Beta-teleradiographic method for the estimation of chlorophyll concentration and the assessment of yield of some cowpea varieties (Vigna unguiculata (L.) Walp.)

Abstract

The objective of this study was to estimate the chlorophyll concentration in the leaves of "UCC-Early". "UCC- White" and "Bengpla·· varieties of cowpea by means of beta-teleradiography and spectrophotometry in order tn compare both methods. Yield parameters were also measured to enable further comparison of the methods. For the beta-teleradiography. the detached middle leaflet of the fourth trifoliate leaf trom the shoot apex of the main stem for each variety was placed on x-ray film in a protective cover (light tight cover) and was irradiated for up tn 45 minutes. The film density was determined for many sections on each variety at the sixth. seventh and eighth weeks after sowing. On the other hand, for the spectrophotometer analysis, the absorbency of chlorophyll from the cowpea leaves solutions were determined at a wavelength of 663nm for each of the cowpea varieties at the sixth, seventh and eighth weeks after sowing. The film density obtained from the beta-teleradiographic method indicated a high positive correlation with the absorbance determined from the spectrophotometric method. "UCC-Early" variety proved to be the best variety in terms of absorbance and optical density of film, followed by "UCC- White" and" Bengpla" varieties. These observations were in the order of the performance of the three varieties of cowpea in terms of grain yield and most of growth parameters in which "UCC-Early" recorded highest values followed by "UCC- White" and "Bengpla" varieties. Based on an accurate interpretation of this beta-teleradiographic method it rnay be possible to determine the economic yield of a plant before the harvesting stage.