Rhs level 2 certificate year 1 week 5 2011

3,109 views

Published on

Published in: Education, Technology
0 Comments
0 Likes
Statistics
Notes
  • Be the first to comment

  • Be the first to like this

No Downloads
Views
Total views
3,109
On SlideShare
0
From Embeds
0
Number of Embeds
18
Actions
Shares
0
Downloads
41
Comments
0
Likes
0
Embeds 0
No embeds

No notes for slide

Rhs level 2 certificate year 1 week 5 2011

  1. 1. RHS Level 2 Certificate Year 1 Week 5: Stems and Leaves
  2. 2. Learning objectives <ul><li>1. Stems – structure and purpose </li></ul><ul><li>1.1 Describe how the stem develops. </li></ul><ul><li>1.2 Describe different types of buds and state where they occur in the plant . </li></ul><ul><li>1.3 Identify the two elements of the vascular system and name their purposes </li></ul><ul><li>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. </li></ul><ul><li>1.5 Describe how the stem is adapted in order to perform specific functions. </li></ul><ul><li>2. Leaves – structure and purpose </li></ul><ul><li>2.1 Describe the structure of the leaf. </li></ul><ul><li>2.2 Describe how leaf shape, size, form and colour can vary. </li></ul><ul><li>2.3 Describe how leaves are adapted in order to perform certain functions </li></ul><ul><li>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. </li></ul>
  3. 3. Stems – Structure and Purpose <ul><li>What are stems for? </li></ul><ul><ul><li>support for leaves and flowers – competition for light and access for pollinators </li></ul></ul><ul><ul><li>transport of water and nutrients around the plant </li></ul></ul><ul><li>What is the internal structure of the stem? </li></ul><ul><ul><li>Stem vascular system </li></ul></ul><ul><ul><li>Differences between stem and roots </li></ul></ul><ul><ul><li>Differences between monocot and dicot stems. </li></ul></ul>
  4. 4. Stems – vascular system <ul><li>Vascular system in a number of bundles – unlike the root where there is only one in the centre. </li></ul><ul><li>Monocots – scattered irregularly </li></ul><ul><li>Dicots – arranged regularly around the circumference </li></ul><ul><li>Xylem – located on the ‘inside’ of the bundle </li></ul><ul><li>Phloem – on the ‘outside’ </li></ul><ul><li>Vascular cambium – meristematic tissue that generates new xylem and phloem. </li></ul>
  5. 5. Young Dicot stem
  6. 6. Buds – different types <ul><li>Apical bud – at the tip of the shoot. What is apical dominance? How can this be manipulated by gardeners? </li></ul><ul><li>Axillary buds – at the joint between leaf and stem (at the node). Usually dormant or leaf producing. </li></ul>
  7. 7. Stem Adaptations <ul><li>Water storage – e.g. Opuntia sp. </li></ul><ul><li>Thorns for protection - Crataegeus monogyna (Common Hawthorn) </li></ul><ul><li>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 </li></ul>
  8. 8. Leaves –function and structure (1) <ul><li>Function of leaves – photosynthesis </li></ul><ul><li>External structure </li></ul><ul><ul><li>Petiole </li></ul></ul><ul><ul><li>Lamina </li></ul></ul><ul><ul><li>Midrib </li></ul></ul><ul><ul><li>Veins </li></ul></ul>
  9. 9. Leaves –function and structure (2) Epidermis – cells that form ‘skin’ of leaf Cuticle –waxy layer on surface that slows water loss Chloroplasts – site of photosynthesis Palisade cells – arranged like picket fence, contain chloroplasts Stomata – active control of entry and exit of gasses and water vapour. Spongy mesophyll – packing cells, allow water vapour and other gasses through Xylem – water and mineral nutrients Phloem – dissolved sugars
  10. 10. Leaf – internal structure
  11. 11. Stomata <ul><li>Pairs of specialised guard cells on either side of small openings in the underside of leaves and in soft stems. </li></ul><ul><li>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 CO 2 in. </li></ul><ul><li>When water levels fall the guard cells empty and the stomata close to conserve water. </li></ul>
  12. 12. Electron-micrograph of lettuce stomata
  13. 13. Leaf Adaptations <ul><li>Tendrils – for climbing e.g. Lathyrus odoratus </li></ul><ul><li>Leaf Hairs – for protection from the sun e.g. Stachys byzantina </li></ul><ul><li>Spines – for protection from grazing animals e.g. Ilex aquifolia </li></ul><ul><li>Food storage – for over-wintering, e.g. Narcissus spp. </li></ul>
  14. 14. Leaf adaptations (2) <ul><li>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. </li></ul><ul><li>Juvenile trees retain dead leaves, protects buds </li></ul>
  15. 15. Leaf form and leaf arrangement (phyllotaxy) <ul><li>Various different leaf forms – known by different descriptive names to enable clear identification </li></ul><ul><li>Phyllotaxy is the name for the arrangement of leaves on a plant. Prevents the leaves from shading each other. </li></ul>
  16. 16. Learning outcomes <ul><li>1. Stems – structure and purpose </li></ul><ul><li>1.1 Describe how the stem develops. </li></ul><ul><li>1.2 Describe different types of buds and state where they occur in the plant . </li></ul><ul><li>1.3 Identify the two elements of the vascular system and name their purposes </li></ul><ul><li>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. </li></ul><ul><li>1.5 Describe how the stem is adapted in order to perform specific functions. </li></ul><ul><li>2. Leaves – structure and purpose </li></ul><ul><li>2.1 Describe the structure of the leaf. </li></ul><ul><li>2.2 Describe how leaf shape, size, form and colour can vary. </li></ul><ul><li>2.3 Describe how leaves are adapted in order to perform certain functions </li></ul><ul><li>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. </li></ul>

×