Solution calcium concentration and application date effects on pod calcium uptake and distribution in florunner and tifton‐8 peanut

Abstract

Abstract Calcium is known to be passively absorbed by developing peanut pods directly from the soil solution. However, the factors influencing the distribution of Ca in the hull and seed have not been thoroughly studied. In this study of two peanut cultivars (Florunner and Tifton‐8) differing in hull and seed size, pod zones containing differing solution concentrations of Ca (0.025, 0.625, 1.875 and 3.75 mM) were separated from the rooting medium. The increased pod surface area, and hull thickness of Tifton‐8 resulted in greater uptake of Ca (mg pod‐1) and higher hull Ca concentrations when compared to Florunner. However, the thin hull of Florunner (0.59 nun, compared to 1.04 mm for Tifton‐8) resulted in a mean seed Ca contribution to total pod Ca uptake of 62.5% compared to 46.5% for Tifton‐8. Increasing the calcium level in the pod zone increased pod dry weight in both Florunner and Tifton‐8. Pods grown in 3.75 mM Ca for the first 30 days after initial pegging, followed by no Ca in the pod zone until 30 days after initial pegging, had significantly lower seed and hull Ca when compared to pods grown in a continuous supply of Ca. Electron microprobe analysis of pod sections revealed high Ca levels in the exocarp, mesocarp and the outer and inner surfaces of the testa. Both the highly lignified endocarp and the seed were significantly lower in Ca concentration than other pod layers. These results were confirmed by direct analysis of the tissue.