Abstract
The aim of the present work was to determine the relationship between photosynthetic pigments extracted in dimethyl sulfoxide (DMSO) and readings obtained by the portable chlorophyll meter, ClorofiLOG ® 1030, to generate mathematical models that are able to report the contents of chlorophyll and carotenoids in the leaves of the castor oil plant. This work was conducted at Embrapa Cotton, located in the city of Campina Grande, state of Paraiba, Brazil, in October 2010. For the indirect analysis, portable equipment was used to read leaf discs of different shades of green. The chlorophyll in these discs was then determined using a classical method: 5 mL of DMSO was added, the samples were incubated in a water bath at 70oC for 30 minutes, and a 3 mL aliquot was removed for spectrophotometric measurements at 470, 646 and 663 nm. The data were subjected to analysis of variance and regression analyses in which the readings obtained using the portable chlorophyll meter were the dependent variable and the photosynthetic pigments that were determined by the classical method were the independent variable. The results indicated that, with the exception of chlorophyll b, the ClorofiLOG ® 1030 portable chlorophyll meter estimated the concentration of photosynthetic pigments with high precision, thus saving time and the chemical reagents that are typically used in conventional procedures.
Highlights
For many plants, the chlorophyll content in the leaves is highly correlated to the nitrogen concentration and yield (SMEAL; ZHANG, 1994)
The aim of this study was to determine the relationship between the photosynthetic pigments extracted in dimethyl sulfoxide (DMSO) and the readings obtained from the portable chlorophyll meter, ClorofiLOG® 1030, to generate mathematical models that are able to report the contents of chlorophyll and carotenoids in the leaves of castor oil
The use of the leaf discs from the BRS Energia and BRS Paraguaçu cultivars indicated that there was a similar relationship between the degree of leaf greenness, as determined by the portable chlorophyll meter, and the chlorophyll a content, which was extracted by the classical method
Summary
The chlorophyll content in the leaves is highly correlated to the nitrogen concentration and yield (SMEAL; ZHANG, 1994). There is an interdependence between nitrogen compounds and chlorophyll (LARCHER, 2000). (MINOLTA CAMERA COMPANY, 1989) and the ClorofiLOG® Regardless of the instrument used, when the sensors receive the signal, they provide a single reading that is proportional to chlorophylls a and b and to the total in a dimensionless unit (FALKER AUTOMAÇÃO AGRÍCOLA, 2008; MINOLTA CAMERA COMPANY, 1989). According to Blackmer and Schepers (1995), the nitrogen that is absorbed in excess by the plant is not accounted for in the reading of the device because photosynthetic pigments do not assimilate nitrate
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