Answer:
a. transcription
Step-by-step explanation:
Sugar transport in phloem is referred to as pressure flow and it involves the movement of sugar through the phloem vascular tissue from the regions where sugar is synthesized (by photosynthesis) to other parts of the plant's body that require sugar.
The parts of plants where sugar is synthesized (usually the leaf) is known as sugar source while the parts where they are transported is referred to as the source. Sources are usually areas of of high osmotic concentration and high water pressure while sinks are usually areas of low osmotic concentration and low water pressure.
Hence, sugar transport in the phloem can be said to be influenced by the rate of sugar production at the source (rate of photosynthesis), turgor pressure as well as sugar concentration in sinks and sources.
The only option that has no known effect on sugar transport in the phloem is transcription.
The correct option is a.