Carbon balance of a whole tomato plant and the contribution of source leaves to sink growth using the 14CO2 steady-state feeding method

To clarify the entire carbon balance of a young tomato plant and the contribution of each leaf to sink growth, the carbon balance of each leaf was quantitatively measured using the 14CO₂ steady-state feeding method to quantitatively measure the photosynthesis, translocation, distribution and respiration of newly fixed 14C. The entire carbon balance of the whole plant was calculated by adding the data of each leaf. The total amount of carbon fixed by all source leaves was 70.2 mg. Of this amount, in a 24-h period, 29% was accumulated in the sinks, 28% remained in the source leaves and 42% was respired. Of the total amount of carbon accumulated in the sinks, the proportion accumulated in the shoot apex, stem and roots were 27, 40 and 29%, respectively. The third and fourth leaves contributed about 30–40% of the total growth of the main sinks. The distribution pattern of each leaf to the shoot apex of the plant was greatest in the first leaf and decreased with decreasing leaf age, whereas it showed an opposite trend in the roots.