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Previous issue date: 2007-02-16 / Coordena??o de Aperfei?oamento de Pessoal de N?vel Superior / About half of planet population depend on rice. In Brazil, this cereal crop is widely spread,
and influenced by harsh climate conditions such as Humid Tropics one. In this region,
certainly nitrogen is the most limiting nutrient. However, low insolation, acid and highly Al3+
satured soils still endangers the culture. In these soils, ammonium can be the single plant s
Nitrogen source for plants. Its assimilatory pathway is economic and fast, although it presents
strong integration with C metabolism. This work intended to recognize ammonium
assimilation integrated with carbon metabolism. Two rice varieties were used: one adapted to
Humid Tropics environment - Piau? - and an improved variety represented by IAC-47,
selected under high N levels. Assays were carried on with 26 days after emergency plants,
cultivated in Hoagland and Arnon (1950) modified solution with N-NH4
+ 0.1 mM and 1.0 mM
N-NH4
+. Plasmalem (P)-H+ATPases; vacuole (V)-H+ATPases; vacuole (V)-H+PPases activity
as well as glutamine sinthetase (GS), glutamate synthase (GOGAT) and glutamate
dehydrogenase (GDH) were analysed. Moreover, it was determined soluble sugars, amino-N,
N-NH4
+, total-N, fresh and dry weight, and nutrition solution pH and N-NH4
+ variation. Also,
seminal root length was measured as well as glycolysis was analyzed through
phosphofructokinase (PFK) activity at plants roots tissue. P-H+ATPases activity was higher
in IAC-47 roots. On the other hand, at Piaui roots, enhances at microsomal protein were
observed, and V-H+ATPases presented higher activity as well as root development was high.
This allowed the adapted variety to absorb N like the improved one. However, both varieties
accumulated fresh weight in shoots at treatment 1.0 mM N-NH4
+ and showed roots/shoots
decrease at the same treatment. Moreover, amino N and NH4
+ concentration was higher at
Piau? shoots under 1.0 mM N-NH4
+. Both Piau? shoots and roots cultivated under 1.0 mM NNH4
+ accumulated less soluble sugars. Also, Piaui shoots had higher a+b chorophyl
concentration. PFK activity was enhanced at every plant, what accompanied ammonium
levels. Piau? plants always presented low sugar oxidation levels. It also seemed to concentrate
its sugars. Probably it happened to later availability for grain fullfil. To ensure this, it has high
ammonium and amino-N pools. Nitrogen absorbed by 1.0 mM N-NH4
+ Piau? seemed to be
substrate for GDH-amination, wich activity was superior. Despite this, GDH deamination was
high. In this way, Piau? could have GDH activity as an anaplerotic pathway to regulate C
skeletons need. Meanwhile, GS increases were observed at IAC-47, toghether with GOGAT
increases at 1.0 mM N-NH4
+ shoots. IAC-47 assimilated ammonium at GS/GOGAT pathway,
wich was fed by glycolysis velocity. These plants would produce constitutive protein, what
doesn t mean later grain stock. / Aproximadamente metade da popula??o do planeta depende do arroz. No Brasil, a cultura
desse cereal ? largamente difundida, sofrendo a influ?ncia de severas condi??es clim?ticas
como ocorre no Tr?pico ?mido. Nessa regi?o, certamente, o fator mais limitante para a
cultura do arroz ? a disponibilidade de nitrog?nio. No entanto, ainda pesam sobre a cultura a
baixa insola??o e os solos ?cidos com alta satura??o de Al+3. Nesses solos, o am?nio pode ser
a ?nica fonte de nitrog?nio mineral para as plantas. Sua assimila??o ? econ?mica e r?pida,
por?m, demanda estreita integra??o com o metabolismo de C. Pretendeu-se neste trabalho,
reconhecer esta integra??o. Foi utilizada a variedade de arroz Piau?, adaptada ?s condi??es
ambientais do Tr?pico ?mido, e a variedade melhorada IAC-47, selecionada sob altos teores
de N. Os ensaios foram feitos em pl?ntulas com 26 dias ap?s a germina??o (DAG) cultivadas
em solu??o de Hoagland e Arnon (1950) modificada com doses de 0,1 mM e 1,0 mM de NNH4
+. Avaliou-se a atividade de H+ATPases de plasmalema (P); H+ATPases de vac?olo (V);
H+PPases de vac?olo (V) e das enzimas glutamina sintetase (GS), glutamato sintase
(GOGAT) e glutamato desidrogenase (GDH) respons?veis pela assimila??o de nitrog?nio.
