CHROMIUM AND WHEAT STRAW EFFECTS ON GROWTH AND PHYSIOLOGICAL CHARACTERISTICS OF SWISS CHARD (Beta vulgaris L.)

Swiss chard (Beta vulgaris L.) is a widely spread promising leafy crop in Iraq, where majority of farmers utilized sewage water for irrigating chard, resulting in health hazards, particularly from heavy metal contaminants including chromium (Cr). This study employed a factorial experimental design to examine the effects of Cr concentrations (0, 5, 10, or 15mg.kg-1 soil) using potassium dichromate (K2Cr2O7) as a source of the Cr, combined with different concentrations of wheat straw (WS) (0, 1, and 2% w/w) on the growth and certain physiological and biochemical traits of the plant. The results showed that the administration of Cr at 10mg.kg-1 concentration significantly increased the percent of seed germination (83.33%), while the use of WS reduced the germination rate. Most vegetative growth characteristics responded inversely to increasing wheat straw percentage, but root performance was enhanced with Cr application of Cr. A high straw percent of 2% diminishes the performance of both roots and shoots in comparison to plants without additional WS, with the exception of leaf thickness. Shoot and root dry matter was higher in Cr15mg.kg-1. Photosynthetic pigments non-significantly affected by application of Cr and significantly decreased by added straw. Applications of Cr and WS reduced the activity of peroxidase enzyme, ascorbic acid, and the percent of total carbohydrate significantly relative to no Cr and WS-treated plants, with the exception of proline levels. This study has indicated that Cr and the phytotoxic effects of wheat straw on chard can be further utilized for sustainable chard cultivation.