Effects of time and duration of short-day treatments under long-day conditions on flowering of a quantitative short-day sunflower (Helianthus annuus L.) ‘Sunrich Orange’

Abstract

The effects of short-day (SD) treatment on differentiation, development and anthesis of flower buds, and on cut flower quality were investigated in a leading cut sunflower (Helianthus annuus L.) cultivar, Sunrich Orange, a quantitative SD plant. Plants 15 were cultivated under long-day (LD) conditions with night interruption lighting from 2200 to 200 HR. SD treatment (11.5 h photoperiod) for 1, 2, or 3 weeks was commenced at the cotyledon, two true leaves, or four true leaves stage. The control plants were 2 grown under LD conditions throughout the experimental period. SD treatment for 1 or 2 weeks promoted flower bud initiation even when delivered at the cotyledon stage (9 days after sowing), indicating that the juvenile phase is very short in this cultivar.Flower differentiation and development were also accelerated by the SD treatment, and resulted in 19-39 days earlier anthesis. The quality of cut flowers was improved by SD 5 treatment to desirable characteristics such as decreased weight, shortened stem and reduced stem diameter. The present study suggests that under LD conditions such as found in summer, SD treatment for 2 weeks from the cotyledon or two true leaves stage can promote LD-delayed flowering of quantitative SD sunflower plants without reducing cut flower quality. 10

Effects of Short-Day and Gibberellic Acid Treatments on Summer Vegetative Propagation of Napier Grass (Pennisetum purpureumSchumach)

“…This may be brought about by two factors; the first was due to the rapid enhancement of stem elongation in the basal several stem nodes by the foliar GA 3 spray [18] as shown in Figures 1 and 2. The second was due to the gradual enhancement of stem elongation by SD treatment [14,17]. Therefore, GA 3 treatment showed the rapid effect and SD treatment showed gradual effect on stem elongation in DL Napier grass.…”

“…Dwarf varieties of Napier grass are blocked in the pathway of gibberellin biosynthesis and thus exhibit severely suppressed stem elongation before the phase transition to the reproductive state [7]. Thus, it is considered as feasible that SD and/or GA 3 treatments could elongate the stem internode [14][15][16][17], which may facilitate the successful vegetative propagation and production of nursery plants for dwarf Napier grass.…”

Year-round Greenhouse Production of Cut Sunflowers in the Rocky Mountain West

“…Significant interactions between time of year and cultivar for stem length and days to harvest were likely associated with changing photoperiods and the different responses to photoperiod displayed by the three cultivars. Different responses of sunflower cultivars to photoperiod are well documented (Blacquière et al, 2002;Gimelli et al, 2003;Hayata and Imaizumi, 2000;Schuster, 1985;Wien, 2009b;Yañez et al, 2004Yañez et al, , 2005Yañez et al, , 2012.…”

“…C ut sunflowers are desirable and available nearly yearround (Nau, 2011) but are especially popular in the fall and summer months (Wien, 2009b;Yañez et al, 2012). Sunflowers are quite popular as fresh cut flowers yearround, largely due to the array of colors and growth habits now available (Dole and Wilkins, 1999;Nau, 2011).…”

Screening Ornamental Sunflowers in the Seedling Stage for Flowering Reaction to Photoperiod

“…Fortunately, the task of daylength screening of sunflower has been made easier by the finding that for many sunflower cultivars, flower primordia are formed within 3 weeks after emergence (Marc and Palmer, 1981;Yanez et al, 2012). If sunflower cultivars are sensitive to daylength before flower initiation, it allows a daylength screening process to be imposed during the seedling stage, and the resulting effects to be observed under field conditions thereafter, as was reported by Blacquière et al (2002).…”