Germination Physiology Of Dormancy-released Seeds Of Manchurian Ash(Fraxinus Mandshurica L.) Dehydrated In Different Conditions

We studied the effects of dehydration temperature, dehydration pattern and pretreatments on dehydrated seeds germination using dormancy-released seeds of Fraxinus mandshurica. The suitable temperature and method for dehydration were determined, and the effects of pretreatments on dehydrated seeds germination were also discussed. Our results provided both theory and technology basis for seeds treatment of F. mandshurica, which is more convenient and efficient for application. The main findings are summarized as follows:(1) The most suitable temperature for dehydration of dormancy-released seeds of F. mandshurica is20℃. Normal dehydration is feasible, and rapid dehydration (dried by silica gel) in low temperature (5℃) reduced germination ability of dehydrated seeds. Pretreatments such as soaked seeds in1×10-3mol/L Ca2+、1×10-4mol/L ABA and10%sucrose solution for24h improved germination ability of dehydrated seeds.(2) Dehydration under different temperature affected membrane permeability differently. Dehydration under20℃is beneficial to keep the membrane permeability, decreased membrane peroxidation and increase activities of antioxidant enzymes (SOD, POD and CAT); Dehydration under lower temperature increased membrane permeability and decreased activities of antioxidant enzymes (SOD, POD and CAT); rapid dehydration (dried by silica gel under5℃) increased membrane permeability and activities of antioxidant enzymes (SOD, POD and CAT), but decreased membrane peroxidation of embryo.(3) For all dormancy-released seeds that pretreated by different methods, the activities of antioxidant enzymes (SOD, POD and CAT) in embryos are higher than that in endosperms, which meant that the antioxidant reaction occurred in embryo mainly. Pretreatments (soaked seeds in1×10-3mol/L Ca2+、1×10-4mol/L ABA and10%sucrose solution) before dehydration under low temperature are beneficial to keep the membrane permeability and decrease membrane peroxidation; pretreatment by Ca2+, ABA and sucrose solution improved SOD activity in embryo; pretreatment under low temperature protected seeds, especially embryos, from damage by dehydration.(4) After dehydration of the dormancy-released seeds, starch content in endosperm is higher than that in embryo, which is in accordance with the theory that starch stored in the. endosperm mainly. Soluble protein content in embryo and endosperm after dehydration under1℃and normal dehydration are higher than that under20℃and rapid dehydration, respectively; soluble protein content in embryo and endosperm of pretreated seeds are lower than control. Dehydration temperature and speed affected protein and sugar content slightly; the total soluble sugar content in embryo of pretreated seeds are higher than control, but not in endosperm; starch content in embryo and endosperm of seeds that pretreated by10%sucrose solution are higher than control.