Journal of the Royal Society of Western Australia, 87:135-138, 2004 
Fruit and seed development in two Hakea species (Proteaceae) 
P K Groom 1,2 & B B Lamont 1 
‘Department of Environmental Biology, Curtin University of Technology, GPO Box U1987, Perth WA 6845 
2 Centre for Horticulture and Plant Sciences, University of Western Sydney, Locked Bag 1797, 
Penrith South DC, NSW 1797 
(present address for corresponding author) 
El p.groom@uws.edu.au 
(Manuscript received: June 2004; accepted February 2005) 
Abstract 
Hakea erinacea and H. trifurcata are related taxa that release their annual seed crop within a year 
of fruit maturity (weak serotiny). Both species produce similar-sized woody fruits (follicles) that 
protect two winged seeds. Fruit and seed development was completed 180 days (H. erinacea) and 
215 days (H. trifurcata) after anthesis, with the fruits of both species reaching their maximum fresh 
mass during their 'green', non-woody state. This was associated with the commencement of wood 
formation in their fruit walls and the redistribution of certain nutrients (particularly phosphorus) 
from the fruit to developing seeds. Both H. erinacea and H. trifurcata retain chlorophyll in the walls 
of developing fruit, with H. trifurcata retaining chlorophyll in the mature fruit. This may have anti¬ 
herbivore properties whereby the developing green fruits are cryptically disguised within a 
background of similarly green leaves. 
Keywords: fruit chlorophyll, seed nutrients, seed protection, woody follicles 
Introduction 
Hakea erinacea Meissn. and H. trifurcata (Smith) R.Br. 
are related taxa (Barker et at. 1999) producing relatively 
small fruits (130-180 mg dry mass) compared with other 
species in the genus (Groom & Lamont 1996, 1997). Both 
species are weakly serotinous (minimal canopy seed 
storage) (Midgley et at. 1991), releasing most of their 
seeds annually from woody fruit (follicles) that open 
within a year of fruit maturing (Lamont et ah 1998, 
Groom et ah 2001). Each follicle possesses a longitudinal 
adaxial suture, which when ruptured exposes two valves 
each containing one compressed winged seed. 
Hakea fruits remain green from anthesis to near 
maturity, except for those species that develop very large 
woody follicles (e.g. H. platysperma). Previous work on 
the seed and fruit development of the closely related 
genus Grevillea suggests that translocation of mineral 
nutrients from the fruit to seeds occurs as the fruit 
matures (Hocking 1981, 1982). Proteaceous seeds are 
packed with nutrients (Pate et ah 1986) and parent plants 
are efficient in redistributing essential nutrients from 
their fruits to their seeds and hence to their seedlings 
(Kuo et ah 1982, Lamont and Groom 2002). 
An understanding of fruit and seed development will 
provide an insight into changes in nutrient content and 
biomass that occur as Hakea fruit develop woody walls. 
This paper records the development of fruits and seeds 
from anthesis to fruit maturity within two ecologically 
similar Hakea species (H. erinacea and H. trifurcata). The 
onset of wood formation (i.e. transition from the non- 
woody 'green' state) will be assessed in terms of changes 
in fresh and dry mass, partitioning of selected nutrients 
(N, P, K, Ca, Mg) between fruit and seeds, and 
chlorophyll content of the fruit wall. 
© Royal Society of Western Australia 2004 
Materials and Methods 
Fruits were collected from a population 
(approximately 150 plants) of H. erinacea shrubs in the 
Corymbia calophylla-Eucalyptus wandoo woodlands of 
John Forrest National Park (31°37’ S, 115°51 ’ E) 
between August 1992 and February 1993. H. trifurcata 
fruits were collected from a stand (approximately 80 
plants) in similar woodlands at Crystal Brook Reserve 
(31°59' S, 116°04' E), Kalamunda, between October 1992 
and March 1993. By counting annual stem increments, 
plants in each population were estimated to be 15-20 
years old. Fifty fruits per species were collected 
fortnightly beginning at the end of flowering 
(anthesis), with each collection representing a 
progressive stage of fruit development. Fruits were 
considered to be mature when there was no change in 
their dry mass and they contained fully developed 
seeds. For each collection, fruits (with seeds) had their 
fresh mass and dry mass (dried for 48 h at 60°C) 
recorded. After 90-100 days of development seeds 
were easily extracted from the developing fruit and 
weighed separately. 
For each collection, dried fruit and seed samples 
(including the wing) were ground and analysed for 
selected nutrients (N, P, K, Ca, Mg) by CSBP and 
Farmers Co., Perth based on 0.8 - 2 mg samples. N was 
determined by standard Kjeldahl digestion on bulked 
samples, whereas the remaining nutrients were 
determined from digestion in 9:1 nitric/perchloric acid. 
P was determined colorimetrically and cations (K, Ca, 
Mg) by atomic absorption spectrophotometry. 
Chlorophyll was extracted from five weighed samples 
per collection (5-10% w/v) of fruit material in N,N- 
dimethyl formamide and analysed 
spectrophotometrically using the extinction coefficients 
of Moran (1982). 
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