Influence of whole-plant net calcium influx and partitioning on calcium concentration in snap bean pods

Snap beans (Phaseolus vulgaris L.) are a food source that can contribute to dietary Ca requirements in humans. Factors which might enhance the concentration of Ca in snap bean pods have been investigated by measuring whole-plant net Ca influx, whole-plant Ca partitioning, and various growth parameters in two snap bean cultivars-Hystyle and Lahrador-that differ in pod Ca concentration. Plants were grown hydroponically under controlled environmental conditions while being provided adequate quantities of Ca. The concentration of Ca in pods (dry weight basis) was 52% higher in 'Hystyle', relative to 'Labrador', but net Ca influx throughout crop development or total plant Ca content at three stages of development were similar in both cultivars, demonstrating that pod Ca concentration differences were not due to differences in total plant Ca influx. However,'Hystyle' partitioned more total plant Ca to pods, relative to 'Labrador'. Calcium flux analysis also revealed that daily rates of whole-plant net Ca influx gradually declined throughout the period of pod growth in both cultivars; this decline was not related to whole-plant water influx. These results suggest that enhancements in whole-plant net Ca influx during pod growth and/or enhancements in the xylem transport of absorbed Ca to developing pods could increase the Ca concentration of snap bean pods.