Dark chilling imposes metabolic restrictions on photosynthesis in soybean

Dark chilling inhibited photosynthesis in two soybean [Glycine max (L.) Merr.] cultivars (Fiskeby V and Maple Arrow). The inhibition of CO2 assimilation was characterized by a simultaneous decrease in stomatal conductance (Gs) and intercellular CO2 concentration (Ci) in Maple Arrow, whereas a simila...
Ausführliche Beschreibung

Dark chilling inhibited photosynthesis in two soybean [Glycine max (L.) Merr.] cultivars (Fiskeby V and Maple Arrow). The inhibition of CO2 assimilation was characterized by a simultaneous decrease in stomatal conductance (Gs) and intercellular CO2 concentration (Ci) in Maple Arrow, whereas a similar decrease in Gs in Fiskeby V occurred without any change in Ci. Dark chilling had little effect on total ribulose-1, 5-bisphosphate carboxylase/oxygenase (Rubisco) activity, Rubisco protein content or Rubisco activation state in the subsequent light period. Chilling reduced the abundance of the nocturnal Rubisco inhibitor, 2-carboxyarabinitol 1-phosphate, only in Fiskeby V. The abundance of Rubisco small subunit transcripts was enhanced in both cultivars as a result of dark chilling. Dark chilling decreased the maximal extractable activities and activation states of stromal fructose-1,6-bisphosphatase (FBPase) and NADP-malate dehydrogenase but had no effect on sucrose phosphate synthase or leaf sucrose and starch contents. It is concluded that dark chilling-induced limitations on CO2 assimilation are predominantly due to metabolic restrictions rather than to direct effects on electron transport reactions and that stromal FBPase is particularly susceptible to dark chilling. Ausführliche Beschreibung