The structure of the rhizosphere of maize seedling roots, a cryogenic scanning electron microscopy study

The surface of primary roots of maize (Zea mays cv. W64A × 182E) seedlings grown in a field soil was examined after cryogenic preparation of samples for scanning electron microscopy. The very short preparation time of this method and the absence of fixation and drying procedures give excellent preservation of the spatial organization of the rhizosphere. As root hairs develop, they carry soil clear of the epidermal surface to form a distinct soil sheath layer. Root hairs remain turgid along the entire length of the primary root of the seedlings studied and are often distorted as a result of their growth around obstructing soil aggregates. The epidermal surface remains remarkably clean along the entire length of the root. Fractures of frozen roots reveal that the epidermis is covered by a thin layer that may be mucilage. Very few microorganisms are observed on the epidermal surface.