LAUSR

Copper (Cu) is important for many aspects of plant function including photosynthesis. It has been suggested that photosynthesis, especially in young leaves is prioritized for Cu delivery after deficiency in hybrid poplar (Shahbaz et al. 2015). To determine relative Cu delivery prioritization, we enriched hydroponic plant growth media of Cu deficient poplar with 98% 65Cu and tracked Cu delivery after deficiency to young leaves, mature leaves, and stems. Young leaves acquired ~ 58% more 65Cu on day 1 and ~ 65% more 65Cu by day 3 compared to mature leaves. Additionally, stomatal conductance (gs) was measured on leaves for 6 weeks and during a 3-day 65Cu pulse resupply period. During deficiency, mature leaves maintained a higher gs than younger leaves but three days after Cu resupply the younger leaves that had recovered showed the highest gs. In conclusion, these results provide a quantitative understanding of how Cu is systemically transported and distributed to photosynthetic and stem tissues.