The Effect of Phosphorus and Root Zone Temperature on Anthocyanin of Red Romaine Lettuce

In this study, phosphorus (P) strength [(full strength: 1x-P, half strength: 0.5x-P and zero strength: 0x-P)] and root zone temperature (10 and 15 degrees C RZT) were investigated in red romaine lettuce to determine their effects on anthocyanin content. This experiment was conducted using a deep-flow technique (DFT) hydroponic system in a greenhouse during the winter in Gangwon province in the Korea Republic. The treatments were 1x-P (15 and 10 degrees C RZT), 0.5x-P (15 and 10 degrees C RZT) and 0x-P (15 and 10 degrees C RZT). The results showed that the P (phosphorus), K (potassium) and Ca (calcium) accumulation contents were lower in the 0x-P -treated red romaine lettuce leaves than in the other treatments. The maximum red romaine lettuce yields per plant, leaf number and leaf length were exhibited during the 1x-P at 15 degrees C RZT treatment. In 0x-P at 10 degrees C, RZT treatment showed lower leaf color values of L*, b*, chrome, oh and higher leaf color a* values. Moreover, in the 0x-P treatment at 10 degrees C RZT, the leaf chlorophyll content (SPAD), chlorophyll a, chlorophyll b and chlorophyll total were the lowest. Anthocyanin content was the highest in the 0x-P treatment, followed by 0.5x-P and 1x-P treatments at both 15 and 10 degrees C RZT. Regardless of the P intensity treatment, anthocyanin content was higher at 10 degrees C RZT than at 15 degrees C RZT. In summary, the 1x-P at 15 degrees C RZT treatment is the best for red romaine lettuce leaf yield, and the 0x-P at 10 degrees C RZT treatment is the best for lettuce leaf anthocyanin content.