HORTICULTURE

Detailed explanation-1: -data from experiments measuring phloem transport rates using aphid stylets and radioactively-labelled carbon dioxide. We can learn about this process through the NOS to understand how it works and why it enables us to understand the flow of sap through the phloem.

Detailed explanation-2: -Aphids possess a protruding mouthpiece (called a stylet), which pierces the plant’s sieve tube to allow sap to be extracted. The penetration of the stylet into the sieve tube is aided by digestive enzymes that soften the intervening tissue layers.

Detailed explanation-3: -Aphids don’t suck; rather, the phloem contents are forced into the aphid (thus the phloem is under pressure) and the excess oozes out the anus (honeydew). Thus, aphid studies demonstrate that the phloem is under pressure. Further, the honeydew can be collected and we can identify its composition.