Ok... lets start with the formulaes..:

1) photosynthesis: carbon dioxide + water -> glucose + oxygen

[6CO2 + 6H2O -> C6H12O + 6O2] * [in the presence of (sun)light and chlorophyll] *

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2) respiration:
Glucose + Oxygen = Carbon Dioxide + Water + Energy
[C6H12O6 + 6O2 -> 6CO2 + 6H2O + Energy]

Ok the common misunderstanding: respiration occurs in plants happens when photosynthesis halts. THIS IS ABSOLUTELY WRONG! respiration is always occurring, to produce energy for the plant. Photosynthesis occurs ONLY in the presence of light and chlorophyll.

Therefore: the typical question of respiration and photosynthesis... a submerged plant is placed under a bright light, after awhile, it is placed in an enclosed room without light. Describe what happens to the oxygen in the water and why.

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If you were to explain it as such: photosynthesis occurs when the plant is under a bright light, thus photosynthesis occurs, the level of carbon dioxide in the water drops and the level of oxygen in the water increases. After the plant was placed in the dark room, respiration takes place and thus the level of oxygen decreases and the level of carbon dioxide increases as photosynthesis does not take place due to the absence of light.

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Seems right? Actually, if this were to be a three mark question, you'd proabably only receive about 1 mark!! why?? because of the way the sentence is phrased. from this, the marker gets the impression that respiration occurs only when the plant is placed in darkness, and the photosynthesis stops.

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So... the right way to phrase the answer is as such: photosynthesis occurs when the plant is under a bright light, thus photosynthesis occurs, the level of carbon dioxide in the water drops and the level of oxygen in the water increases. After the plant was placed in the dark room, respiration continues and thus, the level of oxygen decreases and the level of carbon dioxide increases as photosynthesis does not take place due to the absence of light.

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funny right? with just a difference as minor as that, u lose 2 marks? well with just that change of word, the entire concept of respiration changes. So... in future... be careful of how u phrase ALL your answers, to prevent the opportunity for the marker to deduct marks from your script =)

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Ok now for the transportation in plants:

Xylem vessels and pholem vessels: xylem vessels transport water throughout the plant, while the pholem vessels transport food throughout the plant.

alright, lets link to other sub-topics.

The regular modified cells:

the xylem vessel is modified in such a way to suit its function. The modifications of the xylem vessels are: a lignified cellulose cell wall(extra hard and strong to support the plant), it is hollow and has no nucleus(it is dead) to enable faster transport of water throughout the plant.

the root hair cell is modified for absorption of water, it has an extended area for larger surface area, its cell sap is so as to lower the water potential in the cell, so that osmosis might occur!

Those were the 2 questions usually asked when it comes to modified cells in plants.

As for the transport in plants, a typical question would be: how does osmosis play a part in the absorption of water in plants.

You probably think that it is active transport that takes place instead of osmosis. and you'd probably be stuck. well you require to understand.. active transport only helps in the transportation of water in plants! By evaporation by the stomata, water is *sucked* up the xylem vessel(Think of the syringe). osmosis has to occur in the absorption of water through the root hair cells. Active transportation does not play a part in it! Osmosis is required to absorp water from the surrounding soil, thus the reason of the high concentration of cell sap in the root hair cells!

This is about all i have to post.. so i hope it helps... Just remember! You shouln't memorise Biology! It just requires understanding and passion!!

Signing off~ Jershon