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?

e-

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 CO2 concentration, rate is positively correlated with concentration

CO2 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 CO2 and H2O and energy is released

This takes place in the mitochondria

Carbohydrate plus oxygen carbon dioxide plus water plus energy

C6H12O6 + 6 O2 6 CO2 + 6 H2O + 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 ofcork, cork cambium,and secondary cortex)

secondaryphloem

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