1. Chapter 35 Plant Structure, Growth, & Development

2. Introduction
Most plant buds resemble miniature forms of the whole plant
Plants’ growth patterns follow a repetitive sequence of instructions, that are genetically determined and subject to natural selection
Most plants show much greater diversity in the individual forms because growth is affected by local environment
Ex: oak tree branching arrangments vs. adult lions

3. Hierarchical Organization
Like animals, plants have hierarchical levels of cells, tissues, and organs
Divided into below ground (root system) and above ground (shoot system)
- each dependent on the others’ function
Ex: roots supply water and minerals to stems and leaves
leaves provide photosynthates (sugars & CHOs)
Roots, Stems, and Leaves comprise the main organs of the plant

4. Roots
Primary function is to anchor a vascular plant in the soil, absorb water and minerals, and store CHO’s
Structures of roots:
1. Primary root – emerges from seed embryo
2. Lateral root – branch from primary root to enhance anchoring
3. Root hairs – finger like extensions that increase surface area of root and increase absorption of water and minerals
Ex: taproot – one main vertical root allows for taller erect plants and prevents toppling

5. Stems
Chief function is to elongate and orient to maximize photosynthesis in leaves
Also will elevate reproductive structures to facilitate dispersal of pollen and fruit
Structures of stem:
1. nodes – connect stem to leaves
2. apical bud – shoot tip where most growth takes place
3. axillary bud – forms lateral branch for thorns or flowers

6. Leaves Main photosynthetic organ
Also functions in gas exchange, dissipation of heat, and defense against herbivores and pathogens
Structures:
1. Blade – flattened portion that describes leaf
2. Petiole – connects leaf to node (not present in grasses)
3. Veins – vascular tissue leading to roots
Simple versus Compound:
Simple is one major leaf with an undivided blade
Compound is a blade with multiple leaflets

7. Tissue Systems
All main organs have 3 tissue systems that connect them throughout the plant.
3 tissue systems:
Dermal
Vascular
Ground

8. Dermal Tissue System
Primarily functions as the first line of defense against damage and pathogens
- can also prevent water loss
- guard cells also facilitate gas exchange
Tissues:
1. Epidermis – outer covering for non-woody plants
2. Cuticle – waxy epidermal coating on leaves and stems (water loss)
3. Periderm – wooded outer covering on stems and roots
4. Trichomes – on shoots prevent water loss, reflect excess light, and defend against insects

9. Vascular Tissue System
Functions to facilitate transport of materials through the plant and to provide mechanical support
Tissues:
1. Xylem – conducts water and dissolved minerals from roots to shoots
-tracheids and vessel elements – conduct water; usually dead at functional maturity
2. Phloem – transports sugars, photosynthesis products, from leaves to roots or other needed locations
- sieve cells and companion cells – sugar conducting cells; usually alive at functional maturity

10. Ground Tissue System
Specialized tissue for storage, photosynthesis, support and short distance transport
Tissues:
Pith – internal to vascular tissue
Cortex – external to vascular tissue

11. Plant Cell Types Parenchyma Cells- found in roots, leaves, and stem
- perform most metabolic functions and synthesizing and storing various organic products
- In leaves contain chloroplast for photosynthesis
- In roots and stems have colorless plastids that store starch
- fleshy tissue of many fruits
- have ability to divide and differentiate to other cell types

12. Plant Cell Types Collenchyma cells – mainly in stems and leaves
- provide flexible support without restraining growth
- thicker than parenchyma cells
Sclerenchyma cells – stems and leaves
- provide structural support, but cannot elongate, and most are dead
- more rigid than collenchyma cells
Ex: Sclereids - hardness of nutshells, seed coats, and gritty texture of pears
Fibers – can used for making ropes and flax in weaving linen

13. Primary and Secondary Growth
Indeterminate growth – growth occurs throughout life of plant
- unlike animals where growth is confined to embryonic or juvenile period
Determinate growth – leaves, thorns, and flowers with stop growing at a certain size
Meristems – dividing, unspecialized tissues that keep plants growing
a. Apical meristems – enable growth in length (primary growth)
- located in tips of roots and shoots
b. Lateral meristems – allow growth in thickness (secondary growth)
- located in roots and stems

14. Primary Growth Lengthening of roots and shoots
- Root cap – tip of the root which protects apical meristem as root pushes through soil
- also secretes polysaccharide slime to lubricate soil
Growth occurs in 3 overlapping zones:
Zone of cell division
Zone of cell elongation
Zone of differentiation

15. Primary Growth

16. Primary Growth Organization of Leaves:
Stomata – pores that allow exchange of CO2 and Oxygen between air and cells inside leaves
-accounts for 95% of water lost (1-2% of leaf surface)
- Guard cells – specialized cells that regulate the opening and closing of stomata
- Mesophyll – ground tissue sandwiched between epidermal layers
a. Palisade mesophyll contains the chloroplasts to absorb sunlight
b. Spongy mesophyll connects to exterior through the stomata (pores)

17. Secondary Growth
Increases the diameter of stems and roots in woody plants (lateral meristems)
In woody plants occurs simultaneously with primary growth
Secondary Growth involves 2 tissues:
1. Vascular cambium – adds secondary xylem(wood) and secondary phloem to increase vascular flow and support to shoots
2. Cork cambium – replaces epidermis with tough, thick waxy cells that protect cell from water loss and from invasion of insects, bacteria, and fungi

18. Secondary Growth

19. Transport routes (Chapter 36)
Plant tissues have 2 major comparments for transport: 1. Apoplast – everything external to plasma membranes of living cells including cell walls, extracellular spaces, & interior of dead cells Ex: apoplastic route – moves along cell walls & extracellular spaces 2. Symplast – consists of entire mass of cytosol of living cells, and plasmodesmata & cytoplasmic channels that connect them Ex: symplastic route – moves along cytosol Transmembrane route – moves out of one cell, across cell wall, and into the neighboring cell

20. Transport Routes

21. Transpiration and Root Pressure
Transporting xylem sap (water and dissolved minerals) involves a significant loss of water.
- Transpiration – loss of water vapor from leaves and other parts of plant
Root pressure is created when water flows from the root cortex to push xylem sap.
Guttation – caused from root pressure when more water enters the leaves than is transpired, forms little droplets seen on the tips or edges of leaves
Not dew which is condensed atmospheric moisture