Temporal variations of starch and mass in greenhouse tomato leaves under CO2 enrichment

Edwards, D., Ehret, D. and Jolliffe, P. 2011. Temporal variations of starch and mass in greenhouse tomato leaves under CO2 enrichment. Can. J. Plant Sci. 91: 167-177. A plant-based method of guiding CO2 dosing may improve the effectiveness of CO2 enrichment in commercial greenhouse tomato (Lycopersicon esculentum Mill) production. The temporal dynamics of two plant response indicators, leaf starch and leaf mass per unit area (LMA) were investigated in commercial and research greenhouses throughout day/night periods, as well as after the onset of CO2 enrichment. Both leaf starch and LMA tended to follow the diurnal profile of light but with 3 to 4 h of lag. The magnitude of the response, especially for starch, was affected by leaf position, CO2 enrichment and light. The highest starch contents were measured between 1400 and 1600 and the lowest levels occurred in the morning between sunrise and 1100. In many cases plants carried over substantial starch in upper leaves from one day to the next, indicating a carbon-surplus state. In the onset experiment leaf starch and LMA increased with 4 d of exposure to CO2 enrichment for mid and upper canopy leaves and continued to increase to the end of the monitoring period (7 d). Leaf starch contents and LMA are indicators of plant carbon status that show potential for guiding CO2 dosing.