Study On The Development Of Ovule, Endosperm And Embryo In Stenospermic Seedless Grapes

Cytological observation was conducted on abortion and development of ovules , endosperms and embryos in 3 cultivars of stenospermocarpic seedless grapes (Thompson Seedless, Flame Seedless and Jingkejing) from April, 2002 to December,2004. The changes of the weight, horizontal and vertical diameter of ovules at different development stages were mensurated in the 3 cultivars of stenospermocarpic seedless grapes (Thompson Seedless, Flame Seedless,and Jingkejing) and a seeded grape (Beichun).The main results were as follows:1. Characteristics of internal structure, fertilization and development of ovule in stenospermocarpic seedless grapes.About 85-95% of all ovules were anatropous ovules, nucellar tissue was normal, outer integument, inner integument, micropyle and embryo sac were abnormal. Stenospermocarpic seedless grapes have polygonum type embryo sacs. Fertilization wasn't detected in 15-40% of ovaries. The weight, horizontal and vertical diameter of ovules in seedless grapes with fertilization increased continually in the beginning to maximum at a period, then dropped gradually and degenerated to the vestige that only had remnant seeds in the end.2.Characteristics of abortion and development of endosperms in stenospermocarpic seedless grapes.Characteristics of abortion and development of endosperms in stenospermocarpic seedless grapes were summarized as follows:(1)Pole nucleus were not fertilized.(2)Primary endosperm nucleus remained undivided after fertilization.(3)Endosperm nucleus divided 4-6 times very slowly and formed about 10-24 endosperm nucleus,then stopped dividing and eventually degenerated to remnant vestige.(4)Endosperm nucleus divided normally, the embryo sac were filled with cellular endosperm after 27-30 days of full bloom;endosperm started to degenerate after 29-33 days;all endosperm in most embryo sac had degenerated and the cavities of embryo sac became empty after 48-51 days.3.Characteristics of abortion and development of embryo in stenospermocarpic seedlessgrapes.Embryo and endosperm developed as well at early stage in stenospermocarpic seedless grapes as in seeded grape. Globular embryo and early heart-shaped embryo were observed at this stage. Subsequently young embryos in different developing states aborted. Only a few embryos went on developing into heart-shaped embryo and later embryo development stages, then embryo aborted and died, which resulted in seedless grapes in phenotype.4.Cytological causes of embryo in stenospermocarpic seedless grapes.Cytological cause of embryo in stenospermocarpic seedless grapes were summarized as follows:(l)Poor fertilization resulted in empty embryo sac.(2)Abnormalities in the development of inner integument, micropyle and embryo sac preveted pollen tube elongating and effected a decline in fertilization rate,that is to say the number of young embryos decreased.(3) Because some endosperm nucleus remained undivided or divided only 4-6 times, some ovules fertilized provided with no nourishment to sustain zygote development, which caused zygote not to divide so that young embryos could not been formed.(4)Endosperm nucleus developed very well, but endosperm tissue degenerated during the midway of endosperm development, thus nutrinent deficience of embryo led to embryo's abortion and abnormal seeds's formation.5.The best harvest times for the inoculation in vitro of embryo rescue in the 3 cultivars were ascertained.Different cultivars had different harvest time, the best inoculated time of Sultanina, Flame Seedless and Jingkejing were 39d, 36d, 41d after full bloom respectively.