Chromosome numbers are given of about 100 species of Solanum native, naturalized or cultivated in Australia, the majority of them new records. The origin and distribution of polyploid races of two species is briefly discussed.

AbstvactThe contents of the steroidal alkaloid solasodine and of solasodine-like alkaloids in samples of 85 native Australian Solanum species have been determined. Leaf, stem and fruit of 74, leaf and stem of seven, and leaf only of four species were examined. Samples were extracted with ethanol, the resulting glycoalkaloids were hydrolysed and the amount of alkaloidal aglycone was estimated by a colorimetric procedure based on solasodine as the standard. The solasodine present in the extracts was identified by comparison with an authentic sample by means of thin-layer chromatography. Twenty-nine Australian species were shown to contain appreciable amounts of solasodine. Of all the species examined, S. aviculare, S. laciniatum and S, simile were found to have the highest content of solasodine. Tomatidine has been isolated from S, dimovphospinum. S, callium contains appreciable quantities of the two new alkaloids 25-isosolafloridine and solacallinidine. S, dunalianum, which has probably been introduced into Australia from New Guinea, contains the new alkaloid soladunalinidine and small amounts of tomatidine.

Australian native flora was examined with nuclear magnetic resonance (n.m.r.) techniques for its content of nitrogenous compatible solutes. Plants were sampled from four habitats: two arid, one subhumid, and one saline estuarine marsh. Eight and two of the 15 plants in the subhumid area accumulated proline and glycinebetaine, respectively, whereas many of the plants in the two arid habitats accumulated these solutes. With only two exceptions plants in the saline marsh could be described as either proline accumulators (six species) or glycinebetaine accumulators (eight species). Attempts to correlate the glycinebetaine and proline contents with the relative water content (RWC) were not successful. Some plants accumulate compounds other than, or in addition to, proline or glycinebetaine, such as trans- 4-hydroxy-N-methyl-L-proline, which was accumulated in Melaleuca lanceolata. Exocarpos aphyllus accumulated an as yet unidentified compound.

The N-terminal 40 amino acid sequences of the small subunit of ribulose bisphosphate carboxylase have been determined for 13 species of Solanum, one other species of Solanaceae and two of Convolvulaceae. From these, and previously published sequences from Solanaceae, a minimal phylogenetic tree is derived. This agrees well with current taxonomy; the first dichotomy in the Solanaceae tree is between the two subfamilies Solanoideae and Cestroideae; within Solanum the subgenera Solanum and Leptostemonum separate dichotomously; within subgenus Leptostemonum the African and Asian species diverge from the Australian. Within the Australian species of subgenus Leptostemonum two most unusual substitutions have been noted. The implications for the hypotheses of a 'molecular evolutionary clock' and of biogeographical dispersal by continental drift are discussed.

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