Growth regulators, phytohormones, both natural and artificial, are the main means to control plant ontogenesis. They are involved in regulating the processes of cell differentiation and cell divisions, the formation of tissues and organs, the changes in the rate of growth and development, the duration of the certain stages of ontogenesis. The main classes of phytohormones used in plant biotechnology, in particular, in the induction of haploid structures, are auxins and cytokinins. The mechanism of action of phytohormones on a cell is rather complicated and may have a different character. Understanding the characteristics of the action of phytohormones is complicated by the fact that the system of hormonal regulation of plant life is multicomponent. This is manifested in the fact that the same physiological process is most often influenced not by one, but by several phytohormones, covering a wide range of aspects of cell metabolism. In connection with the foregoing, the purpose of our work was to test a set of nutrient media with different basic composition and different proportions of phytohormones to determine the patterns of their influence on the processes of haploid structure induction in rape anther culture using accessions, developed at the Institute of Oilseed Crops NAAS. The material used was two accessions of winter rapeseed (No. 1 and No. 2) and one sample of spring rapeseed, provided by the Rapeseed Breeding laboratory of the Institute of Oilseed Crops. Incised inflorescences were kept against the background of low temperature of 6–8 ° C for several days, and then, under aseptic conditions, anthers with unripe pollen grains were isolated and planted on nutrient media differing in both basic mineral composition and content of phytohormones. MS (Murashige & Skoog 1962) and B5 (Gamborg et al 1968) media were used as basic media. Phytohormones were added to the basic media in various combinations – BA, 2,4-D, NAA at the concentrations of 0.1-0.6 mg/l. In each treatment up to 300 anthers were cultivated. Differences between treatments were evaluated using standard t-test. Studies have shown that in the anther culture of rapeseed on the tested nutrient media, morphogenic structures of different types (embryoids and callus) were originated. Synthetic auxin 2,4-D, regardless of the composition of the basic medium, caused the formation of structures of both types, though with a low frequency. Phytohormone BA of the cytokinin type had a similar effect. In this case, the frequency of structures was slightly higher, and the developed structures were represented mainly by embryoids. The joint action of cytokinin and auxin was the most favorable for the initiation of morphogenic structures. Such combination of phytohormones caused the formation of these structures with a frequency of 24.5-14.7% in the studied genotypes of winter rape. A similar effect of phytohormones on the induction and development of morphogenic structures was also observed in spring rape. In this case, a single basic MS medium was used. The experiment included treatments where phytohormones were absent (control), as well as various combinations of auxin and cytokinin. In the control treatment, the formation of new structures was not noted. In treatments with phytohormones, in addition to the medium with the combination of auxin and cytokinin, the medium in which only cytokinin was present was also rather effective. The treatment in which the action of auxin 2,4-D was combined with the action of another auxin, NAA, turned out to be practically ineffective. Thus, it was found that for the induction of morphogenic structures from microspores in rape anther culture of the tested genotypes, the combination of cytokinin with auxin, or the use of only single cytokinin BA without other phytohormones, had the most positive effect.
SEM Investigation of Pollen Taxa in Honeys from Autochtone Apis cerana in Godavari, Lalitpur District, Nepal
