Iron administration to iron-starved cocklebur (Xanthium pensylvanicum) plants causes an increase in the iron content of ferritin fractions extracted from mature leaves. Xanthium plants grown under long days (vegetative stage) have more iron and ferritin than similarly iron-treated plants induced to flower under short day regimes. This first demonstration of ferritin in cocklebur (Compositae) le...

The germination of seeds of Xanthium pensylvanicum Wallr. occurs in 2 phases, an initial passive phase of water uptake followed by an active phase of growth. These 2 phases have been separated experimentally, and shown to occur similarly in isolated cotyledons and embryonic axes. Measurements of the physical thrust generated by the entire seed and its separate components of cotyledon and axis r...

Bunning suggested that circadian rhythms provide the basis for time measurement in the photoperiodic responses of plants (2). A classic example is found in Glycine max. L. Merr. (Biloxi soybean), whose flowering response occurs in a rhythmical form having peaks of flowering that were approximately 24 hr apart (6). Recentlv Moore et al. (5) reported that Xanthiuim pensylvanicum did not exhibit a...

Bonner and Thurlow (3) reported that indoleacetic acid (IAA) inhibited the formation of flowers in cockleburs (Xanthium pensylvanicum Walln.) when it was applied as a spray during the long inductive night. In this report, evidence is presented that ethylene also inhibits the flowering of cocklebur plants that have been exposed to a long inductive photoperiod and that the IAA effect is probably ...