The Study On Dehydration Damage And Ca²⁺ Repair Mechanism Of Chestnut

Chestnut seed is a typical recalcitrant seed,and intolerant of dehydration and often also of chilling.The mature chestnut is easy to decay in storage.The germplasm conservation of chestnut is still difficult.Ca²⁺ acting as a second messenger plays a crucial role in stress signal transduction pathways,but less data are available about the relationship between Ca²⁺ and dehydration damage.The objective of this paper is to provide some theoretical basis and technical support for germplasm conservation and long time storage of chestnut.In this paper the experimental material used was Castanea mollissima Blume,and the aim of this work was to ascertain:(1)the main factor affecting the storage effect of chestnut.(2)the mechanism of dehydration damage and Ca²⁺ repair.(3) Preliminary Study on the extraction,purification process and Chemical Properties of the pigment in Chestnut shells.The main results were as follows:(1) Under different storage method,the moisture content and no-rotting chestnut decreased,the MDA content increased in the whole,the main nutrition soluble sugar increased gradually,but the soluble protein declined with the prolonging of storage time.The 4℃-polythene bags storage method could partly restrain the decreasing of soluble sugar and the increasing of soluble protein.The results suggest that moisture content is the critical factor that affects the storage effect of chestnut,and the storage effect of 4℃-polythene bags method is better than others.(2) Under NaCl-room temperature drying and 28℃-silica gel drying method,the germination rate and vigour index decline gradually with the prolonging of desiccation time.The increasing of MDA content may be the cause of that germination rate and vigour index declined.The result showed that the fast drying method could induce the activities of antioxidant enzymes,the upregulating of heat-stable proteins,and reduce the MDA accumulation better than slowly drying method.(3) Under different desiccation temperature,the germination rate and vigour index decreased gradually with the prolonging of time.The activities of antioxidant enzymes increased first and then decreased dramatically,but the MDA content always increased with the prolonging of desiccation time.There are two heat-stable proteins,and the molecular weight of which is about 30KD.The results showed that different temperature has different influence to the expressing of heat-stable proteins.The results showed that desiccation tolerance of chestnut axes was strongly correlation with the activities of antioxidant enzymes and the expressing of heat-stable proteins.Synthetic analysis indicated that 4 hours of 20℃-silica gel drying method had less dehydration damage than other fast drying methods.(4) The treatment of Ca²⁺ has obviously effect on the germination rate and vigour index.With the increasing of Ca²⁺,the germination rate and vigour index increased first and then decreased gradually.The results indicated that the treatment of Ca²⁺ has little effect to the SDS-PAGE.The treatment of Ca²⁺ has dose effects.The treatment of Ca²⁺ could reduce the membrane lipid peroxidation,increase the activities of antioxidant enzymes,and repair the dehydration damage.The optimal Ca²⁺ concentration was 20mmol/L with the treatment time of 4 hours.(5) This pigment was extracted with 1%NaOH,and then extracted 3 times with petroleum ether and ethyl acetate;TLC indicated that high purity of pigment can be get with Ethanol-precipitation method.The UV spectrum of the pigment showed that there were two apparent absorption peaks at 218nm and 264nm in methanol. According to the results of chemical properties analysis.IR spectrum revealed that the main absorption wave numbers of pigment were 3400,3145,3043,1715,1630,1400,1036 and 620cm^-1.According to the results of chemical properties analysis,it is concluded preliminarily that there were benzene ring and phenolic hydroxyl.The absorption at 264nm of the pigment was sensitive to pH value. Quantitative determination of the pigment can be conducted by the optical density at 510nm when pH was 10.0.the pigment can be precipitated by many metal ions, but relatively stable for light,temperature,oxidants and reducing agents.