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Whitmore AP, Whalley WR. Physical effects of soil drying on roots and crop growth. JOURNAL OF EXPERIMENTAL BOTANY 2009; 60:2845-2857. [PMID: 19584120 DOI: 10.1093/jxb/erp200] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/28/2023]
Abstract
The nature and effect of the stresses on root growth in crops subject to drying is reviewed. Drought is a complex stress, impacting on plant growth in a number of interacting ways. In response, there are a number of ways in which the growing plant is able to adapt to or alleviate these stresses. It is suggested that the most significant opportunity for progress in overcoming drought stress and increasing crop yields is to understand and exploit the conditions in soil by which plant roots are able to maximize their use of resources. This may not be straightforward, with multiple stresses, sometimes competing functions of roots, and conditions which impact upon roots very differently depending upon what soil, what depth or what stage of growth the root is at. Several processes and the interaction between these processes in soil have been neglected. It is our view that drought is not a single, simple stress and that agronomic practice which seeks to adapt to climate change must take account of the multiple facets of both the stress induced by insufficient water as well as other interacting stresses such as heat, disease, soil strength, low nutrient status, and even hypoxia. The potential for adaptation is probably large, however. The possible changes in stress as a result of the climate change expected under UK conditions are assessed and it appears possible that wet warm winters will impact on root growth as much if not more than dry warm summers.
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Affiliation(s)
- Andrew P Whitmore
- Department of Soil Science, Rothamsted Research, Cross Institute Programme for Sustainable Soil Function, Centre for Soils and Ecosystem Function, Harpenden, Hertfordshire AL5 2JQ, UK.
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152
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Beebe SE, Rao IM, Cajiao C, Grajales M. Selection for Drought Resistance in Common Bean Also Improves Yield in Phosphorus Limited and Favorable Environments. CROP SCIENCE 2008; 48:582-592. [PMID: 0 DOI: 10.2135/cropsci2007.07.0404] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/21/2023]
Affiliation(s)
- Stephen E. Beebe
- Centro Internacional de Agricultura Tropical (CIAT); A.A. 6713 Cali Colombia
| | - Idupulapati M. Rao
- Centro Internacional de Agricultura Tropical (CIAT); A.A. 6713 Cali Colombia
| | - César Cajiao
- Centro Internacional de Agricultura Tropical (CIAT); A.A. 6713 Cali Colombia
| | - Miguel Grajales
- Centro Internacional de Agricultura Tropical (CIAT); A.A. 6713 Cali Colombia
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153
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154
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155
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Basu P, Zhang YJ, Lynch JP, Brown KM. Ethylene modulates genetic, positional, and nutritional regulation of root plagiogravitropism. FUNCTIONAL PLANT BIOLOGY : FPB 2007; 34:41-51. [PMID: 32689330 DOI: 10.1071/fp06209] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/30/2006] [Accepted: 11/17/2006] [Indexed: 06/11/2023]
Abstract
Plagiogravitropic growth of roots strongly affects root architecture and topsoil exploration, which are important for the acquisition of water and nutrients. Here we show that basal roots of Phaseolus vulgaris L. develop from 2-3 definable whorls at the root-shoot interface and exhibit position-dependent plagiogravitropic growth. The whorl closest to the shoot produces the shallowest roots, and lower whorls produce deeper roots. Genotypes vary in both the average growth angles of roots within whorls and the range of growth angles, i.e. the difference between the shallowest and deepest basal roots within a root system. Since ethylene has been implicated in both gravitropic and edaphic stress responses, we studied the role of ethylene and its interaction with phosphorus availability in regulating growth angles of genotypes with shallow or deep basal roots. There was a weak correlation between growth angle and ethylene production in the basal rooting zone, but ethylene sensitivity was strongly correlated with growth angle. Basal roots emerging from the uppermost whorl were more responsive to ethylene treatment than the lower-most whorl, displaying shallower angles and inhibition of growth. Ethylene sensitivity is greater for shallow than for deep genotypes and for plants grown with low phosphorus compared with those supplied with high phosphorus. Ethylene exposure increased the range of angles, although deep genotypes grown in low phosphorus were less affected. Our results identify basal root whorl number as a novel architectural trait, and show that ethylene mediates regulation of growth angle by position of origin, genotype and phosphorus availability.
