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Biology, structure, and germination characteristics of kùa seeds (Alphitonia

neocaledonica, Rhamnaceae) used for re-vegetation in New Caledonia

Conference Paper · September 2007

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B. Fogliani

Institut Agronomique néo-Calédonien

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D. Saintpierre-Bonaccio1,2, C. Zongo1, C.R. McGill3, S. Bouraïma-Madjèbi1, B. Fogliani1* 1 M.A.Bio.M., University of New Caledonia ; 2 SIRAS Pacifique Society, New Caledonia ;

3 Institute of Natural Resources, Massey University, Palmerston North, New Zealand* corresponding author. Email bruno.fogliani@univ-nc.nc

IntroductionIn New Caledonia there is an increasing awareness of the importance ofusing native plants for re-vegetation, in particular, after mining exploitation.An understanding of the germination requirements of native seeds is vital todevelop successful land restoration procedures. We studied a range ofnative species and focused on kùa seeds. Alphitonia neocaledonica(Rhamnaceae), endemic to New Caledonia, is recognised as a pioneer plantand is traditionally used for re-vegetation of ultramafic rocks. However, littleis known on its germination characteristics enjoining the use of largequantities of seeds. To solve this problem, we investigated the biology,structure and germination characteristics of kùa seeds, in order tounderstand the parameters that inhibit germination and to optimise thegermination percentages.

MethodsMethods described by McGill et al. (2002) were used to determine moisturecontent, characterise FAMEs and analyse, by microscopy, internal structuresof the seed. Germination assays were performed as described by Fogliani etal. (2004). Classical techniques were employed to determine oil content (ISO659), total proteins (Lowry) and sugars (Roe).

ReferencesFogliani B, Bouraïma-Madjèbi S, Medevielle V, Pineau R (2004). Methods to promote germination of two Cunoniaceae species, Cunonia macrophylla and Geissois pruinosa from New Caledonia. Seed Science and Technology 32: 703-715.McGill CR, McIntosh JC, Outred HA, Fountain DW (2002). Seed storage and seed storage reserves in Chatham Island forget-me-not (Myosotidium hortensia, Boraginaceae). New Zealand Journal of Botany 40: 337-346.Sundar Rao K, Sino D (1992). Fatty acid composition of 20 lesser-known Western Australian seed oils. Journal of the Science of Food and Agriculture 58: 585-587.Tibagu M, Odén PC (2001). Effect of scarification, giberrelic acid and temperature on seed germination of two multipurpose Albizia species from Ethiopia. Seed Science and Technology 29: 11-20.

A. neocaledonica produces a hard, round, drupe (11-13mm) that turns black at maturity. The pericarp thendries and falls away, exposing two ovate black seeds(7-8 x 3-4 mm) covered by a red aril, each enclosed ina hard case (Fig. 1).

Composition of Alphitonia neocaledonica storage reserves

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Internal structures of the fruit and the seed aredescribed using light and electron microscopy. Theyrevealed an embryo with well-developed cotyledons,an endosperm and a thick seed coat responsible formechanical inhibition (Fig. 2).

Figure 1 : Photographic illustrations of A. neocaledonica fruitsand seeds.

Figure 2 : Transverse sections of seed observed by binocular (A),Light Microscopy with toluidine blue staining (B) and SEM (C).eb: embryo, ed: endosperm, sc: seed coat.

ConclusionsInternal structures of A. neocaledonica seeds and optimal germination conditions were described for the first time, showing they are orthodox oilseeds and should thussupport conservation under low hygrometry conditions. Assays to confirm this hypothesis are currently being carried out together with priming tests, using PEG and water.The roles of the different storage reserves during germination are also under investigation.At SIRAS Pacifique we are interested in improving growth of plantlets once the seeds have germinated have undertaken experimentations aiming to associate (using coatingmethods) endo-mycorrhize spores with pre-germinated seeds. Once introduced in the hydroseeding mixtures, we expect such seeds to be able to germinate concomitantlywith the mycorrhize spores.

98,93Total fatty acids (%)8,91Unidentified 29,61Unidentified 10,17Lignoceric (C24:0)0,57Behenic (C22:0)0,50Arachidic (C20:0)26,34a-Linolenic (C18:3∆9,12,15)27,72Linoleic (C18:2∆9,12)1,01Vaccenic (C18:1∆11)10,36Oleic (C18:1∆9)3,85Stearic (C18:0)0,35Palmitoleic (C16:1∆9)9,54Palmitic (C16:0)

% fatty acidCommon name (carbon number)

This mechanical inhibition is confirmed by manualscarification of the seeds, which leads to a germinationrate of 75% (compared to 1,25% without scarification).Seeds were also exposed to other pre-treatments: cold;H2SO4; hot water. The most effective and economic isan 80°C water bath (Fig. 3).

A. neocaledonica seeds can thus be considered as oily.Oil content is higher than that observed in theAustralian native A. excelsa seed (11,8%; Sundar Rao& Sino, 1992) but amongst average values forRhamnaceae. TEM observations of albumen andembryo cells showed the presence of lipid and proteinbodies (Fig. 6).

Figure 4 : Effects of temperature on germination of A.neocaledonica.

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Figure 3 : Germination of A. neocaledonica seeds after differenttemperature water baths (30 days from sowing).

Germination tests also showed A. neocaledonica seedsare photosensitive and the optimum temperature is25°C. At this temperature, time before onset ofgermination is 6-14 days (Fig. 4).

Table 1 : FAMES content of A. neocaledonica seeds.

GC analysis of FAMES derived from the lipid storagereserves revealed a high percentage of saturated andunsaturated C18 (70%), two of which (unidentifiedunder investigation) representing about 18% (Table 1).

Figure 5 : Composition ofA. neocaledonica storagereserves.

Moisture content (4,02%) shows the seeds areorthodox. Seed storage reserves were found to bemostly lipids (19,25%) and proteins (12,84%), sugarsrepresent 1,36% dry matter (Fig. 5).

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Figure 6 : TEM observations ofembryo cells. sg: starch grain, pb:protein bodies, lp: lipid bodies

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Biology, structure and germination characteristics of kùa seeds(Alphitonia neocaledonica, Rhamnaceae) used for re-vegetation in New Caledonia

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