Plant Structure, Growth, & Development

1. Plant Structure, Growth, & Development

2. Reproductive shoot (flower) Terminal bud Node Internode LE 35-2 Terminal bud Shoot system Vegetable shoot Blade Leaf Petiole Axillary bud Stem Taproot Lateral roots Root system

3. Roots • Functions of roots: • Anchoring the plant • Absorbing minerals and water • Often storing organic nutrients

4. Root Hairs

5. LE 35-4a Prop roots.

6. LE 35-4b Storage roots.

7. LE 35-4c “Strangling” aerial roots.

8. LE 35-4d Buttress roots.

9. LE 35-4e Pneumatophores.

10. Stems • Stem • Nodes • points at which leaves are attached • Internodes • stem segments between nodes • axillary bud • has the potential to form a lateral shoot, or branch • terminal bud • located near the shoot tip • causes elongation of a young shoot

11. Modified stems Stolons.

12. Storage leaves LE 35-5b Stem Roots Bulbs.

13. LE 35-5c Tubers.

14. LE 35-5d Rhizomes. Node Rhizome Root

15. Leaves • Leaf • main photosynthetic organ • consist of • A flattened blade and a stalk • petiole • Monocots • parallel veins • Eudicots • branching veins

16. LE 35-6a Simple leaf Petiole Axillary bud

17. LE 35-6b Leaflet Compound leaf Petiole Axillary bud

18. LE 35-6c Doubly compound leaf Leaflet Petiole Axillary bud

19. Tendrils. Modified leaves

20. LE 35-7b Spines.

21. LE 35-7c Storage leaves.

22. LE 35-7d Bracts.

23. LE 35-7e Reproductive leaves.

24. Plant Tissues • Dermal • Epidermis (nonwoody) • Periderm (woody) • Vascular • Xylem • Water & dissolved minerals • Upward from roots to shoots • Phloem • organic nutrients • Transports from location made to where they are needed • Ground tissues • Storage, photosynthesis, & support

25. LE 35-8 Dermal tissue Ground tissue Vascular tissue

26. Some major types of plant cells: • Parenchyma • Collenchyma • Sclerenchyma • Water-conducting cells of the xylem • Sugar-conducting cells of the phloem

27. WATER-CONDUCTING CELLS OF THE XYLEM PARENCHYMA CELLS 100 µm Tracheids Vessel LE 35-9 Parenchyma cells in Elodea leaf, with chloroplasts (LM) 60 µm Pits COLLENCHYMA CELLS Cortical parenchyma cells Tracheids and vessels (colorized SEM) 80 µm Vessel element Vessel elements with perforated end walls Tracheids SUGAR-CONDUCTING CELLS OF THE PHLOEM Collenchyma cells (in cortex of Sambucus, elderberry; cell walls stained red) (LM) Sieve-tube members: longitudinal view (LM) SCLERENCHYMA CELLS 5 µm Companion cell Sclereid cells in pear (LM) Sieve-tube member 25 µm Plasmodesma Sieve plate Cell wall Nucleus Cytoplasm Companion cell 30 µm 15 µm Fiber cells (transverse section from ash tree) (LM) Sieve-tube members: longitudinal view Sieve plate with pores (LM)

28. Meristems • Apical meristems • located at the tips of roots and in the buds of shoots • elongate shoots and roots • primary growth • Lateral meristems • add thickness to woody plants • secondary growth • two types: • vascular cambium • adds layers of vascular tissue • secondary xylem (wood) • secondary phloem • cork cambium • replaces the epidermis with periderm • thicker and tougher

29. Primary growth in stems Shoot apical meristems (in buds) Epidermis Cortex LE 35-10 Primary phloem Primary xylem Vascular cambium Lateral meristems Pith Cork cambium Secondary growth in stems Periderm Cork cambium Pith Cortex Primary xylem Primary phloem Secondary xylem Root apical meristems Secondary phloem Vascular cambium

30. Terminal bud Bud scale Axillary buds LE 35-11 Leaf scar This year’s growth (one year old) Node Stem Internode One-year-old side branch formed from axillary bud near shoot apex Leaf scar Last year’s growth (two years old) Scars left by terminal bud scales of previous winters Growth of two years ago (three years old) Leaf scar

31. Primary Growth of Roots • Zone of cell division • Zone of elongation • Zone of maturation

32. Vascular cylinder Cortex Epidermis Key Zone of maturation LE 35-12 Root hair Dermal Ground Vascular Zone of elongation Apical meristem Zone of cell division Root cap 100 µm

33. Apical meristem Leaf primordia LE 35-15 Developing vascular strand Axillary bud meristems 0.25 mm

34. Tissue Organization of Stems Phloem Xylem LE 35-16 Ground tissue Sclerenchyma (fiber cells) Ground tissue connecting pith to cortex Pith Epidermis Key Vascular bundles Cortex Epidermis Dermal Vascular bundles Ground Vascular 1 mm 1 mm A monocot (maize) stem. Vascular bundles are scattered throughout the ground tissue. In such an arrangement, ground tissue is not partitioned into pith and cortex. (LM of transverse section) A eudicot (sunflower) stem. Vascular bundles form a ring. Ground tissue toward the inside is called pith, and ground tissue toward the outside is called cortex. (LM of transverse section)

35. Key to labels Guard cells Dermal Stomatal pore Ground Tissue Organization of Leaves Vascular Epidermal cells Sclerenchyma fibers 50 µm Cuticle Surface view of a spiderwort (Tradescantia) leaf (LM) Stoma Upper epidermis Palisade mesophyll Bundle- sheath cell Spongy mesophyll Lower epidermis Guard cells Cuticle Vein Xylem Vein Air spaces Guard cells Phloem Guard cells 100 µm Cutaway drawing of leaf tissues Transverse section of a lilac (Syringa) leaf (LM)

36. Morphogenesis and Pattern Formation • Pattern formation • development of specific structures in specific locations • determined by positional information • signals indicating to each cell its location • Ex. Polarity