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Formation and structure of the egg shell in Raphidia sp.[Raphidioptera]

100%

Jedrzejowska I.

Acta Biologica Cracoviensia. Series Botanica et Zoologia. Supplement

1997

tom 39

nr 1

Structural and biochemical changes in the micropylar region of Chondrilla juncea apomictic ovule

80%

Koscinska-Pajak M. , Chudzik B. , Zarzyka B. , Pawelec J.

Acta Biologica Cracoviensia. Series Botanica. Supplement

2005

tom 47

nr 1

Differentiation of the synergids in Pulmonaria angustifolia and Pulmonaria mollissima Kern

80%

Izmailow R. , Tarnawska M.

Acta Biologica Cracoviensia. Series Botanica

1995

tom 37

Processes of the cytological differentiation in the synergids of Pulmonaria angustifolia L. (2n = 14) and P. mollissima Kern. (2n = 18) were studied. In both species the process of polyploidization started soon after the formation of the mature embryo sac. The lack of mitoses, rhythmical enlargement of the synergid nuclei as well as their characteristic structures pointed to endoreduplication as the mechanism of polyploidization. Detailed analysis of nuclear volume measurements permitted to distinguish five size-classes of nuclei; they correspond to the degrees of ploidy evaluated as: n, 2n, 4n, 8n and 16n. Moreover, in P. mollissima one nucleus could be identified with 32n level. In polyploid nuclei the occurrence of aggregations of chromatin enlarging with the degree of polyploidization was stated. Their increase in thickness in high polyploid nuclei permitted to suppose that they represented the polytene chromosomes. The synergids in Pulmonaria probably are involved in the nutrition of the egg cell before fertilization. It may be supposed that the persistent synergid retains its physiological activity up to the stage of 4-8-celled embryo.