O. Leprince et al., THE EXPRESSION OF DESICCATION-INDUCED DAMAGE IN ORTHODOX SEEDS IS A FUNCTION OF OXYGEN AND TEMPERATURE, Physiologia Plantarum, 94(2), 1995, pp. 233-240
From the premise that desiccation-induced damage is associated with a
free-radical mechanism of injury, we address the hypothesis that expre
ssion of desiccation damage is dependent on metabolism. The effects of
temperature and O-2 concentration on the expression of damage were st
udied in germinating bean (Phaseolus vulgaris L. cv. Pole Kentucky Won
der) axes and maize (Zea mays L. cv. Kelvedon Glory) radicles submitte
d to flash drying. Damage in desiccation-tolerant and -intolerant mate
rial was assessed by measurements of electrolyte leakage and accumulat
ion of a stable free radical. In desiccation-tolerant material leakage
rates remained low during water removal. In contrast, in desiccation-
intolerant tissues, leakage profiles revealed the presence of a critic
al moisture content below which leakage rates increased sharply. In th
e desiccation-intolerant stage, a highly significant correlation was f
ound between critical moisture contents and temperatures of drying. Th
e concentration of the stable radical was lower if tissues were dried
below 15 degrees C and higher when tissues were dried at 30 degrees C
and above. Both leakage and build up of free radicals were highly sens
itive to O-2 concentrations: damage was lower when tissues were dried
in the presence of N-2, but increased several-fold when tissues were e
xposed to O-2 concentrations between 2 and 100%. In contrast, neither
temperature nor O-2 concentrations affected electrolyte leakage in des
iccation-tolerant samples. Treatment with a respiration inhibitor (KCN
) prior to drying reduced the desiccation sensitivity of tissues, as n
oted by a reduction of the critical moisture content. We conclude that
the expression of desiccation damage depends on the drying history an
d that factors that limit metabolism also reduce the incidence of desi
ccation injury.