MICRO-MORPHOLOGICAL OBSERVATIONS ON FLOWER BUD DIFFERENTIATION OF SUPER PREMATURITY CULTIVATED STRAWBERRY

An important step in the cultivation of super prematurity strawberry is how to determine the start of flower bud differentiation (FBD), and this is the premise of planting strawberry at the early stage. The experiments of low-temperature treatment (night temperature was 17-20ºC with fluctuations) and short photoperiod treatment (dark length was 16 h) were conducted from 23 June to 24 August, 2011. Apexes were separated under an anatomical microscope every 3-5 days, fixed with FAA, dried at critical point, and observed with a scanning electron microscope. On the basis of the observed micro-morphological characteristics, the whole process of FBD was divided into seven phases: pre-differentiation phase, starting phase, reproductive apex swelling phase, inflorescence differentiation phase, top-flower sepal formation phase, flower petal formation phase, stamen formation phase and stigma formation phase. The flower bud non-differentiation phase was before 29 June, and the top bud was in the state of vegetative growth continually. The starting phase was from 29 June to 3 August, and the top bud turned gradually from sharp, narrow vegetative apex into smooth, broad reproductive apex. The reproductive apex swelling phase was from 3 August to 14 August, and the reproductive apex uplifted and swelled. The inflorescence differentiation phase was from 14 August to 20 August, and top flower primordium and lateral flower primordium gradually appeared during top flower primordium differentiation process. The top flower sepal phase, flower petal formation phase were from 22 to 30 August, the differentiation of sepals (including accessory sepals) and the petals were finished in this phase. The stamen formation phase was from 30 August to 10 September, and two stamen primordia differentiated. Stigma formation phase was from 10 September to 21 September, a large number of stigma primordia uplifted gradually and carpel primordia curled, and the FBD process was complete.