DIVISION FREQUENCY OF PEA PROTOPLASTS IN RELATION TO STARCH ACCUMULATION

Division frequency of alginate-embedded pea (Pisum sativum var. Belman ) protoplasts derived from embryonic shoot tips was studied quantitati vely by image analysis in relation to starch accumulation and protopla st size. Protoplast divisions were observed from day 4 on and the numb er of protoplasts undergoing division increased in a stepwise manner t o 70% the following days. The starch content increased rapidly during the first 3 days of culture prior to the onset of division and resulte d a 4.2-fold increase in the intracellular starch area and a 3.0-fold increase (from 27% to 80%) in the number of protoplasts containing sta rch. Subsequent periods with rapid increases the number of dividing pr otoplasts were preceded by further starch accumulation. Dividing proto plasts were 33-60% smaller and contained 8-42% less starch than non-di viding protoplasts. However, calculations showed that, in the dividing protoplasts, the relative area covered by starch was 6-12% higher tha n in non-dividing protoplasts. These data suggest that starch accumula tion precedes division of pea protoplasts.