Study On Bulblet Formation And In Vitro Regeneration Of Lilium Lancifolium Thunb.

Lilium lancifolium Thunb.is a perennial bulbous flower in the genus Lilium of the Liliaceae family.Because of its large and bright flowers,strong resistant and wide distribution,so its often used in landscaping.L.lancifolium is a natural triploid plant with high sterility,it can produce dark brown bulbils in the axils of leaves as asexual reproduction organs.Bulbil propagation can not only maintain the genetic characteristics of the parent plant,but also can be more convenient and efficient than scale cutting and bulb propagation.Therefore,bulbil propagation has become an important means of population expansion of L.lancifolium.In this study,triploid L.lancifolium was used as experimental material to observe the morphogenesis and development process of bulbils by means of freehand section and paraffin section.Different hormone treatments were applied to L.lancifolium,and the effects of different hormones on bulbils were observed,so as to find out the most suitable exogenous hormone to improve the value of bulbils of L.lancifolium.Using the bulbil scales of L.lancifolium as explants,the effects of different hormone combinations and dark culture on the callus induction of bulbils were analyzed,and the in vitro regeneration of bulbils was discussed.The main results are as follows:Through the observation of the growth dynamics of the bulbils of L.lancifolium,the results showed that the bulbils of L.lancifolium began to produce in the middle eraly May and ended in the middle to late July in Shenyang area.The whole growth stage of bulbils lasted about 75 days.In the middle early May,white punctate structure appeared in the leaf axils of L.lancifolium.With the elongation of internodes,the white punctate structure gradually expanded.In the late June,the bulbils gradually matured,and in the middle to late July,the bulbils naturally fell away from the parent plant.According to its development process,it can be divided into six stages:initiation stage,development stage,initial stage of color conversion,middle stage of color conversion,late stage of color conversion and mature stage.Dissecting and observing the bulbils of L.lancifolium at each stage,it can be observed by free-hand section:with the growth and development of the bulbils,the number of bulbil scale layers was increasing,and there was also a direct relationship between the number of bulbil scale layers and the central bud of the bulbils.The growth and development of the inner central bud made the number of bulbil scale layers increase gradually.Through paraffin section,it can be observed that the bulbils formed in the leaf axils where the aerial stem and the leaf base were connected and are derived from the division and differentiation of parenchyma cells under epidermal cells at the base of the petiole,which made the base of the petiole bulge.After the formation of the axillary meristem,the bulbil primordium further grew and developed to form bulbils.In late April,exogenous hormones were sprayed on L.lancifolium.The results showed that auxin and gibberellin of certain concentration could promote the development of L.lancifolium.Among them,the appearance date of IAA bulbils sprayed with 50 mg/L was the earliest,10 days earlier than the control,and the growth was better,while the appearance date of IAA with 200 mg/L concentrations was 2 days later than the control.The germination date of gibberellin was earlier than that of the control.From the size and yield of bulbils,the size and yield of IAA bulbils sprayed at a concentration of 100 mg/L were significantly larger than the control treatment.Compared with other treatments,the size of GA₃bulbils sprayed with50 mg/L was also significantly higher than that of the control treatment,but the number of bulbils produced by a single plant was not as large as the control.In summary spraying 100mg/L of IAA and 50 mg/L of GA₃has better effect on the treatment of bulbils.The bulbils were treated at 5℃,10℃,15℃and normal atmospheric temperature（25℃）for 30 days.The study found that after low temperature treatment,the germination rate,germination potential,root development and plant growth of the bulbils were improved,and the temperature was lower,the more obvious the effect of breaking dormancy of bulbils.When the temperature is 5℃,the germination rate of the bulbils is 80%,the germination potential is 69%,the root length and root thickness are the fastest,and the plant growth is the best.On this basis,the bulbils were treated at 5°C for 0 d,10 d,20 d,30 d,40 d,60 d.The study found that as the treatment time is longer,the breakage of the dormancy of the bulbils is more significant.When the treatment time is 60 d,the budding emergence time is the shortest,it only takes 8 days,the germination rate reaches 96.33%,the germination potential reaches80%,and the bulbils root system develops best,and the plant grows the strongest.To sum up,it is the most conducive to break the dormancy of bulbils when treated at 5°C for 60 days.Bulbil of L.lancifolium were used as explants to study in vitro regeneration of bulbils of L.lancifolium.The results show that:the outer scales of the bulbils are easier to induce callus.Comparing the effects of different hormone ratios on the induction of bulbils callus,the overall effect of BA induction is good,and the combined effect of PIC and BA is better than that of PIC and TDZ.The most suitable medium for callus induction of bulbils is:MS+BA 1.5mg/L+PIC 1.0 mg/L,and the callus induction rate on this medium reaches 67.96%.Comparing the effects of different days of dark culture on the callus induction of bulbils,it was found that 18 days of dark culture could effectively increase the callus induction rate,at this time the callus induction rate was 70.83%.Comparing the effects of different hormone concentrations on callus growth,the optimal hormone combination was MS+NAA 1mg/L+BA 2 mg/L,the callus differentiation rate was 58.67%,and the number of plantlets was 24.