Plant Anatomy

2. Plant Anatomy

4. Basic plant anatomy • root • root tip • root hairs

5. Roots 1 • Roots anchor plant in soil, absorb minerals & water, & store food • fibrous roots(1) • mat of thin roots that spread out • monocots • tap roots(2) • 1 large vertical root • also produces many small lateral, or branch roots • dicots • root hairs(3) • increase absorptive surface area 2 3

6. Basic plant anatomy • root • root tip • root hairs • shoot (stem) • nodes • internodes • buds • terminal or apical buds • axillary buds • flower buds & flowers

7. Modified shoots stolons (strawberries) rhizome (ginger) tuber (potato) bulb (onion)

8. Basic plant anatomy • root • root tip • root hairs • shoot (stem) • nodes • internodes • buds • terminal or apical buds • axillary buds • flower buds & flowers • leaves • mesophyll tissue • veins (vascular bundles)

9. Leaves • Function of leaves • photosynthesis • energy production • CHO production • gas exchange • transpiration simple vs. compound

10. Modified leaves tendrils (peas) spines (cacti) succulent leaves colored leaves (poinsetta)

11. Fig. 35-18 Guard cells Key to labels Stomatal pore 50 µm Dermal Epidermal cell Ground Cuticle Sclerenchyma fibers Vascular Stoma (b) Surface view of a spiderwort (Tradescantia) leaf (LM) Upper epidermis Palisade mesophyll Spongy mesophyll Bundle- sheath cell Lower epidermis 100 µm Cuticle Xylem Vein Phloem Vein Air spaces Guard cells Guard cells (a) Cutaway drawing of leaf tissues (c) Cross section of a lilac (Syringa)) leaf (LM)

12. Tissue Organization of Leaves • Stomata – pores in epidermis which allow CO2 exchange between the air and the photosynthetic cells in a leaf • Each pore is flanked by two guard cells,which regulate its opening and closing • The ground tissue in a leaf, called mesophyll, is sandwiched between the upper and lower epidermis

13. Tissue Organization of Leaves • Below the palisade mesophyll in the upper part of the leaf is loosely arranged spongy mesophyll, where gas exchange occurs • The vascular tissue of each leaf is continuous with the vascular tissue of the stem • Veins are the leaf’s vascular bundles and function as the leaf’s skeleton • Each vein in a leaf is enclosed by a protective bundle sheath

14. Interdependent systems • Both systems depend on the other • roots depend on sugars produced by photosynthetic leaves • shoots depend on water & minerals absorbed from the soil by roots sugars water &minerals

15. Plant Tissues • Dermal • epidermis (“skin” of plant) • single layer of tightly packed cells that covers & protects plant • Ground • bulk of plant tissue • photosynthetic mesophyll, storage • Vascular • transport system in shoots & roots • xylem & phloem

16. Plant Cell Types in Plant Tissues • Parenchyma • “typical” plant cells = least specialized • photosynthetic cells, storage cells • tissue of leaves, stem, fruit, storage roots • Collenchyma • unevenly thickened primary walls • support • Sclerenchyma • very thick, “woody” secondary walls • support • rigid cells that can’t elongate • dead at functional maturity

17. Parenchyma • Parenchyma cells are unspecialized, thin, flexible & carry out many metabolic functions • all other cell types develop from parenchyma

18. Collenchyma • Collenchyma cells have thicker primary walls & provide support • help support without restraining growth • remain alive in maturity the strings in celery stalks are collenchyma

19. Sclerenchyma • Thick, rigid cell wall • lignin (wood) • cannot elongate • mostly dead at maturity • Cells for support • xylem vessels • xylem tracheids • fibers • rope fibers • Hemp/flax • sclereids • nutshells • seed coats • grittiness in pears

20. Vascular tissue vessel elements • Xylem • move water & minerals up from roots • dead cells at functional maturity • only cell walls remain • need empty pipes to efficiently move H2O • transpirational pull vessel element dead cells tracheids

21. Phloem: food-conducting cells • carry sugars & nutrients throughout plant sieve tube companion cell sieve plate plasmodesmata living cells