Development Of Fruit And Seed And Its Evolutionary Implication In Amphidiploid Brassica Plants

The studies of evolution in polyploid plants cover many fields of plant and have been an attractive issue in the research of plants. In this study, three amphidiploids and three diploids in the "U-Triangle" of Brassica plants were used, and style, stigma size, stigma development, the development of basic pod characters, seed and cotyledon cell development were studied from the view of evolutionary developmental biology. The main results of the paper were as follows.Based on the comparative analysis of difference in style, stigma size, pod length and width, pod surface area, seed diameter and dry weight between amphidiploids and their putative diploids, we observed that some accessions of amphidiploids such as 2685 and 2194 revealed intermediate state between the two putative parents, others resembled only one of the two parents. Furthermore, the same amphidiploid showd different representation in different developmental characters, i.e. the amphidiploid resembled one of the two parents according to one character, but it resembled the other of the two parents in another character. Thus it was very complicated to study the close relationship between amphidiploids and their ancestral parents just through the development of style and basic characters of pod.Mature seed coat morphology is known to be an excellent character for taxonomic and evolutionary studies. Scanning electron miscroscope (SEM) studies of seed coat patterns development were carried out on six species (12 accessions), three amphidiploids and their three diploid parents. Twelve types of basic ornamentationpatterns were recognized during the whole developmental process of the seed coat. Six types of seed coat patterns appeared in three accessions of Brassica rapa, five types in B. olercacea, B. nigra and B. carinata, seven types in B. napus, and eight types in B. juncea. There was less difference among seed coat patterns of the three accessions of B. rapa. The reticulate and blister types were two of the most common patterns during the development of seeds in the six species, the blister-pimple and the pimple -foveate patterns were characteristic of B. rapa, and the ruminate of B. oleracea and B. nigra. The development of seed coat pattern in amphidiploids varied complicatedly. Some accessions such as accession 2685 and 2194 simultaneously showed seed coat patterns of the two putative parents, while accessions 1219 and 0857 resembled only one of the two parents. The variation in the patterns of seed coat development chould be used to provide a new and more effective way to analyse the close relationship among amphidiploids and their ancestral parents.The variations in seed coat patterns are successfully employed in the establishment of evolutionary relationships. This research aimed to provide the evolutionary implications in the anatomy of developmental seed coat in amphidiploid Brassica species. Thick sections (l-2um) and microscope technology were used to study the development of seed coat structure in six species (15 accessions), three amphidiploids and their three diploid parents. Four types of epidermis layer, six types of subepidermis and nine types of palisade layer could be recognized during the whole developmental process of the seed coat. The types of epidermis and subepidermis layer in diploids and amphidiploids changed similarly during the development of seed. Although there was little difference in the types of palisade layer among the accessions of diploids and amphidiploids at the early stages, many particular types appeared in these species at middle and later developmental stages. The development of palisade layer in amphidiploids varied complicatedly. Some accessions showed intermediate types in the palisade layer between the two putative parents, while others resembled only one of the two diploid ancestors. The developmental types of epidermis and subepidermis did not show the relationships between amphidiploids and diploids. However, the development in the types of thepalisade layer could be acted as an excellent character that implied the seed coat evolution of amphidiploids.There was difference in the variation of ultrastructure of cotyledons cells among the three basic diploids. The development of protein body was the most characteristic event in the variation of cotylendons cells. Althouth the protein body of cotylendons in the there basic diploids all formed through the ERs and vaculars, there was difference in the process of protein body formation among diploids, especially differed in the protein body formatian pathway of protein deposition in the vacular origination. Based on the comparatve analysis of the variation in the ultrastructure development of cotylendons cells, the close relationships between the three amphiploids and their putative parents were observed. For example, B. napus 2685 simultaneously showed the characteristic of its ancestral parents, B. rapa and B. oleracea. However, B. juncea 0857 and B. carinata 3534 resembled only one of the two putative parents, i.e. B. rapa and B. nigra, respectively. Therefore the present study provided the further evidence of the relationship between the variation of characters in amphidiploids and their ancestral parents from the ultrastructure of cotylendons cells. The relationship demonstrated that many events occured during the development of amphidiploids cotylendons cells were closed related to their putative parents.