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The paper describes the principles and theoretical models of new X-ray optical elements based on the behaviour of Bragg-Fresnel diffraction. The use of volume diffraction permits one to achieve better spatial resolution compared with conventional plane optics and bending mirrors. The construction of Bragg-Fresnel elements combines the advantages of high-resolution Fresnel optics with stability of multilayer mirrors

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Using a direct amplification of genomic DNA from two Brassica rapa forms, we obtained two homologs of the CONSTANS gene, which controls the photoperiodic induction of flowering in Arabidopsis plants. The cloned fragments of B. rapa genome were identified as members of the CONSTANS-LIKE1 class. By aligning the nucleotide sequences of the CONSTANS gene and its homologs, three classes, CONSTANS, CONSTANS-LIKE1 , and CONSTANS-LIKE2 , were distinctly discerned by their primary structure. The pattern of restriction fragment length polymorphisms (RFLP) of the CONSTANS homologs in B. carinata, B. juncea, B. napus, B. nigra, B. oleracea , and B. rapa were genome-specific; in addition, the CONSTANS homologs were classified by plant geographic origin, and we assume that such classification is related to plant photoperiodic response.