1. Basic features of the annual cycle

The annual cycle is the growth and development law of the four seasons of a year along with the change of the climatic rhythm. Peonies, like other trees with flowers, constitute the whole life cycle (life cycle) by alternating annual cycles of growth and dormancy, year after year. The annual cycle of Paeonia Rockii, like that of Central Plain peonies, is also spring germination, summer napping, autumn long roots, and winter dormancy. However, due to the high altitude, low temperature and short frost-free period, its growing period is slightly shorter than that of Central Plain peonies The dormancy period is relatively prolonged. For example, in the middle and lower reaches of the Yellow River, Central Plain peonies generally begin to sprout from mid-february to early March, show their leaves from late March to early April, flower from mid-april to early May, and wither from late October to Mid-november However, Paeonia ROCKII generally germinates from late March to early April, blooms from late April to early June, and has a short growing period from mid October to early November.

2. Types of buds and their developmental characteristics

The buds of Paeonia Rockii are covered with several scales of buds, which belong to scale buds. In nature, there are two types of buds: Leaf Buds, which grow only to form branches and leaves, and mixed buds, which produce flowers at the same time. On the adult plant, almost all shoot tip 1-3 buds, including the Terminal Bud and the lower axillary bud, normally developed into mixed buds in the current year, after winter dormancy, the next year can bloom; Only a few of the long shoots and buds on the buds for leaf bud, only long branches and no flower bud formation. In addition to the above-mentioned active buds, a number of axillary buds at the base of the 1-year-old branch, buds on the perennial branch and a large number of sprout buds formed at the root and stem parts are dormant, belonging to the inactive leaf buds, called dormant buds. The whole process from Bud primordium to flowering and fruiting of mixed shoots of Paeonia Rockii, like that of Paeonia Suffruticosa Var. Central Plain, takes three years to complete. The first annual cycle produced axillary BUD Primordia, the second annual cycle produced leaf Primordia and flower Primordia, the third annual cycle flowering and fruiting (Wang Zongzheng et Al. 1987) . In the annual growth cycle, the process of Bud Germination, growth and flowering in early spring is actually the 3rd annual cycle of mixed bud of the mother generation, while the process of bud differentiation and formation after flowering is the 2nd annual cycle of Bud Development Meanwhile, a new bud primordium was produced in the leaf axils, and the first annual cycle of the next generation buds was completed. Therefore, in the 1-year cycle of peony, the buds of 3 generations are in different stages of their life cycle, and the buds in the 2-year cycle are the key to the formation of flower buds When the accumulation of nutrients and appropriate flowering hormone, complete from vegetative growth to reproductive growth, the formation of mixed buds.

The complete formation of leaf primordium is the critical point of peony bud from vegetative growth to reproductive growth, which is also the critical point of flower bud differentiation (Wang Zongzheng et Al. 1987) . Bud Development into the flower bud stage, including the summer and autumn flower bud differentiation (2nd Annual Cycle) and spring flower development (3rd annual Cycle) two interrelated and independent stages. The Flower Bud differentiation of Paeonia ROCKII began about 1 month after anthesis, that is, from the middle of June, the flower Primordium, bract Primordium, sepal primordium, petal primordium, stamen primordium and Pistil primordium were successively produced on the basis of axillary Bud primordium Finally, it gradually enters the dormancy period after October. The process of flower bud differentiation is also different with different varieties, especially with different flower types. Generally, single and semidouble varieties have faster flower bud differentiation, while double varieties have longer duration But can complete the flower organ’s occurrence in that year, enters the dormancy state smoothly. Therefore, flower bud differentiation had been completed in the autumn of that year. After cold dormancy in winter, flower buds developed further in the following spring. The process of Stamen petalization is a very complicated one, which has a direct effect on the formation of the final flower type. The stamen primordium of Paeonia Rockii is centrifugal, but the stamen petalization can be centrifugal, centripetal or irregular in different varieties.