Data/hora: 01/06/2024 12:22:37

Biblioteca(s): | Embrapa Trigo.
Data corrente: | 10/01/2010
Data da última atualização: | 29/01/2015
Autoria: | MENGEL, K.; JUDEL, G. K.
Afiliação: | Justus-Liebig Univ., Inst. of Plant Nutrition. Giessen, Germany.
Título: | Effect of light intensity on the activity of starch synthesizing enzymes and starch synthesis in developing wheat grains.
Ano de publicação: | 1981
Fonte/Imprenta: | Physiologia Plantarum, Copenhagen, v. 51, n. 1, p. 13-18, 1981.
Idioma: | Inglês
Conteúdo: | The activities of starch synthesizing enzymes were investigated in wheat grains (Triticum aestivum L. cv. Kolibri) throughout the grain development period. Starch phosphorylase (E.C. 2.4.1.1) activity was especially high during the early period of grain development, while starch synthase I (ADP glucose alpha-glucan 4-alpha-glucosyl-transferase, E.C. 2.4.1.21) had a maximum activity during the later stage of grain filling. The synthetic potential of starchphosphorylase measured in vitro was about 16 times higher than the quantity of starch actually produced. It is therefore suggested that starch phosphorylase is of substantial importance in grain starch synthesis, particularly in the early period of grain growth. The synthetic potential of starch synthase I measured in vitro made up 25 to 50 per cent of the starch production and the synthetic potential of starch synthase II (UDP glucose alpha-glucan 4alpha-glucosyl-transferase, E.C. 2.4.1.11) only about 5 per cent. Reducing light intensity (shading) during the grain filling period depressed grain growth and starch production by about 20 per cent. Starch phosphorylase was not significantly affected by the reduced light intensity if enzyme activity is calculated on unit grain weight and not as activity per grain. Starch synthase I activity, however, was depressed by shading during the later stage of grain development. The depressed starch production found under low light conditions, however, cannot only be explained by an affected starch synthase I activity, but probably was also related to other still unknown factors limiting grain growth under low light conditions. The poor starch production in the shaded plants was not due to an insufficient supply of assimilates.
Palavras-Chave: | Fotosíntese.
Thesagro: | Amido; Trigo.
Categoria do assunto: | --
Registro original: | Embrapa Trigo (CNPT)
Exemplares: | CNPT - (22821-1) - ADD - SP - -- - 08902 -  - 08902 - DIS