1. Roots, Stems & Leaves “Principal organs of seed plants”

2. Seed Plant Structure 3 Tissue Types: Dermal Tissue
- outer covering, epidermal cells
Vascular Tissue
- xylem / phloem, transport system
Ground Tissue
(between dermal / vascular)
- parenchyma, collenchyma and
sclerenchyma cells

3. 23-2 Roots – Try This: http://www.virted.org/Plants/RootsQuiz.html
Absorbs water and dissolved nutrients
Anchors plants to ground
Prevents erosion
Protection from soil bacteria and fungus
Transports water & nutrients
Holds plants upright against forces such as wind and rain

4. Roots – Two main types: Plants have taproots, fibrous roots or both
#1 Taproots - Characterized by having one main root (the taproot) from which smaller branch roots emerge. 
When a seed germinates, the first root to emerge is the radicle, or primary root.  In conifers and most dicots, this radicle develops into the taproot.  
Taproots can be modified for use in storage (usually carbohydrates) such as those found in sugar beet or carrot or radishes or turnips …. 
Taproots are also important adaptations for searching for water, as those long taproots found in mesquite and poison ivy.

5. Taproot

6. #2. Fibrous Roots –
Characterized by having a mass of similarly sized roots. 
In this case the radicle from a germinating seed is short lived and is replaced by adventitious roots. Adventitious roots are roots that form on plant organs other than roots. 
Most monocots have fibrous root systems. 
Some fibrous roots are used as storage; for example sweet potatoes form on fibrous roots. 
Plants with fibrous roots systems are excellent for erosion control, because the mass of roots cling to soil particles.

7. Fibrous Roots - A cabbage seedling with white, fibrous roots snaking through the soil

8. Root Overview
(new cells produced here)
(undifferentiated)

9. - only plant tissue that produces new cells by
Meristematic tissue
- only plant tissue that produces new cells by
mitosis
Root Cap
- protects the meristematic tissue, thick cells to push through soil
Apical meristem
- near the tip of roots and stems
- cells increase the length of roots and stems
- undifferentiated
Zone of elongation
- where new cells are enlarging

10. 23-3 Stems Stems have 3 important functions:
Produce leaves, branches, flowers
Hold leaves up to sunlight
Transport substances between roots and leaves

13. 23-4 Leaves
The leaves of a plant are its main organs of photosynthesis.(plant leaves are the world’s most important manufacturers of food)
The structure of a leaf is optimized for absorbing light and carrying out photosynthesis.

15. More about leaves…
The vascular tissues of leaves are connected directly to the vascular of stems, making them part of the plant’s transport system. The vascular bundle (xylem and phloem) appear as “veins” in the leaves.

16. Leaf cross-section

17. Leaf Cross section cont…
Cuticle – (together with epidermal cells) form a waterproof barrier that protects tissue and limits water loss.
Epidermis – the top and bottom layer of leaves made of tough, irregularly shaped cells.
Mesophyll – (palisade/spongy) bulk of most leaves. Where photosynthesis occurs. Sugars are produced and move into the phloem vessels to be carried to the rest of plant
Palisade – rich in plastids (chloro/chromoplasts)
Spongy – rich in plastids/spaces for gas exchange

18. Leaf cross-section cont…
Stomata (stoma) – porelike openings in the underside of the leaf that allow CO2 and O2 to diffuse in and out of the leaf.
Guard cells – each stoma consist of 2 of these that control the opening and closing of stomata by responding to changes in water pressure.

19. Leaves
Photosynthetic organ of the plant, used to convert sunlight into food
Photosynthesis Equation:

20. Notes: cuticle - top / bottom (thicker on top most of the time)
epidermis - top/bottom
air spaces in spongy mesophyll
stoma surrounded by guard cells
generally more stoma on the bottom than on the top (stomata is both stoma and guard cells)
when the plant has lots of water, the guard cells are full and they move apart opening the stoma; when the plant is lacking in water, the guard cells close
finally, stoma are open in the day; its needed for photosynthesis
Most plants, stoma are closed at night when plant doesn't need CO2 (go to link)
plants gain CO2 while losing water