General structure of a plant cell nucleus

Just as the vacuole is the dominant structure in leaf mesophyll cells, the nucleus is normally the predominant protoplasmic organelle of the cell, and is the site of storage and utilization of genetic information. In meristematic (dividing) cells, as shown here in undifferentiated sporogenous tissue of African violet (Saintpaulia ionantha), the nucleus N occupies a major portion of the cell volume.

The nucleus is bounded by a double membrane envelope (NE) which, at certain sites, shows discontinuities (unlabelled arrows) that are the nuclear pores. The genetic material of this interphase nucleus is formed of diffuse (most active), and condensed (less active) chromatin. The large nucleolus (Nu) consists of intermingled granular and fibrillar components.

CW₁ = primary cell wall, M = mitochondrion, RER = rough endoplasmic reticulum, SER = smooth endoplasmic reticulum

Illustration from: Ledbetter & Porter, 1970, Introduction to the Fine Structure of Plant Cells, Springer-Verlag