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Root traits contributing to plant productivity under drought.

Comas LH, Becker SR, Cruz VM, Byrne PF, Dierig DA - Front Plant Sci (2013)

Bottom Line: Root traits associated with maintaining plant productivity under drought include small fine root diameters, long specific root length, and considerable root length density, especially at depths in soil with available water.Rapid resumption of root growth following soil rewetting may improve plant productivity under episodic drought.Examples in lesquerella (Physaria) and rice (Oryza) show approaches to phenotyping of root traits and current understanding of root trait genetics for breeding.

View Article: PubMed Central - PubMed

Affiliation: Water Management Research, United States Department of Agriculture-Agricultural Research Service Fort Collins, CO, USA.

ABSTRACT
Geneticists and breeders are positioned to breed plants with root traits that improve productivity under drought. However, a better understanding of root functional traits and how traits are related to whole plant strategies to increase crop productivity under different drought conditions is needed. Root traits associated with maintaining plant productivity under drought include small fine root diameters, long specific root length, and considerable root length density, especially at depths in soil with available water. In environments with late season water deficits, small xylem diameters in targeted seminal roots save soil water deep in the soil profile for use during crop maturation and result in improved yields. Capacity for deep root growth and large xylem diameters in deep roots may also improve root acquisition of water when ample water at depth is available. Xylem pit anatomy that makes xylem less "leaky" and prone to cavitation warrants further exploration holding promise that such traits may improve plant productivity in water-limited environments without negatively impacting yield under adequate water conditions. Rapid resumption of root growth following soil rewetting may improve plant productivity under episodic drought. Genetic control of many of these traits through breeding appears feasible. Several recent reviews have covered methods for screening root traits but an appreciation for the complexity of root systems (e.g., functional differences between fine and coarse roots) needs to be paired with these methods to successfully identify relevant traits for crop improvement. Screening of root traits at early stages in plant development can proxy traits at mature stages but verification is needed on a case by case basis that traits are linked to increased crop productivity under drought. Examples in lesquerella (Physaria) and rice (Oryza) show approaches to phenotyping of root traits and current understanding of root trait genetics for breeding.

No MeSH data available.


Related in: MedlinePlus

Seasonal root growth of fully and deficit irrigated maize and sunflower in two soil depths. Root growth across the season at two soil depths for Z. mays(A,C) and H. annuus(B,D) is from the same study shown in Figure 2. Each bar represents root growth averaged among four minirhizotron tubes per treatment. Arrows indicate the beginning of the critical reproductive phase for each crop (R1 in maize, July 23; R3 in sunflower, July 20).
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Figure 4: Seasonal root growth of fully and deficit irrigated maize and sunflower in two soil depths. Root growth across the season at two soil depths for Z. mays(A,C) and H. annuus(B,D) is from the same study shown in Figure 2. Each bar represents root growth averaged among four minirhizotron tubes per treatment. Arrows indicate the beginning of the critical reproductive phase for each crop (R1 in maize, July 23; R3 in sunflower, July 20).

Mentions: Root allocation and distribution may depend on plant growth strategies and their general response to water deficits and distribution of available soil water. Maize has high water use efficiency (WUE) but is sensitive to water shortages (Figure 3; Ghannoum, 2009). Maize, which has more conservative hydraulic conductance compared to sunflower, decreases transpiration more quickly than sunflower, which maintains carbon assimilation during drought, even during the course of wilting (Comas, personal observation). Both maize and sunflower decrease shoot size, and increase AR:AL and relative root distribution to deeper depths in response to water deficits, although sunflower, emblematic of a drought avoider, has a generally deeper root system than maize and redistributes an even greater percentage of its roots to deeper soil depths (Figure 2). Root growth in both maize and sunflower continues longer into the season than shoot vegetative growth and the onset of reproduction, with the capacity for even greater overlap of root growth with reproduction under water deficit (Figure 4). As breeding for plant productivity under drought advances, it may be advantageous to consider whole plant strategies and root traits and patterns of spatio-temporal growth with a systems approach. Working with two crops with contrasting hydraulic responses, we might expect different traits to improve productivity under drought in these crops, which highlights the need to take specifics of the genotype, as well as environment and management, into account.


