Effects of assimilate enhancement on grain filling and carbohydrate and nitrogen partitioning in maize.

Source-sink relationhips is a controversial topic. Some workers assert that grain yield in corn is limited by availability of assimilate during the grain filling period. Others have reported the sink size as the limiting factor. In this research, I studied the effects of assimilate availabilibty on kernel growth rate and final weight by investigating the effects of altered source/sink ratios on soluble sugars, starch and nitrogen content in plant parts of maize. Special attention was given to plant's compensatory response such as soluble carbohydrates and nitrogen redistribution to the grain. Two genotypes: M14 x W64A and Pionner-brand '3780', were grown in field plots at St. Paul, Mn in 1982. The treatment were arranged in a split plot manner in a randomized complete block design of four replicates. The alterations of source/sink ratio consisted of partial kernel removal (removing the tip half of the ear), and thinning by a 50% plant population reduction imposed before and after the onset of linear growth (6 days and 24 days after mid-silking, respectively). M14 x W64A responded to early thinning, as indicated by an extended grain filling period, increased starch content of the kernels and greater final kernel weight. However, kernel growth rate, number of kernels per ear and kernel soluble sugars content were not affected. Thinning and partial kernel removel on both dates increased internode dry weight and soluble sugar content. Kernels removal early enhanced the nitrogen content in the internodes and (...)Dissertação (Mestrado) - University of Minnesota, Minneapolis

An AGN Identification for 3EG J2006-2321

We present a multiwavelength analysis of the high-energy gamma-ray source 3EG J2006-2321. The flux of this source above 100 MeV is shown to be variable on time scales of days and months. Optical observations and careful examination of archived radio data indicate that its radio counterpart is PMN J2005-2310, a flat-spectrum radio quasar with a 5-GHz flux density of 260 mJy. Study of the $V=18.7$ optical counterpart indicates a redshift of 0.833 and variable linear polarization. No X-ray source has been detected near the position of PMN J2005-2310, but an X-ray upper limit is derived from ROSAT data. This upper limit provides for a spectral energy distribution with global characteristics similar to those of known gamma-ray blazars. Taken together, these data indicate that 3EG J2006-2321, listed as unidentified in the 3rd EGRET Catalog, is a member of the blazar class of AGN. The 5-GHz radio flux density of this blazar is the lowest of the 68 EGRET-detected AGN. The fact that EGRET has detected such a source has implications for unidentified EGRET sources, particularly those at high latitudes ($|b|>30^{\circ}$), many of which may be blazars.Comment: 22 pages, 6 figures. To appear in ApJ v569 n1, 10 April 200

Características morfofisiológicas e de produção de seis genótipos de sorgo submetidos ao estresse hídrico.

xbitstream/item/25548/1/Bol-22.pd

Avaliação de genótipos de sorgo cultivados em solo ácido sob estresse.

O sorgo e uma planta que possui a habilidade de diminuir suas atividades metabolicas durante periodos adversos de umidade no solo. Quando ha o restabelecimento no suprimento de agua o sorgo reage de maneira surpreendente, muitas vezes ultrapassando o desenvolvimento de plantas nao estressadas. O presente trabalho teve por objetivo identificar genotipos de sorgo tolerantes ao estresse hidrico, avaliar o grau de recuperacao dos mesmos apos a suspensao do deficit hidrico bem como estudar os mecanismos de tolerancia ao estresse hidrico e correlaciona-los com a tolerancia a acidez do solo. Utilizou-se doze genotipos de sorgo, cultivados em um Latossolo Vermelho-Escuro, com ph4,5. Esses materiais foram avaliados em blocos casualizados com seis repeticoes, adotando-se irrigacao normal em tres repeticoes e estresse hidrico nas demais. O estresse acontece no período de pre-floracao e teve a duracao de 20 dias apos o termino do periodo de deficit. Os parametros estudados foram: altura de plantas, areas foliar, peso seco de plantas, peso das paniculas, indice de graos e rendimento de graos. Ficou evidenciado,para a maioria dos parametros que tanto o fator agua como a aluminio influenciaram no comportamento dos genotipos estressados. Houve, no entanto, materiais, que apresentaram melhor desempenho nessa condicao do que em sistema irrigado. Quanto a producao de graos ficou evidente que o hibrido CMSXS 370 e as linhagens CMSXS 136 e CMSXS 187 tiveram os melhores desempenhos

Cultivo do milho: germinação e emergência.

bitstream/CNPMS/15595/1/Com_39.pd