Growth Regulators and Flowering. II. The Cobaltous Ion.

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Abstract
Cobaltous ion extends the minimum single period of darkness required by the cocklebur (Xanthium pennsylanicum) for the 1st perceptible signs of flowering. This effect can be reversed completely by sulfhydryl protectors such as cysteine and glutathione but is unaffected by manganeous ion or by 2,4-dinitrophenol. The effects of cobaltous ion upon the timing reactions of the flowering process were studied by kinetic experiments on the effective times of red light interruption of the inductive dark period, the effect of duration of such an interruption given at a specific time, and the reversal of red interruption with far-red. The effect of a low intensity, red light interruption of the inductive dark period depended not only upon the total length of the dark period, but upon the extent to which the timing reactions had been completed at the time of interruption. Thus it seems likely that such an interruption does not completely reverse the timing reactions which are begun at the time the plant was placed in darkness. Although the timing mechanisms of flowering are strongly influenced by the cobaltous ion, the timing mechanisms of leaf movements were not so affected in experiments carried out under varying temperature contions. It may be significant that effects upon flowering and leaf movements can be so separated.