Unusual Nucleolar Behaviour of the Rice Shoot Apex

Abstract

SUMMARYAfter histological examination of young seedlings of rice shoot apex, a group of prominent nucleoli, localized in a few sub-apical cells, was detected. Three different staining techniques for cytochemical localization of nucleic acids, including enzymatic digestion, revealed a presence of small nucleolar bodies, which were pepsin resistant, and an amorphous susbstance, which was pepsin susceptible.The pair of nucleolar bodies adopted frequently either a parallel or perpendicular position with respect to the surface of shoot apex. The possible dependence of nucleolar orientation upon the nuclear rotation, as a consequence of deeply penetrating nucleolar chromatin, is admitted.The apparent resemblance with other examples of unusual nucleolar behaviour (in both plant and animal gametogenesis and in some cases of induced structural alterations) is discussed.