Effects Of LED Spectra On Morphogenesis And Flowering Of Balloon Flower Plantlets In Vitro

Light is one of the most important factors that influence the growth and development of plants.Plants recieve the different light signals by light receptors to activate different response and then regulate the process of physiological response,which was presented as morphological change ultimately.To date,there are many reports on the effects of light-emitting diodes(LEDs)on the growth of tissue culture plantlets,but there are few reports on the effects of spectra on the whole growth period of planlets in vitro from adventitious buds differentiation,plant morphogenesis,to floral bud development phase.In this experiment,the effects of LED spectra on adventitious buds differentiation,morphological,physiological and biochemical characteristics,and floral bud development of balloon flower(Platycodon grandiflorum(Jacq.)A.DC.)plantlets in vitro were investigated.Main research results were as follows:1.During the process of adventitious bud differentiation from the petiole of balloon flower plantlets in vitro,25%blue + 75%red LEDs(BR13)produced higher shoot regeneration rate,and formed nodes and shoots of better development.BR13 prevented the formation of hyperhydric shoots,which might result from the significantly higher indole-3-acetic acid content and the significantly lower gibberellic acid content in these two treatments.The results showed that BR13 could be applied as a priority light source for adventitious buds differentiation of balloon flower from the petiole.2.Blue LEDs(B)and 75%blue + 25%red LEDs(BR31)induced larger leaf area,leaf and leaf tissue thickness,higher leaf number and produced vigorous stem and root.B and BR31 induced large and nearly rectangular palisade cells,B-and BR31-treated leaves possessed normal elliptical stomata with an intermediate frequency.All these factors induced the higher ETR,φPSII,and qp and lower NPQ in the B and BR31-treated balloon flower leaves and thus the resulted higher dry mass of whole plant than treatment W or R.Our data revealed that blue light may be essential for the growth of balloon flower plantlets in vitro,moreover,B and BR31 would be a better suited spectrum.3.Alabastrum formation was observed in the W-,RGB-and BR11-treated balloon flower plantlets in vitro cultured for 60 days with a low percentage(all were lower than 10%),and no normally bloom flower was developed in all the treatments.The results showed that the effects of spectra applied in the experiment on floral bud development were indistinctive and instable,and the apprppriate spectra still need to be further explored.