Long- and short-term effects of decreased sink demand on carbohydrate levels and photosynthesis in wheat leaves |
| |
Authors: | R. MORCUENDE,P. PÉ EREZ,R. MARTÍ NEZ-CARRASCO,I. MARTIN DEL MOLING,L. SANCHEZ DE LA PUENTE |
| |
Affiliation: | Instituto de Recurssos Noturales y Agrobiologia de Salamanca, CSIC, Apartado 257, E-37071 Salamanca, Spain |
| |
Abstract: | Wheat (Triticum aestivum L.) ears were removed to investigate long-term regulation of photosynthesis by sink demand at ambient CO2 and 22 °C. The CO2 level was also increased to 660 μmol mol?1 and temperature was lowered to 5 °C to examine short-term responses of photosynthesis to low sink demand. Sink removal inhibited photosynthesis and increased leaf levels of glucose, fructose and ribulose-1, 5-bisphosphate (RuBP), and the glucose-6-phosphate (G6P)/fructose-6-phosphate (F6P) and RuBP/3-phosphoglycerate (PGA) ratios under growth conditions, but had no effect on the activity and activation state of ribulose-1, 5-bisphosphate carboxylase oxygenase (Rubisco) either under growth or short-term conditions, suggesting an inhibition of photosynthesis by decreased in vivo catalysis of Rubisco. Photosynthesis increased similarly in eared and earless shoots after a rise in CO2 concentration, and the ratio of triose-phosphates (glyceraldehyde 3-phosphate and dihydroxyacetone phosphate, TP) to PGA was similar or higher for removed than intact ears, suggesting that feedback inhibition of photosynthesis was not caused by a limitation of ATP synthesis in chloroplasts. Under short-term conditions (660 μmol mol?1 CO2, 5 °C), TP and RuBP levels and the TP/PGA and TP/RuBP ratios were increased by sink removal, indicating an additional limitation of photosynthesis by the rate of RuBP regeneration. |
| |
Keywords: | Triticum aestivum L. Gramineae wheat carbohydrates carbon metabolism feedback photosynthesis Rubisco sink regulation |
|
|