The life of phi: the development of phi thickenings in roots of the orchids of the genus Miltoniopsis
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Phi thickenings, bands of secondary wall thickenings that reinforce the primary wall of root cortical cells in a wide range of species, are described for the first time in the epiphytic orchid Miltoniopsis. As with phi thickenings found in other plants, the phi thickenings in Miltoniopsis contain highly aligned cellulose running along the lengths of the thickenings, and are lignified but not suberized. Using a combination of histological and immunocytochemical techniques, thickening development can be categorized into three different stages. Microtubules align lengthwise along the thickening during early and intermediate stages of development, and callose is deposited within the thickening in a pattern similar to the microtubules. These developing thickenings also label with the fluorescently tagged lectin wheat germ agglutinin (WGA). These associations with microtubules and callose, and the WGA labeling, all disappear when the phi thickenings are mature. This pattern of callose and WGA deposition show changes in the thickened cell wall composition and may shed light on the function of phi thickenings in plant roots, a role for which has yet to be established.
KeywordsCallose Cellulose deposition Orchids Microtubule organization Miltoniopsis Mycorrhizae Phi thickenings Wheat germ agglutinin
Wheat germ agglutinin
We thank Manfred Ingerfeld for microscopy technical support, David Conder (School of Biological Sciences) for help maintaining the orchids, Dr John Clemens (Christchurch Botanic Gardens) and John Clements (Canterbury Orchid Society) for supplying the orchids. NAI acknowledges the Malaysian Education Ministry for the PhD scholarship (SLAB) and funding by School of Biological Sciences at the University of Canterbury.
Supplementary movie 1. Confocal 3D reconstruction of berberine hemisulfate stained longitudinal root section with phi thickenings aligned in long bands between cells running through the root length and parallel to the vascular tissue. (WMV 677 kb)
Supplementary movie 2. Confocal 3D reconstruction of a cross sectioned root stained with berberine hemisulfate showing some phi thickenings perfectly aligned between adjacent cells (Φ) and others which do not (Þ). (WMV 1052 kb)
- Burr B, Barthlott W (1991) On a velamen-like tissue in the root cortex of orchids. Flora 185:313–323Google Scholar
- Deshmukh S, Hückelhoven R, Schäfer P, Imani J, Sharma M, Weiss M, Waller F, Kogel K-H (2006) The root endophytic fungus Piriformospora indica requires host cell death for proliferation during mutualistic symbiosis with barley. Proc Nat Acad Sci USA 103:18450–18457PubMedCentralPubMedCrossRefGoogle Scholar
- Hogekamp C, Arndt D, Pereira PA, Becker JD, Hohnjec N, Küster H (2011) Laser microdissection unravels cell-type-specific transcription in arbuscular mycorrhizal roots, including CAAT-box transcription factor gene expression correlating with fungal contact and spread. Plant Physiol 157:2023–2043PubMedCentralPubMedCrossRefGoogle Scholar
- Russow E (1875) Betrachtungen über das Leitbündel- und Grundgewebe aus vergleichend morphologischem und phylogenetischem Geschichtspunkt. Schnakenburg’s Anstalt Dorpat, EstoniaGoogle Scholar
- Strivastava LM (1966) Histochemical studies on lignin. Tappi 49:173–183Google Scholar
- van Tieghem P (1871) Mémoire sur la racine. Ann Sci Nat 13:187–195Google Scholar
- van Tieghem P (1888) Le réseau de soutien de l'écorce de la racine. Ann Sci Nat Botanique Series 7:375–378Google Scholar