The movement of phloem sap is an active process.
Which of the following is the most suitable explanation for this?
Phloem sap flows from the source to the sink.
ATP is required to load organic compounds into the phloem at the source.
Water leaves the phloem sieve tube at the sink.
Water moves into the phloem at the source by osmosis.
Which of the following is not a structural feature of phloem tissue?
Lignified cell walls to withstand the hydrostatic pressure.
Columns of sieve tube cells.
Companion cells containing cell components that facilitate the loading and unloading of organic compounds.
Sieve plates with pores allows for the continuous movement of organic compounds.
Which of the following aphid characteristics makes them suitable to use when investigating phloem transport rates?
I and IV only.
I, III, and IV only.
II, III, and IV only.
I, II, III, and IV.
The micrograph below shows part of a cross section of a plant stem.
Which of the structures A-D represents the xylem tissue?
Image courtesy of Doc. RNDr. Josef Reischig, CSc. Licensed under Creative Commons Attribution-Share Alike 3.0 Unported license. Reused and distributed under conditions found at: https://creativecommons.org/licenses/by-sa/3.0/
Which row correctly identifies a structure and its related function in a companion cell?
| Structure | Function | |
| A. | Many mitochondria present | Translation of polypeptides that will form cell surface membrane proteins |
| B. | Nucleus and cell organelles | Carrying out the cell processes of the sieve tube cells |
| C. | Plasmodesmata | Linking adjacent companion cells with each other |
| D. | Small amount of cytoplasm present | Facilitating the movement of assimilates |
