Element uptake and physiological responses of Lactuca sativa upon co-exposures to tourmaline and dissolved humic acids.

Element migration and physiological response in Lactuca sativa upon co-exposure to tourmaline (T) and dissolved humic acids (DHAs) were investigated. Different fractions of DHA1 and DHA4 and three different doses of T were introduced into Hoagland's solution. The results indicated that T enhanced the contents of elements such as N and C, Si and Al in the roots and shoots. The correlation between TF values of Si and Al (R2  = 0.7387) was higher than that of Si and Mn (R2  = 0.4961) without the presence of DHAs. However, both DHA1 and DHA4 increased the correlation between Si and Mn, but decreased the one between Si and Al. CAT activities in T treatments were positively correlated to the contents of N and Al in the shoots, whose R 2 was 0.9994 and 0.9897, respectively. In the co-exposure of DHAs and tourmaline, DHA4 exhibited more impacts on element uptake, CAT activities, as well as ABA contents in comparison with the presence of DHA1 , regardless of the T exposure doses. These results suggested that DHAs have effects on mineral element behaviors and physiological response in Lactuca sativa upon exposure to tourmaline for the first time, which had great use in guiding soil remediation.