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Response of millet and sorghum to a varying water supply around the primary and nodal roots

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† Background and Aims:
Cereals have two root systems. The primarysystem originates fromthe embryowhenthe seed germinates and can support the plant until it produces grain. The nodal system can emerge from stem nodes throughout the plant’s life; its value for yield is unclear and depends on the environment. The aim of this studywas to test the
role of nodal roots of sorghum and millet in plant growth in response to variation in soil moisture. Sorghum and millet were chosen as both are adapted to dry conditions.

† Methods:
Sorghum and milletwere grownin a split-pot system that allowed the primaryand nodal roots to bewatered
separately.

† Key Results:
When primary and nodal roots were watered (12 %soil water content; SWC), millet nodal roots were seven times longer than those of sorghum and six times longer than millet plants in dry treatments, mainly from an 8-
fold increase in branch root length. When soilwas allowed to dry in both compartments, millet nodal roots responded and grew 20 % longer branch roots than in the well-watered control. Sorghum nodal roots were unchanged. When only primary roots received water, nodal roots of both species emerged and elongated into extremely dry soil (0.6–1.5 % SWC), possibly with phloem-delivered water from the primary roots in the moist inner pot. Nodal roots were thick, short, branchless and vertical, indicating a tropism that was more pronounced in millet. Total nodal root length increased in both species when the dry soil was covered with plastic, suggesting that stubble retention or leaf mulching could facilitate nodal roots reaching deeper moist layers in dry climates. Greater nodal root length in millet than in sorghum was associated with increased shoot biomass,water uptake andwater use efficiency (shoot mass perwater). Millet had a more plastic response than sorghum to moisture around the nodal roots due to (1) faster growth and progression through ontogeny for earlier nodal root branch length and (2) partitioning to nodal root length from primary roots, independent of shoot size.

†Conclusions:
Nodal and primary roots have distinct responses to soil moisture that depend on species. They can be selected independently in a breeding programme to shape root architecture. A rapid rate of plant development and
enhanced responsiveness to local moisture may be traits that favour nodal roots and water use efficiency at no cost to shoot growth.

Key words: Millet,Pennisetum glaucum, plasticity, adventitious roots, crownroots, lateral roots, sorghum, Sorghum bicolor, split-root system, soil moisture.

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Informasi Detail

Judul Seri

Annals of Botany

No. Panggil

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Penerbit

Oxford : Oxford University Press on behalf of the Annals of Botany Company., 2013

Deskripsi Fisik

Annals of Botany 112: 439–446, 2013

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

112: 2013

Subjek

EKOFISIOLOGI TANAMAN

Info Detail Spesifik

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Pernyataan Tanggungjawab

agus

Versi lain/terkait

Lampiran Berkas

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