Germination and Seedling Growth in Echinochloa crus-galli var. oryzicola Under Anoxic Conditions: Structural Aspects

Abstract

The morphological and cellular basis of anoxic germination in Echinochloa crus-galli var. oryzicola is reported. The embryo of E. crus-galli var. oryzicola is typically panicoid in its overall morphology, and is relatively large with a prominent coleoptile and mesocotyl. The response to anoxia is essentially the same in light and dark. Shoot growth occurs in both mesocotyl and coleoptile by cell elongation with no cell division. There is no emergence of the radicle without oxygen. Under anoxia the growth response is not the same as etiolation; there is no plumule elongation within the coleoptile, no protochlorophyll(ide) is found, and limited mesocotyl elongation occurs without oxygen. Air-dark treatment after anoxic germination results in a typical etiolated morphological response, including a resumption of mesocotyl growth, elongation of the plumule within the coleoptile, and initiation of pigment synthesis. These results indicate the effects of anoxia are not permanent but rather limiting and reversible.