Al?m disso, acompanharam-se os teores de a??cares livres, N-amino, N-NH4
+, N-total, massa
fresca e massa seca e a varia??o do pH e do N-NH4
+ da solu??o nutritiva. Foi ainda medido o
comprimento da raiz seminal e o fluxo glicol?tico atrav?s da atividade da enzima
fosfofrutocinase (PFK) do tecido radicular das plantas. A atividade das P-H+ATPases mostrouse
maior nas plantas IAC-47. No entanto, a variedade Piau? mostrou maior teor de prote?na na
fra??o microssomal, maior atividade V-H+ATPases e maior desenvolvimento de ra?zes, o que
possibitou uma absor??o de am?nio semelhante ? da planta melhorada. Ambas as variedades
apresentaram maior ac?mulo de massa fresca na parte a?rea e decaimento na rela??o
raiz/parte a?rea no tratamento com 1,0 mM N-NH4
+. Observou-se ac?mulo de N-amino e NNH4
+ na parte a?rea de plantas Piau? no tratamento 1,0 mM de N-NH4
+. Tanto a parte a?rea
quanto a raiz da variedade Piau? cultivada a 1,0 mM N-NH4
+ apresentaram menor ac?mulo de
a??cares sol?veis e maiores teores de clorofila a+b. A atividade da PFK em todas as plantas
foi aumentada com os n?veis de am?nio nutricionais. A variedade Piau? apresentou sempre
menor oxida??o de a??cares. A variedade adaptada pareceu concentrar seus a??cares
possivelmente para disponibilidade em est?dios posteriores de enchimento de gr?o. Para isso,
manteve um maior pool de am?nio e N-amino. Houve ind?cios de que o am?nio absorvido por
plantas Piau? cultivadas no tratamento 1,0 mM N-NH4
+ teria sido drenado pela a??o aminativa
da enzima GDH, que se mostrou exacerbada. No entanto, a fun??o desamina??o da GDH
tamb?m se mostrou aumentada. Dessa forma, a Piau? poderia ter utilizado-se da GDH como
via anapler?tica para regular a necessidade de esqueletos carb?nicos. A atividade de GS foi
maior para a variedade IAC-47, acompanhada da atividade de GOGAT de parte a?rea no
tratamento 1,0 mM N-NH4
+. As plantas IAC-47 assimilaram o am?nio prontamente a partir da
via GS/GOGAT, a qual foi alimentada pela glic?lise acelerada. Essas plantas produziriam
prote?na constitutiva n?o aplicando em reservas para o posterior enchimento do gr?o.
| Identifer | oai:union.ndltd.org:IBICT/oai:localhost:tede/307 |
| Date | 16 February 2007 |
| Creators | Garrido, Rodrigo Grazinoli |
| Contributors | Fernandes, M?nlio Silvestre, Souza, Sonia Regina de |
| Publisher | Universidade Federal Rural do Rio de Janeiro, Curso de P?s-Gradua??o em Agronomia - Ci?ncia do Solo, UFRRJ, Brasil, Ci?ncias Agr?rias |
| Source Sets | IBICT Brazilian ETDs |
| Language | Portuguese |
| Detected Language | English |
| Type | info:eu-repo/semantics/publishedVersion, info:eu-repo/semantics/doctoralThesis |
| Format | application/pdf |
| Source | reponame:Biblioteca Digital de Teses e Dissertações da UFRRJ, instname:Universidade Federal Rural do Rio de Janeiro, instacron:UFRRJ |
| Rights | info:eu-repo/semantics/openAccess |
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