The Study On The Physiological Mechanism Of Frost Injury To Apricot Floral Organs

In this paper, Branches and pear trees were used as experimental materials, which were treated at artificial climate chamber for imitating cold wave to study LT50, electrolyte leakage rate of pear flower and young fruit in different periods,the change of pro-aa、MDA、 anti-oxidant defence system、hardiness of floral organs、the growth of pollen tube under low temperature, Combined with the investigation of frost damage on the field experiment, the effect of bagging and and the reagent on frost resistance of pear floral organs. The main results are as follows:1. Branches were used as experimental materials, to study the frost resistance of pear in different periods, the results show that, different periods have different frost resistance, electrolyte leakage rate gradually increased with decreasing temperature, Conductance method combines the Logistic equation obtained LT50, the size of the frost resistance as follows, Bud stage> First blossom> Full blossom> One week after Full blossom> Two weeks after Full blossom,LT50were respectively-5.269℃、-4.179℃、-4.091℃、-1.447℃、-1.349℃.The effects of low temperature on antioxidant defence systems, osmolytes contents were showed as follows:enzymes of different floral organs showed certain difference, but the general trend is increasing firstly, and decreasing secondly, along with the decreasing of temperatures, POD gradually increased with decreasing temperature in the former four periods, significantly higher than control, but POD decreased under-4℃in two weeks after full blossom, MDA content gradually increased with decreasing temperature, significantly higher than control.2.5-year-old trees of Pyrus pyrifolia cv’Cui Guan’were used to study the effects of low temperature on pear floral organs,anti-oxidant denfence system,pollination and fertilization,under minus0℃. Results showed that no freezing injury on pear floral organs and no influence on fruit set appearsd under0℃. Then rate of freeing injury increased to43.56%and rate of fruit set decreased to50%under-2℃for1.5hours.While,as the temperature went down and elongation of low temperature treatment,rate of freezing injury continued to go up to85.5%and100%,and rate of fruit set continues to go down to24.01%and0%, respectively, eunder-2℃for3hours and-4℃.Enzymes indifferent floral organs showed certain differences:activities of SC、CAT、 POD of petal were in a trend of increasing firstly, and decreasing secondly, along with the increasing of temperatures and duration. The enzymatic activity of the stamen and pistil showed alomost the same trend, while pistil was more sensitive to low temperature than petal and stamen. Change of MDA and proline-content in pear floral organs showed the same tendency, increased along with the decreasing of temperatures and increasing of duration.The pollen germination was not inhibited by low temperature at-2℃for3hours, however it could recover when the temperature got right, and there no significant difference on germination rate with the control. But it cost more time for pollen tube to grow to the base of style, which may miss the right time of fertinization.3. Pyrus pyrifolia Nakai. cv.’Hosui’were used to study the effective pollination period, the best pollination time, the growth of pollen tube and the effect of vitro pollen germination and growth of pollen tube under different temperature. Results showed that the effective pollination period of’Hosui’is six days, the best pollination time is from8:00to16:00in one day. pollen germinating after2h and Pollen tubes at the base of style after72h; the effect of the pollen germination and the growth of pollen tube is this, Pollen germination and pollen tube growth was inhibited when the temperature is below10℃, Cleavage of partial pollen tube under35℃cultured for4hours.4. We investigated the frosted symptom of Pyrus bretschneideri Rehd. cv. Dang-shansuli in Minquan country and Ningling country in He Nan city.The result is this: Frost damage rate of pear floral organs was17.1%in Ningling country under0℃-2℃, and frost damage rate of pear floral organs was80%-96%under-3℃in Minquan country, basically no harvest. Stigma has the ability to accept the pollen if it is not browning.Litter pollen tubes at the base of style48h after pollination in the environment of suitable temperature and humidity, no frosted damage of the ovary can fertilize normally. 5. Frost damage rate of pear floral organs was43.3%and the fruit setting rate was about33.3%with bagging, while serious frost damage of pear floral organs and no fruit set with no bagging under low temperature; young fruits with bagging had little frosted, the protruding organization is on the fruit epidermis, young fruit all fall off with on bagging. The content of pro-aa and MDA is higher than the control, while SODs CAT%POD of young fruit is lower than the control. The content of pro-aa in pear flower is higher with spraying0.2g/l ALA, the effect of antifreeze is very good.