This thesis examines a broad spectrum of physiological and silvicultural features of the highly
valued woody angiosperm hemi-parasite Santalurn album L. (Indian sandalwood) in relation to
its culture in plantations in northern Western Australia. Topics covered include allometry of
host and Santalum when grown as single plant pairings in both field and pot culture, nutritional
interactions between Santalum and beneficial and non-beneficial hosts, deleterious influences
of parasitism on plantation productivity and heartwood induction in young trees.
In Western Australia sandalwood is grown in the nursery for 8 months before establishment in
the field and during this time a pot host is introduced. Survival of Santalurn after field
establishment and its subsequent growth were significantly affected by the time of introduction
of the pot host, Alternanthera nana. Increasing the period of the Santalum : Alternanthera
association in the nursery to 109 days prior to field establishment markedly increased early
growth of Salztalum plantations. Introduction at 134 days prior to field establishment was
detrimental to the parasite as the Alternanthera was too vigorous for the small Santalum
seedlings. Santalurn plants had a lower root : shoot ratio lower when cultured with
Alternanthera in the nursery prior to field establishment compared with seedlings grown
without Alternanthera. Alterrzantlzera survival in the field was high when it had been grown
with Santalum for 12 weeks or more in the nursery prior to field establishment. After 1 1 weeks
in the field a strong negative linear relationship was shown between Santalunz root : shoot ratio
and Alternarzthera dry weight, and a positive linear relationship between Salztalum DW and
Alternanthera DW.
In Western Australia Santalu~n is established in the field with an intermediate host which
nourishes the parasite for 3-5 years before Santalum becomes dependent on its long-term host
and the intermediate host dies. The relationship between Santalum and several species tested as
intermediate hosts was examined by pairing Santalum seedlings with intermediate host
seedlings in 25 litre pots over a 10 month period. Growth of Santalum in pot culture with three
N2-fixing woody intermediate hosts (Sesbania forrnosa, Acacia traclzycarpa and A. ampliceps),
the woody non N2-fixing Eucalyptus camaldulensis or without a host varied considerably
between host treatments. Santalum growth was greater and root : shoot ratio lower for
seedlings grown with N2-fixing hosts compared with seedlings grown with E. carnaldulensis or
with no host. The root : shoot ratio of unattached Santalum increased exponentially over time,
whereas for all other treatments it remained relatively constant. An assessment of the value of
the hosts, termed host use efficiency, was computed as Santalum shoot DW / host shoot DW.
The host use efficiency of A. trachycalpa was greater than that of the other hosts.
The xylem sap of hosts and Sarztalum, and ethanolic extracts of endophytic tissue of haustoria
of Santalzkm were analysed for amino acids, organic acids and sugars to determine which
solutes were available in the host and which were extracted by the Santalum haustoria from
different hosts. There were similarities between Santalum and legume hosts in concentration
and composition of xylem sap amino acids, and in the amino acid spectra of the corresponding
Santalum endophytic tissue, whereas there were low N levels in xylem sap of E. camaldulensis
and dissimilarities between its amino acid composition and that of Santalum. This indicated
substantial direct intake of xylem N by Santalum from legume hosts but little N from the xylem
sap of E. canzaldulensis. There were high concentrations of asparagine, glutamate, aspartate
and y-amino glutamate in the xylem sap of the legume hosts, while in the non-legume the most
common amino acids were glutamate, aspartate, glutamine and arginine. Proline, the
predominant amino acid in the xylem sap of Santalum acurninatum growing in natural
vegetation (Tennakoon et al. 1997) was not detected or present in very low concentrations in
Santalurn album under these conditions. in the non-legume. Xylem sap of hosts contained
variable amounts of sugars (sucrose, glucose and fructose) and organic acids (fumaric, citric
and malic acid), whereas that of the parasitic Santalum was dominated by fructose and malic
acid. Dissimilarities in the proportional amounts of xylem-borne sugars and organic acids were
particularly evident for the E. camaldulensis : Santalum partnership.
