Effect of titanium application on lettuce growth under Mn stress

Titanium (Ti) is classified as a beneficial element for plants. The aim of this study was to determine the effect of various Ti concentrations in nutrient solution on the alleviation of Mn-stress in hydroponically grown lettuce (Lactuca sativa L. cv. Zeralda). Plants were fertigated with nutrient solution of the following chemical composition (mg dm-3): N-NH4 < 10, N-NO3150, P-PO4 50, K 150, Ca 150, Mg 50, Fe 3.00, Mn 19.2, Zn 0.44, Cu 0.03, B 0.01, pH 5.50, EC 1.8 mS cm-1. The following Ti levels were tested (in mg Ti dm-3 of nutrient solution): 0 (control), 0.36; 0.72; 1.09 (denoted as Ti-I, Ti-II, Ti-III). The Ti source was Ti4+ ascorbate (Tytanit®). Ti had a positive effect on plant yielding: significantly the highest mean weight of a lettuce head and also the highest percentage of dry matter in leaves were found at Ti-II (+24.1% and 36.6%, respectively when compared with the control). Increasing Ti nutrition positively influenced the chlorophyll content (which was the highest at Ti-II and Ti-III), while it did not modify the Relative Water Content (RWC) in leaves. Despite the improved plant yielding, there were no differences in concentrations of macroelements (N, P, K, Ca, Mg) and some metallic microelements (Fe and Mn) in leaves. In turn, Ti nutrition significantly modified the nutrient uptake by aerial parts of plants, which increased up to Ti-II, while decreasing at Ti-III. The highest uptake of nutrients was recorded at Ti-II. Given the significant improvement in yield, Ti nutrition could be considered as an effective method to alleviate Mn-stress in lettuce.