Plant Growth and Structure

1. Plant Growth and Structure Chapters 24 and 27

2. Growth and Development of Embryos • embryo develops from the zygote • fertilization  diploid zygote  mitotic divisions  embryo • embryos contained and develop within protective seeds • structure of embryos • one or two cotyledons (“seed leaves”) • main part of embryo • first to begin photosynthesis • epicotyl • develops into shoot system (stem) • hypocotyl • radicle portion  develops into root system • suspensor • connects embryo to endosperm

3. Fig. 27.7 Development of a eudicot embryo

4. Growth and Development of Seeds • after fertilization, eachovule develops into a seed • seeds consist of 3 basic parts • developing plant embryo (with all its parts) • endosperm • outer seed coat • develops from the ovule integuments • viability and dormancy of seeds Fig. 27.8 Monocot vs. eudicot seeds

5. Growth and Development of Fruits • after fertilization, the ovary develops into a fruit • fleshy vs. dry fruits • simple vs. aggregate vs. multiple fruits • function of all fruits is seed dispersal

6. Fig. 27.9 Different types of fruits and fruit anatomy

7. Seed Germination • requires proper conditions • process • radiclethrusts through seed coat and into soil • formation of primary root  development of root system • mycorrhizalassociations (mycorrhizae) • epicotylbreaks through seed coat and into air • formation of shoot system • beginnings of photosynthesis

8. Fig. 27.11 Bean (eudicot) vs. corn (monocot) germination

9. Primary Growth • apical meristems • found at tips of roots and shoots • increases in length, both up and down • occurs in both herbaceous and woody plants • after division, the cells become primary meristems • protoderm • becomes plant's protective tissues • epidermis • procambium • becomes plant's vascular tissues • primary xylem and primary phloem • some cells become the vascular cambium • ground meristem • becomes plant's support/structure tissues • cortex, pith, and other tissues • cells are parenchyma, collenchyma, or sclerenchyma • parenchyma also perform metabolic functions • some cells of the cortex become the cork cambium • primary tissues • xylem, phloem, pith, cortex, epidermis

10. Fig. 24.5 Cells of the ground meristem

11. Fig. 24.13 Shoot tip and primary meristems

12. primary growth of roots • radicleportion of hypocotyl • root apical meristems • protected by a root cap • several zones of growth: • zone of cell division • apical and primary meristems active mitosis • zone of elongation and differentiation • cells growing and developing into their appropriate tissue • zone of maturation • cells fully grown and functioning as their tissue • contains root hairs • increase absorptive surface area • roots contain two unique tissues: • endodermis • regulates amount of water entering vascular tissues of root • pericycle • divides to form lateral roots

13. Fig. 24.8 Eudicot root tip

14. functions of roots • anchor the plant • how to improve anchoring • development of a root system • tap vs. fibrous root system • adventitious roots • develop from stem tissues • accompany others • absorbing water and nutrients • root hairs increase surface area for absorption • root hairs  lateral roots  main roots • vascular tissues in central portion • storing sugars (and other carbs.) as starch • plants rely on stored food during winter Fig. 24.11 Types of root systems

15. primary growth of stems • epicotylportion of embryo • shoot apical meristems • no “shoot caps” (why?) • same zones of growth as roots • nodes • specialized regions where leaves form • leaves begin as leaf primordia • internodes • regions where no leaves grow • axillary(lateral) buds • special regions that become new stems or flowers • functions of stems • produce/support leaves, flowers, fruits • transport of water and minerals • occurs in vascular bundles • lateral transport of materials • xylem and phloem rays • minor photosynthesis • storing sugars (and other carbs.) as starch Fig. 24.1 Organization of a plant body

16. leaves • blade and petiole • classified as simple or compound • leaflets Fig. 24.21 Classification of leaves

17. leaf structure and anatomy • cuticle • waxy layer  protection and water retention • epidermis (upper and lower) • protection and gas exchange • contains numerous small pores called stomata • gas exchange  CO2in; H2O vapor and O2 out • guard cellsopen and close the stomata • mesophyll • photosynthetic tissue of plants (chloroplasts) • palisade layer • pillar-shaped cells found in eudicots only • spongy mesophyll • contains numerous air spaces • vascular bundles • xylem and phloem that form “leaf veins” (leaf venation) • net vs. parallel venation • support and structure • leaf functions • photosyn., gas exch., cons. of H2O, structural support

18. Fig. 24.20 Leaf structure

19. Fig. 25.13 Opening and closing of stomata

20. Secondary Growth • lateral meristems (cambia) • only found in woodyplants • primarily in stems, but also in roots • occur in rings • increases in width • secondary tissues • secondary xylem and phloem, cork • sec. xylem forms annual growth rings and becomes wood • bark vs. periderm • two types of lateral meristems • vascular cambium • near center of stem • derived from the procambium • forms new secondary xylem and secondary phloem • cork cambium • near outside of stem • derived from cortex that develops from ground meristem • forms new cork and cortex cells

21. Fig. 24.16 Secondary growth of stems

22. Fig. 24.17 Three-year-old woody twig

23. Secondary Tissues Primary Meristems Primary Tissues Lateral Meristems Protoderm Epidermis Apical meristem of stem Secondary phloem Primary phloem Procambium Vascular cambium Secondary xylem Primary xylem Ground meristem Pith and Cortex Cork cambium Cork A summary of primary and secondary growth in woody stems