RHS Level 2 Certificate Week 10 overview

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

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

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

Why does a leaf look green?

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.

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.

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

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

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?

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

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#

Secondary Growth

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

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

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

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)

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

RHS Level 2 Certificate Week 10 overview

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