1. RHS Level 2 Certificate
Year 1 Week 5: Stems
and Leaves

2. Quiz answers
1. Cytoplasm - Jelly like substance that contains and supports
the organelles
Mitochondria – Organelle that is the site of respiration.
Nucleus - Contains the DNA and RNA of the cell
Vacuole - Contains water, some nutrients and cell waste
products - helps the cell maintain its shape.
Chloroplast - The site of photosynthesis within the cell
Middle lamina -Membrane that physically connects cells
together into plant tissues.
2. The release of stored energy from carbohydrate in the
mitochondria for use by the plant.
3. At the meristems (apical and lateral)

3. Quiz answers
4. The DNA of the cell and the location of the cell in the plant.
5. (a) tissue that transports water and dissolved mineral
nutrients from roots
(b) tissue that transports sugars/carbohydrate made during
photosynthesis from the leaves
6. All except (a)
7. (a) and (c)
8. (a)
9. (c)
10. ? What did you chose?

4. Learning objectives
1. Stems – structure and purpose
1.1 Describe how the stem develops.
1.2 Describe different types of buds and state where they occur in the plant.
1.3 Identify the two elements of the vascular system and name their purposes
1.4 Describe transverse sections of the young dicotyledon stem, should
include the location of the following: epidermis, cortex, xylem, phloem, pith,
cambium, vascular bundles, endodermis.
1.5 Describe how the stem is adapted in order to perform specific functions.
2. Leaves – structure and purpose
2.1 Describe the structure of the leaf.
2.2 Describe how leaf shape, size, form and colour can vary.
2.3 Describe how leaves are adapted in order to perform certain functions
2.4 Describe transverse sections of the young dicotyledon leaf; this should
include the location of the following: epidermis, xylem, phloem, vascular
bundles, palisade & spongy mesophyll, cuticle, stomata.

5. Stems – Structure and Purpose
o What are stems for?
o support for leaves and flowers – competition for
light and access for pollinators
o transport of water and nutrients around the plant
o What is the internal structure of the stem?
o Stem vascular system
o Differences between stem and roots?
o Differences between monocot and dicot stems?

6. Stems – vascular system
 Vascular system in a number of bundles – in a
dicot root there is a single vascular bundle, in a
monocot there is a regular circular arrrangment.
 Monocots in the stem – scattered irregularly
 Dicots in the stem – arranged regularly around
the circumference
 Xylem (in both)– located on the ‘inside’ of the
bundle
 Phloem (in both) – on the ‘outside’
 Vascular cambium – meristematic tissue that
generates new xylem and phloem.

7. Young Dicot stem

8. Stem Adaptations
 Water storage – e.g. Opuntia sp.
 Thorns for protection - Crataegeus
monogyna (Common Hawthorn)
 Dormancy – storing food to allow avoidance
of hostile conditions over winter or during
summer drought e.g. Zingiber officinale
(Ginger ) has a rhizome, Solanum tuberosum
ssp. Tuberosum (potato) has stem tubers
 Climbing – stems twine to aid the plant in
climbing e.g. Wisteria sinensis.

9. Buds – different types
 Apical bud – at the tip of the shoot.
 Axillary buds – at the joint between leaf and
stem (at the node). Usually dormant or leaf
producing.
 Fruit buds – produce flowers, usually a
distinct shape and form, differing from…
 Wood buds – produce new stems,
sometimes only if the apical bud is removed.

10. Fruit or wood?

11. Leaves –function and structure (1)
 Function of leaves –
photosynthesis
 External structure
– Petiole
– Lamina
– Midrib
– Veins

12. Leaves –function and structure (2)
Cuticle –waxy layer on
surface that slows water
loss
Epidermis – cells that form
‘skin’ of leaf
Palisade cells – arranged
like picket fence, contain
chloroplasts
Chloroplasts – site of
photosynthesis
Spongy mesophyll – packing
cells, allow water vapour
and other gasses through
Stomata – active control of
entry and exit of gasses
and water vapour.
Phloem – dissolved sugars Xylem – water and mineral
nutrients

13. Leaf – internal structure

14. Stomata
 Pairs of specialised guard cells on either side
of small openings in the underside of leaves
and in soft stems.
 Guard cells swell when the plant has enough
water – pulling apart to open the stomata and
allowing water vapour and waste gasses out
and oxygen and CO2
in.
 When water levels fall the guard cells empty
and the stomata close to conserve water.

15. Electron-micrograph of lettuce
stomata

16. Leaf Adaptations
 Tendrils or suckers – for climbing e.g. Lathyrus
odoratus
 Leaf Hairs – for protection from the sun e.g. Stachys
byzantina
 Spines – for protection from grazing animals e.g. Ilex
aquifolia
 Food storage – for over-wintering, e.g. Narcissus
spp.
 Attracting pollinators – modified, highly coloured
leaves known as bracts surround insignificant
flowers e.g. Euphorbia pulcherima.

17. Leaf adaptations (2)
 Leaf fall for deciduous
trees – recovery of
chemical components of
chlorophyll; formation of
abscission layer, a layer
of weak cells; vascular
bundles plugged; leaf fall.
 Juvenile trees retain
dead leaves, protects
buds

18. Leaf form and leaf arrangement
(phyllotaxy)
 Various different leaf forms – known by
different descriptive names to enable clear
identification
 Phyllotaxy is the name for the
arrangement of leaves on a plant.
Prevents the leaves from shading each
other.

19. Learning outcomes
1. Stems – structure and purpose
1.1 Describe how the stem develops.
1.2 Describe different types of buds and state where they occur in the plant.
1.3 Identify the two elements of the vascular system and name their purposes
1.4 Describe transverse sections of the young dicotyledon stem, should include the
location of the following: epidermis, cortex, xylem, phloem, pith, cambium,
vascular bundles, endodermis.
1.5 Describe how the stem is adapted in order to perform specific functions.
2. Leaves – structure and purpose
2.1 Describe the structure of the leaf.
2.2 Describe how leaf shape, size, form and colour can vary.
2.3 Describe how leaves are adapted in order to perform certain functions
2.4 Describe transverse sections of the young dicotyledon leaf; this should include
the location of the following: epidermis, xylem, phloem, vascular bundles,
palisade & spongy mesophyll, cuticle, stomata.