No abstract

No abstract

No abstract

1 H magnetic resonance microtomography imaging was applied to study vascular systems in devel oping bean (Phaseolus limensis L.) seeds. Using the gradient echo method, we recorded 2D tomographic sec tions in the sagittal and axial planes of the fruits sampled from a vegetating plant on days 10, 17, 24, and 31 after fertilization. Any vascular connection between the tissues of maternal plant (bean pod and seed coat) and the embryo were undetectable. The embryo has an autonomous branched network of procambial strands in the cotyledons, converging to the embryonic axis. The bean pods are covered with a network of vascular bundles; large vascular strands run along the dorsal and ventral sutures. The seed coat vascular bundles are formed in the process of seed ripening and are represented by a developed vascular system multiply branching in the middle part of the ground parenchyma at the stage of physiological maturity. They are connected with the source of assimilates via the lateral pod veins and a large vascular bundle, entering the seed below the hilum via the placenta. Assimilates enter the external part of the seed coat, which contains no vascular bun dles, via the funiculus vascular bundles and hilum tissue.

No abstract

Data on real structure of crystals obtained by universally accepted ~ec~iques ~EP~, ot ical spectroscopy, comblna~lonal dlsslpatlon etcf may be far more numerous and complete if dielectric spectroscopy is used as a further-aid. It is especially important when point defects of the studied crystals are non paramagnetic, optically inactive though electrically active in non-excited state. Quartz is a good example of these crystals. Electrically active point defects in quartz are known to be alkali metal ions that dominate there as the type. We have compared experimental temperature/ frequency dependencies 8" at temperatures of 300-800 K with Debye theoretical curve and presented Cole-Cole and Scafe diagrams. As a result we state a presence of a broad ener9Y spectrum of impurity alkali ions. Energy dlstribution is not Gaussian,the observed asymmetrv of normalized Elf(W't) function proving it. The distribution parameter of relaxation time (~) increases with crystallization temperature and with lower rates of growth. We have postulated presence of H 2 0 molecules in structure voids of cancrinite crystals using energy parameters o£ relaxation polarization in a temperature range of 350-500 K. We have calculated the ol-value to change from 0.05 to 0.40 at temperatures of 350-500 K. This change may result from multiple structure positions of H 2 0 molecules and their reorientations at various temperatures (Kolodieva et al., Sintez miner. i exper. issled., Moskva (1981) 41). Dielectric spectroscopy approach to non-relaxation maxima Eff(T) should be very careful. In interpreting of the experimental result~ special attention should be paid to reverSlbility of the observed change of the dielectric characteristics and to their correlation to other physical properties. For example, we can state that the non-relaxation maximum E If in the region of 650-800 K in cancrinite is not reproducible at repeated heating. This fact may result from irreversible changes of cancrinite structure further corroborated by substantial weakening of its piezo effect after heating to 800 K. Similar maxima of E'f(T) obtained during heating of fluorphlogopite (up to 900 K) are reproducible though after certain intervals of time. This is a case of reversible processes with great relaxation time of the crystal to the initial state. General phenomenology may describe this process as a recombination of defects that determine dielectric losses with acceptor centers thermally activated in this temperature range to form metastable pairs (or complexes) that dissociate later on (Kolodiev et a1., Vses. nautchn. koufer. "Physika dielektrikov". Sektsyia "Protsessy elektroperenosa". Thes. dokladov, Baku (1982) 63). 21.1-2 NMR AND EPR SPECTROSCOPY OF ALKlILI SELENITES. By I.S. Vinogradova, L.V. KirenskyInstitute of Physics, Academy of Sciences, Siberian Branch, Krasnoyarsk, USSR.The results of the study of single crystals of NeHS03 (He = Li, Na, K, Rb, Cs) by lH, 2D, 7Li, 23Na , 87Rb , 133 cs and 77S8 nuclear magnetic resonance spectroscopy are reported.In addition...

No abstract

No abstract