Alterações fisiologicas no algodoeiro causadas pelo nematoide Meloidogyne incognita raça 3 : influencia do nivel de inoculo e do fornecimento de nitrogenio

AUTOR(ES)
DATA DE PUBLICAÇÃO

1998

RESUMO

Growth and variation in the contents of soluble sugars, phenols and chlorophyll, and nitrate reductase activity were determined in cotton plants (Gossypium hirsutum) of cv. Acala (susceptible) and cv. IAC-20 (tolerant) inoculated with eggs (O, 500 e 5.000) of Meloidogyne incognita race 3. In a second experiment the same parameters were also determined in plants inoculated with 7.500 eggs of the nematode, which were fertilized with different amounts of nitrate or ammonium as the N source. In the first experiment it was determined that cvs. Acala and IAC-20 are, respectively, susceptible and tolerant to M. incognita race 3. Plants receiving 500 eggs were taller and accumulated more dry matter in the shoot and roots. They also showed increased values of photosynthesis, nitrate reductase activity and chlorophyll contento Inoculated plants were also subjected to controlled water stress and the leaf water potential determined with apressure pump. Lower potentials were observed in the plants of cv. IAC-20, which increase in root dry matter was lower (12%) than plants of cv. Acala (52%). In the second experiment the plants received: water, Hoagland solution without N, Hoagland 1xN-NO3, Hoagland 3xN NO3, Hoagland 1xN-NH4 or Hoagland 3xN-NH4. Here, IAC-20 was also tolerant to the nematode, independently of the N source and the amount applied. Increases of dry matter of shoot and roots were also observed for both cultivars. Plants receivinc more N accumulated more dry matter. Chlorophyll content waenhanced in Acala plants by N fertilization, however, less when ammonium was used. Phenols were always higher in plants receiving only water or nutrient solution -N. Nitrate reductase activity increase with N application. In general, nematode infection induced higher enzyme activity, this beinc more pronounced in cv. IAC-20 and plants receiving nitrate

ASSUNTO(S)

clorofila nitrogenio nematoda em plantas açucar algodão - doenças e pragas fotossintese

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