Morphology and changes in metabolites during floral bud differentiation of chili pepper

【Objective】The flower differentiation process and its relation with physiological and biochemical indices of four chili peppers cultivars(lines)were studied.【Method】Using four chili pepper varieties,M5-21,M34-1,2011-9,and Shaanjiao 2006as materials,samples were collected from the growing point every 3days after the third true leaf emerged for observation of flower differentiation using paraffin section method,and another set of samples were collected from the third and fourth true leaves every 5days for determination of soluble sugar,starch,soluble protein,chlorophyll,and activities of POD,PAL andPPO.【Result】The flower differentiation process included six phases:physiological differentiation,initial differentiation,sepal differentiation,petal differentiation,stamen differentiation and pistil differentiation.There were 6true leaves in the stalk at the start of flower bud differentiation,and 28days were needed for the whole process of the first flower bud differentiation with 14true leaves expanded at the end of differentiation.The contents of soluble sugar and starch accumulated to the maximum in the physiological differentiation phase,and decreased gradually since the start of the flower bud differentiation,indicating that the accumulation of soluble sugar and starch were helpful to flower bud differentiation.Soluble protein content in leaves peaked at the physiological differentiation phase,then decreased gradually and maintained a steady state from sepal differentiation stage to the end of the flower bud differentiation.From physiological differentiation phase to flower bud differentiation early,chlorophyll content showed a slight upward trend followed by agradual decrease,and there was a substantial increase in the late stage of flower bud differentiation.During the flower bud differentiation,POD and PAL activities trends were generally identical:achieving a relatively high level in the physiological differentiation phase and decreased since the stage of flower bud differentiation with the minimum levels at the sepals differentiation phase and the petals differentiation phase,respectively.PPO activity showed a bimodal trend with the two peaks at the sepal differentiation stage and stamen differentiation phase,and the lowest point at the pistil differentiation stage.The trends of indexes of the 4chili pepper cultivars were consistent with differences in the absolute levels.【Conclusion】High contents of soluble sugar,starch,protein and chlorophyll,and high activities of POD,PAL and PPO were beneficial to the flower bud differentiation of chili pepper.