Preliminary Studies On Flowering Control By Means Of Photoperiod In Callistephus Chinensis 'Meteor'

Callistephus chinensis 'Meteor' is an excellent cut flower cultivar of the Pan-American Seed Company with large and upright plant type,strong stem and big double flower trait.It is not only a good choice for greenhouse growth-promoting cultivation,but also an ideal cultivar of field and garden cut flower cultivation.Flowering control is necessary to meet the floriculture and consumption,in which manipulating photoperiod is easy and whithout environmental pollution.A quantitative analysis of photoperiod on Callistephus chinensis 'Meteor' by reciprocal transfer could be directly used in guiding mass cultivation.The results are as follows:â‘ Callistephus chinensis 'Meteor' is a long-short day plant.The plant tended to have an upright habit with increase in height and bigger flower diameter under long days, a compact habit with increase in branch mumber but smaller flower diameter under short days.Long days condition can induce the differentiation and development of flower bud. The plant flowering is earier under long days than short days.Accordingly,long days is more important than short days for flowering of Callistephus chinensis 'Meteor'.â‘¡Reciprocal transfer plants from LD to SD and SD to LD according to growing weeks of seedling with leaf number observed.It is concluded that the juvenile phase of Callistephus chinensis 'Meteor' ended at 2 weeks after seedling,corresponding at the 2 leaf number stage.The duration of limited inductive photoperiod is 13 weeks,it also means long days induced phase of Callistephus chinensis 'Meteor' ended at 15 weeks after seedling,corresponding at the 12 leaf number stage.The process study is simplified by light transferring resting on growing weeks of seeding,simultaneously,a reliable parameter for floriculture is provided by observation on leaf number.â‘¢The flower bud differentiation process of Callistephus chinensis 'Meteor' could be divided into 8 phases:vegetative growth prophase,vegetative growth anaphase, inflorescence primordium differentiation phase,bract differentiation phase,ligulate flower primordium differentiation phase,tubular flower primordium differentiation phase, tubular flower stamen primordium differentiation phase,tubular flower pistil primordium differentiation phase.The reponse of flower bud differentiation of Callistephus chinensis 'Meteor' to photoperiod started at 8 leaf stage,which is at inflorescence primordium differentiation phase.â‘£Very significant linear relationships existed between growing weeks of seedling, plant heiht,crown diameter and leaf number of Callistephus chinensis 'Meteor' and its flower bud differentiation phase,the regression equations are as follows: y=0.4289x-0.6573(R~2=0.9549)(leaf number),y=0.4839x-1.0391(R~2=0.951)(crown diameter),y=0.4151x-1.9073(R~2=0.9047)(growing weeks of seedling),y=0.26x-0.3787 (R~2=0.8611)(plant height).It indicates that the most significant relationship between leaf number and flower bud differentiation phase,the most sensitive of leaf number to photoperiod.It could be drawn that the end of the long days flowering induction of Callistephus chinensis 'Meteor' is at bract differentiation phase.