Data/hora: 31/05/2024 06:32:30

Biblioteca(s): 	Embrapa Mandioca e Fruticultura.	
Data corrente: 	16/04/2004	
Data da última atualização: 	16/04/2004	
Autoria: 	CALATAYUD, P. A.; DUCHON, S.; LAMAZE, T.	
Título: 	Estimation of carbon and nitrogen modification during water deficiency in leaves of cassava (Manihot esculenta Crantz).	
Ano de publicação: 	1998	
Fonte/Imprenta: 	Revista Brasileira de Mandioca, Cruz das Almas, v. 17, p. 39, nov., 1998. Suplemento.	
Idioma: 	Inglês	
Conteúdo: 	Abstract: Several pests (mealybugs, whiteflies and mites) affect cassava yield, causing severe crop damage. It is well known that the population dynamics of these pests depend on environmental factors, including drought. Long dry periods frequently induce a strong outbreak in the number of these pests on cassava. This phenomenon partly depends on the changes in the trophic quality of the plant. Our general purpose is to determine the effect of water stress on cassava pest behavior and population dynamics. At present, our research is focused on the chances that water limitation may trigger in the biochemistry of cassava leaves (carbon and nitrogen metabolism). After limited water supply for 45 days in a glasshouse, cassava leaves exhibited an increase in 5 l 3C and phosphoenolpyruvate carboxylase activity. This was associated with a very low leaf conductance (not shown). Enhanced phosphoglycolate phosphatase activity indicates that photorespiration may have increased. The free amino acid level was higher in stressed plants. The amino acid composition was also affected showing mainly a decrease in aspartic acid, glutamic acid and alanine proportion and an increase in asparagine and arginine. Glucose, fructose and sucrose showed variable modification of their accumulation levels but the total carbohydrate amount of all three increased following water limitation. This was associated with higer sucrose phosphate synthase activity. According to the increase in free amino acid (especially serine and glycine) and to the relative low shift in 513C values in the leaves of drought-adapted cassava plants, our working hypothesis is that the highphosphoenolpyruvate carboxylase activity is due to an increase in photorespiration leading to acceleration of respiratory ammonium assimilation requiring a high anapleuretic phosphoenolpyruvate carboxylase functionning.	
Categoria do assunto: 	--	
Registro original: 	Embrapa Mandioca e Fruticultura (CNPMF)	
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