Xylem Phloem

If an insect were to pierce the xylem of a plant, the hole would disrupt water flow. In the xylem, water flows from the roots of the plants, to the leaves, where it diffuses out of the leaf in the form of water vapor. The water maintains an upward motion up the plant because the diffusing water vapor creates a pull. Water transport can only work if there is a constant continuation of water flow from the roots to the leaf. If there is a hole in the tube, this would create a disruption in the flow of water. The tensile force of water pulls the walls of a xylem in. If there was a hole, air might leak into the xylem tube due to the inward direction of tensile force. The air would expand under the tensile force, and disrupt water flow. If there is a disruption, roots would no longer be able to absorb water because its ability to absorb water is controlled by the leaf transpiring, which creates the upward force that allows water to flow. The air bubble blocks that force. If the hole was closer to the roots, the leaf would be able to continue transpiring for longer than if the hole occurred closer to the leaf, because the leaf is the source of the force that allows water to flow through the xylem tube. The plant would wilt, and eventually die from dehydration if the problem could not be fixed

If an insect were to pierce the phloem of a plant, the sap in the phloem would leak out. The cell walls of the phloem are inflexible and this creates turgor pressure, which pushes outwards. This turgor pressure is what would push the sap out of the phloem. Turgor pressure is higher when closer to a source (e.g. leaf) than when close to a sink (e.g. root) so if the hole was closer to a sink, more of the contents would leak out due to the higher pressure compared to near a sink, where the pressure would be lower so less sap would flow out. If a lot of sap was lost (a hole close to the source), the energy source of the plant would diminish, and it would eventually die. If the loss of...