Preliminary Studies On Flowering Control By Means Of Photoperiod In Coreopsis Grandiflora 'Early Sunrise'

Coreopsis grandiflora is one of the most impotant perennial herbaceous plants ingarden. The cultivar 'Early Sunrise' in the plant design is maily fit to be used inflowerborder which is very popular presently. Flowering control is necessary to meet thefloriculture and consumption, in which manipulating photoperiod is easy and whithoutenvironmental pollution. A quantitative undersdanding of photoperiod on Coreopsisgrandiflora 'Early Sunrise' could be directly used in guiding mass cultivation.The results are as follows:â‘ Coreopsis grandiflora 'Early Sunrise' is a facultative long day plant (FLDP).Plant tended to have an upright habit with increase in height, crown diameter and branchnumber under LDs, and there is no different in leaf number at two photoperiods.Accordingly, LDs should be provided to accelerate floriculture by inducing flowering ofCoreopsis grandiflora 'Early Sunrise', while short days provided to improve quality bylower plant height.â‘¡Transferring plants between SD and LD according to leaf number or growingweeks of seeding, it is concluded that the juvenile of Coreopsis grandiflora 'EarlySunrise' ended at 20-26 leaf stage, the process of which could be accelerated by LDs.The process of juvenility study is simplified by light transferring resting on growingweeks of seeding, simultaneously, a reliable parameter for floriculture is provided byobservation on leaf number.â‘¢The flower bud differentiation process of Coreopsis grandiflora 'Early Sunrise'could be divided into 8 phases: Vegetative growth prophase, Vegetative growth anaphase,Inflorescence primordium differentiation phase, bract differentiation phase, Ligulateflower primordium differentiation phase, Tubular flower primordium differentiationphase, Tubular flower stamen primordium differentiation phase, Tubular flower pistilprimordium differentiation phase.The reponse of flower bud differentiation of Coreopsisgrandiflora 'Early Sunrise' to photoperiod started at 17 growing weeks of seeding, whichis at Inflorescence primordium differentiation phase under LD and Vegetative growthprophase under SD respectively.â‘£Significant linear relationships existed between each growth characteristics ofCoreopsis grandiflora 'Early Sunrise' and flower bud differentiation phase, theregression equations are as follows: y=0.1308x+0.3052 (height; R~2=0.8490), y=0.1855x-0.7608 (branch number; R~2=0.8096), y=0.1239x-0.2228 (crown diameter;R~2=0.7857), y=0.1855x-0.7608 (leaf number; R~2=0.5603), y=0.2258x-2.1650 (growingweeks of seeding; R~2=0.4471) and y=0.3117x+1.660 (leaf split number; R~2=0.1902). Itindicates that the more sensitive of growth characteristics to photoperiod, the moresignificant relationship between growth characteristics and flower bud differentiationphase. It could be drawn that it was from Inflorescence primordirum differentiation phaseto bract differentiation phase that Coreopsis grandiflora 'Early Sunrise' accepted thefloral induction by LDs.