03057naa a2200325 a 450000100080000000500110000800800410001910000220006024501750008226000090025752021530026665000130241965000150243265000150244765000100246265000160247265000130248865300110250165300120251265300150252465300180253965300100255765300100256770000190257770000220259670000180261870000210263670000220265777300520267914841572018-06-08       2000    bl uuuu     u00u1 u    #d1 aPURCINO, A. A. C.  aGrain filling in maizebthe effect of nitrogen nutrition on the activities of nitrogen assimilating enzymes in the pedicel-placento-chalaza region.h[electronic resource]  c2000  aIn a developing maize kernel, the pedicel-placento-chalaza (PPCh) is a heterogeneous tissue between the cob vascular system and the endosperm. Its major role is to modify the cob vascular system amino acid pool composition to better suit the requirements of the developing endosperm. Nitrogen metabolism in the PPCh tissue may, therefore, influence individual kernel development and consequently play an important role in determining grain yield capacity in maize. The objectives of the two experiments reported in this work were: (1) to determine the effect of nitrogen supply on the activities of the nitrogen assimilating enzymes glutamine synthetase (GS), NADH-dependent glutamate synthase (NADH-GOGAT), glutamate dehydrogenase (GDH) and of phospho-enolpyruvate carboxylase (PEPC) in the pedicel-placentochalaza (PPCh) tissue of maize genotypes contrasting in their responsiveness to nitrogen (N) fertilization, and (2) to verify if the activities of these enzymes in the PPCh tissue are correlated to individual kernel weight. Hybrids were grown in the field under low (16 kg/ha) and high (116 kg/ha) N supply and hand pollinated at silking. Enzymes activities were measured 30 days after pollination (DAP) and individual kernel weight was determined after black layer formation. Nitrogen supply did not influence individual kernel weight, soluble protein, GS and PEPC activities. However inconsistent results were observed for NADH-GOGAT and GDH over experimental years. Enzyme activities varied among genotypes, but correlation determinations indicated that individual kernel weight was not associated with soluble protein content and GS activity, with discrepant results observed for NADH-GOGAAT and GDH over years. However, a positive and significant correlation was observed between kernel weight and PEPC activity in both experiments. This finding merits further investigations over a larger number of genotypes and different environmental conditions. It suggests that genotypes with increased PEPC activity in the PPCh tissue have increased kernel weight and that this enzyme plays an important role in determining grain yield in maize.  anitrogen  aphysiology  aFisiologia  aMilho  aNitrogênio  aZea Mays  aEfeito  aEffects  aEnchimento  aGrain filling  aGraos  aMaize1 aSILVA, M. R. e1 aANDRADE, S. R. M.1 aBELELE, C. L.1 aPARENTONI, S. N.1 aSANTOS, M. X. dos  tMaydica, Bergamogv. 45, n. 2, p. 95-103, 2000.