Flow Rate as a Major Physiological Factor Influencing Calcium Content on Six Commercial Cultivars of Snap Beans (Phaseolus vulgaris L.)

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  • 1 Dept. of Horticulture, Univ. of Wisconsin–Madison, Madison WI 53706

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 (R2 = 0.83), flow rate and Ca concentration of sieve sap (R2 = 0.36), and Ca content and Ca concentration (R2 = 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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