Abstract
Two sets of healthy or virus infected Nicotiana sylvestris plants (four plants per set) were allowed to grow for four weeks after inoculation. Leaf disks were taken randomly from equivalent positions in the rosette and on the stem axis of systemically infected and healthy leaves and placed into culture. Pak. J. Agri. Sei., Vol 31, No. 4, 1994 disks taken from rosette leaves (Fig. 1). Thus, the disks taken from leaves of different developmental states responded differentially to virus infection despite the fact that virus titters in both types of leaves were the same at the time of initiation of tissue cultures. To investigate this phenomenon further, two additional experiments were performed that included disks from leaves of different developmental state from healthy and infected plants. The data presented in Fig. 1 and 2 indicate that significant differences occurred among several treatments. For the first three weeks of culture, disks taken from uninfected leaves from the stem axis grew considerably faster in terms of fresh and dry weight accumulation than disks from virus-infected leaves on the stem axis. Disks taken from rosette leaves at the base of the plant grew more slowly still, but infection by the virus did not affect their growth during the first two weeks of culture. In the fourth week of culture, the growth of disks from axis leaves of infected plants reached about the same level as that of the uninfected axis leaf disks.
