Plant Form and Function

1. Plant Form and Function Chapter 35 Structure, Growth, and Development

2. The plant body has a hierarchy of organs, tissues, and cells • There are three basic plant organs: • Roots • Stems • Leaves

3. Fibrous Roots Tap Roots Micorrhizae – fungus that forms a symbiotic relationship with some plants Roots • Rootsare multicellular organs with important functions: • Anchoring the plant • Absorbing minerals and water • Storing organic nutrients

4. Stems – function primarily to display the leaves. Terminal Bud – area of growth at the top end of stem Axillary Buds – area of growth located in the V area between the leaf and the stem (branches) Leaves – main photosynthetic organ in plants Shoot System: Stems and Leaves Reproductive shoot (flower) Apical bud Node Internode Apical bud Shoot system Vegetative shoot Blade Leaf Petiole Axillary bud Stem Taproot Lateral branch roots Root system

5. There are three basic groups of plant tissues: • Dermal Tissue • Single layer of closely packed cells • Protects plant against water loss and invasion by pathogens and viruses • Cuticle – waxy layer in leaves • Vascular Tissue • Xylem and phloem • Ground Tissue • Any tissue that’s not Dermal or Vascular tissue • Pith – ground tissue located inside vascular tissue • Cortex – ground tissue located outside the vascular tissue

6. Plants have 5 major types of cells: • Parenchyma • Most abundant • present throughout plant • most metabolism (photosynthesis) • Collenchyma • Grouped in cylinders, supports growing parts of plant • Strings of celery (vascular tissue) is supported by collenchyma cells • Sclerenchyma • Exists in parts of the plant that are no longer growing • Tough cell walls utilized for support • Xylem • Phloem

7. Fig. 35-10a Parenchyma cells in Elodea leaf, with chloroplasts (LM) 60 µm

8. Fig. 35-10b 5 µm Collenchyma cells (in Helianthus stem) (LM)

9. Fig. 35-10c 5 µm Sclereid cells in pear (LM) 25 µm Cell wall Fiber cells (cross section from ash tree) (LM)

10. Fig. 35-10d 100 µm Vessel Tracheids Pits Tracheids and vessels (colorized SEM) Perforation plate Vessel element Vessel elements, with perforated end walls Tracheids

11. Fig. 35-10e Sieve-tube elements: longitudinal view (LM) 3 µm Sieve plate Sieve-tube element (left) and companion cell: cross section (TEM) Companion cells Sieve-tube elements Plasmodesma Sieve plate 30 µm 10 µm Nucleus of companion cells Sieve-tube elements: longitudinal view Sieve plate with pores (SEM)

12. Meristems generate cells for new organs • Apical meristems • Are located at the tips of roots and in buds of shoots. • Sites of cell division that allow plants to grow in length (primary growth) • Lateral meristems • results in growth which thickens the shoots and roots (secondary growth)

13. Primary Growth lengthens roots and shoots Cortex Vascular cylinder Epidermis Key to labels Zone of differentiation • Zone of cell division • Includes apical meristem • New cells produces • Root cap is located in root • Zone of elongation • Elongation of cells • Zone of maturation • Cell differentiation • Cell become functionally mature Root hair Dermal Ground Vascular Zone of elongation Apical meristem Zone of cell division Root cap 100 µm

14. Secondary Growth add girth to stems and roots in woody plants • Two lateral meristems • Vascular cambrium • Produces secondary xylem (wood) • Secondary phloem • Cork cambrium • Produces tough covering that replaces epidermis early in secondary growth • Bark includes all the tissues outside the vascular cambrium.

15. Growth, morphogenesis, and differentiation produce the plant body • Morphogenesis – the development of body form and organization. This is the process of cell specialization

16. Resource Acquisition and Transport in Vascular Plants Chapter 36

17. Transport occurs by: • Short-Distance • Diffusion • Active transport • Cotransport – the coupling of the steep gradient of one solute (H+) with a solute like sucrose • Long-Distance • Bulk flow – the movement of water through the plant from regions of high pressure to regions of low pressure • Aquaporins

18. Water Potential • Water potential is abbreviated as Ψand measured in units of pressure called megapascals (MPa) • Ψ = 0 MPa for pure water at sea level and room temperature • Water potential is a measurement that combines the effects of solute concentration and pressure • Water flows from regions of higher water potential to regions of lower water potential

19. Both pressure and solute concentration affect water potential The solute potential (ΨS) of a solution is proportional to the number of dissolved molecules Solute potential is also called osmotic potential Pressure potential (ΨP) is the physical pressure on a solution Turgor pressure is the pressure exerted by the plasma membrane against the cell wall, and the cell wall against the protoplast How Solutes and Pressure Affect Water Potential

20. Measuring Water Potential • Consider a U-shaped tube where the two arms are separated by a membrane permeable only to water • Water moves in the direction from higher water potential to lower water potential

21. Fig. 36-8a (a) 0.1 Msolution Purewater H2O ψP= 0ψS = −0.23 ψP= 0ψS= 0 ψ= −0.23 MPa ψ= 0 MPa

22. The addition of solutes reduces water potential

23. Fig. 36-8b (b) Positivepressure H2O ψP= 0.23ψS = −0.23 ψP= 0ψS= 0 ψ= 0 MPa ψ= 0 MPa

24. Physical pressure increases water potential

25. Fig. 36-8c (c) Increasedpositivepressure H2O ψP =  ψS = −0.23 ψP= 0ψS= 0 0.30 ψ= 0.07 MPa ψ= 0 MPa

26. Negative pressure decreases water potential

27. Fig. 36-8d (d) Negativepressure(tension) H2O ψP =ψS = −0.23 ψP = −0.30ψS = 0 0 ψ= −0.30 MPa ψ= −0.23 MPa

28. Fig. 36-8 (a) (d) (b) (c) Positivepressure Increasedpositivepressure Negativepressure(tension) 0.1 Msolution Purewater H2O H2O H2O H2O ψP = 0ψS= 0 ψP = 0ψS= −0.23 ψP = 0ψS= 0 ψP = 0.23ψS= −0.23 ψP= 0ψS = 0 ψP = 0.30ψS= −0.23 ψP = −0.30ψS= 0 ψP = 0ψS= −0.23 ψ ψ= 0 MPa ψ= 0 MPa ψ= 0.07 MPa ψ= −0.30 MPa ψ= −0.23 MPa ψ= 0 MPa = −0.23 MPa ψ= 0 MPa

29. Vegetative Propegation

30. Tropical Tropismstropism – turning response to a stimulus

32. Table 39-1