Recovery from cellular damage in vegetative shoot apices of Capsicum annuum L. after acute gamma irradiation

Abstract

Seedlings of Capsicum annuum were irradiated with acute gamma rays ( 60Co) at cotyledonary, 4-leaf, 8-leaf and 12-leaf stages of development. They were exposed to doses of 1, 2, 3, 4, 5, 7·5 and 10 kR. The responses of shoot apices subsequent to radiation damage were studied. Following a dose of 1–2 kR resumption of normal growth can take place by direct recovery of the shoot meristem. In this case enlargement of cells surrounding the damaged area fills the gap left after the disorganization of the damaged cells. In a few cases recovery takes place either by the development of new meristematic centers at the apex or by the formation of an adventitious meristem well below the damaged apical meristem. Depending upon the number and position of meristematic centers the main apex may be reconstituted, dichotomized, or fasciation may result. No recovery takes place at the higher exposures of 4–10 kR. It is concluded that the percentage of cell deaths at different exposures determines the various ways in which a normal pattern of organization and growth of the shoot apex is restored.