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Affiliation(s)
- Paramita Basu
- Intercollege Program in Plant Biology, The Pennsylvania State University, University Park, PA 16802, USA
| | - Yuan-Ji Zhang
- Department of Horticulture, The Pennsylvania State University, University Park, PA 16802, USA
| | - Jonathan P Lynch
- Intercollege Program in Plant Biology, The Pennsylvania State University, University Park, PA 16802, USA
| | - Kathleen M Brown
- Intercollege Program in Plant Biology, The Pennsylvania State University, University Park, PA 16802, USA
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156
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Denton MD, Sasse C, Tibbett M, Ryan MH. Root distributions of Australian herbaceous perennial legumes in response to phosphorus placement. FUNCTIONAL PLANT BIOLOGY : FPB 2006; 33:1091-1102. [PMID: 32689320 DOI: 10.1071/fp06176] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/18/2006] [Accepted: 10/03/2006] [Indexed: 06/11/2023]
Abstract
Many Australian plant species have specific root adaptations for growth in phosphorus-impoverished soils, and are often sensitive to high external P concentrations. The growth responses of native Australian legumes in agricultural soils with elevated P availability in the surface horizons are unknown. The aim of these experiments was to test the hypothesis that increased P concentration in surface soil would reduce root proliferation at depth in native legumes. The effect of P placement on root distribution was assessed for two Australian legumes, Kennedia prorepens F. Muell. and Lotus australis Andrews, and the exotic Medicago sativa L. Three treatments were established in a low-P loam soil: amendment of 0.15 g mono-calcium phosphate in either (i) the top 50 mm (120 µg P g-1) or (ii) the top 500 mm (12 µg P g-1) of soil, and an unamended control. In the unamended soil M. sativa was shallow rooted, with 58% of the root length of in the top 50 mm. K. prorepens and L. australis had a more even distribution down the pot length, with only 4 and 22% of their roots in the 0-50 mm pot section, respectively. When exposed to amendment of P in the top 50 mm, root length in the top 50 mm increased 4-fold for K. prorepens and 10-fold for M. sativa, although the pattern of root distribution did not change for M. sativa. L. australis was relatively unresponsive to P additions and had an even distribution of roots down the pot. Shoot P concentrations differed according to species but not treatment (K. prorepens 2.1 mg g-1, L. australis 2.4 mg g-1, M. sativa 3.2 mg g-1). Total shoot P content was higher for K. prorepens than for the other species in all treatments. In a second experiment, mono-ester phosphatases were analysed from 1-mm slices of soil collected directly adjacent to the rhizosphere. All species exuded phosphatases into the rhizosphere, but addition of P to soil reduced phosphatase activity only for K. prorepens. Overall, high P concentration in the surface soil altered root distribution, but did not reduce root proliferation at depth. Furthermore, the Australian herbaceous perennial legumes had root distributions that enhanced P acquisition from low-P soils.
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Affiliation(s)
- Matthew D Denton
- School of Plant Biology, M084, The University of Western Australia, 35 Stirling Hwy, Crawley, WA 6009, Australia
| | - Camille Sasse
- School of Plant Biology, M084, The University of Western Australia, 35 Stirling Hwy, Crawley, WA 6009, Australia
| | - Mark Tibbett
- Centre for Land Rehabilitation, School of Earth and Geographical Sciences, The University of Western Australia, 35 Stirling Hwy, Crawley, WA 6009, Australia
| | - Megan H Ryan
- School of Plant Biology, M084, The University of Western Australia, 35 Stirling Hwy, Crawley, WA 6009, Australia
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157
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Conlin TSS, van den Driessche R. Influence of nutrient supply and water vapour pressure on root architecture of Douglas-fir and western hemlock seedlings. FUNCTIONAL PLANT BIOLOGY : FPB 2006; 33:941-948. [PMID: 32689304 DOI: 10.1071/fp05317] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/20/2005] [Accepted: 05/25/2006] [Indexed: 06/11/2023]
Abstract
Root growth responses of Douglas-fir [Pseudotsuga menziesii (Mirb.) Franco] and western hemlock (Tsuga heterophylla Raf. Sarg.) seedlings to three nutrient concentrations and two shoot vapour pressure deficits were measured. Both species gained dry mass at high and medium nutrient treatments throughout the experiment, but not at low nutrition. Low nutrition gave highest ratios of projected leaf surface area to total root length in both species. Douglas-fir geometry differed from that of hemlock, with longer interior link lengths, particularly at the lowest nutrition. Douglas-fir showed greater numbers of exterior-interior links than hemlock. More links were observed at medium and high nutrition than at low nutrition for both species. Exterior-interior links increased over time for the two highest nutrient treatments. Significant topological differences were observed between species, the lowest and two highest nutrient treatments, and high and low vapour pressure deficits. Both species showed herring-bone root architecture at the lowest nutrition. This architectural configuration became more pronounced in hemlock seedlings grown under higher vapour pressure deficits. Faster-growing Douglas-fir had a dichotomous architecture at medium and high nutrition that was not influenced by increased vapour pressure deficits. Douglas-fir topology appears to be adapted to exploit soil nutrient patches while hemlock appears to rely on efficient exploitation of soil volume.
