Dynamic Carbohydrate Supply and Demand Model of Vegetative Growth: Response to Temperature, Light, Carbon Dioxide, and Day Length

Predicting the growth response of seedlings from the environmental responses of photosynthesis and metabolism may be improved by considering the dynamics of non-structural carbohydrate (NSC) over a diurnal cycle. Attenuation of growth metabolism when NSC content is low could explain why some NSC is conserved through the night. A dynamic model, incorporating diurnal variation in NSC, is developed to simulate growth of seedlings hour-by-hour. I compare predictions of this model to published growth and NSC data for seedlings that varied according to temperature, light, day length, or CO₂. Prolonged-darkness experiments show a temperature dependent upper limit on the respiration capacity. Respiration is attenuated as NSC is depleted. Furthermore, when NSC is high at dawn, inhibition of photosynthesis could attenuate the accumulation of NSC under low temperature, high light, or high CO₂. These concepts are used to simulate plant metabolism and growth rates and diurnal variation of NSC in tomato seedlings under two light levels and various temperatures. Comparison of other results using the same model parameters show the dynamic model could predict results for starch and starch-less plants, and when growth was affected by CO₂ enrichment and day length.