Preliminary Studies On Relationships Between Chilling Requirements And Heat Requirements Of Peach In Protected Culture

The experiment was carried out in protected fruit cultivation demonstration garden in horticulture experimental station of Shandong Agricultural University. Relations between chilling requirements and heat requirements, as well as changes of heat requirements in condition of different chilling accumulation were studied systematically using 5-year-old peach trees of 10 varieties cultured in greenhouse, which were'Chunjie','Foluolidawang','Hongfenjiaren','Nanfangzaohong','Nanmiyihao','Sanyuecui','Siyuetezaohong','Tainongtianmi'and'Tainongzaimi'. Besides, 3-year-old potted'Shuguang'nectarine (Prunus persica var. nectariana cv. Shuguang) trees were used to study effects of different chilling accumulation on heat requirements and main physiological processes. The main results were as follows:1. For the 10 varieties, there were no regular relations between chilling requirements of leaf buds and flower buds. Flower buds with relatively high chilling requirement did not always exist in varieties whose leaf buds have relatively high chilling requirements. Relations between heat requirements of leaf buds and flower buds showed no regularity, either.2. The distribution of chilling requirements and heat requirements followed certain rules. For flower buds, varieties with lower chilling requirements usually had higher heat requirements. However, for leaf buds, warieties with lower chilling requirements usually also had lower heat requirements.3. Durations of chilling expose affected heat requirement of varieties. In case of deficient chilling expose, although budburst exsited, the budburst rate were far less than meeting the need of production, and the heat requirements tended to infinity. In case of sufficient chilling expose, heat requirements declined as chilling expose increased. It was discovered that there was a best quantity of chilling expose which minimize the total duration from dormancy to sprouting. The quantity was higher than the chilling requirement. 4. The deficiency of chilling expose affected the operation of correlative physiology processes in buds. In condition of chilling deficiency, the activation of water, the transformation of carbohydrate and the transition of resiparation mode from PPP dominating to TCA dominating were all inhibited. The activation of PPP during dormancy was not inhibited by the earlier cold deprivation.5. Respiration in flower buds showed high sencitivity to Na₃PO₄ (inhibitor of PPP) during dormacy and sprouting. When Na3PO4 was used, total respiration rates of buds increased sharply. However, when malonic acid (inhibitor of TCA) was used together, the respiration increase was inhibited. Considering that TCA increased sooner after PPP declined, the reaction might be part of respiration mode transition in buds.6. In case of deficient chilling expose, the use of growth regulator show little effects on heat requirements of buds, and the heat requirements still tended to infinity. In case of sufficient chilling expose, GA₃, 6-BA and IBA all had the effect of reducing heat requirements of buds. GA₃ had the highest efficiency of reducing heat requirement. The effects of ABA were nor obvious.