Allan Sangster on a visit to Oxford
Mineral deposition in the conifers
My work at Birmingham in the late 1980's led me to wonder whether aluminium and silicon were associated in any way in the conifers. Could Si ameliorate Al toxicity? In 1994 I began some work on mineral deposition in the conifers while on sabbatical in Canada. This work has been in collaboration with my friend and colleague Allan Sangster, from York University in Toronto, Canada. The first stage involved an extensive survey of silica deposition in the needles of the gymnosperms. Much of this early work was conducted by my undergraduate project student, Sarah Williams. We were able to publish two papers from this study in the Madrid phytolith symposium:
HODSON, M.J., WILLIAMS, S.E. & SANGSTER, A.G. (1997) Silica deposition in the needles of the gymnosperms. I. Chemical analysis and light microscopy. In The State-of-the-art of Phytoliths in Soils and Plants. eds A. Pinilla, J. Juan-Tresserras & M.J. Machado. Monografia 4 del Centro de Ciencias Medioambientales, CISC. Madrid. 123-133.
SANGSTER, A.G., WILLIAMS, S.E. & HODSON, M.J. (1997) Silica deposition in the needles of the gymnosperms. II. Scanning electron microscopy and x-ray microanalysis. In The State-of-the-art of Phytoliths in Soils and Plants. eds A. Pinilla, J. Juan-Tresserras & M.J. Machado. Monografia 4 del Centro de Ciencias Medioambientales, CISC. Madrid. 135-146.
We then went on to conduct a series of microanalytical investigations of conifer needles. The first of these concerned white spruce:
HODSON, M.J. & SANGSTER, A.G. (1998) Mineral deposition in the needles of white spruce [Picea glauca (Moench.) Voss]. Annals of Botany 82, 375-385.
Allan Sangster presented some of our results on larch at an international tree symposium in Montreal, Canada. The book of the conference L'arbre 2000 The Tree was published in 2001. Our contribution is:
SANGSTER, A.G., HODSON, M.J., & HUANG, C.X. (2001) X-ray microanalytical studies of mineral composition in cell walls of needle tissues of American larch [Larix laricina (Du Roi) K. Koch] and European larch [L. decidua (L.) Mill.] In “L'arbre 2000 The Tree” (ed. M. Labrecque) pp. 160-167. 4th International Symposium on the Tree, Montreal Botanic Garden. Isabelle Quentin Press, Montreal, Canada.
A much more detailed account of mineralization in white pine was then published in Annals of Botany:
HODSON, M.J. & SANGSTER, A.G. (2002) X-ray microanalytical studies of mineral localisation in the needles of white pine (Pinus strobus
L.). Annals of Botany 89
, 367-374. Abstract
We considered Douglas fir in the special volume from the Prague "Acid Rain 2005" conference:
SANGSTER, A.G., LING, L., GERARD, F. & HODSON, M.J. (2007) X-ray microanalysis of needles from Douglas fir growing in environments of contrasting acidity. Water, Air and Soil Pollution: Focus 7
, 143-149. Abstract
Our final paper on this topic concerns hemlock. This work has now been published: SANGSTER, A.G., HODSON, M.J. & LING, L.E.C. (2009) Biomineralisation / environment interactions in conifers: illustrated by hemlock, Tsuga canadensis (L.) Carr. Quaternary International 193, 3-10.
In the course of our work we have often found that aluminium is codeposited with silicon, and this may represent a tolerance mechanism. We reviewed this possibility in:
HODSON, M.J. & SANGSTER, A.G. (1999) Aluminium/silicon interactions in conifers. Journal of Inorganic Biochemistry 76, 89-98.
However, just finding Al and Si in the same locations in the needles does not prove that Si ameliorates Al toxicity in conifers. So we need to do some physiology! Go to Aluminium/silicon interactions in conifers