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It is widely known that various brush treatments can trigger alterations in tree morphology. However, less is known about associated changes in physiology under these treatments and how that may affect how follow up treatments should be applied. Therefore, the objective of this study was to determine how leaf-level stress indicators [gas exchange (photosynthesis (A), transpiration (E) and stomatal conductance (gs)) and pressure-volume parameters] in mesquite (Prosopis glandulosa Torr.) are affected by leaf area reductions caused by partial-top killing from aerial spraying with a mixture of clopyralid and triclopyr (10.7 oz + 8 oz ac-1). Leaf-level responses were measured monthly in summer 2017 in untreated control trees and individuals treated in 2007 and 2014. Rainfall prevented August pressure-volume measurements. Gas exchange measurements were taken at 900, 1200, and 1500 hr. On average, treated individuals had 22, 21, and 27% greater A, E, and gs, respectively, than untreated individuals. Gas exchange rates decreased from June to July and remained low in August. Daily average A decreased from 23.6 �mol CO m-2 s-1 in June to 14.2 �mol CO2 m-2 s-1 in August. From June to July, osmotic potential at full turgor (?FT), turgor loss point (?TLP), and leaf bulk modulus of elasticity (?) decreased by 11, 14, and 17%, respectively. However, capacitance at full turgor (CFT) and turgor loss point (CTLP) were unchanged. Results suggest that treated trees have a greater capacity for gas exchange which may result from alterations to the leaf:root area ratio or leaf:sapwood area ratio, and subsequent changes to water availability. Leaf-level gas exchange and pressure-volume characteristics appear to be coordinated and results suggest that mesquite utilizes osmotic adjustment to maintain gas exchange during times of low soil moisture availability. These findings are fundamental to understanding mesquite success following partial top-kill and will help guide future treatments.