Studies On Seed Glass Tansition And Cryopreservation Of Three Coniferous Species

The seeds of Pseudolarix amabilis, Cunninghamia lanceolata and Pinus massoniana were investigated by differential scanning calorimetry (DSC) for evidence of existence of glassy state. Moreover, the effects of biological substances of C. lanceolata seed embryo on the glass transition were identified by studying the relationship between glass transition and biological components. Furthermore, P. amabilis, C. lanceolata and P. massoniana seeds were also cryopreserved and the effects of seed water content and cryoprotectants on the preservation were studied by determining the biological and biochemical changes of cryopreserved seeds.The results were as follows:1. The glass transitions of different species were obviously different. The glass transition could be observed in the P. amabilis seed embryos and endosperms; and the DSC thermograms of P. massoniana seed embryos and endosperms were featureless and no glass transition could be observed; but two glass transitions could be observed in the thermograms of C. lanceolata seed embryos and endosperms.2. Tg1 of C. lanceolata seed embryos seemed little affected by water contents, but Tg2 was declined with increasing water contents. Moreover, the glassy state in C. lanceolata seeds was affected by many biological components of seed embryos. It was found that lipids were the major components responsible for the thermal transitions in C. lanceolata seed embryos and that sugar could shift the Tg2 to some higher temperature.3. The seeds of P. amabilis, C. lanceolata and P. massoniana could be cryopreserved. The germination percentage, simplified seed vigor and dehydrase activity of cryopreserved seeds of P. amabilis, C. lanceolata and P. massoniana were declined with increasing water contents. The germination percentage, simplified seed vigor of cryopreserved seeds of P. amabilis and C. lanceolata could not be enhanced by pretreating with cryoprotectants; but those of cryopreserved seeds of P. massoniana could be enhanced by the pretreatment.4. The relative electrical conductivity, contents of O 2? and MDA would ascend as a whole after cryopreservation. The membranes could not be protected by pretreating with cryoprotectants, but the contents of O 2? and MDA of P. massoniana seeds declined after the pretreatment.5. The activities of CAT, POD and SOD declined as a whole after cryopreservation. The CAT activity of cryopreserved seeds of P. massoniana could not be protected by pretreating with protectants; but the activities of POD and SOD of cryopreserved seeds of P. massoniana could be protected by some cryoproctants.6. The seed proteins of P. amabilis, C. lanceolata and P. massoniana did not change obviously in the cyopreservation, but the contents of seed proteins declined after cryopreservation. Furthermore, a band between 44.3~66.4KDa disappeared after cryopreservation in the SDS-PAGE electrophoresis of P. massoniana seeds, but a new band appeared between 14.3~20.1KDa after cryopreservation.