A review of dipterocarps - Center for International Forestry Research

Seed Physiology 63
Table 4. Lowest-safe moisture content values (wet weight basis) for mature seeds*.
Species Source LSMC (%)
Dipterocarpus alatus** Tompsett (unpub.) 25
Shorea siamensis Tompsett (unpub.) 51***
Shorea singkawang Yap (1986) 55
Shorea xanthophylla Tompsett (unpub.) >41***
Stemonoporus canaliculatus Tompsett (unpub.) 43***
Vatica umbonata Mahdi (1987) 74****
*: no slopes and intercepts available for these species;
**: seed is OLDA (orthodox with limited desiccation ability);
changes accompanying loss of viability of S. robusta
have also been reported (Nautiyal et al. 1985).
Some authors have confused the effects of
desiccation itself with the effects of ageing; in order to
determine the effects of ageing, moisture contents
should be kept constant. However, in studies by Song et
al. (1983) on Hopea hainanensis it is clear that
desiccation effects per se were being examined. At 36%
moisture content the ultrastructure was intact, but on
desiccation to 26% moisture content, which severely
reduces germination percentage, various changes were
observed. Vesicles appeared in the cytoplasm, vacuolar
membranes ruptured and cell contents became less
distinct. Cell walls and cytoplasm became separated and
nuclear membranes could not be distinguished from the
nucleolus. These changes illustrate a general
deterioration of cellular structure rather than an effect
confined to the cell membrane. In a further study (Song
et al. 1986), desiccation to 31% was shown to disturb
the ribosomes and endoplasmic reticulum, but these
changes were reversed on re-hydration.
More recently, Krishan Chaitanya and Naithani
(1994) measured changes in superoxide, lipid
***: based on at least 25 seeds per germination;
****: unusually high value.
peroxidation and superoxide dismutase for seeds of S.
robusta during desiccation. They concluded that the loss
of viability observed may be caused by the cumulative
effect of peroxidation products of polyunsaturated fatty
acids and peroxidation of the membrane lipids.
Storage Physiology
Some aspects of seed storage are considered elsewhere:
practical aspects, including the effects of gases, are
discussed in Chapter 4; chilling physiology is considered
above under germination effects. Topics discussed below
include the following: best recorded storage periods; use
of viability constants; the significance of oil contents;
some aspects of tissue culture; and various associations
with storage physiology.
Best storage records
An up-to-date summary of best storage records is given
in Table 5. These records should not be confused with
practical recommendations; if the recommended storage
conditions were employed, longer storage would be
expected in many cases. The best record for an OLDA
species is 2829 days for Dipterocarpus alatus and the