Developmental studies on leafy spurge (Euphorbia esula). Histology of the adventitious shoot apex

摘要

Histological analyses of adventitious shoot apices of leafy spurge (Euphorbia esulaL.) showed variation in the number of mantle layers at various stages of development. The older shoots (stages III and IV) tended to have a larger number of mantle layers than the younger ones (stages I and II) some of which contained two or three layers. The procambial differentiation was acropetal extending from the axis into the leaf primordium and the same pattern was noticed in all stages of development of adventitious buds and shoots. The shoot apex contained larger nuclei and nucleoli in the midsector than in the peripheral sectors and the nuclei in the former had fewer nucleoli. The total volume of nucleoli per nucleus was more in the midsector than in the peripheral sector. However, the ratio of total nucleolar volume to nuclear volume was very similar in all the sectors, suggesting uniform metabolic activity in the adventitious shoot apex.