Study On The Floral Bud Stage Sensitive To The Low Temperature In Paeonia Lactiflora

The flowering regulation technology can effectively prolong the flower time of herbaceous peony to meet the rising demands of the domestic and international flower market, and its basis is to have a deep understanding on the flower bud differentiation and development. Under the field condition, the herbaceous peony will experience a low temperature period in winter and then bloom in spring. Therefore, a systematic study on the flower bud differentiation stage sensitive to the low temperature and later high temperature can provide a guidance to initiate the chilling treatment and the heat accumulation during the flowering regulation. It also has a theoretical significance in studying the flower bud differentiation in Paeonia lactiflora.To figure out the sensitive stages, this paper firstly studied the floral bud differentiation of 7 peony cultivars in different flower types. Then, observing the floral bud differentiation stage of 12 peony cultivars under field condition both when the soil naturally frozen and thawing, and explore its law with the cultivars’flowering time and flower type. Lastly, on the basis, starting the chilling treatment in the different flower bud development stages by artificial cold storage to explore the suitable scope of the floral bud differentiation that can be acceptable to the chilling treatment and heat accumulation. The results are as follows:(1) The flower bud differentiation in different flower types of peony can be divided into three types:The first can be summarized as the following process, bract primordium,sepal primordium,petal primordium,stamen primordium,pistil,primordium, such as P.’Fen Yu Nu’; The second,bract primordium.sepal primordium, petal primordium, stamen primordium, pistil primordium, such as P. ’Lian Tai’; The third, bract primordium, sepal primordium, petal primordium, stamen primordium, second flower tray formation period, the up floral structure forming stage, valve stage, such as P.’Da Fu Gui’. It is consistent with the cultivar classification of herbaceous peony.(2) When the soil frozen,11 of 12 cultivars, over 50% of the flower buds were in pistil primordial differentiation phase; when the soil thawing in spring, for the early-flowering cultivars, over 90% of the flower buds were in pistil primordial differentiation phase, late-flowering cultivars was more than 50%.(3) The floral bud differentiation of the potted plants without chilling treatment kept going without a obvious dormant period, and its process has no significant difference with the plants in the field. However, compared to control group that after cold storage (10W,2℃), the branches number, inflorescence and flower diameter were significantly reduced, respectively from the 11.1,4.5,10.8cm fell to 7.4,0.9,6.7cm, suggesting that the chilling accumulation has nothing to do with the flower bud differentiation process, but has a great impact on the later growth and flowering in Paeonia lactiflora.(4) Starting the cold storage to 6 peony cultivars potted plants advanced the field,60-80% of flower buds were in petal primordial differentiation phase when initiating the chilling treatment and 100% were in the pistil primordial differentiation stage.The results showed that in addition to the two early-flowering cultivars (P.’Fen Yv Nu’and P.’Hongyan Zhenghui’), the other four cultivars all bloomed normally as the control group, suggesting that when the flower buds were in petal primordial differentiation stage, the peony plants can be sensitive to the low temperature.(5) Starting cold storage to potted plants of P.’Da Fu Gui’ almost one month later than the field, 100% of the flower buds were in the stamen and pistil petaloid stage when start the chilling treatment and it stayed the same when the chilling treatment ended. The results showed that almost all the flower buds abortion, suggesting that when the flower buds were in the stamen and pistil petaloid stage, the peony plants can be not sensitive to the low temperature.In summary, the flower bud can be normal differentiation without chilling accumulation and the flower buds have no obvious dormant period without a low temperature. The potted peony plants can be acceptable to the chilling treatment when the flower buds were in the "petal primordium, stamen primordium, pistil primordium" differentiation stage, during the flowering regulation, starting chilling treatment when sampling observed over 60-80% of the flower buds were in the petal primordial differentiation stage can guarante the flowering effect; all the peony can be sensitive to the heat accumulation when its fower buds were in the pistil primordial stage.