Root traits contributing to plant productivity under drought.

Comas LH, Becker SR, Cruz VM, Byrne PF, Dierig DA - Front Plant Sci (2013)

Seasonal root growth of fully and deficit irrigated maize and sunflower in two soil depths. Root growth across the season at two soil depths for Z. mays(A,C) and H. annuus(B,D) is from the same study shown in Figure 2. Each bar represents root growth averaged among four minirhizotron tubes per treatment. Arrows indicate the beginning of the critical reproductive phase for each crop (R1 in maize, July 23; R3 in sunflower, July 20).
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3817922&req=5

Figure 4: Seasonal root growth of fully and deficit irrigated maize and sunflower in two soil depths. Root growth across the season at two soil depths for Z. mays(A,C) and H. annuus(B,D) is from the same study shown in Figure 2. Each bar represents root growth averaged among four minirhizotron tubes per treatment. Arrows indicate the beginning of the critical reproductive phase for each crop (R1 in maize, July 23; R3 in sunflower, July 20).
Mentions: Root allocation and distribution may depend on plant growth strategies and their general response to water deficits and distribution of available soil water. Maize has high water use efficiency (WUE) but is sensitive to water shortages (Figure 3; Ghannoum, 2009). Maize, which has more conservative hydraulic conductance compared to sunflower, decreases transpiration more quickly than sunflower, which maintains carbon assimilation during drought, even during the course of wilting (Comas, personal observation). Both maize and sunflower decrease shoot size, and increase AR:AL and relative root distribution to deeper depths in response to water deficits, although sunflower, emblematic of a drought avoider, has a generally deeper root system than maize and redistributes an even greater percentage of its roots to deeper soil depths (Figure 2). Root growth in both maize and sunflower continues longer into the season than shoot vegetative growth and the onset of reproduction, with the capacity for even greater overlap of root growth with reproduction under water deficit (Figure 4). As breeding for plant productivity under drought advances, it may be advantageous to consider whole plant strategies and root traits and patterns of spatio-temporal growth with a systems approach. Working with two crops with contrasting hydraulic responses, we might expect different traits to improve productivity under drought in these crops, which highlights the need to take specifics of the genotype, as well as environment and management, into account.

Bottom Line: Root traits associated with maintaining plant productivity under drought include small fine root diameters, long specific root length, and considerable root length density, especially at depths in soil with available water.Rapid resumption of root growth following soil rewetting may improve plant productivity under episodic drought.Examples in lesquerella (Physaria) and rice (Oryza) show approaches to phenotyping of root traits and current understanding of root trait genetics for breeding.

View Article: PubMed Central - PubMed

Affiliation: Water Management Research, United States Department of Agriculture-Agricultural Research Service Fort Collins, CO, USA.

ABSTRACT
Geneticists and breeders are positioned to breed plants with root traits that improve productivity under drought. However, a better understanding of root functional traits and how traits are related to whole plant strategies to increase crop productivity under different drought conditions is needed. Root traits associated with maintaining plant productivity under drought include small fine root diameters, long specific root length, and considerable root length density, especially at depths in soil with available water. In environments with late season water deficits, small xylem diameters in targeted seminal roots save soil water deep in the soil profile for use during crop maturation and result in improved yields. Capacity for deep root growth and large xylem diameters in deep roots may also improve root acquisition of water when ample water at depth is available. Xylem pit anatomy that makes xylem less "leaky" and prone to cavitation warrants further exploration holding promise that such traits may improve plant productivity in water-limited environments without negatively impacting yield under adequate water conditions. Rapid resumption of root growth following soil rewetting may improve plant productivity under episodic drought. Genetic control of many of these traits through breeding appears feasible. Several recent reviews have covered methods for screening root traits but an appreciation for the complexity of root systems (e.g., functional differences between fine and coarse roots) needs to be paired with these methods to successfully identify relevant traits for crop improvement. Screening of root traits at early stages in plant development can proxy traits at mature stages but verification is needed on a case by case basis that traits are linked to increased crop productivity under drought. Examples in lesquerella (Physaria) and rice (Oryza) show approaches to phenotyping of root traits and current understanding of root trait genetics for breeding.

No MeSH data available.


Related in: MedlinePlus