The Black Layer and Grain Maturity in Corn<sup>1</sup>

Daynard, T. B.; Duncan, W. G.

doi:10.2135/cropsci1969.0011183x000900040026x

Cited by 177 publications

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“…Preparation of Samples Kernels were harvested when physiologically mature, as indicated by the appearance of black layer (4). Because nearly all of the starch and most of the protein stored in the kernel are found in the endosperm, the embryo was removed from most samples and discarded.…”

mentioning

confidence: 99%

Growth and Composition of Maize Kernels Cultured in Vitro with Varying Supplies of Carbon and Nitrogen

Singletary¹,

Below²

1989

Plant Physiol.

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This study employed in vitro seed culture to determine how C and N supply influence the growth (i.e. starch accumulation) and protein composition of maize (Zea mays L.) endosperm. Immature kemels were grown to maturity on liquid medium containing various concentrations of C (sucrose at 234 millimolar [low] and 468 millimolar [high]) and N (amino acid mixture ranging in N from 0 to 144 millimolar). Low C supply limited starch, but not N, accumulation in the endosperm. With high C, endosperm starch and protein content increased concomitantly as N supply increased from 0 to 13.4 millimolar. Endosperm growth was unaffected by additional N until concentrations exceeding approximately 72 millimolar reduced starch accumulation. A similar inhibition of starch deposition occurred with lower N concentrations when kernels were grown with low C. Endosperm total N content reached a point of saturation with approximately 36 millimolar N in the medium, regardless of C supply. Zein synthesis in the endosperm responded positively across all N levels, while glutelin content remained static and albumin/globulin proteins were reduced in amount when N supply was greater than 36 millimolar. A reciprocal, inverse relationship was observed in mature endosperm tissue between the concentrations of free amino acids and soluble sugars. Our data suggest that under N stress starch and protein accumulation in the endosperm are interdependent, at least in appearance, but are independent otherwise.Maize endosperm comprises approximately 83% of the mature kernel and is composed of about 88% starch and 8% protein (8). Because starch and protein deposition in the endosperm constitute the bulk of kernel growth and represent the majority of kernel dry weight and N accumulation, respectively, these terms are often used interchangeably (i.e. starch for dry weight and protein for N) in this paper. Learning how processes of starch and protein deposition are controlled in the endosperm is important to understanding factors which affect grain development. The supply of C and N substrates provided to the seed by vegetative portions of the plant is one obvious factor which can affect the synthesis of these storage products. Regulation may also occur through an interdependency of the starch and protein synthetic pathways. For example, maize kernel dry weight and protein content often increase concomitantly in response to N fertilization (25,28) (27). On the other hand, starch and protein formation are also commonly thought to be negatively related, as grain yield and protein percentage are inversely correlated in cereals (6, 21). This inverse relationship is based on the concentration, rather than the content, ofprotein in the grain. In contrast to theories of coupled regulation between starch and protein formation, source-sink and postanthesis fertilization experiments with maize have shown that the N concentration of the grain can be increased without significantly affecting kernel size (11,22,29). These results suggest that starch and protein dep...

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mentioning

confidence: 99%

Growth and Composition of Maize Kernels Cultured in Vitro with Varying Supplies of Carbon and Nitrogen

Singletary¹,

Below²

1989

Plant Physiol.

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“…The 50-day harvest was selected as approximating physiological maturity for corn grown in this climate. One sign of physiological maturity is the development of the black layer across the base of the kernel (8). Many of the samples did show a brown layer, an early stage development of black layer.…”

Section: Resultsmentioning

confidence: 99%

Plant Nucleases

Wilson

1980

Plant Physiol.

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The nuclease activity of developing corn endosperms was found to consist mainly of plant RNase I during the period of major deposition of dry weight. The RNase concentrations in most inbred lines and hybrids increased throughout development, but there were large differences among genotypes in the enzyme levels at all stages. Crosses were made among inbreds classified as containing high or low RNase levels. In most cases, the general patterns of enzyme levels during development of the hybrid endosperms were not changed greatly, or showed intermediate levels of activity compared to the inbred parents. When Oh43 was used as a maternal parent, two contrasting developmental patterns were produced by using two low RNase inbreds as poUen parents. There appear to be genetic controls not only on the gross RNase levels, but also on the timing of RNase synthesis and on its stability after the cells mature. Environmental influences on RNase levels in the endosperm were noted one year.At 18 days after polination, the RNase levels in the endosperm crown were as much as 10 times higher than in the base. By 35 days after polination, the enzyme levels were generaUly uniform; at 50 days, the basal tissue usually contained the highest levels. In some genotypes, however, the enzyme levels feDl in the crown while they rose in the base. These changes suggest that RNase may be associated with developmental controls that operate as the different portions of the endosperm cease ceDl division and begin synthesis of starch and zein.

