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1. In a study of the effects of photoperiod and nitrogen nutrition on the expression of certain morphological characteristics of soybean, plants of Morse, Virginia, Lincoln, and T-48 varieties were grown either in controlled-environment rooms or in the greenhouse and in either soil or sand cultures. 2. In experiments in which nitrogen nutrition was not a factor, all varieties flowered on all durations of photoperiod, but first-flower primordia were formed at a higher node on the plant axis with the longer photoperiods. 3. Position of first-flower primordia did not vary with nitrogen treatment when the plants were grown with short photoperiods. When grown with long photoperiods, however, plants of certain varieties initiated first-flower primordia at higher nodes as the amount of nitrogen in the nutrient solution was increased. Variety T-48 was outstanding in this respect, Lincoln was intermediate, while Morse and Virginia were least responsive. 4. Plants of Lincoln and Morse grown on long photoperiods sho...

1. A study was made of the several effects of photoperiod and nitrogen nutrition upon the bulb and flower-stalk development of onion. Plants were grown from seed, sets, and mature bulbs, and with soil and in sand culture. 2. Plants grown on photoperiods substantially longer than that critical for bulb formation showed no difference in bulb development when supplied different amounts of nitrogen. 3. Plants grown on a photoperiod at or near that critical for bulb formation exhibited the greatest bulb development with the lowest nitrogen concentration and the least with the highest concentration. 4. Under certain environmental conditions nitrogen and photoperiod can interact to influence bulb development of certain onion varieties. 5. Onion plants of sister lines gave similar bulbing response on photoperiods of identical duration. However, the two lines differed in their production and development of visible floral stalks, especially on the shorter of the photoperiods. Development of floral stalks was favore...

1. The purposes of this investigation were to obtain quantitative data on the photoreactions that prevent flowering of short-day plants, from which an action spectrum relating wave length to photoperiodic effectiveness of light could be derived, and to draw such inferences concerning the nature of the photoreactions as the action spectrum would permit. 2. Experiments designed to give the action spectrum made use of a specially designed prism spectrograph having a dispersion of 15 A. per cm. at 5000 A. At this wave length and with an effective slit width of 100 A. the energy was about 3000 ergs per sq. cm. per second with the slit illuminated by a carbon arc operated at 12 kw. input. 3. Plants investigated were soybean, Soja max (L.) Piper var. Biloxi, and cocklebur, Xanthium saccharatum Wallr. To facilitate irradiation, the foliar surface of the plants of each species at the beginning of an experiment was reduced to a single leaflet or leaf, respectively. 4. The experimental treatment was based on the fac...

The genetic and morphological effects of radiocarbon when incorporated into plants of the common snapdragon were investigated. Plants of an F/sub 1/ hybrid heterozygous for flower color and plants of the variety Windmillers Lilac were exposed to atmosphers containing carbon dioxide enriched with C/sup 14/O/sub 2/. The estimated radiation dosages were phase specific activities of 4, 25, 150, and 900 mu c per gram carbon, respectively. The frequency of somatic mutations increased from 0.61 mutant areas per flower in controls, to phase activities of 4, 25, 150, and 900 mu c per gram carbon, respectively. The relationship between air-phase specific activity and frequency of mutant areas appeared to be linear at air-phase specific activities from 25 to 900 mu c per gram carbon; the efficiency of radiocarbon treatment was greatest at 4 mu c per gram carbon. Only two phenotypic classes of mutant areas, pink and white, were classified accurately. Neither the pink nor the white areas were attributed to mutation at specific loci. On the average, pink mutations were observed 7.5 times as frequently as white. No morphological changes in plants of the F/sub 1/ hybrid and Windmillers Lilac were observed at the three lower air-phase specific activities. Plantsmore » exposed to the 900 mu c per gram carbon air-phase activity exhibited reduced lateral branching and flower production, increases in leaf thickness, stem diameter, plant height, abnormalities in flowers, and dichotomous branching of the main stem. Comparisons with other results indicate that radiocarbon treatment was slightly more effective than equivalent amounts of ionization from chronic gamma irradiation in producing certain morphological changes. Radiocarbon and chronic gamma irradiation were not shown to differ in effect in the induction of somatic flower color mutations in snapdragons. (auth)« less

1. Flower primordia were present on plants of Taraxacum kok-saghyz collected from several localities in the central or northern parts of the United States during the late fall or winter months. Photoperiods of 8, 10, 12, 14, 16, and 18 hours did not inhibit the development of these primordia into mature flowers when the plants were transplanted in the greenhouses. 2. Wide variability of leaf pattern was observed in the seedlings, but morphological characteristics of the flowers indicated that almost all were kok-saghyz plants. Seedling plants subjected to six different lengths of photoperiods varying from 8 to 18 hours flowered under all conditions, but more of them flowered with photoperiods of 12 hours or longer than with shorter photoperiods. 3. Plants that received low temperatures during their early development flowered more abundantly than those that received no low temperature. Ninety-eight per cent of one lot of seedlings that had received several weeks of cold weather during the spring flowered, ...

1. Flowering of hemp, Cannabis sativa L., variety Kentucky, occurred in all plants at photoperiods of 8-14 hours, inclusive. At photoperiods of 16-20 hours flowering was incomplete and greatly delayed. 2. Seedling plants 3-5 weeks old flowered within about 2 weeks when shifted from 16-hour to 8-hour photoperiods. Five-week-old plants required fewer 8-hour photoperiods than did 3-week-old plants for equal promotion of flowering. 3. When one branch of a two-branched plant was subjected to short photoperiods, the production of flowers was restricted to that branch. Temperatures as low as 55⚬ F. applied during the dark periods did not inhibit flowering. 4. Intensities of light from an incandescent-filament lamp greater than 0.03 ft-c. inhibited flower-bud initiation of hemp when applied daily during the 16-hour periods between successive 8-hour periods of natural light outdoors. 5. Pollination of female plants with pollen from male flowers produced on female plants resulted in seed that produced only female p...

1. Sets of the Ebenezer variety of onion grown in the special nutriculture chamber at the Argonne National Laboratory under controlled temperature and humidity conditions had their natural atmospheric carbon dioxide supply supplemented by the addition of C14O2 so that the total concentration varied from 0.03% to 0.1%. The photoperiod was extended to 16 hours by means of incandescent lamps. 2. One leaf from a plant of approximately a dozen grown showed a chlorophyll-deficient streak along its entire length. There were no chlorotic streaks in control plants. 3. Roots from the carbon 14 plants showed both chromosome and chromatid breaks and fragments in dividing cells, bridging, and micronuclei. No aberrancies were observed in dividing cells of control roots.

1. Studies were made of the effects of photoperiod and light intensity upon flower formation in plants of several genetically different populations of castor bean. Plants were grown in soil in the greenhouse, field, or controlled-environment rooms. The node position of the first flowers and the total number of nodes on nonflowering plants were the criteria used for measuring the responses of plants to duration and intensity of light. 2. In experiments concerned with photoperiod alone, marked variation in degree of flowering response was observed for a number of varieties. Some failed to flower on either long or short photoperiods, while those of other varieties flowered on both photoperiods. In the case of one variety, flowers developed only on plants grown with long photoperiod. 3. Plants of two parents and their F1 and F2 progenies, the last of which contained plants that remain flowerless when grown under normal field conditions at Beltsville, Maryland, were grown with controlled photoperiod. Plants of...