Study On The Formation Of Pollen Tube Pathway And The Introduction Of Exogenous DNA On Upland Cotton

The technique for introducing exogenous DNA into plants, based on DNA fragments crossing hypothesis, is used to directly introduce total DNA or target gene into plants , so as to produce a large quantity of variant materials for variety improvement by means of screening. The technique is brifly as follews: after self pillination, the exogenous DNA is allowed to pass along the pathway of the pollen tube in the nucellus to enter the embryonic sac and transform the egg , zygote or early embryonic cell. The cell or cell to be transformed in that time do not have normal cell wall. The transformed seed then the plant could be obtained directly.As it is simple and not subject to restriction of species of plants, more and more breeders accepted and used the technique in rice , wheat , cotton, soybean, maize and vegetables, have bred new cultivars with disease resistance, pest resistance or other good characteristics. Foundation of the technique gave an impetus to plant molecular breeding research. And also, studies indicated that technique for introducing exogenous DNA be very inportant to improve crop varieties.In this paper, we observed the growth process of pollen tubes and investigated the formation date of pollen tube pathway by using paraffin methods on microscope on upland cotton. The results as follews:(1)Within 15 hours after pollination, the pollen tubes ran through the micropyle to the embryo sac and released the contents.(2)The egg cell was fertilized after 24 hours. The first division of zygote comes forth after 48 hours.(3) The best time of transform is 18 hours to 48 hours after pollination by pollen tube pathway. In this paper, the other objective is to study the distribution of exogenous DNA in ovule by pollen tube pathway in several periods. Its methods include 32P tracer method, redioactive dectetion and radioautography. We known as follews:(4)We observed that the data of redioactive dectetion by dripping is lower than by injecting exogeous DNA. No matter what dripping exogeous DNA and injecting exogeous DNA, the data of redioaction dectetion after 33 hours of pollination is the largest.(5)In several autoradiagrams of ovule, the sliver grains can be easily observed,and the number of sliver grains is more than the controls.