Cuticular wax load and surface wettability of leaves and fruits collected from sweet cherry (Prunus avium) trees grown under field conditions or inside a polytunnel

In this work, the effect of microclimate at the tree level inside a polytunnel and in an uncovered orchard of Prunus avium was studied through the observation of leaf and fruit micromorphology and the accumulation of cuticular waxes. Records of environmental parameters showed a significantly higher daytime temperature in the polytunnel (on an average 4°C), whereas the night temperature did not differ between treatments. Furthermore, photosynthetic active radiation and UV-B radiation inside the polytunnel were 43 and 97% lower, respectively, than the radiation measured outside. Leaves grown in the polytunnel had lower contact angles and higher load of cuticular wax per unit area, irrespective of cultivar. The impact of the microclimate was observed at the first sampling and did not increase with exposure time of leaves. Fruits of the cultivars ‘Souvenir’ and ‘Prime Giant’ grown outside had significantly less cuticular wax despite their delayed harvest time of 11 and 5 days, respectively. The relationship of higher cuticular wax load and lower contact angles of protected leaves might have practical importance for plant protection activities and the retention and uptake of leaf-applied agrochemicals.

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