Genotypic Variation in Response of Rainfed Lowland Rice to Prolonged Drought and Rewatering

et al. 2009

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: Previously, we demonstrated that root tips in drying soil communicate with shoots for stomatal closure in rainfed lowland rice, despite further water being available at depth. This study examines variation between two lines in root signals. Rice lines CT9993 and IR62266 were grown in the fi eld, and in the greenhouse with the split-root root-sever wax-layer system, to investigate their responses to mild and severe water defi cit by monitoring stomatal conductance (g s ), leaf water potential and leaf ABA concentration. In the greenhouse, root systems were divided, withholding water from one portion, and in some cases, severing the droughted portion of roots to remove the signal. Wax layers differing in strength were placed at hardpan depth. Roots of CT9993 were better able to penetrate the wax layers. IR62266 exhibited stronger responses than CT9993, with IR62266's stomatal conductance dropping sharply under water defi cit, and recovering at slower rates but less completely, when roots subjected to drying soil were severed. The greater stomatal response in IR62266 was associated with a higher leaf ABA concentration during early water defi cit, which in turn was associated with its greater number of roots in drying soil. In the fi eld, a second reduction in g s was observed under severe water defi cit, with stronger signals in IR62266 associated with more conservative water use as soil drying intensifi ed. To better exploit subsoil water in mild or transient water defi cit, selection for reduced root signals might be warranted.

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Section: Discussionsupporting

confidence: 90%

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confidence: 99%

Stomatal Responses in Rainfed Lowland Rice to Partial Soil Drying; Comparison of Two Lines

Siopongco

Sekiya

et al. 2009

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“…The S treatment then tested whether severing the portion of roots subjected to drought in the outer container would result in any recovery in Ψ L , g s , and/or Tr, with the hypothesis that severing of roots in drying soil would remove the source of the positive signal from root tips. The lowland indica rice line, IR62266-42-6-2 (IR62266), was used in this experiment, as it performs well when subjected to drought in the fl uctuating water (fl ood-drought) environment of the rainfed lowlands (Wade et al, 1999b), and is noted for its more gradual water extraction from depth and its greater ability for osmotic adjustment (Kamoshita et al, , 2004. The seminal root of each pre-germinated seed was carefully inserted through the hole in the petri dish of each pot, allowing the root system to be split, with the seminal and some nodal roots growing through the hole and into the inner pot, and the remaining nodal roots being deflected by the petri dish to the outer container (Fig.…”

Section: Greenhouse Experiments I (1) Cultural Detailsmentioning

confidence: 99%

Stomatal Responses in Rainfed Lowland Rice to Partial Soil Drying ; Evidence for Root Signals

Siopongco

Sekiya

et al. 2008

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“…Therefore, the response of lateral roots to different moisture stresses directly determines plant growth through their capacity for water and nutrient uptake. For example, the plastic development of lateral roots under drought (Bañoc et al, 2000b) was responsible for increased root surface area and thus, increased soil water extraction (Kamoshita et al, 2000(Kamoshita et al, , 2004Siopongco et al, 2005). The lateral roots under waterlogged (O 2 -deficient) conditions are effective sites for radial oxygen loss, which is essential for detoxifying phytotoxins and oxidizing reduced nutrient element and thus, maintaining the viability of roots for efficient nutrient and water uptake (Revsbech et al, 1999;Kirk, 2003;Armstrong and Armstrong, 2005).…”

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confidence: 99%

Genotypic Variations in Responses of Lateral Root Development to Transient Moisture Stresses in Rice Cultivars

Suralta

Inukai

2008

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