A CYTOCHEMICAL STUDY OF EMBRYO DEVELOPMENT IN STELLARIA MEDIA

Abstract

The caryophyllad type of embryogenesis in Slellaria media was investigated using topological cytochemical methods for the demonstration of nucleic acids, proteins and polysaccharides. The primary suspensor cell initially contained high levels of cytoplasmic RNA, but these declined rapidly after the first few cell divisions. Cytoplasmic protein levels were high throughout the existence of the primary suspensor cell, becoming concentrated into proteinoplasts at the time of cotyledon initiation in the embryo. These plastids were RNA‐ and DNA‐negative, and only slightly positive with methods for polysaccharides and lipids. Cytoplasmic and nucleolar RNA and protein levels were high in the embryo throughout its development. The cotyledons and endosperm also showed high RNA and protein levels. Cytoplasmic DNA was present in the embryonic apical meristematic cells in the form of Feulgen‐positive, deoxyribonuclease‐removable granules. Cytoplasmic histones were present in the embryo and endosperm. Polysaccharides were demonstrable in the cotyledons, cortex, endosperm, and nucellus.