Plants II

1. Plants II Plant organs

2. Plant organs • Root system – roots • Shoot system – stem and leaves • Vegetative organs – (allow to live and grow): roots, leaves, stem • Reproduction: flowers, seeds and fruits

3. Roots • Underground, usually equal to shoot system in size • Anchors and gives support • Absorbs water and minerals • Penetrates soil as it grows • Root hairs increase surface area • Produce hormones

4. stems • Main axis of plant • Support leaves so that leaves are exposed to as much light as possible • Node – where leaf is attached • Internode – space between nodes • Vascular tissue used in transport • Can store nutrients and water and conduct photosynthesis

5. leaves • Photosynthesis • Size, shape and texture vary and is used in identification • Blade – wide portion of leaf • Petiole – stalk, attaches blade to stem • Axillary bud – where branch or flower may originate

6. Monocot vs Eudicot fig 25.3 • Compare seed leaf, root, stem, leaf and flower • Monocot – 1 seed leaf, xylem and phloem in a ring, vascular bundles scattered, leaf veins parallel, flower parts in 3’s and multiples of 3 • Eudicot – 2 seed leaves, phloem between arms of xylem, vascular bundles in ring, leaf veins in net pattern, flower parts in 4’s, 5’s • Eudicots make up larger group and include most familiar flowering plants • Monocots include grasses and most of food sources, like rice, wheat and corn

7. Plant tissues • Meristematic tissue = embryonic • Apical meristem – located on tip of stem and roots, growth • produces 3 types of meristem • Protoderm epidermis • Ground meristem  ground tissue • Procambium  vascular tissue • Woody (non herbaceous), non woody (herbaceous – perennial, dies back in winter)

8. Epidermal tissue • Forms outer protective covering of plant • Walls of epidermal cells exposed to air are covered with a waxy cuticle • Roots – form root hairs • Stems and leaves – trichomes – hairs that protect form too much sun and moisture reserve • Leaves – guard cells, stomata • Periderm – old woody plants, replaces epidermis • Cork cells – protection • Cork cambium – new cork cells made from • Lenticels – areas of overproduction of cork cells, gas exchange

9. Ground tissue • Bulk of a plant • 3 types: • Parenchyma cells – most abundant, found in all organs of plant, least specialized • Collenchyma – thick primary walls, flexible support to immature regions, celery strand • Sclerenchyma – thick secondary walls that contain lignin (make walls tough), support mature region of plant

10. Vascular tissue • Xylem – water and minerals, roots to leaves • Phloem – sucrose and organic molecules (hormones) form leaves to roots • Complex tissues – contain 2 or more kinds of cells • Both extend from roots to leaves • Roots- located in vascular cylinder, stem – vascular bundles, leave – leaf veins

11. Xylemfigure 25.6 • 2 types of conducting cells, hollow and non-living • Tracheids – tapered ends, contain pits where secondary wall does not form • Vessel elements – larger, perforation plates • Parenchyma cells that store substances

12. Phloem – fig 25.7 • Sieve tube members – continuous sieve tube – no nucleus • Companion cells – have nucleus • Connected to sieve tube member by plasmodesmata

13. Root organization • Root cap – apical meristem, replaced often • Zones • Cell division – primary meristem, mitosis • Elongation – cells lengthen and specialize • Maturation – root hairs, fully differentiated

14. Eudicot root tissue • Epidermis – single outer layer, root hairs • Cortex – thin walled parenchyma, food storage • Endodermis – boundary between cortex and vascular tissue • Casparian strip – prevents water and mineral ions between cell walls • Vascular tissue – xylem and phloem • Pericycle – first layer of cells • Monocots similar, differ in arrangement of xylem and phloem in a ring, ground tissue is pith

15. Root diversity • Taproot – grows straight down, fleshy, stores food, carrot, beet • Fibrous root system – in monocots – seen in grasses, strong anchorage • Adventitious roots – develop from shoot system instead of root system, seen in corn, can come above soil line • Root nodules – beans, peas…, nitrogen fixation • Mycorrhizae – plant roots and funugs

16. Stem organization • Terminal bud – shoot tip protected by bud scales • Leaf and bundle scars – location of leaves that have dropped • Axillary buds – give rise to branches or flowers • Bud scale scar – indicates age of stem, one for each year of growth • Primary meristem  primary tissues • Protoderm  epidermis • Ground meristem  pith (ground tissue) • Procambium  cortex (vascular tissue)

17. Herbaceous stems • Non woody, die off in winter, perennial • Only primary growth • Eudicot, vascular bundle in rings, cortex separate from pith • Monocot – vascular bindles scattered, no well defined cortex or pith

18. Woody Stems • Primary (length) and secondary (girth of trunks) tissues • Secondary tissues form from lateral meristem: vascular cambium and cork cambium • Vascular cambium produces new xylem and phloem each year • 3 distinct areas: bark, wood and pith

19. Bark and Wood • Contains periderm • when stem becomes woody, replaces epidermis • Cork, cork cambium and phloem • Removing bark and be fatal to tree • Wood is secondary xylem, girth • Vascular cambium is dormant in winter • Annual ring – sapwood, inner rings - heartwood

20. Stem diversity • Stolons – aboveground horizontal stems, reproduce where nodes touch ground, runners, strawberries • Rhizomes – underground, horizontal stems, some contain tubers (food storage) like potatoes • Corm – bulbous underground stems, gladiolus

21. Leaf organization • Consist of blade and petiole • Veins are netted in eudicots, parallel in monocot

22. Cross section leaf • Trichomes – protective hairs • Cuticle – prevent desiccation but prevent gas exchange • Stomata on underside • Mesophyll tissue • Palisade • spongy

23. Leaf diversity • Simple • Compound • Pinnately compound • Palmately compound • Arrangement • Alternate • Opposite • Whorled • Leaves based on adaptation to environment