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Caracteriza??o fisiol?gica da resposta a aduba??o nitrogenada em duas cultivares de arroz

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Previous issue date: 1996-07-11 / CNPq / An experiment was carried out to study the seasonal pattern of dry mass and nitrogen (N) distribution in the vegetative and reproductive parts of two rice cultivars of contrasting aerial architecture, as a function of the application of N in the maximum tillering stage. Substrate from the Ap horizon of a Red Yellow Podzolic soil was used as substrate. The cultivars Comum Branco (dryland) and IAC 4440 (irrigated) were combined with five application levels of N (as Ammonium Sulfate): 0, 2, 4, 6 and 8 g N m-2 in the maximum tillering, and grown in pots arranged in a completely randomized, greenhouse. During the plant cycle, seven successive collections were carried out in order to follow the phasic development as days after planting (DAP): beginning of tillering, maximum tillering, panicle differentiation, stem elongation, flowering, milky / pasty grain and physiological maturation of the grain, which corresponded to collections at 20, 40, 60, 80, 100, 115 and 135 DAP respectively. In each collection were determined the dry mass of: green and senescent leaves, stems and sheaths and roots. The green leaf area and root area were also determined. The N contents were determined in all these fractions by micro Kjeldhal technique. In the final collection the components of the production were evaluated: mass and number of panicle, viable and sterile grain, and their corresponding N contents. The experimental data were combined for the purpose of analysis of variance, in the form of a cultivar factorial x dose x DAP . Primary functions were adjusted from the data of dry mass and total N, foliar and root area, from which the growth and accumulation rates were derived, to obtain net assimilation rates and N influx rates. it was observed that during the period prior to flowering there were no differences in accumulation of total dry matter between the cultivars. There was a higher dry mass allocated in stalks and sheaths, and lower weight of senescent leaves mass in IAC 4440. The partition of dry mass in favor of roots was similar in both cultivars. The cultivar IAC 4440 established a potential productive superiority due to its greater number of tillers. As a consequence, it maintained a longer duration of photosynthetically active leaf area, resulting in a higher daily accumulation rate of dry matter and leaf area. Regarding the N accumulation patterns in the different biomass fractions, the same trend as that observed for dry mass accumulation was observed. However, the maximum rate of maximum accumulation of N occurred in both cultivars, rather than the maximum dry matter accumulation. Leaf N contents in both cultivars were similar until flowering. IAC 4440 had greater specific leaf area in the period, suggesting greater leaf N dilution. When compared to leaf area equality, the net assimilation rate was higher in IAC 4440, which indicates that the overproduction of area, affected the photosynthetic potential in this cultivar, to a greater degree than in Common White. In the post-flowering period, the dry matter partitioning pattern, which was rigidly fixed in pre-flowering, was manifested in a sustained remobilization of photoassimilates and N to the panicle in IAC 4440, evidenced by the reduction of dry mass and N contents of stalks and sheaths during the first 15 days post-flowering and additional contribution of N and C from marked leaf senescence in the maturation period. There was detention of the photo-assimilates and N remobilization of the panicle in Common White, after 15 days post-flowering, with consequent accumulation of dry matter and N in leaf stems and sheaths. The development of a secondary drainage originated in post-flowering neo-tillering may have subtracted photosynthates, otherwise able to be applied in the filling of the growing panicle. A