Ontogeny of the Inflorescence in Chenopodium album

Gifford, Ernest M., Jr., and Herbert B. Tepper. (U. California, Davis.) Ontogeny of the inflorescence in Chenopodium album. Amer. Jour. Bot. 48(8): 657–667. Illus. 1961.—Chenopodium album, a short-day plant, was induced to flower by subjecting it to successive cycles of 7 hr light and 17 hr darkness. After 4 inductive days, the first macroscopic change is evident in the appearance of precocious axillary bud primordia. After 5–6 days, a primordial inflorescence is visible, and after 7–8 days a terminal flower appears on the main inflorescence axis. The vegetative apex has a biseriate tunica, the cells of which are larger than those of the corpus. The cells of the tunica stain lighter, possess larger nucleoli, and are more vacuolate than cells of the subjacent corpus. After photoinduction, the tunica-corpus organization is maintained, and after 4 short-days, the shoot apex possesses a mantle of 3–4 layers of cells because there are few periclinal divisions in the cells of the outer corpus. The cells of the mantle stain uniformly and are more chromatic than those of the underlying tissue. Mitotic activity was recorded in the upper 40-μ segment of the apex. In the vegetative apex, mitotic activity is greater in the lower portion of the segment. Following photoinduction, mitoses increase throughout the apex until a maximum is reached on the 4th day. Also, the plastochronic interval decreases after photoinduction. Nucleoli of cells of the corpus enlarge following induction until all nucleoli of the apex are nearly equal. Included in the paper are discussions of the general morphological differences between vegetative and flowering shoots.