterized by the inability to reproduce sexually. –The duration of the juvenile phase varies from a week or two up to thirty or forty years in some tree species.

© 2011, 2007, 2002, 1988 Pearson Education, Inc. Pearson Prentice Hall - Upper Saddle River, NJ Practical Horticulture 5 th edition By Margaret J. McMahon, Anton M. Kofranek and Vincent E. Rubatsky tab Chapter 7 - Plant Growth and Development Phase Change: Juvenility, Maturation, Senescence The morphology of juvenile and adult plants is often quite different. Juvenile acacia leaves are bipinnately compound, while the adult form appears linear