Light Absorption and Carotenoid Synthesis of Pot Marigold (Calendula officinalis L.) in Response to Phosphorous and Potassium Varying Levels

In order to provide additional information on the effects of elemental deficiency on factors that affect plant production in medicinal plants, a factorial field experiment as randomized complete block design was conducted on Calendula officinalis. Treatments were four phosphorus levels (P2O5) including 0, 40, 80 and 120 Kg ha-1 and four potassium levels (K2O) as 0, 50, 100 and 150 Kg ha-1. Results showed that applied treatments had significant effects on petal carotenoids and the highest amount of ? - carotene obtained at 80 and 150 Kg ha-1 P2O5 and K2O, respectively. Effect of K2O on light interception and light use efficiency was significant and the highest radiation use efficiency achieved by applying 150 Kg ha-1 K2O. The highest yield of grain and dry flowers was recorded in the mixture of 80 and 150 Kg ha-1 P2O5 and K2O, respectively. In conclusion, using of K2O had greater effects on studied traits than P2O5.