higher grain weight per plant in IAC 4440 was explained by a higher number of panicles and a higher number of viable seeds, and lower crude protein levels, compared to White Common. Regarding the dry mass and nitrogen distribution patterns during the cycle of the cultivars, the effects resulting from the single application of N at the maximum tillering were diluted during the development of the plants, so that they had very little effect on the dynamics of retranslocation of C and N after flowering. This dilution effect was responsible for the non-significance of the interaction of practically none of the primary descriptive growth parameters of the cultivars. No effect of N on phasic development was also noted. The higher levels of N applied favored an increase in net assimilation due to an increase in leaf N content. At higher levels of N application, leaf mass increased without area promotion, which was evidenced by the increase in its specific weight. However, the N content did not significantly reduce leaf senescence; The application of N did not affect significantly the production, only affecting an increase in the percentage of sterility of the spikelets, which counterbalanced the gain of one panicle per plant. As a global result of the work, it was concluded that the patterns of dry matter production and C and N remobilization to the grain, are regulated genetically, showing cultivar specificity. Therefore, nitrogen fertilization is efficient only in order to ensure high rates of physiological activity of panicles and other organs related to grain filling, but not in changing the pattern itself. / Foi instalado um experimento com o objetivo de estudar o padr?o sazonal de distribui??o de massa seca e nitrog?nio (N) nas partes vegetativas e reprodutivas de duas cultivares de arroz de arquitetura a?rea contrastante, em fun??o da aplica??o de N no est?gio de m?ximo perfilhamento. Usou-se como substrato terra proveniente do horizonte Ap de um solo Podz?lico Vermelho Amarelo. As cultivares Comum Branco (de sequeiro) e IAC 4440 (irrigada) foram combinadas com cinco n?veis de aplica??o de N (na forma de Sulfato de Am?nia): 0, 2, 4, 6 e 8 g N m-2, no est?gio de m?ximo perfilhamento, e cultivadas em potes dispostos de forma inteiramente casualizada, em casa de vegeta??o. Durante o ciclo das plantas foram realizadas sete coletas sucessivas, de forma a acompanhar o desenvolvimento f?sico como dias ap?s plantio (DAP): in?cio do perfilhamento, perfilhamento m?ximo, diferencia??o da pan?cula, elonga??o de colmos, flora??o, gr?o leitoso/pastoso e matura??o fisiol?gica do gr?o, o que correspondeu ? coletas aos 20, 40, 60, 80, 100, 115 e 135 DAP respectivamente. Em cada coletas foram determinados a massa seca de: folhas verdes e senescentes, colmos e bainhas e ra?zes. A ?rea foliar verde e ?rea radicular foram tamb?m determinadas. Os teores de N foram determinados em todas estas fra??es, por t?cnica de micro Kjeldhal. Na coleta final foram avaliados os componentes da produ??o: massa e n?mero de pan?cula, gr?o vi?vel e est?ril, e seus correspondentes teores de N. Os dados experimentais foram combinados para finalidade de an?lise de vari?ncia, na forma de um fatorial cultivar x dose x DAP. Fun??es prim?rias foram ajustadas a partir dos dados de massa seca e conte?do total de N, ?rea foliar e radicular, das quais foram derivadas as taxas de crescimento e de ac?mulo, para f?ns de obten??o das taxas de assimila??o l?quida e influxos de N. Concluiu-se que durante o per?odo anterior ? flora??o, n?o existiram diferen?as em ac?mulo de mat?ria seca total entre as cultivares. Houve maior massa seca alocada em colmos e bainhas, e menor peso de massa de folhas senescentes em IAC 4440. A parti??o de massa seca em favor de ra?zes resultou similar em ambas as cultivares. A cultivar IAC 4440 estabeleceu uma superioridade produtiva potencial em fun??o de seu maior n?mero de perfilhos. Como consequ?ncia, manteve maior dura??o de ?rea foliar fotossinteticamente ativa, resultando em maior taxa de ac?mulo