Effects Of Pruning And Fertilization Techniques And Plant Growth Regulator On Flowering And Physiological Characteristics Of Lagerstroemia Indica ’Ebony Embers’

Lagerstroemia indica ’Ebony Embers’ is an excellent new variety of Lagerstroemia indica belonging to Lythraceae,with bright colors,bright leaves,long flowering period and strong erect branches,which is a garden plant of great ornamental value in summer.The reports on the regulation of flowering period of Lagerstroemia indica mainly focus on the growth of tree potential and flowering characteristics after pruning,but there are few studies on physiology of Lagerstroemia indica after pruning,foliar fertilizer application and plant growth regulators.In this study,Lagerstroemia indica ’Ebony Embers’ was used as the experimental material,the flower bud differentiation process of ’Ebony Embers’ was observed by paraffin section method,and then the flowering period regulation experiment was carried out by pruning,spraying foliar fertilizer and plant growth regulators.The effects of pruning,foliar fertilizer,and plant growth regulator measures on flowering phenology,endogenous hormones,and carbon and nitrogen contents were analyzed,and the relationship between flowering and major physiological substances was discussed to support the practical application and popularization of Lagerstroemia indica flowering regulation technology.The results showed that:(1)Observation by conventional paraffin section method showed that Lagerstroemia indica ’Ebony Embers’ bloomed immediately after completing the differentiation process.The terminal buds began to differentiate into inflorescence differentiation in early-May,entered sepal differentiation and petal differentiation in mid-May,pistil primordia appeared in late-May,megasporogenesis and male and female gametophyte developmented in late-May to early-June,and in mid-June,mature pollen and mature embryo sac were formed.The flower bud differentiation process lasted about 34 days.(2)Different pruning periods and pruning intensities had significant effects on the flowering period and physiological characteristics of ’Ebony Embers’.The last flowering period was delayed to the end of August after pruning in mid-May,and the late flowering period was delayed to mid-to-late September after pruning in mid-to-late June.After pruning in early July and August,the end of the flowering period was delayed to early and mid-October,with a delay of about 2 months at most.With the increase of pruning intensity,the flowering period of heavy pruning was later than that of light pruning,and the total flowering period was the longest after heavy pruning and the longest full-flowering period after moderate pruning.Moderate and heavy pruning from mid-July to early-August was the most effective for prolonging the flowering of ’Ebony Embers’.After moderate and severe pruning in early August,the content of endogenous ZR and GA3 in the secondary flower buds of ’Ebony Embers’ increased significantly during the flowering period,while the content of IAA decreased,which was beneficial to prolong the flowering period.After heavy pruning,the soluble sugar,starch and total nitrogen contents of the secondary flower buds increased slightly,and the C/N increased slightly to prolong the flowering period of Lagerstroemia indica ’Ebony Embers’.(3)Different nitrogen,phosphorus and potassium foliar fertilizers have significant effects on the flowering period and carbon and nitrogen content of ’Ebony Embers’.Balanced fertilizer,high nitrogen fertilizer,high phosphorus fertilizer and high potassium fertilizer all prolonged the total flowering period of ’Ebony Embers’.High phosphorus fertilizer had the best effect on prolonging the total flowering period,which was about 22 days longer than the control.Balanced fertilizer made ’Ebony Embers’ bloom about 5 days earlier,while high nitrogen fertilizer delayed flowering by 3 days,and high potassium fertilizer had no significant effect.Balanced foliar fertilizer treatment significantly increased the soluble sugar content of flower buds,which was beneficial to the early flowering of ’Ebony Embers’.High nitrogen foliar fertilizer treatment significantly increased total nitrogen content and significantly decreased C/N during flower bud differentiation,inhibiting flower bud differentiation and delaying flowering.High phosphorus foliar fertilizer treatment significantly increased the soluble sugar and starch content of flowers,and significantly increased the C/N during flowering to prolong the flowering period.(4)Different plant growth regulators had significant effects on the flowering period and endogenous hormones of ’Ebony Embers’.Spraying 5-25mg·L-1 NAA made flowering earlier,and 5 mg·L-1 NAA bloomed at most about 8 days earlier,and NAA solution had no significant effect on flowering time.Spraying different concentrations of B9 all delayed flowering,1000 and 2000 mg·L-1 B9 delayed flowering for about 9 days,and within the B9 concentration of 500-1000 mg·L-1,the flowering period increased with the concentration of B9 increase and prolong.Spraying low concentrations of 100-250 mg·L-1 GA3 extended the flowering period by about 43 days at most,while high concentrations of 500-1000 mg·L-1 GA3 significantly shortened the flowering period by about 10 days.5 mg·L-1 NAA was suitable for flowering early of ’Ebony Embers’,1000 mg·L-1 B9 was more suitable for delaying flowering,and 100 mg·L-1 GA3 was beneficial to prolong flowering.After ’Ebony Embers’ was treated with NAA,the endogenous ZR and GA3 contents increased during the flower bud differentiation stage,while the ABA content decreased significantly,which promoted flower bud differentiation and facilitated flowering early.After treatment with B9,the content of endogenous ZR significantly decreased in the early stage of flower bud differentiation,while the content of IAA was significantly increased,and the content of ABA increased while the GA3 content decreased slightly during the flower bud differentiation stage,which inhibited flower bud differentiation and delayed flowering.After treatment with exogenous GA3,the contents of endogenous ZR and GA3 were significantly increased,and the contents of ABA and IAA were significantly decreased during flowering,which was beneficial to prolong the flowering period of Lagerstroemia indica ’Ebony Embers’.The above results showed that pruning,foliar fertilizer and plant growth regulators all affected the flowering period and physiological characteristics of Lagerstroemia indica ’Ebony Embers’.Moderate and heavy pruning in mid-July was the most beneficial to prolong the flowering period.And spraying high phosphorus fertilizer and 100 mg·L-1 GA3 could also effectively prolong the flowering period.5 mg·L-1 NAA was more suitable for early flowering of ’Ebony Embers’,and 1000 mg·L-1 B9 is suitable for delayed flowering.The content of endogenous ZR and GA3 increased and the content of ABA and IAA decreased,and the content of soluble sugar and C/N value increased,which was beneficial to the flowering of Lagerstroemia indica ’Ebony Embers’.