|Stephens, Brian - BAYLOR COLL OF MEDICINE|
|Merhaut, Donald - USDA/ARS/CNRC|
Submitted to: Journal of American Society of Horticulture Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: March 26, 1996
Publication Date: N/A
Interpretive Summary: We are interested in increasing the amount of calcium in snap bean pods, to improve the nutritional quality of this commonly consumed vegetable. To understand what goes on inside the plant, we studied two types of snap bean, Hystyle and Labrador, which have different concentrations of calcium in their pods. Because calcium enters the plant through the roots, we investigated whether total calcium uptake into the plant was related to differences in pod calcium concentration. Plants were grown in a hydroponic nutrient solution under controlled conditions with a sufficient calcium supply. When they were harvested, we separated the plants into parts and quantified the amount of calcium to determine how it was distributed within the plant, and in particular, in the pods. We found not differences in total calcium uptake into the plants, but Hystyle, the high- calcium variety, was found to move more of its absorbed calcium into the pods. We also learned that at the time that pods are developing on the plant, the plants start to absorb less calcium through their roots. These results suggest that it is possible to increase the calcium in snap bean pods, by improving the whole-plant absorption of calcium during pod growth, or by improving the movement of absorbed calcium to the growing pods. That's encouraging because US consumption of dairy products, the main source of dietary calcium, is decreasing and we need to find other food sources to provide adequate calcium to people for strong bones and good health.
Technical Abstract: Snap beans (Phaseolus vulgaris L.) are a food source which can contribute to dietary Ca requirements in humans. In order to understand the factors which might enable us to enhance the Ca concentration of snap bean pods, we emeasured whole-plant net Ca influx, whole-plant Ca partitioning, and various growth parameters in two snap bean cultivars ("Hystyle" and "Labrador") which differ in pod Ca concentration. Plants were grown hydroponically under controlled environmental conditions while being provided adequate quantities of Ca. Although pod Ca concentration (dry weight basis) was 52% higher in "Hystyle", relative to "Labrador", there were no differences between cultivars in net Ca influx throughout crop development or total plant Ca concentration differences were not due to differences in total plant Ca influx. However, there was a significant difference in the percent of total plant Ca partitioned to pods, with "Hystyle" partitioning more than "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.