Study on the improvement of bulb soaking and foliar spraying of CaCl₂ on the flowering period and quality of Lilium casa blanca

Objectives The experiment was to study the effects of calcium supplemental levels and methods on the dynamics of endogenous hormones and nutrition during the flowering period of Lilium casa blanca, toprovide a cost effective way for high quality of blossom production.

Methods Pot experiments were conducted using Lilium casa blancaas materials. The CaCl₂was supplied by soaking bulbs for 10 h before planting and foliar spraying 3 times in interval of 3 days during the initial growing stage. The tested CaCl₂levels included 0,0.4%,0.8%,1.2%,1.6% for both the supplying ways. The growth and flower shape indicators (plant height, stem diameter, bud length, flower diameter, blossom rate, blossom cleanliness) and the flowering period indicators (days to blossom, flower lasing days) were investigated. The endogenous hormones and carbon andnitrogen nutrient contents during whole flowering phase were analyzed.

Results 1) In bulb soaking treatment,the Ca levels were significantly and positively correlated with the plant height, bud length and flower diameter, butextremely significant and negatively correlated with the stem diameter. In spraying foliar treatment, the Ca levelswere highly significant and positively correlated with plant height, stem diameter, bud length and flower diameter.Bulb soaking with 1.2% and foliar spraying with 1.6% of CaCl₂had the highest blossom rate, and bulb soakingwith 0.8% and foliar spraying with 1.6% of CaCl₂had the highest blossom cleanliness. The CaCl₂levels in bothbulk soaking and foliar spraying treatments were extremely significantly negative correlated with the days toflower, days of squaring, and extremely significantly positive correlated with the days to end flowering and the days of blossom. 2) During flowering, the differences in leaf Ca content were significant between Ca level of 0.4% and 0.8% in bulb soaking treatment, and the leaf Ca content declined when the bulbs were soaked in 1.6% or foliarsprayed with 1.6% of CaCl₂. 3) In both the bulb soaking and foliar spraying treatments, the contents of IAA, GA₃,ZR, ZR/ABA, (IAA + GA₃)/ABA were significantly and positively correlated with the CaCl₂levels, and those ofABA, IAA/GA₃, IAA/ZR were significantly and negatively correlated with CaCl₂levels. Calcium supplements improved the contents of IAA (15.77%-42.93%), GA₃(35.57%-65.67%) in the early stage of the bloom, anddecreased those of ABA (66.14%-26.27%). As a result, the days to flower were earlier. Calciumsupplements increased the contents of ZR (46.66%-60.42%) in the end stage of the bloom, and as a result, thedays of blossom were prolonged from 3 to 11 days. 4) In bulb soaking treatment, the soluble sugar contents were significantly and positively correlated with CaCl₂levels, but the contents of protein, the ratio of total sugarand total N were not significantly correlated. While for foliar spraying treatments, the correlations were allsignificant and positive. Both bulb soaking and foliar spraying of calcium increased the soluble sugar and starchcontents in the early stage of bloom. During full blossom stage, the soluble protein content treated with foliarspraying was 22.5% higher than that treated with bulb soaking, and the flower of Lilium casa blanca lasted3-5days more.

Conclusions Bulk soaking with CaCl₂solution has positive effect in increasing the blossom quality of Lilium casa blanca, advancing the days to blossom, and delaying the aging of Lilium casa blanca. Bulbsoaking with 1.6% CaCl₂solution will increase plant height, bud length and flower diameter, with the 0.4% CaCl₂solution will lead to earlier blossom stage. Foliar spraying of CaCl₂solution performs better in increasing theblossom rate and prolonging the blossom days. Generally, bulb soaking with 1.2% and foliar spraying with 1.6%CaCl₂solution are recommended for satisfactory flowering of Lilium casa blanca.