1. PLANTS basic Evolution & Classification
Anatomy & Physiology of Roots, Stems & Leaves

2. Plants Overview Evolution of plants and plant classification
Plant anatomy:
Tissues, Roots, Stems, Leaves
Transport in plants
Plant growth (primary & secondary)
The role of Hormones in coordinating growth & response to stimuli
For another time…
Plant Sexual Reproduction
Alternation of Generations

3. What is a plant? Plants are multicellular, eukaryotic photoautotrophs
Plants have a waxy cuticle covering that helps them retain water
Gas exchange occurs through holes, or stomata, in the leaf surfaces
They have organs such as roots, stems and leaves
A vascular system carries water and minerals up and nutrients down (and sometimes up again!)
Reproductive structures, called gametangia, contain gamete-producing cells

4. What is a plant?

5. Plant Evolution from water to land: major adaptations & plant groups

6. Vascular Plants (tracheophytes) Seedless Vascular Plants
Plant Kingdom
Byrophytes
(aka non-vascular or non-tracheophytes)
Mosses
Vascular Plants (tracheophytes)
235,000 species
720 species
Seedless Vascular Plants
Ferns, etc
Angiosperms (“vessel seed”)
Flowering plants
Gymnosperms (“naked seed”)
Conifers, etc
65,000 species
170,000 species
Monocots (“one cotyledon”)
Grasses, orchids, bamboo, palms, lilies, grains
Dicots (“two cotyledons”)
Most shrubs & trees, many food crops

7. Angiosperms are broken into 2 groups: Monocots and Dicots

8. Monocots & Dicots Cotyledons are the embryonic seed leaves
Monocots: orchids, bamboos, palms, and lilies AND the grasses, including wheat, corn and rice (these are WAY important, for obvious reasons!)
Dicots: all the rest…(oak, maple. roses, cabbage, beans, potatoes, most fruit trees, etc). So if you’re asked which is more common, choose this one

9. Seed germination begins the life of a new plant

10. The plant: root system & shoot system

11. Modifications of roots and stems
Many roots are adapted for storing food
Rhizomes are actually modified stems that store food
Modified stems can also act as “runners”, allowing a plant to reproduce asexually

12. Three tissue systems make up a plant:
Epidermal tissue = outer layer of r, s, l
Vascular tissue = conducts water & food (xylem & phloem)
Ground tissue = the bulk of a young plant, fills in space between epidermis and vascular tissue

13. How do things move around inside plants?
Vascular Tissues
XYLEM tissue = Water-conducting: made of tracheids and vessel elements – are both dead, hollow tubes when mature
PHLOEM tissue = Food-conducting: made of sieve-tube members (dead when mature) & companion cells (alive when mature)
Ferns, gymnosperms and angiosperms have these vascular tissues and are called vascular plants or tracheophytes.
Bryophytes (mosses) do not have xylem and phloem and so they are non-vascular (lack specialized transport system).

14. ROOTS anchor the plant and allow for absorption of water & nutrients from soil
Dissolved nutrients move into root by active transport … water follows by osmosis! Beautiful.
Plasmodesmata are openings in the walls and plasma membranes between plant cells that allow free flow of liquids and dissolved molecules.

15. From root hairs into xylem – then up
From root hairs into xylem – then up!! The endodermis acts as the gate-keeper

16. Tissues of the leaf
Guard cells regulate opening and closing of stomata (openings for gas exchange: O2, CO2, H2O vapor)
Mesophyll cells (palisade & spongy mesophyll), the ground tissue of leaves, contain chloroplasts and perform photosynthesis

17. Guard Cell Action: Bringing K+ into guard cells causes water to follow by osmosis; cells become turgid and stoma opens. Magic! (Flaccid guard cells = closed stoma … not a bad idea if you’re not photosynthesizing and trying to conserve H2O ...Like at night!)

18. How does water get to the top of trees
How does water get to the top of trees? Combo of root pressure, capillary action & transpiration pull!

19. Plant growth is “indeterminate” growth - never ceasing (at root & shoot tips at least)
• Plants grow in length (primary growth) and in thickness (secondary growth)
Meristem tissue: unspecialized cells that divide to generate all kinds of new plant tissue
Apical meristem: meristem at the tips of roots and shoots, allow them to grow in length
Vascular cambium & Cork cambium: meristem that allows stems & roots to thicken and branch out

20. Roots & stems exhibit both primary and secondary growth
Stem Cross-section
Root Cross-section

21. Vascular cambium makes xylem & phloem while cork cambium makes… cork!
Why do trees in temperate climates have annual rings?

22. Plant hormones coordinate growth, development & responses to stimuli
Auxin: directs stem & root growth, responsible for phototropism (growth towards light) and geotropism (growth up away from gravity).
Gibberellins: stimulate seed & bud germination, stem elongation, flowering & development of fruit; found in meristems of apical buds, roots, young leaves, embryo.
Cytokinins: promote cell division, germination & leaf expansion; determine timing of cellular differentiation (esp. in roots)
Ethylene: stimulates the ripening of fruit and the abscission (dropping) of leaves, flowers, and fruits.

23. The effect of gibberellin treatment on seedless grapes (treated grapes on right).

24. Plant Tropisms Plant responses to external stimuli
Can you guess what these are?
Phototropism:
Gravitropism:
Thigmotropism:

25. Classic Light/Growth Experiments with Grass Seedlings

26. MORE Classic Growth Experiments with Grass Seedlings
In 1926, F.W. Went extracted the chemical messenger for phototropism, naming it auxin.

27. Plant Growth vocabulary
Annuals: complete their life cycle in one year
Biennials: complete their life cycle in two years, usually flowering during the 2nd year
Perennials: plants that live many years