This document provides an overview of topics to be covered in RHS Level 2 Certificate Week 10, including photosynthesis, respiration, secondary thickening, and pollination/fertilization. Photosynthesis uses carbon dioxide, water, and sunlight to produce glucose and oxygen through light-dependent and light-independent reactions. Respiration uses glucose and oxygen to produce carbon dioxide, water, and energy. Secondary thickening occurs in woody stems and results in the growth of secondary xylem and phloem tissues. Pollination involves the transfer of pollen from anther to stigma, and fertilization is the fusion of sperm and egg cells within the ovule leading to seed formation.

1. RHS Level 2 Certificate Week 10 – Review and revision of photosynthesis, secondary thickening and pollination/fertilization

2. RHS Level 2 Certificate Week 10 – Revision week. Photosynthesis and respiration review Secondary thickening Pollination – cell division in pollen germination

3. Learning outcomes To identify the end product and waste product of photosynthesis To state the equation for photosynthesis in words To describe the light dependent and light independent phases of photosynthesis in overview To state the limiting factors of photosynthesis To state the equation for respiration in words To identify the end product and waste products of respiration To identify the tissue involved in secondary thickening To describe the process of secondary thickening To define pollination To describe the process of fertilization

5. Why does a leaf look green?

6. e -

7. High energy electrons are passed through the electron chain and the energy is used to split molecules of water (H2O) into their component hydrogen and oxygen. The oxygen is released as a by-product into the atmosphere. The energy released by breaking the chemical bonds in the water is incorporated, with the hydrogen, into energy carrying molecules called ATP and NADPH2.

10. Limiting factors If a process is influenced by more than one factor, the rate of the process will be limited by the factor that is in lowest supply Therefore if temperature is low (10 °C) increasing light intensity or carbon dioxide concentration will not increase the rate of photosynthesis. Why does this matter ? The slower the rate of photosynthesis the slower the rate of growth.

11. plateau At low CO 2 concentration, rate is positively correlated with concentration CO 2 is a substrate in an enyme-catalysed light-dependent reaction.

12. At low light intensity, rate of photosynthesis is proportional to light intensity. plateau

13. Increased temp. gives increased energy and increased rate of photosynthesis Optimum temperature Above the optimum temp., enzymes are denatured and rate drops steeply. Which enzymes are used in respiration?

14. Process of Cellular Respiration Food (glucose) is broken down using oxygen into CO 2 and H 2 O and energy is released This takes place in the mitochondria Carbohydrate plus oxygen  carbon dioxide plus water plus energy C 6 H 12 O 6 + 6 O 2  6 CO 2 + 6 H 2 O + energy (ATP) This energy can be stored (as ATP) - to be used later for things like growth

15. Secondary Growth Occurs in perennials A ring of vascular cambium produces secondary xylem and phloem Wood is the accumulation of these secondary tissues, especially xylem http://www.cnr.vt.edu/dendro/forestbiology/syllabus3.htm#

16. Secondary Growth

17. Woody Stem periderm (consists of cork, cork cambium, and secondary cortex) secondary phloem BARK HEARTWOOD SAPWOOD vascular cambium

18. Annual Rings Concentric rings of secondary xylem Alternating bands of early and late wood Early wood Xylem cells with large diameter, thin walls Late wood Xylem cells with smaller diameter, thicker walls

19. Pollination and fertilization- overview 1 Pollination is the transfer of pollen from the anther to the stigma of the flower 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

20. 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)

21. Learning outcomes To identify the end product and waste product of photosynthesis To state the equation for photosynthesis in words To describe the light dependent and light independent phases of photosynthesis in overview To state the limiting factors of photosynthesis To state the equation for respiration in words To identify the end product and waste products of respiration To identify the tissue involved in secondary thickening To describe the process of secondary thickening To define pollination To describe the process of fertilization