Week 11 2015 powerpoint
- 1. RHS Level 2 Certificate Year 1 Week 11 – Review week
- 2. Learning outcomes To define pollination To describe the process of fertilization and distinguish this from pollination To state the nature of diploid and haploid cells To state the parts of the seed and the stages of germination. To state the differences between monocot and dicot roots (form and internal structure). To name the tissues involved in transportation within the plant. To name and define the processes involved in transportation. To review stem adaptations – corms, bulbs and stem tubers
- 3. Pollination and fertilization- overview 1 •Pollination is the transfer of pollen from the anther to the stigma of the flower •If the pollen is compatible, there are two sex cells in the pollen grain (each with one set of chromosomes – half the usual number). One cell from the pollen grain forms a pollen tube. The pollen tube grows down the style. •The second cell divides into two identical cells– one new cell becomes the tube nucleus which ‘drives’ the pollen tube. •The remaining cell divides again to produce two haploid sperm cells
- 4. Pollination and fertilization- overview 2 •The pollen tube finds a tiny opening in the ovule and enters it •The two sperm cells enter the ovule- in the ovule are a diploid cell called the polar nucleus and a haploid female gamete •One sperm cell fuses with the diploid polar nucleus – this forms the triploid endosperm •The other fuses with the haploid female gamete and forms the zygote (the new plant embryo) which is diploid
- 6. Parts of the Seed Testa – coat Cotyledon – seed leaf Plumule – first shoot Radicle – first root Hypocotyl – first stem below the seed leaves Micropyle – small hole where seed joined plant. Dicots and monocot differences. Monocots have endosperm, dicots generally do not.
- 7. Germination Stage one (Imbibition phase) – water enters the seed (imbibition). The seed swells and the testa splits Stage 2 (Lag phase)– respiration begins to speed up, the food in the cotyledons/endosperm is broken down. Called the ‘lag phase’ because nothing obvious is happening. Stage 3 (Emergence phase) – rapid cell division begins, the radicle emerges followed by the plumule and the shoot begins to grow. The process of germination ends when the shoot reaches the surface and begins to photosynthesise.
- 8. Roots – formation, structure and adaptation. Dicots – branching roots, tap roots. Monocots – fibrous roots. Roots emerge first on germination – first root is the radicle. Roots grow downwards because they are positively geotrophic due to the action of auxin in the roots. Vascular bundles in dicot roots arranged regularly in the centre of the root, monocots in a ring. Note the differences between this and the stem. Root adaptations – for climbing, dormancy, survival in water logged soil, support.
- 11. Transportation within the plant Diffusion – movement from an area of high concentration to one of lower concentration. Osmosis – movement of water molecules from an area of high concentration to one of lower concentration through a semi-permeable membrane. Transpiration – the diffusion of water vapour formed by evaporation in the leaves out through the stomata.
- 12. Transportation within the plant Xylem – transports water and dissolved mineral nutrients from roots to leaves. Mature xylem cells are dead. Phloem – transports products of photosynthesis from leaves to sites of use or storage. Phloem composed of sieve cells and companion cells and is living tissue.
- 13. Stem adaptations for dormancy Enable survival below ground in cold or very dry conditions. Corms – thickened stem, the roots grow from a base plate and are contractile, pulling the corm down to the correct level in the soil. Leaves form the papery skin, axillary buds can sometimes be seen between the nodes on the thickened stem. Rhizomes – thickened stems that usually remain at the surface of the soil. Shoots develop from the axillary buds on the top surface whilst adventitious roots develop on the lower surface.. Stem tubers – enlarged side shoots from the stem of a plant below ground, have all the usual structure – vascular tissue and axillary buds, but the nodes may not be obvious.
- 14. Learning outcomes To define pollination To describe the process of fertilization and distinguish this from pollination To state the nature of diploid and haploid cells To state the parts of the seed and the stages of germination. To state the differences between monocot and dicot roots (form and internal structure). To name the tissues involved in transportation within the plant. To name and define the processes involved in transportation. To review stem adaptations – corms, rhizomes and stem tubers