Revision for Biology: Photosynthesis and Transportation in plants


Photosynthesis – the process by which plants manufacture carbohydrates from raw materials using energy from light.

Transpiration – loss of water vapour from plant leaves by evaporation of water at the surface of the mesophyll cells followed by diffusion of water vapour through the stomata.

Autotroph – Example – plant
Organisms that produce their own food out of non-organic materials such as carbon dioxide and water (notice, water is non-organic). These simple compounds are built into complex substances that might oxidize to produce energy.

Heterotroph –
An organism that does not manufacture its own food and energy and instead take in organic materials. These complex food substances were broken down into simple substances, which could be absorbed or oxidized to release energy.

Glucose is simple sugar while starch is complex carbohydrate that includes a large amount of glucose unit.

Stomata / stoma – The space found between guard cells.

Elements and Compounds

Nitrates – compounds found in fertilisers used for making amino acids which can then be built up into proteins
to make lot’s of amino acids ~

Phosphate – compounds found in fertilisers, needed for energy production (ATP), a component of cell membranes and DNA
a component of DNA~ (and cell membrane~)

Magnesium – mineral ion used for making chlorophyll molecules
help with photosynthesis~ (by making chlorophyll!)

Potassium – From fertilizers. Substance needed to make the enzymes involved in respiration and photosynthesis
help with photosynthesis~ (and respiration~ by producing enzymes)
Too much for lyrics ?

Fertilizers – products that contain minerals sucha s nitrogen (not nitrate), potassium and phosphorus, which help plants to grow and increase crop yields.

Xylem – vessel present in plants that transports water and nutrients from soil to stems and leaves, and provides mechanical support to plants.

Phloem – vessel present in plants that transport glucose made in the leaves to all other parts of the plant. For storage or cell respiration.

Upper epidermis – a single layer of cells containing no chloroplasts. It is thin and transparent to allow the maximum amount of light to pass through to the palisade mesophyll layer. (contains the waxy cuticle)

Lower epidermis – A single layer of cells containing no chloroplasts and many stomata (it does not need chloroplast since sun light cannot reach the underneath of the leaves)

Spongy mesophyll – A layer of cells in the interior of leaves, consisting of loosely arranged, irregularly shaped cells that have chloroplasts. Air spaces allow carbon dioxide to diffuse through the leaf and increase the surface area.

Palisade Mesophyll – A layer of cells located right below the upper epidermis and waxy cuticle. They contain many chloroplasts for maximum light absorptions. Their main role is to do photosynthesis.

amount of chlorophyll in each layer

Plant nutrition

Definition of photosynthesis – the process by which plants manufacture carbohydrates from raw materials using energy from light

Word equation – Carbon dioxide + water → glucose + oxygen

Chemical equation (balanced)

Chlorophyll transfers light energy into chemical energy in molecules, for the synthesis of carbohydrates (叶绿素为了碳水化合物的合成将光能转换成化学能,储存在分子里,稍后再用)

Plants subsequently store the product of photosynthesis as carbohydrates and use it later.

Appropriate amounts of carbon dioxide, light, chlorophyll is necessary for photosynthesis.

Investigate and describe the effect of varying light intensity and temperature on the rate of photosynthesis (e.g. in submerged aquatic plants, cabomba)

rate of photosynthesis against light intensity
rate of photosynthesis against temperature
rate of photosynthesis against CO2 concentration
Three variables together

Parts of a leaf:

  • chloroplasts
  • cuticle
  • Guard cells
  • stomata
  • Upper epidermis
  • Lower epidermis
  • palisade
  • mesophyll
  • Spongy mesophyll
  • Vascular bundle
  • xylem
  • Phloem
  • dicotyledonous – 双子叶植物
parts of a leaf

Starch Test:

If a plant is left without sunlight, regardless of other factors, it is going to be brown and orange
If a plant is exposed in sunlight without Carbon dioxide, it is going to be brown?
If a plant is blocked from sunlight but has carbon dioxide, it is going to be brown, blue, or black?

A blue or black color shows that a plant contains starch.

a variegated leaf

Leaves that has different colors for different parts (for example green and white) are called variegated leaves. Some parts of their leaves have chlorophyll while some do not.

Scientists put Sodium hydroxide to absorb Carbon dioxide so that plants cannot absorb it.

Describe the significance of features of a leaf in terms of functions, to include:

  • Palisade mesophyll and distribution of chloroplast – photosynthesis
  • Stomata, spongy mesophyll cells and guard cells – gas exchange
  • Xylem for transport and support
  • Phloem for transport

Describe the importance of:

  • Nitrate ions for making amino acids
  • Magnesium ions for making chlorophyll

Explain the effects of nitrate ion and magnesium ion deficiency on plant growth

First we have,
a component of DNA
Potassium, Magnesium
Both help with photosynthesis,
Nitrate is,
The complex one
combines with glucose,
to make lots of amino acids

No Nitrates,
plants won’t grow
no phosphate then discolored leaves,
Without them then yellow leaves

Let it grow
Let it grow…

root hair cells through binoculars
position of xylem and phloem

Transportation in Plants

State the functions of xylem and phloem

Identify the position of xylem as seen in sections of roots, stems and leaves, limited to non-woody dicotyledonous plants

Identify root hair cells, as seen under the light microscope, and state their functions

Phloem is always on the outside xylem is on the inside, whether it is down on the roots or up on the stems. When in the leaves, phloem is always underneath xylem, imagine the stem and roots being split up.

The large surface area of root hairs increases the rate of absorption of water and ions

The pathway water takes from the root to the stem and finally to the leaf is root hair cells, root cortex cells, xylem and finally mesophyll cells.

What does different parts of a leaf do?

Lower epidermis – this layer has guard cells which control the opening and closing of stomata

Waxy cuticle – This layer decreases water loss. It is transparent so that light can pass through

Spongy mesophyll layer – loosely-packed cells covered with a thin film of water allows diffusion of carbon dioxide. Large air spaces.

Upper epidermis – Supports the leaf when the cells are turgid. Covered by waxy cuticle.

Vascular bundle – Composed of xylem and phloem. Provide transport and support.

Xylem – Cell wall thickened with lignin. Conducts water and mineral salts and gives mechanical support.

Phloem – Transports sugar made during photosynthesis. Sieve plates separate adjacent cells.

Palisade mesophyll – cells are tightly-packed and contain many chloroplasts for maximum light absorption

Water is transported from roots to leaves through the xylem vessels

?? How does water actually moves up ??

Water move upwards in the xylem because of the transpiration pull, helping to create a water potential gradient that draws up a column of water molecules, held together by cohesion.

Investigate and describe the effects of variation of temperature and humidity on transpiration rate.

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