The transport tissues of plants are phloem and xylem. The role of xylem is the transport of water and mineral ions from the soil solution to the different parts of the plant body. The role of phloem is the translocation of assimilates and other substances from sources to sinks.

1. (a)The source of mineral ions for the plant is the soil solution. These mineral ions are transported from the roots in the xylem. Mineral ions are also found in the phloem sap within phloem sieve tubes. Suggest why mineral ions are found within phloem sieve tubes and state how they are transported within phloem sieve tubes.[3]
2. (b)Phloem tissue consists of different cell types. Complete the passage using the most appropriate terms to summarise some of the features of phloem tissue. The end walls of sieve tube elements are modified to allow efficient flow of phloem sap by the formation of ................................................................................ . These structures also prevent the cells from bursting under pressure. The cytoplasm of sieve tube elements is very much reduced and is found at the ................................................................................ of the cells. Most of the organelles in the cell are absent. Adjacent to sieve tube elements are ................................................................................ cells that carry out the metabolic processes of the missing organelles, allowing the sieve tube elements to function.[3]