Effect of highly processed calcined kaolin residues on apple water use efficiency

• Published in: Scientia horticulturae 2016-06, Vol.205, p.127-132
• Main Author: Glenn, D.M.
• Format: Article
• Language: English
• Subjects: apples; application rate; Biomass; carbon; Carbon isotopic discrimination; Evapotranspiration; Fruit yield; Gas exchange; horticultural crops; insects; kaolin; leaves; lysimeters; Malus domestica; Malus x domestica; mechanism of action; particle films; Photosynthesis; Radiation use efficiency; stomatal conductance; temperature; Transpiration; trees; vapor pressure; water use efficiency
• ISSN: 0304-4238; 1879-1018
• DOI: 10.1016/j.scienta.2016.04.022

•Increasing water use efficiency (WUE) is a strategic goal of agriculture.•The study evaluated particle film (PKPF) effects on whole tree WUE.•WUE was negatively correlated with fruit yield and total biomass.•Apple trees treated with PKPF had higher yield but lower WUE.•PKPF reduced stress and increased yield in apple at the cost of reduced WUE. Processed calcined kaolin particle films (PKPF) have been shown to repel some insects and reduce various environmental stresses often resulting in improved yield and quality of horticultural crops. PKPF studies in the literature have various water use efficiency (WUE) responses. The purpose of this study was to evaluate 2 application rates of PKPF (3% and 12%) on the whole tree water use efficiency and compare gas exchange values with carbon isotopic discrimination and seasonal water use efficiency in order to determine if there are consistent effects on WUE in apple and infer the mechanisms of action. Fruit yield and total biomass influence WUE whether WUE is measured directly in whole plant chambers, estimated by biomass/unit evapotranspiration, or Δ13C. Δ13C analysis of WUE generally found that the untreated control had lower values and therefore higher WUE than PKPF treatments. Whole plant gas exchange analysis of WUE generally lacked the sensitivity to identify the treatment differences observed using Δ13C analysis and those treatment differences identified were contrary to Δ13C analysis. A lysimeter study supported the reduced WUE of PKPF treated plants by demonstrating increased E with a range of PKPF residue amounts. The lysimeter results suggest that for well-watered and presumably non-stressed conditions, gas exchange is limited by leaf temperature and the concomitant leaf-air vapor pressure deficit that influence stomatal conductance. When leaf temperature is reduced by PKPF, the response results in increased stomatal conductance and gas exchange, as measured by increased E. The reduction in WUE by PKPF treatment is balanced by an increase in overall gas exchange and increased yield and quality.