A review of dipterocarps - Center for International Forestry Research

Seed Handling 80
Table 3. Mean insect infestation statistics for species received
at Kew (Tompsett and Kemp 1996a, b).
Genus Mean
percent
infestation
more recently, species with OLDA seeds have been
considered. Successful long-term storage has been
achieved in the case of some OLDA species.
In the case of recalcitrant seeds, some methods
currently available are useful to ensure the survival of
seed material during extended field collection trips, for
planting and for storage in the short to medium term.
However, the methods cannot ensure a continuous supply
of planting materials throughout the long periods when
mother trees are not fruiting.
Work on dipterocarp seed storage is reviewed in the
Seed Physiology chapter but some practical storage
methods are briefly discussed.
Imbibed Storage in Media such as Sawdust,
Perlite and Vermiculite
Storage of recalcitrant dipterocarp seeds in sawdust,
ground charcoal, perlite and vermiculite has been
employed to maintain high moisture content. This is the
most commonly used method for prolonging recalcitrantseed
viability. With care, seeds can be kept viable in this
way for several months. Table 4 shows some of the work
carried out on imbibed storage but the limitations of the
method are:
a) a proportion of the seeds may germinate due to the
high moisture content under these conditions; and
b) in many cases, because of the difficulties in
controlling aeration and moisture content, necrosis
may occur and microbial infection may set in; seed
viability is then severely affected.
Storage in Airtight Containers
Dry seeds of the OLDA type have been successfully
stored in airtight containers. For example, Dipterocarpus
intricatus has been retained for 2829 days with no loss
of viability observed (Tompsett and Kemp 1996a, b).
Storage under a partial vacuum has been attempted
for seeds of the recalcitrant species Shorea robusta at
15°C (Khare et al. 1987); 54% viability after a period
of 49 days in storage was reported, beyond which further
storage resulted in the death of most of the seeds.
Unfortunately, moisture content was not measured during
storage so the extent to which this factor contributed to
viability loss is unknown. Seed storage in airtight
containers is not appropriate for recalcitrant-seeded
species as it leads to an increasing depletion of oxygen
in the containers, associated with progressive loss of
viability.
Storage in Inflated Bags with Different Gaseous
Environments
Sasaki (1980), working on recalcitrant-seeded
dipterocarps of Malaysia, reported that ventilation with
ambient air was essential for dipterocarp seeds to
preserve viability. For example, he found that the viability
of S. roxburghii (syn. S. talura) seed could be prolonged
to seven months with adequate ventilation.
Table 4. Examples of optimum recorded storage in various media for imbibed seed of recalcitrant-seeded Shorea,
Hopea and Parashorea species.
MC: moisture content.
Number of
species
examined
Number of
species
infested
Dipterocarpus 35 10 10
Shorea 16 18 12
Hopea 8 5 4
Parashorea 4 2 2
Dryobalanops 1 3 1
Species Source
Optimum storage recorded
Days Temp.
( o C)
Germination
(%)
MC
(%)
Medium
Shorea platyclados Tang (1971) 20 16 64 27 Vermiculite
Hopea ferrea Tompsett (1992) 300 16 40 30-50 Mainly perlite
Parashorea smythiesii Tompsett (1992) 317 18 46 45 Perlite
Shorea fallax Tompsett (1992) 50 21 50 40 Sawdust