The botany and proximate analyses of some edible species of the New Zealand flora : a thesis presented in partial fulfilment of the requirement for the degree of Master of Science in Plant Biology at Massey University

Abstract

1. The edible organs of some New Zealand plant species have been assessed at light microscope level for their botanical basis, and for their nutritional basis by proximate analysis and Plasma Emission Spectrometry. 2. The species investigated, listed by Colenso (1880) as the most valued plant foods of the pre-European Maori, were: Pteridium esculentum (rhizome), Corynocarpus laevigatus (kernel), Elaeocarpus dentatus, (pericarp), Sonchus asper (herb), Calystegia sepium (rhizome), Cyathea medullaris (frond stipe), Cordyline australis (leaf bases, root), Rhopalostylis sapida (apical shoot), Typha orientalis (pollen and rhizome), Beilschmiedia tawa (kernel), Marattia salicina (rhizomal scale), Porphyra columbina (frond), Auricularia polytricha (basidiocarp), Arthropodium cirratum (rhizome), Bolboschoenus fluviatilis (rhizomal tuber), Gastrodia cunninghamii (rhizome) and Asplenium bulbiferum (immature frond). 3. Specimens were collected at the appropriate traditional seasons (except for Gastrodia cunninghamii) and samples prepared by freeze-drying and milling. Samples were also prepared of the cooked organs of Corynocarpus laevigatus, Elaeocarpus dentatus, Sonchus asper, Cyathea medullaris, Beilschmiedia tawa and Porphyra columbina. 4. Analytical determinations were made for lipid, by extraction with di-ethyl ether; nitrogen, by micro-Kjeldahl method and colorimetric measurement of ammonia using indophenol; protein, by Bradford procedure using Coomassie Brilliant Blue and colorimetry; dietary fibre, by Englyst procedure using enzymatic digestion and colorimetry; soluble sugar, by acid hydrolysis and colorimetry; and starch, by enzymatic digestion and colorimetry. 5. Botanical investigations were made following histological procedures and microtechnique using paraffin wax embedding and staining with safranin and fast green; and by differential staining of hand-cut sections using Sudan Blue, iodine and Coomassie Brilliant Blue. 6. Analytical determinations were made for 23 trace, minor and major constituent elements, using inductively-coupled argon plasmas in a simultaneous emission spectrometer. 7. Proximate analyses showed high levels of lipid in Corynocarpus laevigatus, Cyathea medullaris, and Sonchus asper, of protein in Corynocarpus laevigatus, Sonchus asper, Rhopalostylis sapida, Typha orientalis (pollen) and Asplenium bulbiferum; of dietary fibre in Auricularia polytricha, Beilschmiedia tawa, Marattia salicina (root) and Porphyra columbina (uncooked); of soluble sugar in Cyathea medullaris, Cordyline australis (leaf bases and root), Typha orientalis (rhizomes and pollen) and Pteridium esculentum; and of starch in Corynocarpus laevigatus, Elaeocarpus dentatus, Marattia salicina, Calystegia sepium and Gastrodia cunninghamii. 8. High levels of essential minerals and trace elements were measured in many samples, and some excess levels of toxic metals were recorded. 9. The nutritional and ethnobotanical aspects of a pre-European Maori diet were related to the analytical and botanical findings of the investigation.