Effect of lithium and lanthanum on herbicide induced hormesis in hydroponically-grown cotton and corn

Pretreatment of hydroponically-grown cotton and corn with lithium (Li+) and lanthanum (La3+) chlorides, respectively, inhibited 2,4-dichlorophenoxyacetic acid (2,4-D) and metribuzin [4-amino-6-tert-butyl-3-methylthio-1,2,4-triazin-5(4H)-one (MTZ)]-induced hermetic growth in both plant species. Lithium chloride proved to be a more effective inhibitor of hermetic growth. This may be due to the fact that the Li+ ion readily crosses cell membranes and interferes with calcium (Ca2+) metabolism Lanthanum, on the other hand, has a relatively high affinity for specific sites in various types of Ca2+ channels and can displace Ca2+ from the cell wall, but cannot penetrate the cell membrane via the channel pore. Thus It acts as an inhibitor of Ca2+ channel activity and regulation. This work provides indirect evidence that a Ca2+ influx is involved in a hermetic (growth stimulation) response by cotton and corn plants when exposed to sublethal dosages of herbicide.