A. Palliotti et G. Bongi, FREEZING-INJURY IN THE OLIVE LEAF AND EFFECTS OF MEFLUIDIDE TREATMENT, Journal of Horticultural Science, 71(1), 1996, pp. 57-63
Foliar application of mefluidide, a synthetic plant growth regulator,
at 1000 ppm concentration on three year old potted olive plants cv. Fr
antoio, which is sensitive to frost, induced a hardening effect by inc
reasing 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 degrees C, K+, Na+ and
Ca++ concentration were lower in the effusate from mefluidide-treated
plant leaves than in controls. Electrolyte leakage studies and differe
ntial thermal analysis revealed that both the lethal freezing temperat
ure (LT(50)) and the threshold supercooling temperature were significa
ntly lower in mefluidide-treated than untreated plants. Clear water-so
aked areas and permanent browning of tissues were evident in the leave
s of treated and untreated olive plants at temperatures below LT(50) T
he combined action of these physiological effects reduced the lethal t
emperature in the leaves of mefluidide treated plants about 3.8 K belo
w that of control plants and shifted the leaf tissue LT(50) from -11.1
degrees C to -14.9 degrees C.