Document Type : Research Article
MSc Student, Department of Horticultural Science, Gorgan University of agricultural science and natural resources, Gorgan, Iran.
Department of Horticultural Sciences, Gorgan University of agricultural sciences and natural resources, Gorgan, Iran.
Associated Prof. Department of Horticultural Science, Gorgan University of agricultural science and natural resources, Gorgan, Iran.
Department of Horticultural Science, Gorgan University of Agricultural Sciences and Natural Resources, Gorgan, Iran
Asparagus, scientifically named Asparagus officinalis. L is a perennial plant belonging to the Asparagaceae family. Asparagus is a large genus in this genus that has about 200 species. The most important species for agricultural purposes is A. officinalis. Somatic embryogenesis is the formation of an embryo from an-asexual cell in vitro that similar to a seed embryo, is able to develop into a complete seedling. Somatic embryogenesis is a complex molecular and biochemical process based on cellular potentiogenicity and a model in the study of plant growth. In this unique process of embryogenesis, the growth cells acquire the capacity for embryogenesis under conditions of cellular stress. Sucrose is the predominant sugar in plants for energy production and facilitates vital functions. Sucrose is converted to glucose and glucose. Sucrose is the most common source of carbohydrates used in plant tissue culture.
Materials and Methods
The present study was performed in the tissue culture laboratory of the horticulture department of Gorgan University of Agricultural Sciences and Natural Resources in 1399 and 1400. Native Iranian asparagus seeds with octaploid ploidy level were used in this experiment. B5 medium containing 2, 4-D with a concentration of 2 mg /l was used to induce the embryo. Concentrations of 3, 6, 9, 12 and 15% in liquid medium were used to evaluate the effect of sucrose. The pH of the culture media were adjusted to 5.7. After the induction phase, the samples entered the realization phase and the subculture were cultured in the previous environments but with the aim of emerging the embryos (realization phase) while the hormone was removed from them. After 4 weeks in the embryonic development stage, the number of globular and bipolar embryos was observed using a computer-connected stereoscope at 20 and 40 micron magnifications.
Results and Discussion
The results obtained from this study showed that there is a significant difference between different concentrations of sucrose in terms of embryogenesis formation at different stages of embryogenesis. According to the presented results, change in sucrose concentration caused a change in the formation of embryos and the highest number of spherical embryos was observed with a significant difference (p <0.001) in 9% sucrose concentration. According to the comparison results, the concentration of 9% sucrose showed the highest amount of bipolar embryo among other different concentrations. Statistical results of photosynthetic pigments and anthocyanins showed that there was a significant difference between different concentrations of sucrose. As shown in Figures 2 and 3, the highest levels of chlorophyll a, b, total and carotenoids were observed at a concentration of 9% sucrose and the lowest amount of chlorophyll a at concentration of 12% and total chlorophyll and carotenoids at concentration of 3%. Also, the results obtained from regression analysis showed that the highest amount of photosynthetic pigments and starch was observed in 9% sucrose concentration. Finally, in this study, it was found that the best concentration affecting the vegetative embryogenesis of octaploid asparagus is 9% sucrose.
Carbohydrates are the main constituents of the plant and are most used in tissue culture medium, especially sucrose for growth and differentiation. It is noteworthy that high concentrations of sucrose are not only nutritional but also change the osmotic pressure in the culture medium. The relationship between glucose status and embryonic formation has been proven. In the meantime, the capacity of sucrose to support embryonic growth is greater, so that increasing sugars such as sucrose increase the potential for embryogenesis. According to the results of the present study, 9% sucrose in B5 culture medium showed an important role in chlorophyll production and caused photosynthesis and carbohydrate metabolism in this medium to increase, and as a result, the amount of sugar and its accumulation in culture explants. Increased in this medium and eventually caused the emergence of embryos with photosynthetic pigments in the resulting seedlings. Increasing the level of sucrose also prevents rapid germination and helps the development of the root system.