Negative Halotropism Expressed by 3-input-3-output Tomato Root Arithmetic-Logic Gate

Root foraging is affected by environmental stimuli that dictates its propagation vector. Multiple-root interaction has the potential to provide relevant information about asynchronous systems like the natural soil system. In this study, tomato root was used as the information producing element in three fabricated three-input-three-output negative chemotropism root logic gates: synchronized (rNHG1), and desynchronized (rNHG2 and rNHG3). Specific output channels in rNHG2 and rNHG3 were fertigated with highly acidic sodium chloride solutions (30 mM and 75 mM) and only one channel was enriched with control solution providing additional desynchronization in the system computing the logic functions of $(x,y,z) = (y + z + x\bar z)$ for rNHG1, $(x,y,z) = (xy + xz,y + z + x\bar z)$ for rNHG2, and $(x,y,\bar z) = (\bar xyz + x\bar yz,y + z + x\bar z)$ for rNHG3 where x, y, and z represent the presence of root in the output channel, whereas negated variables indicate the absence of root. Overall, root channels fertigated with control nutrients for all root logic gates resulted in the same Boolean function and negative halotropism not only repelled the growth direction of root, but it also reduced the radicle, xylem, and phloem diameters. As the root channels become more desynchronized, root fresh and dry weights decreased due to energy utilization in bending response. Here, it was proven that plant roots manifest computation and signaling based on repellant chemical. Hence, the developed root logic provides valuable information that can be extended in developing plant root-based robotic applications.