ETUDE HISTOLOGIQUE DE LA BIGARRURE NERVALE, DE LA GRISELURE DU LIMBE ET DE LA MEDIANE NOIRE, TROIS DESORDRES DU CHOU EN ENTREPOT

The evolution in storage of three physiological disorders of cabbage (Brassica oleracea var. capitata) has been studied by means of histological tests done in situ or after fixation and staining. The tissues tested were sampled on necrotic and healthy parts from the three outer-head leaves of the susceptible cv. Safekeeper and of the resistant cv. Hitoma. The tissues affected by vein streaking, grey speck disease or black midrib showed a similar response to the many tests: the absence of lipids, lignin and suberin in the necrotic cells, but the presence of unidentified phenolic compounds, concomitantly with a modification of birefringence of the cell wall and an alteration of the cytoplasmic matrix. Vein streaking is associated with creases on the adaxial epidermis of the midrib, grey speck disease with abundant wax on the abaxial blade, and black midrib with large vesicles in the necrotic parenchyma cells of the midrib.Key words: Brassica oleracea var. capitata, chemical composition, cytology, pepper spot, physiological disorder, storage