Blossom-End Rot (BER) in tomatoes and sweet peppers is rarely caused by a simple lack of calcium in the rootzone; rather, it is a hydraulic partitioning failure. Because calcium is strictly phloem-immobile and translocated almost exclusively via the transpiration stream (xylem), excessive midday VPD diverts calcium to transpiring foliage, starving rapidly expanding distal fruit tissue.
1. The Calcium Accumulation Flux Equation
J_{Ca,fruit} = Q_{xylem,fruit} \times [Ca^{2+}]_{xylem}
Nighttime root pressure ($RH > 90\%$ under closed screens) plays a vital role by pushing calcium-rich sap directly into low-transpiring fruit clusters.
2. Interactive BER Risk Model
Quantify your calcium partitioning risk with our online tool: