Physiological Influences of Solid and Transparent Foliar Reflective Material Treatments in Almond Trees

The use of reflective materials has become commonplace in agriculture as the negative effects of drought, high temperature limitation, and solar radiation on plant physiology have been better understood. This study was conducted to compare the effects of different reflective materials on some physiological characteristics of almond trees. For this purpose, a method was developed in which two solid and two transparent reflective materials were foliar sprayed at two different doses in two different deficit irrigated almond orchards (cv. ‘Ferragnes’) in 2021. Net photosynthesis rate, stomatal conductance (gS), leaf temperature (T_leaf), relative water content (RWC), SPAD chlorophyll index, proline (P), malondialdehyde (MDA), as well as some macro- and micro-nutrient contents of leaf samples taken from the treated trees were examined. The applications reduced T_leaf from 2.7 to 7.9 °C. Generally, titanium dioxide (TiO₂) 0.50% and 0.25% doses consistently reduced T_leaf. The effect of reflective materials on photosynthesis was not clear. TiO₂ 0.25% consistently increased gS irrigated with ET₇₅ (irrigated at %75 crop evapotranspiration, full season). The RWC of TiO₂ 0.25% and 0.50% treatments was the highest in the first and second measurements. Micronized calcite (CaCO₃) 2.5% and 1.25% had a negative effect on RWC after the second treatment in severe drought conditions. However, there was no difference in ET₇₅. The treatments had a significant effect on SPAD. The results of kaolin (KAO) 5% and CaCO₃ 1.25% treatments were significant, but the result was not clear.