Effect of starvation on the genetic activity of nucleus and nucleolar organizer.

The investigations of root meristems and hypocotyls of Lupinus albus L. starved, and then fed with 2% sucrose were carried out and several variations in nuclear and nucleolar dimensions, their ultrastructure, template activity of DNA, activities of RNA polymerases and transcriptional activity, were found. As a result of starvation, the surface area of nuclei and nucleoli decreases several times; after 24 hours, in the presence of sucrose, it grows again, but the control state is not achieved. Moreover, in a starved material the area of condensed chromatin in nucleus is increased by 1/3; after feeding, its partial recovery to the initial state is observed. The intensity of binding of 3H AMD in a fed material is increased by 1/3 as compared with the starved one. Transcriptional activity, estimated on the basis of 3H uridine incorporation is decreased in a starved material, especially in the meristematic tissue; feeding intensificates the transcriptional activity whereas the activity of endogenous RNA polymerase, investigated in hypocotyl, is drastically lowered in a starved material. Sucrose feeding does not restore the control state, though the per cent of nuclei and nucleoli revealing the activity of RNA polymerase is much higher in a fed material than in a starved one.