Plant Structure

1. Plant Structure By Kolby Lundgren

2. Objectives • to understand the concept of phenotypic plasticity • to know the three main plant organs and be able to recognize the adaptations that each separate organ can display • to know the economic importance of plant organs • to know the three main tissues that exist in a plant’s organs • be introduced to two types of plant cells, including their location and their characteristics

3. Phenotypic Plasticity • Ability to alter phenotypic form in response to environmental conditions • Why would plants need phenotypic plasticity?

4. Immobile organisms must adapt to their environment or they will die • Leaf sizes and thicknesses are a prime example of phenotypic plasticity Redwood Bonsai (Sequoia tree)

5. Morphology of vascular plants • Roots and shoots rely on one another • Three main organs: roots, stems and leaves. • Each is capable of making novel modifications to meet their needs • The three main organs are homologous structures in land plants • Homology similar in structure and evolutionary origin, though not necessarily in function • Analogy corresponding in function, but not evolved from corresponding organs

6. Roots • Anchor plants in soil and absorb minerals and water • Some store carbohydrates • Root hairs near tips increase surface area • Two types of root systems

7. Taproot vs. Fibrous • Taproots develop from embryonic root • Lateral roots • Angiosperms store sugar and starches to consume during flower and fruit production • Fibrous roots form from stem; no one functions as main root • Can you name some examples of taproots?

8. Economic Importance of Roots • Most root crops are predominantly taproots, such as carrots, turnips, beets, and radishes • Important sources of food for human consumption

9. Modifications (pg. 740) • Support or anchorage • Store water and nutrients • Absorb more oxygen from the air Pneumatophores (air roots) Storage Roots- carrots Prop roots (support)- Banyan Tree

10. Stems • Has alternating system of nodes and internodes • Apical bud at tip; has developing leaves and series of nodes and internodes • Axillary bud can form lateral shoots; dormant in young shoots because of apical dominance • Can you come up with reasons for an axillary bud to break its dormancy?

11. Modifications(pg. 741) • Food storages • Asexual reproduction • Bulbs and stolons Stolons- strawberry Bulb- onion

12. Economic Importance • Major staple crops: sugarcane stems, potato and taro. • Vegetables such as asparagus • Cinnamon is bark from a tree (stem) • Medicines obtained from barks of tree (stem)

13. Leaves • Main photosynthetic organ • General structure is a flattened blade and a stalk (petiole.) • Monocots have parallel major veins; eudicots have a branched network of veins • Simple, compound or doubly compound leaf shapes • What might be the advantage of having compound or doubly compound leaf structures?

14. Modifications Storage leaves- succulent • Support • Protection • Storage • Reproduction Asexual reproduction- Bryophyllum Trichomes

15. Economic Importance of Leaves • Tobacco leaves • Lettuce, cabbage, spinach, celery • Tea • Eucalyptus • Culinary- bay leaf, basil, cilantro

16. What modified plant organ is garlic?

17. Plant Tissues • Each plant organ has dermal, vascular, and ground tissues • Form tissue system • Specific characteristics and spatial arrangement vary

18. Dermal Tissue • Dermal tissue system is outer protective covering epidermis, cuticle and periderm • Protect plant from water loss and disease; unique jobs in each organ • Examples are root hairs and trichomes

19. Vascular Tissue • Vascular tissue system carries out long distance transport of materials • Two types: xylem and phloem • Xylem takes minerals and waters up; phloem transports sugars down to roots and sites of new growth • Stele is vascular tissue of roots or stem arrangement varies in species and organs

20. Ground Tissue • Ground tissue system is neither dermal nor vascular • Internal to vascular tissue is pith • External to vascular tissue is cortex • Includes cells with specialized functions storage, photosynthesis and support

21. Types of Cells • Parenchyma cells have primary cells walls that are flexible • “typical” plant cells • Photosynthesis occurs here • Fleshy tissue of fruits • Retains ability to divide

22. Types of Cells • Collenchyma cells are grouped in strands or cylinders • Young stems and petioles have strands of cells below epidermis • Thicker walls; strings in celery • Lack secondary walls; absence of lignin allows them to provide flexible support without restricting growth

23. QUIZZY TIME • Name two of the three plant organs that can be modified for reproduction? • Name one example each of a modification for roots, stems and leaves. • What is the difference between a homologous structure and an analogous structure? • What organ of the human body is analogous to dermal tissue? • Write the plant tissue name next to the number that corresponds to its general location.