UV reflectance patterns in the flowers of Australian native plants

Summary of final report on the Australian Flora Foundation funded project:

Dr B.R. Randell, Department of Botany, University of Adelaide

Grant Details    Final Report

The project was carried out during the spring and summer of 1988, in the Mt Lofty Ranges near Adelaide. The first part of the project involved perfecting a technique to record the UV-reflectance patterns. This was done successfully, and the technique was described in a paper published in the Newsletter of the Australian Systematic Botany Society; viz: Randell B.R. and B.C. Rowland (1989), A method for recording UV-reflectance patterns in flowers. Aust. Syst. Bot. Soc. Newsl. 59: 2-4

Using this technique, some 50 species of native plants, belonging to 37 genera, were surveyed. Fourteen genera contained species which showed UV reflectance in their flowers, 23 did not (Table). One genus contained species with and without reflectance [Cassia], and one family showed genera with and without reflectance abilities [Goodeniaceae].

In the Labiateae, a unique pattern of reflectance was evident. Petals of Prostanthera and Westringia were non-reflective, but spots and hairs within the throats of the flowers were reflective, so the flowers had, in effect, a bright spot near the reproductive organs.

All seven of the surveyed genera of the Papilionaceae showed evidence of UV reflectance, usually by having highly-reflective petals, with a non-reflective dark spot on the standard petal, near the reproductive organs. This corresponded closely with the dark spot on the petals visible to the naked eye. One species, Phyllota pleurandroides, did not have this visible dark spot on the standard. Nevertheless, it had a standard petal that was highly UV-reflective with a non-reflective dark spot at the base.

In the Goodeniaceae, fresh flowers of several species of Goodenia had highly-reflective petals, with a dark spot near the reproductive organs, while Dampieria rosmarinifolia was not reflective. Two species of Scaevola did not have reflective petals, but Scaevola crassifolia had petals which were slightly reflective. I also determined that flowers of dried herbarium specimens of Goodenia geniculata and Velleia paradoxa had highly-reflective petals and a conspicuous dark spot.

Within the Caesalpiniaceae, Senna charlesiana had reflective petals and a conspicuous dark centre, as did the introduced Cassia fistula. However, the native Cassia brewsteri had non- reflective petals.

The study revealed that UV-reflectance patterns may be common in Australian wildflowers.