Diurnal profiles of photosynthesis and transpiration of Santalum were closely similar to those
for corresponding hosts, whereas the midday leaf water potential of Santalum was consistently
more negative than that of corresponding hosts. Net photosynthesis and water use efficiency
was lower, but transpiration rates were similar to that of corresponding hosts. Nitrogen
concentrations of foliage of Santalum were higher than their hosts, and higher when on legume
hosts than on E. camaldulensis, or without a host. Nitrogen concentrations of Santalum foliage
was strongly correlated with net photosynthesis and water use efficiency of Santalum. 813C
values of shoot dry matter of Santalum were poorly correlated with instantaneous water use
efficiency of Santalum. Tissue water relations of Santalum were similar to that of water-stress
tolerant species.
S. formosa proved the best host followed by Acacia ampliceps and A. traclzycarpa based on dry
matter gains of Santalum. Estimates of heterotrophic gain of C of Santalum when grown in
association with the legume hosts over a nine week period indicate 57.9% of C was derived from A. ampliceps, 45.5% from A. trachycarpa and 34.6% fiom S. fomosa. Abundance of
haustorial attachments on roots of hosts was poorly correlated to Santalum shoot DW. Root
nodules of legume hosts were parasitised by a small proportion of Santalum haustoria.
Sodium and phosphorus concentrations of foliage of Santalum were generally higher than that
of corresponding hosts. Net gains of calcium, potassium, phosphorus and sodium in Santalum
was greatest when grown in association with hosts richest in the corresponding element. Net
losses or only small gains of calcium, potassium, phosphorus and sodium were recorded when
Santalum was grown with E. camaldulensis or without a host suggesting that Santalum has
limited ability for uptake of those minerals through its own root system.
To understand the effect of hosts on the productivity of a Santalum plantation a young
plantation of Santalum with three host species Cathormion umbellatum, Sesbania formosa and
Acacia anuera was selected to study the relationship between host quality and distance of hosts
from Santalunz on Santalum health. The selected plantation showed marked decline in health
and vigour of both Santalum and hosts between years 3 and 5. Parameters of the host plants
were assessed to select the best predictor of Santalunz crown health. The height and diameter
growth increment of Santalum between years 3 and 5 was strongly correlated to Santalum
crown health. Santaluin crown health and growth increased as host quality increased, and the
distance of host fiom Santalum decreased. An index, which combined host quality and the
distance of the host from that of Santalum, was a better predictor of Santalum crown health
than host distance or quality alone.
The age at which heartwood is initiated in Santalum album under plantation conditions in
Western Australia in unknown, but in natural stands in India it occurs between 10-13 years of
age (Rai 1990). A field experiment was conducted to determine the efficacy of stem injections
of paraquat andlor ethrel in initiating heartwood formation in five year old Santalum trees in a
plantation. Trees injected with paraquat alone had a significantly greater extension of induced
heartwood, both radially and vertically, than those trees injected with ethrel alone or distilled
water. Eight months after treatment with paraquat or ethrel or a combination of these
chemicals induced heartwood was formed, which had high lipid, and low starch and
polysaccharide concentrations compared to the sapwood. Induced heartwood from both
chemical treatments and their combinations contained total volatile oil and santalol oil (alpha
and beta santalol) concentrations that were equal to or greater than that of naturally formed
heartwood and greater than that of sapwood. Moisture content, and concentrations of K and
Mg, and in some treatments Ca of induced heartwood were significantly lower than that of sapwood.
The thesis concludes with a synthesis of the findings and suggestions for future research, with
special reference to mid-rotation aspects of Santaltrm plantation silviculture.
| Identifer | oai:union.ndltd.org:ADTP/221744 |
| Date | January 1998 |
| Creators | Andrew M Radomiljac |
| Publisher | Murdoch University |
| Source Sets | Australiasian Digital Theses Program |
| Language | English |
| Detected Language | English |
| Rights | http://www.murdoch.edu.au/goto/CopyrightNotice, Copyright Andrew M Radomiljac |
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