O-LevelBiologyPlant Nutrition5090/21 · Oct/Nov 2021 · Q210 Marks

A farmer is growing a crop of tomato plants. (a) The tomato plants carry out photosynthesis. Describe the process of photosynthesis. (b) The farmer grows the tomato plants in a glasshouse instead of in an open field. (i) Suggest reasons why this is an advantage to the farmer. (ii) Suggest one disadvantage, other than cost, of growing plants in this way. (c) The graph shows how the rate of photosynthesis can vary with light intensity when all other environmental conditions are kept the same. rate of photosynthesis 0- 0 P Q light intensity

(a)The tomato plants carry out photosynthesis. Describe the process of photosynthesis.[3]
(b)(i)The farmer grows the tomato plants in a glasshouse instead of in an open field. Suggest reasons why this is an advantage to the farmer.[3]
(b)(ii)Suggest one disadvantage, other than cost, of growing plants in this way.[1]
(c)(i)Explain how this graph shows that light intensity is the limiting factor for photosynthesis at light intensity P but not at light intensity Q.[2]
(c)(ii)Name one environmental condition that could be limiting photosynthesis at light intensity Q.[1]

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Mark scheme

Marking points from the official mark scheme (Oct/Nov 2021). The mark or mark type is shown in brackets.

[1] any three from: light (energy) absorbed / captured AW ;
[1] chlorophyll / chloroplasts ;
[1] water + carbon dioxide are needed AW;
[1] glucose / carbohydrate / sugar / starch produced ;
[1] oxygen produced ;
[1] any three from: more / optimum + growth / tomatoes / yield / photosynthesis ;
[1] higher / optimum temperature / glass traps heat ;
[1] for enzymes;
[1] protects from bad weather / example ;
[1] protects from insect / pests / plant pathogens ;
[1] carbon dioxide / light intensity / wavelength + controlled ;
[1] any one from: have to water / no rain ;
[1] increase + pathogens / disease ;
[1] pollination may be difficult ;
[1] at P increase light intensity + up (photosynthesis / rate / gradient) ;
[1] at Q increase in light intensity + no change (photosynthesis / rate / gradient);
[1] any one from: carbon dioxide ;
[1] temperature ;
[1] water / precipitation ;

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