LIGHT QUALITY AND INTENSITY EFFECTS ON THE GERMINATION OF SPECIES FROM THE JARRAH (EUCALYPTUS-MARGINATA) FOREST OF WESTERN-AUSTRALIA

Eucalyptus marginata Donn. ex Sm. (jarrah) produces a canopy that redu ces light intensity, but has only minimal effects on the relative prop ortions of particular wavelengths (light quality). Under controlled la boratory conditions, variation in light quality did not affect the ger mination of the representative jarrah forest species. In Eucalyptus ma rginata, E. calophylla Lindley, Acacia drummondii subsp. candolleana L indley, and Kennedia prostrata R.Br., however, percentage germination under controlled laboratory conditions was greater in full darkness an d seven restricted wavelength treatments than in full white light. Dif ference in response between full white light treatment (86 mu mol m(-2 ) s(-1)) and the s restricted wavelength trials (2-8 mu mol m(-2) s(-1 )) indicated a possible effect of light intensity. Compared with compl ete darkness and a white light intensity of 1 mu mol m(-2) s(-1), whit e light intensities of 26 and 146 mu mol m(-2) s(-1) reduced germinati on percentage in the canopy species, E. marginata, E. calophylla, and the understorey species, Acacia lateriticola Maslin, Bossiaea aquifoli um Benth., Gompholobium knightianum Lindley, G. marginatum R.Br., G. t omentosum Labill. and Sphaerolobium vimineum Smith. By comparison with dark conditions, no light-inhibited germination at 146 mu mol m(-2) s (-1) was recorded for Acacia drummondii subsp. candolleana, Chorizema ilicifolium Labill., Kennedia coccinea Vent. and Xanthorrhoea gracilis Endl. An ability to sense light and remain dormant is adaptive in rel ation to seed burial and a subsequent increase in the survival potenti al of seedlings due to greater moisture availability. This light-sensi ng capacity was most prevalent in the small-seeded (< 10 mg) species o f this Mediterranean-type climate forest. Most of the small-seeded spe cies are likely to be buried by ants facilitated by elaiosomes or by f alling into minute cavities in the gravelly soils of the jarrah forest .