(a(i))[1]
State the identity of the structures labelled W in Fig. 4.1.
(a(ii))[2]
Describe the role of structure W.
(b(i))[2]
Outline the main structural characteristics of a virus.
(b(ii))[5]
Many plant viruses can move through the plant to reach companion cells in the phloem tissue. The viruses then move with assimilates in the phloem sap to other regions of the plant. Explain the mechanism that enables assimilates and viruses to move through phloem sieve tubes to other regions of the plant.