Canopy profiles of starch and leaf mass per area in greenhouse tomato and the relationship with leaf area and fruit growth

Better knowledge of patterns of carbon allocation in plants growing in CO2-supplemented atmospheres may help to guide more efficient management of CO2 applications in tomato greenhouses. Leaf starch and LMA (leaf mass per unit area) were investigated in commercially grown greenhouse tomato plants to determine the distribution and influence of leaf area and fruit load on these measures.Leaf starch concentration and LMA exhibited similar profiles for the upper but not the lower shoot canopy. Maximum leaf starch was 10–20 g m−2 for uppermost leaves and then declined rapidly with canopy depth, becoming negligible for leaves mid-canopy and lower. The canopy profile for LMA usually exhibited a linear decline with canopy depth, falling from 60 to 20 g m−2. Accordingly, the relationship between LMA and leaf starch was stronger for upper canopy leaves. Maximum starch on a per leaf basis occurred in the top third of the canopy where leaves were close to full expansion. This was also the region where fruit growth was lowest. We concluded that leaves in canopy positions 7–9 are likely the most informative of plant carbon status. These leaves are high enough in the canopy to accumulate starch and are adjacent to fruit of significant growth rate.