Dark Tolerance in Plants of Dunes

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Abstract
1 The ability to survive sand burial involves both a plant''s ability to grow up through the sand, and also the ability to survive darkness whilst it does so. Ability to survive temporary sand deposition is also important on dunes. 1 An experiment with 29 native and introduced New Zealand dune species examined the length of time the species survived complete darkness in a lightproof box. 3 Survival times ranged from 19 to 140 days. The longest survivor was a small herb Hydrocotyle novae-zelandiae.dbldag. but the shortest survivor was another small herb Gnaphalium audax. Marram grass, Ammophila arenaria, survived twice as long as the foredune grass Elymus farctus. Plantago triandra, a rosette herb, responded to darkness by its leaves moving towards the vertical. 4 Sand burial responses from an earlier experiment correlated significantly with results from this study. Some species, e.g. Hydrocotyle novae-zelandiae, were tolerant of both sand burial and darkness per se, and some intolerant to both, e.g. Gunnera albocarpa. In some species there was little correlation, e.g. Centella uniflora reached the sand surface from the deepest burial depth but needed to achieve this in less than 29 days. 5 Dark survival showed a poor correlation with field distribution. 6 Ordination of a number of varieties from four autecological studies involving salt spray, root salinity, sand burial and dark survival gave one axis based on salt tolerance; species were well distributed along the axis. The second axis involved dark survival and burial. Species'' responses were individualistic, and it is suggested dark survival of dune species is often a pre-adaptation.

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