The Effect of Parameters Related to Soil Salinity on Madder (Rubinia tinctorum) Pigment Quality

The roots of the madder plant (Rubinia tinctorum) contain some pigments that can be used to produce the red dyes. In order to study the effect of salinity on alterations in the amount of plant pigment an experiment was conducted according to a completely randomized design with three replications. Based on the CIE XYZ color space model designed close to human color vision, the results showed that increasing soil salinity decreased the value of The lightness value parameter (L*), but the A* (redness and greenness) and B* (yellowness and blueness) values were increased with increasing soil salinity up to the level of 8 dSm-1. There was a significant positive correlation between A* value and Ca + Mg and a significant negative correlation between L* value and Ca+Mg at the 5% level. Fitting three nonlinear regression model to data, simulated and described the variation of colorimetric specification of woolen samples dyed under different madder dyes and salinity conditions. These models proved to be an appropriate and reasonable link between madder growth conditions and colorimetric specification of woolen samples dyed such as L*, A* and B* values. Due to the high resistant characteristics of madder to salinity, increasing salinity in the madder root zone lead to acceptable quality and efficiency of pigment production and to expand the possibilities for economic production of Rubinia tinctorum in soil salinity in the central arid region of Iran