Comparative Studies Of Storage Reserve Accumulation During Somatic And Zygotic Embryogenesis Of Quercus Variabilis

Cork oak (Quercus variabilis Blume.)is one of the very important forest trees and a kind of deciduous broad leaved trees species in China with valuable functions. The tree is not only the primary industrial source of cork, but also is beneficial to maintain ecological environment. It plays an effective role in water and soil conservation and improving soil fertility. In addition, it serves as the sources of lumber, fuel wood, the cultivation of mushroom and tannin extract. Owing to the seeds being refractory for storage, late seed setting age, low seed yield, long palingensis period, rooting difficultly and having a pattern of biennial bearing, the conventional mode of reproduction of Q. variabilis is sexual reproduction. At present, the growth of trees depends mainly on natural regeneration. What's more, it's difficult to preserve the genetic resources, rapid propagation and genetic improvement since adult materials are not susceptible to be used for organogenesis on account of physiologic aging. Somatic embryogenesis technology provides a novel approach of micropropagation, genetic breeding, silviculture and germplasm resources conservation of forest trees. To carry out the study of somatic and zygotic embryo in Q. variabilis has profound and special significances.Although the regenerated plants via somatic embryogenesis have been obtained, it has a low plantlet formation rate. So it brings out a nodus to apply the efficient technology to further research. Thus, the paper presented the physiological biochemistry characteristics between the course of the development of the somatic and zygotic embryo. By analyzing the comparative studies of storage reserve accumulation of somatic and zygotic embryo in Q.variabilis especially storage proteins, these will demonstrate the regularity of the physiological and biochemical changes during different developmental stages and provide sensible theoretical foundations for establishment of plantlet regeneration system from somatic embryogenesis of Q.variabilis. The results are as follows:1. The soluble sugars and reducing sugars reached the maximum in the late development stages of zygote embryos in Q.variabilis and most of them concentrated in the embryos part of the seeds primarily. However, with the development of the somatic embryo, their content reached the lowest in the phase of heart-like while they have a high level in the globular phase and come up to maximum in the two cotyledons phase. Besides, the sugars' content cultured on MS medium supplemented with 200mg/L casein hydrolysate combination with 400mg/L glutamic acid was higher than other treatments.2. The accumulated soluble starch mainly centralized in the two cotyledons stage of zygote embryos of Q.variabilis. It had a highest content in the globular stage and a lowest content in the heart-like stage while increased at the torpedo-shaped stage and had a declined tendency in the two cotyledons stage. In the whole duration of accumulating, in contrast to the content cultured on MS medium supplemented with 400mg/L glutamic acid had a higher level than other treatments.3. The soluble proteins had stockpiled in the germ of zygote embryos of Q.variabilis. In the process of maturation, contrast to the four kinds of zygote embryos storage proteins, the contents in turn are as follow: glutelins, globulins, albumins, gliadins. And yet, it had a lower content in the globular stage and had dynamic accumulation to the top in the heart-like stage. Subsequently, its content was a downturn and remained falling. In addition, the storage proteins content cultured on MS medium supplemented with 200mg/L casein hydrolysate combination with 400mg/L glutamic acid was higher than other treatments.4. The result studied with polyacrylamine gel electrophoresis revealed that at the early development of zygote embryo, it occurred from a band with a molecular weight about 98KD first. Meanwhile, the color of the band turns much darker with the development of zygote embryos. At the following development, some new bands turned up. At the end of the development periods, the color of six different bands (100, 63, 42.5, 35, 24, 15KD) turned much darker as time went on. In zygote embryos, albumins and globulins were quite abundance and the electrophoreto gram showed they had well polymorphism. Moreover, there were three larger molecular weight (97.40, 110.79, 130.34 KD) bands of globulins.The number of the bands was different during different periods of somatic embryos development. There were a lot of bands in the globular stage with a molecular weight between 12.73 and 90.41 KD. In the heart-like stage, the number decreased to 13 and 5 new bands emerged. These 5 new bands disappeared in the torpedo-shaped stage. However, 3 new bands appeared. In the two cotyledon stage, the number of bands was 11 as the same as in torpedo-shaped stage. Two new bands (17.75KD) occurred but some (14.4KD) faded away. Under different treatments, there was no distinct diversity in the development of somatic embryo in Q.variabilis.