a. movement can occur both upward and downward in the plant
Explanation:
The phloem loading causes the accumulation of sugars in the sieved elements generating a negative solute potential (quedas), with a drop in water potential (ψw), so water enters the sieved elements increasing the turgor pressure (ψp). With the discharge of phloem in the drain occurs lower concentration of sugars in the screened elements, increases the solute potential, becoming positive, thus the phloem water potential increases and thus the water leaves the conducting vessel. In the specific case of sugar movement in the phloem, it can be stated that this movement can occur both up and down in the plant.
Basically ionic bonds can be formed between a metal atom and something called a radical ion. The radical ion could have covalent bonds within themselves, for example, CO3- is a radical ion.
