A) vertical transmission is transmission of a virus from a parent plant to its progeny, and horizontal transmission is one plant spreading the virus to another plant.
B) vertical transmission is the spread of viruses from upper leaves to lower leaves of the plant, and horizontal transmission is the spread of a virus among leaves at the same general level.
C) vertical transmission is the spread of viruses from trees and tall plants to bushes and other smaller plants, and horizontal transmission is the spread of viruses among plants of similar size.
D) vertical transmission is the transfer of DNA from one type of plant virus to another, and horizontal transmission is the exchange of DNA between two plant viruses of the same type.
E) vertical transmission is the transfer of DNA from a plant of one species to a plant of a different species, and horizontal transmission is the spread of viruses among plants of the same species.

A) They can be controlled by the use of antibiotics.
B) They are spread via the plasmodesmata.
C) They have little effect on plant growth.
D) They are seldom spread by insects.
E) They can never be passed vertically.

A) ability of the infected cell to undergo normal cell division
B) ability of the infected cell to carry on translation
C) whether the infected cell produces viral protein
D) whether the viral mRNA can be transcribed
E) how much toxin the virus produces