Phloem Study

Phloem sap is difficult for scientists to study. This is because plants are highly evolved to minimize phloem loss in the case of external damage. When a sieve tube is penetrated, it signals throughout the plant, triggering the release of callose which clogs the pores of the sieve plate. This causes all phloem movement through the sieve tube to stop. Luckily, scientists have figured out two ways to study the phloem uninterrupted. The first is to use a normal extraction tool that has been coated in an anti-slime. This allows scientists to observe the plant’s phloem without the interruption of sliming. The second way is by zapping aphids off of the plant after they have inserted their stylet. Aphids are able to access the phloem without triggering the release of callose. By removing the aphid without removing the stylet it acts as a phloem pump. Both of these methods are effective at extracting phloem from a plant without sliming occurring.