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Juan M. Quintana, Helen C. Harrison, and James Nienhuis

Calcium is an essential element for human nutrition. The lack of it causes various problems, such as osteoporosis. Snap beans rank as good sources of calcium among vegetables and are well-liked by most teenagers. In this study, pod yield and Ca concentration were analyzed for 64 genotypes of snap beans, plus four checks. The experimental design was a 8 x 8 double lattice, repeated at two locations (Arlington and Hancock, Wis.). Snap beans were planted in June 1993 and machine-harvested 67 days later, in Aug. 1993. Calcium analyses were made using an Atomic Absorption Spectometer. Results indicated significant differences for pod Ca concentration and yield. Pod size and Ca concentration showed a strong negative correlation (R = 89.5). Clear differences among the locations were also observed. Results were consistent—high-Ca genotypes remained high regardless of location or pod size. Selected genotypes appeared to have the ability to absorb Ca easier than others, but this factor was not related to yield.

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Juan M. Quintana, Helen C. Harrison, James Nienhuis, and Jiwan Palta

Pod stomatal density and Ca concentration levels were analyzed for six commercial snap bean cultivars harvested at four planting dates in an attempt to find morphological traits that are related to cultivar differences in pod Ca concentration. The experimental layout was a randomized complete-block design with two replications per planting date, all grown in one location. Snap beans were planted at 1 week intervals beginning 9 June 9 1995 and were harvested in August. Sampling consisted of five pod sizes (1, 2, 3, 4, and 5 according to commercial standards) from each genotype. Stomatal countings were performed using a microscope linked to a television camera. Determinations for pod Ca concentration were made using an atomic absorption spectrophotometer. No differences were detected for pod Ca concentration among planting dates, although there were differences for pod Ca concentration and stomata density among cultivars. Pod stomatal density was positively correlated to pod Ca concentration (R 2 = 0.60), while pod maturity appeared to be negatively correlated to pod Ca concentration (R 2 = 0.37) and pod stomatal density (R 2 = 0.49).

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Juan M. Quintana, Helen C. Harrison, James Nienhuis, and Jiwan P. Palta

We have previously observed significant variation for pod Ca concentration among snap bean genotypes. In the present experiment, we compare pod Ca concentration between snap bean and dry bean genotypes. Eight snap bean cultivars and eight dry bean cultivars were chosen to be evaluated for pod Ca concentration in summers of 1995 and 1996 at Hancock, Wis. The experimental design consisted in randomized complete blocks with three replications in 1995 and six in 1996. Snap and dry beans were planted in June and hand-harvested in August for both experiments. Soil analysis showed 430 ppm of Ca in soil at time of planting. No additional Ca was applied. Plots consisted of 10 plants each. Harvesting was made by collecting a pooled sample of medium size pods from the 10 plants. Ca determinations were made using an atomic absorption spectrophotometer. Data was presented as mg of Ca per gram of dry weight, pooled from both years, and analyzed using SAS. Results reflected significant differences between genotypes. Checkmate (5.5) showed the highest pod calcium concentrations and Labrador (3.9) the lowest among snap beans. G0122 (5.1) resulted in the highest and Porrillo (3.6) the lowest within dry beans Results were consistent across years. Snap beans (4.6) presented significantly higher pod calcium concentration than dry beans (4.2). Apparently, snap bean genotypes have the ability to absorb calcium from the soil more efficiently than dry bean genotypes, and this phenomenon is not significantly influenced by environmental factors.

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Juan M. Quintana, Helen C. Harrison, Jiwan P. Palta, and James Nienhuis

To understand physiological factors associated with genetic differences for pod Ca concentration between snap bean genotypes, flow rate and Ca uptake of sieve sap were measured, as well as pod Ca concentration. Measurements for flow rate and Ca uptake were done at three developmental stages (fl owering and 1 and 3 weeks after) in two commercial snap bean cultivars (Hystyle and Labrador) grown aeroponically. Pods were collected 2 weeks after flowering only. Flow rate and Ca uptake sampling began 4 weeks after transplanting and consisted of: 1) decapitation of the plant at the first node; 2) covering the stem with pre-weighed dry cotton; and 3) removing the cotton, reweighing it, and saving it for Ca determination. Flow rate was defined as the difference in cotton weight (expressed as ml) per 17 hr divided by foliage mass. Ca uptake was defined as mg of Ca per total volume of sieve sap after 17 hr divided by foliage mass. Ca determinations were made using an atomic absorption spectrophotometer. A positive correlation between flow rate and total Ca uptake of sieve sap (R 2 = 0.90), flow rate and pod Ca concentration (R 2 = 0.47), and Ca uptake and pod Ca concentration (R 2 = 0.42) were found. Hystyle reflected 1.5 times more flow rate and pod Ca concentration than Labrador. Significant differences between genotypes for pod Ca concentration, Ca uptake, and flow rate were observed. Results were consistent across developmental stages.

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Juan M. Quintana, Helen C. Harrison, James Nienhuis, and Jiwan P. Palta

Flow rate, Ca content, and Ca concentration of sieve sap were measured at four developmental stages (flowering and 1, 2, and 3 weeks after flowering) in six commercial snap bean cultivars to better understand physiological factors associated with genetic differences for pod Ca concentration. Sampling began 5 weeks after greenhouse planting and consisted of 1) decapitation of the plant at the first node; 2) covering the stem with preweighed dry cotton; and 3) removing the cotton, reweighing it, and saving it for Ca determination. Flow rate was defined as the difference in cotton weight (expressed as milliliter) per 12 hours. Ca determinations were made using an atomic absorption spectrophotometer. Calcium content was defined as milligram of Ca per total volume of sieve sap after 12 hours. Concentration of Ca was the quotient of Ca content by flow rate (expressed as milligrams Ca per milliliter sap). A positive correlation between flow rate and total Ca content of sieve sap (R 2 = 0.83), flow rate and Ca concentration of sieve sap (R 2 = 0.36), and Ca content and Ca concentration (R 2 = 0.80) were found. Maturity appeared to be an important factor affecting flow rate and Ca influx in snap bean plants. Significant differences between genotypes for Ca content and flow rate were observed. High Ca genotypes reflected a high flow rate regardless developmental stage.

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Juan M. Quintana, Helen C. Harrison, James Nienhuis, Jiwan P. Palta, and Michael A. Grusak

To assess nutritional potential, pod yield, and Ca concentration of pods and foliage were determined for a snap bean population, which included sixty S1 families plus four commercial varieties. The experimental design was an 8 × 8 double lattice, repeated at two locations (Arlington and Hancock, Wis.). Snap beans were planted in June 1993 and machine harvested in August 1993. Calcium analyses were made using an atomic absorption spectrophotometer. Significant differences were detected in pod Ca concentration and yield among the S1 families. Pod size and Ca concentration were inversely correlated (R 2 = 0.88). Distinct differences between the locations were not observed, and higher Ca genotypes remained high regardless of location or pod size. Low correlation (R 2 = 0.21) between pod and leaf Ca concentration was found. Pods of certain genotypes appeared to have the ability to import Ca more efficiently than others, but this factor was not related to yield.