journal of forest science

asis of browning and changes in consistency of root tissue
(ig. 1).
The influence of different ways of autoclaving and
interval of second measurement on electrolyte leakage
Next, the influence of different duration of autoclaving
and second measurement on the rate of electrolyte
leakage was examined. No marked difference between
EL values was found. In this study, EL values slightly
decreased with longer time of autoclaving and interval
of second measurement. It probably means that a longer
time of autoclaving is necessary for leakage of all electrolytes.
On the other hand, there is in practice an applicable
(fast) method to find the physiological quality of
planting stock: sufficient time interval of autoclaving
10 min and allowing 24 h before second measurement. It
is suitable to use 24 h interval of second measurement
with respect to speed of the method, whereupon time for
total measurement of electrolyte leakage is 48 h. Also,
10 min interval of autoclaving is sufficient to destroy cell
membranes and to extract of cell sap in deionized water.
By using this methodology (10 min of autoclaving allowing
24 h before measurement) SCHÜTE and SARVAŠ
(1999) found strong correlations (r 2 = 0.97) between electrolyte
leakage from tap root and later regrowth of the
terminal shoot. This correlation was detected on container
and bare-rooted planting stock of oak after frost
(n = 15) and desiccation (n = 12) stress treatments.
The same results of the influence of different length of
autoclaving on EL from fine roots were reported MC-
KAY (1997, unpublished). On the other hand, DEANS et
al. (1995) concluded that allowing 5–7 days after treatment
for electrolyte leakage equilibration, followed by
autoclaving 90–120 min at 121°C and allowing 24 h before
measurement provides a reliable method for assessing
freezing injury in small pieces of leafless stem tissues.
Electrolyte leakage after stress treatment of the same
intensity on different dates
Changes of EL values were tested after stress factors
of the same intensity, acting on different dates. The highest
leakage was found for both stress factors in vegetation
period. This increase in vegetation period against
EL for planting stock in dormant status was about 40%
after desiccation stress and about 33% after frost stress.
COLEMAN et al. (1992) found that the average increase
in hardiness of four subalpine conifers from August to
December was 2.4 times for foliage and 1.4 times for
roots. The same results are reported in several studies in
which it is stated that planting stock in dormancy is hardier
than during vegetation period (MEXAL, CARLSON
1981; RITCHIE 1986; RITCHIE, SHULA 1984).
CONCLUSION
– Measurement of electrolyte leakage from tap root is
rapid, precise method for finding actual physiological
quality of planting stock at relatively low cost.
– The rate of electrolyte leakage can be influenced not
only by injury of cells but also by methodology of
measurement and therefore it is problematic to make
a comparison of results obtained by different methods
of measurement.
– It is necessary to use for determining the physiological
quality of planting stock the same method of measurement
of electrolyte leakage for all variants.
Acknowledgement
This study was carried out with financial support from
the Commission of the European Communities, Agriculture
and isheries (aIR) specific RTD programme CT
95-047: A European approach for assessing: regrowth
potential of woody plants: parameters for plant vitality
and dormancy of planting stock. The author thanks the
Germany Academic Exchange Service for PhD. fellowship
at orestry Institute in Escherode and thanks Z. Al-
Attasová for her English correction of the text.
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