Plant Structure (Leaves, Stems, Roots)

1. Plant Structure (Leaves, Stems, Roots) Honors Biology

2. Plant Body • Shoot system = leaves + stem • Root system • Meristem = cells that divide for life of plant, can give rise to all plant structures 3 BASIC Organs • Roots • Stems • Leaves

3. 2 BASIC Systems • BOTH SYSTEMS DEPEND ON THE OTHER • Root System (roots) receive sugars and other nutrients from photosynthetic parts • Shoot System (leaves and stems) depends on water & minerals absorbed from the soil by roots.

4. Tissue Types in Vascular Plants • Dermal Tissue • Covers/ protects plant • Makes cuticle on stems/ leaves • Allows for better H2O absorption (root hairs) • Make guard cells • Vascular Tissue (xylem & phloem) • Transport and support • Throughout the plant • Called “veins” in leaves • Called the “stele” in stem or root • Ground Tissue • Between dermal and vascular tissues • Storage • Photosynthesis (makes sugars) • Support Dermal tissue Ground tissue Vascular tissue

5. Blade Petiole Plant Body-LEAF Leaf = blade + petiole Functions • Exposes surface to sunlight • Major site of photosynthesis • Conserves water • Provides for gas exchange • Transpiration-water movement throughout the plant; evaporation of water from plant leaves Stoma = opening in the leaf for gas exchange, water evaporation

6. Leaf Structure-Dermal layers • Cuticle-The thin waxy covering on the outer surface of the leaf has a thin waxy covering This layer's primary function is to prevent water loss within the leaf. (Plants that live entirely within water do not have a cuticle). • Directly underneath the cuticle is a layer of cells called the epidermis(upper and lower)

7. Leaf Tissues • Mesophyll • Ground tissue between upper and lower epidermis • Two types: • Palisade parenchyma (mesophyll) cells • Lots of chloroplasts in these cells • Most photosynthesis occurs here • Spongy parenchyma (mesophyll) cells • Lots of air spaces where O2 and CO2 circulate • Near stomata (Think: sponges have lots of air spaces) • Veins • Xylem and phloem are continuous from roots through stem to leaves

8. Vascular Tissue (Veins) • Transports materials in roots, stems, & leaves. • Xylem (dead cells-water conducting) • Carry water & minerals up from roots • Tube-shaped dead cells • Their walls are used as water pipes • Phloem (living cells-food conducting) • Carry nutrients (food) throughout plant • SUGARS (sucrose), amino acids…. • Tube-shaped living cells

9. Stomata and Guard Cells • The underside portion of a leaf has stomata and is the site of transpiration (water loss) and gas exchange.

10. Stomata help regulate the rate of transpiration • Guard cells • 2 cells on either side of stomata (surrounds stomata) • regulate water loss • What conditions will promote closing of guard cells? • Hot, dry, windy conditions

11. Stoma Opening/Closing • http://academic.kellogg.edu/herbrandsonc/bio111/animations/0021.swf

12. Plant Body- ROOTS Root Functions • Anchors plant in soil • Takes up water and minerals from soil

13. & gymnosperms

14. Modified Roots • Some plants have modified roots • Adventitious roots arise aboveground spread over large areas • Storage roots hold “food”  called root tubers

15. Phloem transports sugar Xylem conducts water and minerals Plant Body-STEM Stem: series of nodes and internodes Functions • Support for the plant body • Holds leaves up to light • Transports nutrients throughout plant

16. Division of Meristem Cells Causes Plant Growth • Apical Meristem • tips of root and shoot • increase in height • Lateral Meristem • cylinders within plant body • increase in width

17. Types of Meristems (like embryonic stem cells) • Apical meristemsare located at the tips of roots and in the buds of shoots • elongate shoots and roots, a process called primary growth • Lateral meristems • add thickness ONLY to woody plants, a process called secondary growth

18. MONOCOT PLANTS vs. DICOT PLANTS • Monocots: grasses, lilies, orchids, corn, palms, onions • Dicots (aka-Eudicots): broadleaf trees, shrubs, most flowers, and vegetables.