Damage to leaf veins suppresses root foraging precision.

Premise Plants generally increase root growth in areas with high nutrients in heterogeneous soils, a phenomenon called foraging precision. The physiology of this process is not well understood, but it may involve shoot-root signaling via leaf veins. If this is true, then damage to leaf veins, but not to nearby mesophyll, would reduce plant foraging precision. Methods To test this hypothesis, we imposed two leaf damage treatments on Plantago asiatica and Prunus jamasakura, removing either the tip of each main vein or mesophyll tissue between the veins with a 3-mm-diameter hole punch. After 30 days or 20 weeks of plant growth, we measured root biomass in the soil in response to soil nutrient concentration. Results When leaf mesophyll was damaged, root biomass of both species was greater in nutrient-rich patches than in nutrient-poor patches. However, when leaf veins were damaged, root biomass was similar between patches. Conclusions These results suggest the importance of shoot-root signaling in plants, emphasizing that physiological processes are not necessarily restricted to single organs. The idea that herbivores that damage leaf veins may affect a plant's ability to selectively forage in high-nutrient patches is novel, with implications for natural and managed systems.