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- Author or Editor: Robert P. Doss x
When compared to non-ethephon treated bulbs, time to flowering of U.S.-grown Dutch iris (Iris hollandica Hoog) ‘Ideal’ and ‘Blue Ribbon’ was shortened by 14 and 27 days, respectively, by dipping bulbs for 1 hr in a solution of ethephon at a concentration of 0.25 g·liter–1 and then heat curing at 32°C for 3 days. This treatment also decreased leaf number and maximum leaf length. Thus, the plants were commercially more acceptable than those not treated with ethephon. With ‘Blue Ribbon’, treatment with ethephon at 5.0 g·liter–1 reduced flowering percentage relative to that obtained with several lower concentrations because of prevention of flower initiation. Chemical name used: (2-chloroethyl)phosphonic acid (ethephon).
Shoots of ‘Cara Mia’ rose (Rosa hybrida L.) arising from buds higher on the parent shoot become salable more quickly than those arising from lower buds. Those developing above the 10th or below the 6th true leaf are shorter, of smaller diameter and weigh less. Shoot development is also strongly influenced by shoot diameter at the point of origin. Larger parent shoots give rise to shoots that become salable more quickly, are longer, weigh more, and are larger in diameter than those from smaller parent shoots. Buds from larger-diameter shoots are of larger diameter and have more leaf primordia than those from smaller-diameter shoots, but the diameter of their apical dome is not greater.
Knowledge of the chromosome number in Rubus would be valuable when planning crosses and identifying plants, etc., however, preparation of tissue for microscopic evaluation and chromosome counting is difficult and time-consuming. Flow cytometry offers a more-efficient approach to this task. DNA flow cytometry was used to determine the nuclear DNA content in 22 Rubus genotypes. The genotypes represented a range of reported chromosome numbers from 2x to 12x. Six of the genotypes were representatives of Rubus ursinus, which is reported to have both 8x and 12x forms. Samples of nuclei were prepared from leaf discs of newly emerged and mature leaves following published protocols with some modifications. The DNA content was estimated by comparison of the fluorescence of Rubus nuclei with an internal DNA standard. There was an increase in nuclear DNA content concurrent with the increase in chromosome number. In these studies DNA flow cytometry could differentiate genotypes that differed by 2x, such as 6x and 8x, but could not reliably distinguish genotypes that differed by 1x, such as 7x vs. 8x or 6x. Aneuploids cannot be differentiated at this time.
Plants of the ‘Cara Mia’ rose (Rosa hybrida L.) grown at elevated day temperatures with long photoperiodic cycles or at reduced night temperature with short photoperiods differed in shoot growth rate, petal number, final stem length, and harvest date when compared to plants grown at suggested day and night temperatures. Node number remained nearly constant under all growing conditions. Plants of ‘Town Crier’ rose grown with a night temperature of 13°C (minimum) during the first 3 weeks following shoot removal produced flowering shoots of the same length in the same amount of time as did those grown at a minimum night temperature of 17°C throughout shoot development. Cooler night temperatures during the second 3-week period after shoot removal increased flower development time by four days but did not affect stem length. Results indicate that some rose cultivars can tolerate lower than normal night temperatures for a portion of the growing cycle without reduced growth and/or yield.