| Empty-shell chestnut is one of the main factors affecting the yield of Chinese chestnut. In the recent decade, many researchers from various level have put in a lot of efforts in this field. However, although some positive progress has been made and many reports has been published, the physiological mechanism of forming the empty-shell chestnut is still to be clarified. In order to deal with this problem, in this thesis the variations of endogenous hormone contents in ovary and their physiological effects on embryo development were analyzed by means of comparative experiments between the typical empty-shell chestnut trees and the normal (non-empty-shell) chestnut trees during the periods of pollination and fruit development and, on the bases of the concentration trials and orthogonal design (L16215) of chemical regulators respectively. The main results were shown as follows:1. The contents of endogenous GA1/3, iPAs and the ratio of (GA1/3+iPAs)/ABA in normal chestnut ovary were high on the 25th day after bloom (mid-June) and the 75th day after bloom (mid-August) and were low during the early phase of pollination (late-May), the 45th day after bloom (early-July) and the fruit maturation period (early-September), shown as a "Double peaks" model, while the content of endogenous ABA in ovary tends to reversely change by a small range. In contrast, the endogenous hormone contents and their ratio in empty-shell chestnut ovary showed no obvious peak, and the contents of endogenous GA1/3, iPAs and the ratio of (GA1/3+iPAs)/ABA appeared a descending trend while the endogenous ABA content appeared an ascendingtrend during whole embryo developmental period.2 No obvious difference of the average involucre diameter was exist between empty-shell chestnut and normal chestnut before the 65th day after bloom (late-July) until then the nut diameter of empty-shell chestnut started to be less than that of normal chestnut while the maximum nut diameter of empty-shell chestnut had started to be less since the 25th day after bloom (mid-June) and to be nearly at a standstill since the 45th day after bloom. The changes of fruit diameter rate coincided with the content changes of endogenous GA1/3, iPAs and the ratio of (GA1/3+iPAsXABA in normal chestnut ovary.3 On the 15th day after pollination, the contents of the endogenous GA1/3,iRAs and the ratio of (GA1/3+iPAs)/ABA in the pollinated ovary increased rapidly white the ABA decreased sharp and, in the unpollinated ovary, the increase of endogenous GA1/3 content came to relatively slow down, and the content of endogenous iPAs and the ratio of (GA1/3+iPAs)/ABA started to decline obviously, but the content of endogenous ABA began to increase sharp. The variation trend of endogenous hormone content between unpoffinated ovary and normal pollinated ovary showed a similar pattern to those between empty-shell chestnut ovary and normal chestnut ovary around the pollinating period, meanwhile the endogenous hormone levels in unpollinated ovary were parallel to those in empty-shell chestnut ovary.4 The contents of main nutritious substances in empty-shell chestnut ovary started to decline or maintained in a declining state on the 45th day after bloom (early-July), meanwhile, those in normal chestnut ovary tended to rise up or remained high level. On the whole, the contents of reducing sugar, starch, phosphorus, potassium and boron in empty-shell chestnut ovary were significantly less than those in normal chestnut ovary during the embryo developmental period. The positive effects of endogenous GA1/3 and iPAs content increasing and endogenous ABA content declining in normal chestnut ovary on the diameter growth of nut were mainly achieved by means of promoting theaccumulation of reducing sugar, starch and the consumption of nitrogen in ovary, while the limiting effects of endogenous GAira, iRAs content declining and endogenous ABA content increasing in empty-shell chestnut ovary on it were chiefly brought about by restraining the transportation of...
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