Phytochrome effects on stem carbon gain in light-grown mustard seedlings are not simply the result of stem extension-growth responses

CASAL, JJ.; SANCHEZ, R.A.; PAGANELLI, A.R. AND IZAGUIRRE,M.

PHYSIOLOGIA PLANTARUM

Blackwell Publishing

Año: 1995 vol. 94 p. 187 - 196

0031-9317

Phytochrome effects on stem carbon gain in light-grown mustard seedlings are not simply the result of stem extension-growth responses J. J. Casal 1 , R. A. Sánchez 1 , A. R. Paganelli-Blau 1 M. Izaguirre 1   1 Dept de Ecología, Facltad de Agronomía, Univ. de Buenos Aires. Av San Martín 4453, 1417-Buenos Aires, Argentina   1 Dept de Ecología, Facltad de Agronomía, Univ. de Buenos Aires. Av San Martín 4453, 1417-Buenos Aires, Argentina   1 Dept de Ecología, Facltad de Agronomía, Univ. de Buenos Aires. Av San Martín 4453, 1417-Buenos Aires, Argentina   1 Dept de Ecología, Facltad de Agronomía, Univ. de Buenos Aires. Av San Martín 4453, 1417-Buenos Aires, Argentina , R. A. Sánchez 1 , A. R. Paganelli-Blau 1 M. Izaguirre 1   1 Dept de Ecología, Facltad de Agronomía, Univ. de Buenos Aires. Av San Martín 4453, 1417-Buenos Aires, Argentina  J. J. Casal (corresponding author) Copyright Physiologia Plantarum 1995 KEYWORDS Carbon partitioning • mustard • phytochrome • Sinapis alba • stem growth ABSTRACT Carbon allocation and partitioning were investigated in the first internode of light-grown Sinapís alba L. seedlings exposed to white light (WL) with or without supplementary far-red light (FR). In the internode, supplementary FR increased the rates of extension-growth and the accumulation of radiolabeled carbon (fed through the leaves), reducing sugars (even per unit volume), starch, hemicellulose and cellulose, but had no effect on the levels of sucrose and ammonium oxalate-solubilised cell wall carbohydrates, on invertase activity or on the use of additional sucrose fed through the leaves. In source leaves, supplementary FR had no effect on photosynthesis rates and reduced the accumulation of radiolabeled carbon. Mechanical reduction of stem extension-growth responses to supplementary FR did not affect internode carbohydrate or carbon accumulation responses. Supplementary FR provided only to one leaf had no effect on internode extension growth but increased carbon accumulation in the internode. provided that supplementary FR and radiolabeled carbon were both given to the same leaf. Phytochrome-mediated effects on carbon partitioning are not the mere consequence of internode extension-growth responses. Some additional control point(s) (e.g. leaf-source strength) must be under the direct influence of phytochrome.