A new woody perspective on copper homeostasis: systemic copper transport and distribution, effect of copper on lignification, and water transport in hybrid poplar
Date
2022
Authors
Hunter, Cameron Ross, author
Pilon, Marinus, advisor
Gleason, Sean, advisor
Pilon-Smits, Elizabeth, committee member
Argueso, Cristiana, committee member
Bush, Daniel, committee member
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Abstract
Copper (Cu) is an essential micronutrient for plants. Chapter 1, as background for this dissertation, reviews the functions and homeostasis of Cu. We know at the cellular level how Cu is delivered to target proteins in the chloroplasts, thus explaining in a large part why Cu deficient plants have reduced photosynthetic capacity. However, Cu is also a cofactor of lignin polymerization enzymes that affect cell wall and xylem structures required for water and mineral transport. How Cu deficiency affects water transport, mineral nutrition, and photosynthesis at a whole plant level is underexplored. To address this knowledge gap, we used hybrid white poplar as a model. In chapter 2, a stable isotope method to trace Cu movement in poplar tissues was coupled with analysis of photosynthesis and stomatal conductance. Upon resupply of Cu, priority targets identified were stems and younger leaves which recovered quickly and was associated with higher stomatal conductance. In chapter 3, the effect of Cu deficiency on the elemental composition of leaves and stems of different age were analyzed. Interestingly, tissue type and age, as well as Cu deficiency, were found to all significantly affect within-plant nutrient partitioning patterns. In chapter 4, the effects of Cu deficiency on cell wall chemical composition and water transport traits were determined. Although Cu deficiency strongly affected cell wall chemistry, it did not significantly impact hydraulic capacity nor the density and size of xylem vessels in stems. However, Cu deficiency resulted in markedly stiffer mesophyll cell walls, possibly arising from changes to cell wall chemistry or structure. Together, these results, as discussed in chapter 5, indicate that although xylem lignification was adversely affected by Cu deficiency, the water transporting vessels remained largely unaffected, thus allowing efficient recovery. This work opens new avenues to explore the effects of plant nutrition on whole-plant physiology and function.
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Subject
copper
plant physiology
nutrient homeostasis
anatomy