Tipburn occurrence and growth of lettuce as affected by electrical field in a plant factory with artificial light

Tipburn occurrence of vegetables has become a serious problem in plant factories with artificial light, and therefore the commercial value of vegetables is significantly reduced. It is popularly agreed that calcium deficiency, low transpiration rate and fast growth rate, are the direct reason of tipburn occurrence in a closed environment. Thus, to improve plant growth and alleviate tipburn occurrence, an electric field generation system with an electric voltage of 15 kV was employed in the cultivation area. The electric field generation system for operating whole day was set up in this experiment. The treatment without electric field was used as the control (CK). Lettuce (Lactuca sativa L.) was chosen as a model plant. Tipburn occurrence of lettuce, calcium content of inner leaves and plant growth as affected by the electric field were investigated in the current experiment. The results showed that: 1) tipburn occurrence of lettuce plant was observed in the CK on day 15, while that under electric field was shown on day 18. Ratio of leaves with tipburn injury to total leaves was reduced by 61.8% under electric field than that under the CK; 2) calcium content of the newly developed lettuce leaves was 1.3 times greater by using the electric field than that of CK; 3) the fresh and dry weight of lettuce plant increased by 19.8 and 22.2% under the electric field on day 21 after transplant, compared with those under the CK, respectively. The above results indicated that the electric field can significantly improve lettuce growth and alleviate tipburn occurrence in a plant factory with artificial light.