Tree architecture of pillar and standard peach affect canopy transpiration and water use efficiency

• Whole plant gas exchange of standard and pillar peach architectures was measured.
• There was no genetic difference in gas exchange mechanisms between trees.
• Pillar architecture had greater transpiration than standard.
• Pillar architecture may require additional irrigation in order to maximize quality.

The development of productive high density peach orchards is often limited by the excessive vegetative growth of the trees that reduces productivity and quality. Dwarfing rootstocks are not available but upright tree architectures have been developed for high density peach production. The purpose of this study was to determine the water use efficiency of upright pillar and standard architecture peach trees in a production setting in order to understand the factors that differentiate transpiration and water use efficiency of the two tree architectures.There were no differences in leaf area index (LAI) of the pillar and standard types but the standards architecture had significantly greater leaf area density (LAD) than the pillar. There was no significant difference in the photosynthetically active radiation (PAR) response of photosynthesis (A) and transpiration (E) for the pillar and standard trees over a range of LAI's and vapor pressure deficits (VPD) for the 3 year period indicating that there was no genetic difference in gas exchange mechanisms between the genotypes of the two tree architectures. For high light conditions, the pillar and standard trees had a similar and non-significantly different E: VPD relationship for LAI < 2.25, however, for LAI > 2.25, the pillar had a significantly (P = 0.05) greater E than the standard architecture at similar VPD levels due to the decreased LAD of the pillar architecture that more effectively distributed light within the canopy. The increased illumination and interception of PAR by the pillar canopy increased both photosynthesis and transpiration at the same WUE as the standard. The present work demonstrated that as pillar growth types are integrated into production systems, more research will be needed to efficiently schedule the water needs of the pillar architecture in order to maximize fruit size and quality due to the reduced LAD of this tree architecture and the greater illumination of the canopy interior.