di?rio de mat?ria seca e ?rea foliar. Com rela??o aos padr?es de ac?mulo de N nas diferentes fra??es da biomassa, foi observado a mesma tend?ncia que a verificada para ac?mulo de massa seca. Por?m, a taxa m?xima de m?ximo ac?mulo de N, aconteceu em ambas as cultivar, antes do que os m?ximos de ac?mulo de mat?ria seca. Os teores de N foliares em ambas as cultivares foram similares at? a flora??o. IAC 4440 teve maior ?rea foliar espec?fica no per?odo, sugerindo maior dilui??o de N foliar. Quando comparadas ? igualdade de ?rea foliar, a taxa de assimila??o l?quida foi superior em IAC 4440, o que indica que a sobreprodu??o de ?rea, prejudicou o potencial fotossint?tico nesta cultivar, em maior grau que em Comum Branco. No per?odo p?s-flora??o, o padr?o de parti??o de mat?ria seca ao gr?o, o qual foi rigidamente fixado na pr?-flora??o, manifestou-se em uma remobiliza??o sustentada de fotoassimilados e N ? pan?cula em IAC 4440, evidenciado pela redu??o de massa seca e conte?do de N de colmos e bainhas durante os primeiros 15 dias p?s-flora??o e contribui??o adicional de N e C a partir de acentuada senesc?ncia foliar no per?odo de matura??o. Houve deten??o da remobiliza??o de fotoassimilados e de N ? pan?cula em Comum Branco, ap?s os 15 dias p?s-flora??o, com consequente ac?mulo de mat?ria seca e N em colmos e bainhas foliares. O desenvolvimento de um dreno secund?rio originado em neo-perfilhamento p?s-flora??o, pode ter subtra?do fotossintatos, de outra forma, pass?veis de serem aplicados no enchimento da pan?cula em crescimento. Um maior peso de gr?os por planta em IAC 4440 foi explicado por maior n?mero de pan?culas e maior n?mero de sementes vi?veis, e menores teores de prote?na bruta, em rela??o a Comum Branco. Com rela??o aos padr?es de distribui??o de massa seca e nitrog?nio durante o ciclo das cultivares, os efeitos decorrentes da aplica??o ?nica de N por ocasi?o do m?ximo perfilhamento foram dilu?dos durante o de desenvolvimento das plantas, de forma que tiveram efeito muito reduzido sobre a din?mica de retransloca??o de C e N p?s-flora??o. Esse efeito de dilui??o foi respons?vel pela n?o significa??o da intera??o de praticamente nenhum dos par?metros prim?rios descritivos de crescimento das cultivares. Tamb?m n?o foi notado efeito do N no desenvolvimento f?sico. Os maiores n?veis de N aplicados, favoreceram um aumento da assimila??o l?quida devido ? um aumento no teor de N foliar. Aos maiores n?veis de aplica??o de N, o peso de massa foliar aumentou, sem promo??o de ?rea, o que foi evidenciado pelo aumento do seu peso espec?fico. Entretanto, o teor de N n?o reduziu significativamente a senesc?ncia foliar; A aplica??o de N n?o afetou significativamente a produ??o, incidindo apenas num aumento da percentagem de esterilidade das espiguetas, que contrabalanceou o ganho de uma pan?cula por planta. Como resultado global do trabalho, foi concluido que os padr?es de produ??o de mat?ria seca e de remobiliza??o de C e N ao gr?o, est?o regulados geneticamente, mostrando especificidade de cultivar. Portanto, a fertiliza??o nitrogenada ? eficiente apenas no sentido de assegurar altas taxas de atividade fisiol?gica das pan?culas e demais ?rg?os relacionados ao enchimento de gr?os, mas n?o na mudan?a do padr?o em s?.

Identiferoai:union.ndltd.org:IBICT/oai:localhost:jspui/2043
Date11 July 1996
CreatorsZONTA, Everaldo
ContributorsROSSIELLO, Roberto Oscar Pereyra, Rossiello, Roberto Oscar Pereyra, Fernandes, Manlio Silvestre, Jacob Neto, Jorge
PublisherUniversidade Federal Rural do Rio de Janeiro, Curso de P?s-Gradua??o em Agronomia - Ci?ncia do Solo, UFRRJ, Brasil, Instituto de Agronomia
Source SetsIBICT Brazilian ETDs
LanguagePortuguese
Detected LanguageEnglish
Typeinfo:eu-repo/semantics/publishedVersion, info:eu-repo/semantics/masterThesis
Formatapplication/pdf
Sourcereponame:Biblioteca Digital de Teses e DissertaƧƵes da UFRRJ, instname:Universidade Federal Rural do Rio de Janeiro, instacron:UFRRJ
Rightsinfo:eu-repo/semantics/openAccess

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