Question

Long-distance transport in phloem requires which of the following processes?

i) a positive water potential (positive pressure)
ii) active transport through parenchyma cells
iii) cohesion between water molecules
iv) evaporation of water molecules

a. I and ii only
b. ii and iii only
c. I, ii, and iii only
d. I, ii, iii and iv

Answer 1

The correct answer is option d. I, ii, iii and iv.

Step-by-step explanation:

Long-distance transport in the phloem of plants involves several critical processes. Active transport plays a crucial role in moving sugars into phloem sieve tubes, which causes water to move into the phloem from the xylem due to a decrease in water potential. This results in a higher internal pressure within the phloem, facilitating the movement of the sap through the phloem tubes to various parts of the plant.

The cohesion-tension theory describes the movement of water in the xylem, which is driven by evaporation (transpiration) from the leaves, resulting in a negative pressure that pulls water up the xylem from the roots. In essence, the processes of active transport, cohesion and adhesion of water molecules, and transpiration contribute to the efficient movement of substances through the plant's vascular system.