e-journal

Development and persistence of sandsheaths of Lyginia barbata (Restionaceae): relation to root structural development and longevity

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Background and Aims Strongly coherent sandsheaths that envelop perennial roots of many monocotyledonous
species of arid environments have been described for over a century. This study, for the first time, details the roles played by the structural development of the subtending roots in the formation and persistence of the sheaths.
Methods The structural development of root tissues associated with persistent sandsheaths was studied in
Lyginia barbata, native to the Western Australian sand plains. Cryo-scanning electron microscopy CSEM,
optical microscopy and specific staining methods were applied to fresh, field material. The role of root hairs was clarified by monitoring sheath development in roots separated from the sand profile by fine mesh.
Key Results and Conclusions The formation of the sheaths depends entirely on the numerous living root hairs which extend into the sand and track closely around individual grains enmeshing, by approx. 12 cm from the root tip, a volume of sand more than 14 times that of the subtending root. The longevity of the perennial sheaths depends on the subsequent development of the root hairs and of the epidermis and cortex. Before dying, the root hairs develop cellulosic walls approx. 3 mm thick, incrusted with ferulic acid and lignin, which persist for the life of the sheath. The dead hairs remain in place fused to a persistent platform of sclerified epidermis and outer cortex. The mature cortex comprises this platform, a wide, sclerified inner rim and a lysigenous central region – all dead tissue. We propose that the sandsheath/root hair/epidermis/cortex complex is a structural unit facilitating water and nutrient uptake while the tissues are alive, recycling scarce phosphorus during senescence, and forming, when dead, a persistent essential structure for maintenance of a functional stele in the perennial Lyginia roots.
Key words: CSEM, lignified and suberized root hairs, Lyginia barbata, perennial drought-tolerant roots,
persistent root hairs, phosphorus recycling, Restionaceae, rhizosheaths, root hair histochemistry, sandbinding roots.

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Informasi Detail

Judul Seri

Annals of Botany

No. Panggil

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Penerbit

: Oxford University Press on behalf of the Annals of Botany Company., 2011

Deskripsi Fisik

Annals of Botany 108: 1307–1322, 2011

Bahasa

English

ISBN/ISSN

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Klasifikasi

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Tipe Isi

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Tipe Media

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Tipe Pembawa

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Edisi

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Subjek

PERTANIAN.

Info Detail Spesifik

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Pernyataan Tanggungjawab

yuli/agus

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