Notes
DP Biology
Plant Structure
Plant Diversity
Bryophytes:
Bryophytes are mosses and liverworts. They
live in damp areas and still require water for
reproduction. They are small simple plants.
They do not have vascular tissue or true
roots, leaves or stems. Absorption of water
takes place over all surface areas. Mosses do
not produce flowers. The male gamete is
motile, swimming to the female gamete.
Rhizoids (no true roots)
multicellular
leaves with or without a midrib
Filicinophytes
Over 10,000 species. Most are found in the tropics
where tree ferns — with their above-ground stems
— may grow as high as 40 feet. In temperate
regions, the stems of ferns — called rhizomes —
grow underground. The leaves — called fronds —
grow up from the rhizome each spring.
The fertile fronds bear groups of sporangia on the
lower surface. Haploid spores are produced in the
sporangia following meiotic divisions. These spores grow into gametophytes which
then produce haploid male and female cells which on fertilization produce a diploid
sporophyte (dominant).
Coniferophytes
Conifers such as pine, spruce, and juniper. Vascular plants with true roots,
stems, and leaves. Sporophyte generation is dominant. Macrospores give
rise to embryo sac in female cones. Microspores give rise to pollen grains
released by male cones. Gametes are non-motile, disseminated by wind.
Seeds not enclosed in ovary, plant bears no fruit.
Angiospematophytes
Produce flowers that develop into fruits after fertilization. Xylem contains vessels
and phloem contains companion cells. Following meiosis, haploid spores develop
within flower parts; male and female sporangia may be in same flower or in
different flowers (ex. male and female holly trees). Seeds are enclosed in an
ovary which develops into fruit

Complete the table to show the differences and similarities
between the major plant groups
Feature
Example
Roots
Leaves
Vascular tissue
Reproduction
Distribution
Other
Bryophytes
Filicinophytes
Coniferophytes
Angiosperms
Two groups of flowering plants
They differ in the number of seed leaves. Monocots have one seed
leaf, whereas, dicotyledonous plants have two. Monocots have
parallel veins on leaves, dicots have branched veins. Monocots
have adventitious roots, dicots have tap roots.
Typical dicotyledonous plant structure
Structure
Leaves
Stem
Roots
Vascular tissue
Root hairs
Flowers
Function
Plant adaptations
Xerophytes
Hydrophytes
Air filled spaces in stem and leaves
Little strengthening tissue
Reduced roots
Finely divided submerge leaves
Reduced leaves
Spines
Waxy cuticle covering leaves and stem
Stem adapted for water storage
Low growth form
Leaves rolled
Hairs on leaves
Reduced number of stomata
Tendrils
A tendril is a specialized stem, leaf or petiole with a threadlike shape that is used by
climbing plants for support and attachment, generally by twining around whatever it
touches.
Bulbs
A bulb is a short stem with fleshy leaves . The leaves often function as food storage organs during dormancy . Roots
emerge from the underside of the base, and new stems and leaves from the upper side.

For each of the above features state why it is of benefit to the plant

Tissue distribution in dicotyledonous plant
Distribution of tissue in a dicotyledonous stem

Use the plan diagram above to label the following transverse section of a dicot stem
Distribution of tissue in a dicotyledonous root

Use the plan diagram above to label the following transverse section of a dicot root
Distribution of vascular tissue in a dicot leaf

Use the plan diagram above to label the following transverse section of a dicot leaf

Explain the relationship between distribution and function of tissue in leaves, with reference to
absorbtion of light, gas exchange, support, water conservation, transport water and products
photosynthesis
Growth hormones in plants
Plants just like animals respond to stimuli. Some plants are able to respond very quickly, for example the venus fly
trap. These fast responses are brought about by electrical signals. The large majority or responses in plants are
brought about by hormones.
Hormone – this is a chemical substance produced by the plant or animal, usually in small quantities, and transported
to the target site where it has an effect.
Hormones produced in plants are sometimes called plant hormones or plant growth substances.
Auxin and Tropism
Auxin is a plant hormone produced by cells near the tip of the roots and shoots. This is where the plant cells are
dividing, as the plant grows.
All the time, new cells are being produced by the dividing region at the tip, and new cells eventually find themselves
further back from the tip as even newer cells are constantly made at the end. These slightly older cells do not divide
but they do grow. They grow by getting longer
It is auxin that makes the cells get longer. The auxin made by the dividing cells in the tip diffuses backwards. Auxin
stimulates cells to lengthen (this is not always the case)
Q – Why do plants grow more bushy when the stem tip is removed?
What use is made of this in horticulture
Phototropism
If light shines from one direction onto a plant, the auxin tends to accumulate on the shady side. The cells on this side
therefore lengthen faster than those on the sunny side. This makes the shoot bend towards the light.
This is called phototropism. A tropism is a growth response by a plant, in which he direction of the growth is
determined by the direction of the stimulus. ‘Photo’ means light, so phototropism is a growth response to light. As
the plant grows towards the light it is called positive phototropism.
Q – what is the advantage to the plant of this process
Q – In what way would roots respond to light?
What do you think this sort of response is called?
Q -- What affect does auxin have on the elongation of cells in the root?