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“…Esse processo, entretanto, requer tempo para a secagem dos grãos, ou a utilização de aparelhos eletrônicos nem sempre disponíveis para os produtores. Outro modo para caracterizar a maturidade fisiológica se refere à formação de uma camada preta ("black layer") na região compreendida entre o endosperma basal e a área vascular do pedicelo dos grãos, quando estes maturam (Daynard & Duncan, 1969). Nessa fase, as células basais condutoras do endosperma do grão se tornam desorganizadas e são esmagadas tangencialmente, paralisando a translocação de metabólitos para os grãos (Daynard & Duncan, 1969).…”

Section: Introductionunclassified

“…Outro modo para caracterizar a maturidade fisiológica se refere à formação de uma camada preta ("black layer") na região compreendida entre o endosperma basal e a área vascular do pedicelo dos grãos, quando estes maturam (Daynard & Duncan, 1969). Nessa fase, as células basais condutoras do endosperma do grão se tornam desorganizadas e são esmagadas tangencialmente, paralisando a translocação de metabólitos para os grãos (Daynard & Duncan, 1969). Desse modo, estresses ambientais, como temperaturas muito baixas, seca e auto-sombreamento podem induzir a formação precoce da camada preta no milho (Tollenaar & Daynard, 1978;Afuakwa et ai., 1984), provavelmente em decorrência da baixa disponibilidade de fotoassimilados para os grãos (Afuakwa et ai., 1984).…”

Section: Introductionunclassified

“…Desse modo, estresses ambientais, como temperaturas muito baixas, seca e auto-sombreamento podem induzir a formação precoce da camada preta no milho (Tollenaar & Daynard, 1978;Afuakwa et ai., 1984), provavelmente em decorrência da baixa disponibilidade de fotoassimilados para os grãos (Afuakwa et ai., 1984). A caracterização da maturidade fisiológica, portanto, através da formação da camada preta na base do grão, apresenta problemas, como o momento em que é formada, que pode oscilar entre 17 e 75% de umidade dos grãos, dependendo das condições ambientais (Daynard & Duncan, 1969;Rench & Shaw, 1971;Carter & Poneleit, 1973;Afuakwa et ai., 1984). Apesar disso, o desenvolvimento da camada preta, critério bastante utilizado, não permite monitorar os estádios intermediários do processo de maturação do grão.…”

Section: Introductionunclassified

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Avaliação da maturação de grãos de milho através da linha do leite para aplicação de dessecantes químicos

Fahl

Carelli

Moniz³

et al. 1994

Bragantia

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Neste trabalho, avaliou-se a utilização da linha do leite ("milk line") como meio visual de monitorar a maturação do grão de milho, para determinar o melhor momento de aplicação de dessecantes, visando antecipar a colheita sem ocasionar decréscimos na produção. O experimento foi instalado em 1993 em uma cultura de milho híbrido HT 8551 da Zeneca Sementes Ltda, no município de Holambra (SP), em um podzólico vermelho-amarelo. A maturação foi monitorada pelo movimento da linha do leite no grão, e comparada com a perda de umidade, acúmulo de massa seca e desenvolvimento da camada preta ("black layer"). O dessecante foi aplicado em seis épocas, espaçadas de sete dias, consistindo em pulverizações da planta toda com paraquat (íon 1,1-dimetil-4,4-bipiridílio dicloreto) na dose de 400 g/ha. A linha do leite foi uma característica facilmente visível para acompanhar a maturação e estimar o teor de umidade do grão. Não houve mais acúmulo significativo de massa no grão quando a linha do leite se posicionava na metade do grão, que apresentava 35% de umidade. Todas as aplicações com o dessecante paraquat, efetuadas quando os grãos apresentavam umidade inferior a 42% (linha do leite posicionada no terço superior do grão), não alteraram significativamente o decréscimo na umidade que ocorre durante a maturação. A produção de grãos não foi alterada pelos tratamentos com dessecante efetuados 127 dias após o plantio (linha do leite posicionada na metade do grão). Nas aplicações anteriores, ocorreram decréscimos na produção. A porcentagem de germinação das sementes não foi prejudicada pelas aplicações com paraquat.

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The Black Layer and Grain Maturity in Corn¹

Cited by 177 publications

References 0 publications

Growth and Composition of Maize Kernels Cultured in Vitro with Varying Supplies of Carbon and Nitrogen

Growth and Composition of Maize Kernels Cultured in Vitro with Varying Supplies of Carbon and Nitrogen

Plant Nucleases

Avaliação da maturação de grãos de milho através da linha do leite para aplicação de dessecantes químicos

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The Black Layer and Grain Maturity in Corn1

Cited by 177 publications

References 0 publications

Growth and Composition of Maize Kernels Cultured in Vitro with Varying Supplies of Carbon and Nitrogen

Growth and Composition of Maize Kernels Cultured in Vitro with Varying Supplies of Carbon and Nitrogen

Plant Nucleases

Avaliação da maturação de grãos de milho através da linha do leite para aplicação de dessecantes químicos

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The Black Layer and Grain Maturity in Corn¹