Age dependence of cowpea protoplasts for uptake of spermidine and infectibility by alfalfa mosaic virus.

Cowpea protoplasts were prepared from plants of different ages and examined for their ability to take up polyamines and for their infectibility by alfalfa mosaic virus. A lag period of ∼20 h was necessary before the onset of rapid polyamine uptake; the occurrence of this rapid uptake depended on the age of the leaves used for protoplast preparation. The percentage of infection of cowpea protoplasts by alfalfa mosaic virus, and the amount of virus produced also depended on the age of the plants used for protoplast preparation. In contrast, the uptake of amino acids was rapid in all cowpea protoplasts tested.