Abstract
Ultrastructural changes in chloroplasts of peanut (Arachis hypogaea L. var. Lokal) seedling mesophyll cells and mesophyll protoplasts treated with electric fields were investigated. Generally, chloroplast profiles in mesophyll cells were biconvex, whereas those in mesophyll protoplasts were oval and round and some were divided. When the protoplasts were treated with electric fields, some chloroplasts were paired. Some of these seemed to result from division and others from fusion. This electric field treatment may stimulate chloroplast division and fusion, related to the activation of protoplasts which has been known to occur by the same treatment. There are two types of division, i.e. partition and fission. The division by partition was usually observed by invagination of the inner membrane of the chloroplast envelope. The fission type of division was recognized by a dumbbell-shaped profile and electron dense material was usually observed in the neck region. Some chloroplast profiles seemed to be produced by fusion of two chloroplasts, because the two parts had a common envelope and two thylakoid systems at the fusion area were disharmonious.
