Comparison of Corn and Rice Sensitivity to Cyanobacterial Extract and Anatoxin-a in Soil and Hydroponic Media

Cyanobacterial toxins (cyanotoxins) produced in harmful algal blooms are toxic to eukaryotic cells. Plants exposed to cyanotoxins through irrigation can accumulate toxins and have decreased yields, so an understanding of the effects of cyanotoxins on major crop plants is important. Although the effects of some cyanotoxins on growth and photosynthesis of common agricultural crops have been studied, how cyanotoxin uptake may be impacted by differences in root anatomy has not been studied. Hence, we exposed corn and rice, plants lacking and possessing a constitutively well-developed root exodermis, respectively, to cyanobacterial extracts or pure anatoxin-a to test how root structure impacts cyanotoxin sensitivity. We conducted three comparative experiments: (1) a pot study in which corn and rice were watered with cyanobacterial lysed-cell extracts, (2) a hydroponic study wherein plants were treated with cyanobacterial extracts, and (3) a study wherein plants were grown in pots and watered with pure anatoxin-a. We hypothesized that the constitutive exodermis produced by rice would make rice plants less sensitive to cyanotoxins than corn. However, for all three experiments, photosynthesis, chlorophyll, and growth of corn and rice plants were reduced when roots were exposed to either extracts or anatoxin-a, compared to non-treated controls, although corn plants were affected sooner and/or more dramatically than rice. Our results indicate the root exodermis of rice did not prevent cyanotoxin uptake by roots nor prevent cyanotoxin effects.