1. Biologists studied about food transportation in plants with the help of aphids.
2. Aphids feed on the plant juices of young stems.
3. Aphid uses its long needle like organ proboscis to extract plant juices from phloem tissue.
4. The proboscis of the Aphid only penetrates up to a phloem sieve tube.
5. It is found experimentally that the contents of the phloem sieve tubes are under slight pressure the fluid slowly comes out from the cut end of the proboscis in the form of drops.
6. These drops were collected and analysed and it contain sugars and amino acids.
7. Aphids absorb so much sugar from the phloem that they cannot assimilate all of it and it excretes out of the body as sticky syrup called honey dew.
