Vol. 71 No: 1

Title:
Freezing Injury in the Olive Leaf and Effects of Mefluidide Treatment

Authors:
A. PALLIOTTI and G. BONGI

pp: 57-64

Abstract:
Foliar application of mefluidide, a synthetic plant growth regulator, at 1000 ppm concentration on three year old potted olive plants cv. Frantoio, which is sensitive to frost, induced a hardening effect by increasing the freezing resistance without provoking phytotoxic effects. The main effects of mefluidide treatment seem to be related to induced water stress caused by a reduction in the relative water content (10.5%) and water potential (0.75 MPa) in the leaves and to an increase in the stability of biological membranes. At -18°C, K⁺, Na⁺ and Ca⁺⁺; concentration were lower in the effusate from mefluidide-treated plant leaves than in controls. Electrolyte leakage studies and differential thermal analysis revealed that both the lethal freezing temperature (LT₅₀) and the threshold supercooling temperature were significantly lower in mefluidide-treated than untreated plants. Clear water-soaked areas and permanent browning of tissues were evident in the leaves of treated and untreated olive plants at temperatures below LT₅₀. The combined action of these physiological effects reduced the lethal temperature in the leaves of mefluidide treated plants about 3.8 K below that of control plants and shifted the leaf tissue LT₅₀ from -11.1°C to -14.9°C.

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