1. Stems

8. Stem Functions support food storage photosynthesis in green stems
conducts water and materials from roots to other plant organs

9. Stems function as a point of attachment for leaves, roots, fruits and flowers
More leaf attachment
means more
photosynthesis

10. More flowers and fruits attached to
the stem means the plant has
a greater ability to reproduce

12. Stem Evolution
…fossil evidence from millions of years ago showed stems evolved before other plant organs, preceding the development of leaves + roots

13. Stem Functions
aid plant growth by increasing height, mass and surface area
stems branching patterns allow this growth

15. Stem Structure and growth
node – area where leaves are attached to a stem
internode – the stem region between the nodes

17. Plant growth guides stem structure
Plant growth occurs in
Meristems/Meristematic tissue which are the permanent regions of growth where mitosis (cell division)occurs

18. Apical Meristem
located at the tips of roots and shoots:
(branches, twigs and leaves)
grow in length
considered an area of primary growth
(grows before other tissues)

19. Primary Meristems – 3 types
1. protoderm – the outside area, 1 cell thick, covered by the cuticle (the thin waxy, protective layer that retains moisture)

20. Primary Meristems – 3 types
2. ground meristems – produces 2 tissues made of parenchyma cells
pith – tissue in the center of a stem or root
cortex – located between epidermis + vascular tissues

21. Primary Meristems – 3 types
3. procambium – becomes the vascular tissues, xylem + phloem

22. All 3 primary meristems produce primary tissues for the stem
epidermis – outside
primary xylem
primary phloem
pith
cortex

23. Lateral Meristems (lateral = side)
grow in girth (thickness or width)
provide support and conduct substances through the plant

26. Monocot – scattered pattern
Dicot – radial pattern

27. Stem Classification Monocot stems
Herbaceous stems – have soft green stems that last 1 year or more
xylem + phloem pattern in cross section is scattered
Dicot stems
Woody Dicotlyledenous stems
- xylem + phloem pattern in radial pattern

29. Stem structure + growth
stems grow from the terminal bud/end
the terminal bud grows out and away, leaving bud scars
bud scales – leaf-like structures that cover and protect the soft growing point

32. Wood basics…Dendrology
bark – the outer layer of woody stems that protects from diseases, injury, and evaporation
cambium – next layer, functions to produce new cells for growth
new wood – produced spring + summer and counted as
annual rings – studied in Dendrochronology