CAIE A-Level Biology AS 7.2.6 Assimilate Transport in Phloem Questions
Explain assimilate transport in phloem from sources to sinks using evidence from each question and mark scheme.
- Syllabus
- 2028–2030
- Course
- Biology 9700
- Level
- AS
Exam points
- Explain assimilate transport in phloem from sources to sinks.
CAIE A-Level Biology AS 7.2.6 Assimilate Transport in Phloem Questions question 1
Nerium oleander is a xerophytic plant. A photomicrograph of a section through the leaf of N. oleander is shown in Fig. 3.1.
Fig. 3.1
Question (a)
(a)
Explain the difference between a source and a sink.
One of the enzymes involved in the synthesis of sucrose in the cytoplasm of palisade mesophyll cells is known as cyFBPase. The gene coding for this enzyme is cyFBP.
The importance of cyFBPase in plant growth can be investigated using plants with a mutation in gene c y F B P. These plants cannot synthesise cyFBPase.
[ 2 ]
Question (b)
(b)
Investigations have shown that plants with the c y F B P mutation grow to a much smaller height and have proportionately far less starch stored in their roots than normal plants.
Suggest why plants with the cyFBP mutation will store less starch in their roots.
[ 2 ]
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