Seed-setting in potatoes as affected by spraying with a-naphthaleneacetamide and by light
SummarySpraying potato plants with dilute concentrations of a-naphthal-eneacetamide was not effective in increasing flower or seed ball production in the greenhouse at Beltsville Maryland, or Greeley, Colorado. Higher concentrations reduced flower production at Presque Isle, Maine.Sebago and Irish Cobbler produced more seed balls at Greeley than at Beltsville. Less cloudy weather at Greeley during the winter months is probably the chief factor responsible for this result.S 245–25, when self-pollinated, produced as many seed balls at Beltsville as at Greeley. It appears that this variety flowers and sets seed more readily under fairly unfavorable light conditions than either Sebago or Irish Cobbler.
Effectiveness of Several Growth Substances on Parthenocarpy in Holly
An earlier paper (3) gave the results of experiments on inducing parthenocarpy in American holly, flex opaca, by spraying the open blossoms with dilute aqueous solutions of growth substances. Data were presented as to the relative potency of four compounds, indoleacetic, indolepropionic, indolebutyric, and naphthaleneacetic acids, the last named being very much more effective than any of the other three. Recently several other substances have been similarly tried on a comparative basis, and the results, of seeming interest because of their variance in some cases from other reported evaluations of relative effectiveness in plant response, are presented here with the hope that they may eventually help in piecing together the picture of how and why the hormone-like substances bring about the numerous and varied responses associated with their application. The methods used were essentially those previously reported. The growth substances' were dissolved in distilled water and sprayed on the open flowers by means of an atomizer. The tests were applied to small potted plants flowering in the greenhouse and to flowering branches on trees growing on the grounds of the United States Horticultural Station, Beltsville, Maryland. In table i are presented some preliminary results with several compounds of naphthalene on young holly plants flowering in the greenhouse. These plants were found to vary considerably in their ability to set parthenocarpic fruit, depending on their vigor, nutrition, and previous treatment. While only plants selected for their uniformity were used in these tests, yet since ioo per cent setting of fruit was not obtained with treatments which in previous trials had given complete setting, the comparisons were repeated under more uniform conditions. Accordingly the data in table 2 show repetition
Histological Comparison of Fruits Developing Parthenocarpically and Following Pollination
An earlier issue of this journal (2) gave an account of parthenocarpy induced by spraSving the open blossoms of the American holly, Ilex opaca, with dilute aqueous solutions of several growth substances, including indoleacetic acid. It was pointed out that the development and external appearance of the parthenocarpic fruits were quite like the fruits set following pollination. Even at maturity it has not been possible to distinguish between normal and parthenocarpic fruits except by cutting open the seeds which in the latter case were invariably devoid of embryos. GIJSTAFSON (3) has also given a list of fruits whose development has been induced to a greater or lesser degree by growth promoting substances, but has not recorded histological details. In view of the marked and extensive histological changes which occur in stems of the bean (5, 4) and the tomato (I) when treated with lanolin mixtures of certain growth substances, and as a matter of general interest in studies on development, a study of the tissues of the pistil of Ilex opaca as affected by these compounds was undertaken. The holly is dioecious and the pistillate plants, if isolated from possible pollination and otherwise untreated, do not set fruit. For the experiments here reported small pistillate plants with freshly opened flowers were divided into two lots, one of which was pollinated and the other sprayed once with a o.o4 percentage aqueous olution of indoleacetic acid. At frequent intervals from six to 57I hours after pollination or spraying, flowers or developing fruits togetherwith their pedicels were taken from each lot and placed in Navashin's solution for subsequent histological preparation. Although the ap-