JXB Advance Access originally published online on August 23, 2005
Journal of Experimental Botany 2005 56(420):2755-2763; doi:10.1093/jxb/eri269
| ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
RESEARCH PAPER |
Localization and movement of mineral oil in plants by fluorescence and confocal microscopy
1Centre for Horticulture and Plant Sciences, University of Western Sydney, Locked Bag 1797, Penrith South Distribution Centre, New South Wales 1797, Australia
2CSSIP and School of Integrative Biology, Queensland University, St Lucia 4072, Queensland, Australia
3CSIRO Division of Plant Industry, GPO Box 1600, Canberra, Australian Capital Territory 2601, Australia
* To whom correspondence should be addressed. Fax: +64 3 3259946. E-mail: binglin.tan{at}agresearch.co.nz
Fluorescence and confocal laser scanning microscopy were explored to investigate the movement and localization of mineral oils in citrus. In a laboratory experiment, fluorescence microscopy observation indicated that when a ‘narrow’ distillation fraction of an nC23 horticultural mineral oil was applied to adaxial and opposing abaxial leaf surfaces of potted orange [Citrus x aurantium L. (Sapindales: Rutaceae)] trees, oil penetrated steadily into treated leaves and, subsequently, moved to untreated petioles of the leaves and adjacent untreated stems. In another experiment, confocal laser scanning microscopy was used to visualize the penetration into, and the subsequent cellular distribution of, an nC24 agricultural mineral oil in C. trifoliata L. seedlings. Oil droplets penetrated or diffused into plants via both stomata and the cuticle of leaves and stems, and then moved within intercellular spaces and into various cells including phloem and xylem. Oil accumulated in droplets in intercellular spaces and within cells near the cell membrane. Oil entered cells without visibly damaging membranes or causing cell death. In a field experiment with mature orange trees, droplets of an nC23 horticultural mineral oil were observed, by fluorescence microscopy, in phloem sieve elements in spring flush growth produced 4–5 months and 16–17 months after the trees were sprayed with oil. These results suggest that movement of mineral oil in plants is both apoplastic via intercellular spaces and symplastic via plasmodesmata. The putative pattern of the translocation of mineral oil in plants and its relevance to oil-induced chronic phytotoxicity are discussed.
Key words: Apoplast, confocal laser scanning microscopy, fluorescence microscopy, localization, mineral oil, penetration, phloem, symplast, translocation