Developing plastids in excised etiolated leaves respond more rapidly to a 100 fc light intensity than to 60 fc. Under 100 fc, they measurably increased in thickness and diameter during four hours of exposure. Another 20 hours of light was required for measurable increases in diameter. There was some indication that plastids in older leaves reacted more rapidly than those in younger ones. Alternatively, they could have, been larger at zero time in the experiment. Internally, a steady increase in size of starch grains (and/or vacuoles) was observed. Small grana (Granascheibchens) developed early and appeared to coalesce to form the primary granum. There is good evidence that plastids develop more slowly in excised etiolated than in attached leaves, although the studies were not comparable in all respects. Plastid development in variety 18a of aromatic tobacco followed, in general, the pattern described for other species. The 1size obtained by starch grains (and/or vacuoles) under experimental conditions seemed unique but paralleled that in plastids developed under greenhouse conditions.

(Full article published with kind permission from "Tobacco International")