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Affiliation(s)
- Timothy S S Conlin
- Forested Ecosystems Research, 3119 Glasgow Street, Victoria, B.C., Canada V8X 1L8
| | - R van den Driessche
- Centre for Forest Biology, University of Victoria, P.O. Box 3020, Victoria, B.C., Canada V8W 3N5
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158
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Manschadi AM, Christopher J, deVoil P, Hammer GL. The role of root architectural traits in adaptation of wheat to water-limited environments. FUNCTIONAL PLANT BIOLOGY : FPB 2006; 33:823-837. [PMID: 32689293 DOI: 10.1071/fp06055] [Citation(s) in RCA: 128] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/14/2006] [Accepted: 06/14/2006] [Indexed: 05/19/2023]
Abstract
Better understanding of root system structure and function is critical to crop improvement in water-limited environments. The aims of this study were to examine root system characteristics of two wheat genotypes contrasting in tolerance to water limitation and to assess the functional implications on adaptation to water-limited environments of any differences found. The drought tolerant barley variety, Mackay, was also included to allow inter-species comparison. Single plants were grown in large, soil-filled root-observation chambers. Root growth was monitored by digital imaging and water extraction was measured. Root architecture differed markedly among the genotypes. The drought-tolerant wheat (cv. SeriM82) had a compact root system, while roots of barley cv. Mackay occupied the largest soil volume. Relative to the standard wheat variety (Hartog), SeriM82 had a more uniform rooting pattern and greater root length at depth. Despite the more compact root architecture of SeriM82, total water extracted did not differ between wheat genotypes. To quantify the value of these adaptive traits, a simulation analysis was conducted with the cropping system model APSIM, for a wide range of environments in southern Queensland, Australia. The analysis indicated a mean relative yield benefit of 14.5% in water-deficit seasons. Each additional millimetre of water extracted during grain filling generated an extra 55 kg ha-1 of grain yield. The functional implications of root traits on temporal patterns and total amount of water capture, and their importance in crop adaptation to specific water-limited environments, are discussed.
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Affiliation(s)
- Ahmad M Manschadi
- APSRU, Queensland Department of Primary Industries & Fisheries, PO Box 102, Toowoomba, Qld 4350, Australia
| | - John Christopher
- Queensland Department of Primary Industries & Fisheries, Leslie Research Centre, PO Box 2282, Toowoomba, Qld 4350, Australia
| | - Peter deVoil
- APSRU, Queensland Department of Primary Industries & Fisheries, PO Box 102, Toowoomba, Qld 4350, Australia
| | - Graeme L Hammer
- APSRU, School of Land and Food Sciences, The University of Queensland, Brisbane, Qld 4072, Australia
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159
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Zhu J, Mickelson SM, Kaeppler SM, Lynch JP. Detection of quantitative trait loci for seminal root traits in maize (Zea mays L.) seedlings grown under differential phosphorus levels. TAG. THEORETICAL AND APPLIED GENETICS. THEORETISCHE UND ANGEWANDTE GENETIK 2006; 113:1-10. [PMID: 16783587 DOI: 10.1007/s00122-006-0260-z] [Citation(s) in RCA: 75] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/14/2005] [Accepted: 03/06/2006] [Indexed: 05/10/2023]
Abstract
Suboptimal phosphorus availability is a primary constraint for terrestrial plant growth. Seminal roots play an important role in acquisition of nutrients by plant seedlings. The length and number of seminal roots may be particularly important in acquisition of immobile nutrients such as phosphorus by increasing soil exploration. The objective of this study was to identify quantitative trait loci (QTL) controlling seminal root growth in response to phosphorus stress in maize, and to characterize epistatic interactions among QTL. Seminal root length and number were evaluated in 162 recombinant inbred lines derived from a cross between B73 and Mo17 in seedlings grown in a controlled environment. B73 and Mo17 significantly differed for seminal root length under low phosphorus, but not under adequate phosphorus conditions. Seminal root length of the population grown under low phosphorus ranged from 0 to 79.2 cm with a mean of 32.3 cm; while seminal root length of plants grown under high phosphorus ranged from 0.67 to 59.0 cm with a mean of 23.4 cm. Under low phosphorus, one main-effect QTL was associated with seminal root length and three QTL with seminal root number; under high phosphorus, two QTL with seminal root length and three QTL for seminal root number. These accounted for 11, 25.4, 22.8, and 24.1% of the phenotypic variations for seminal root length and number at low phosphorus, and seminal root length and number at high phosphorus, respectively. Di-genic epistatic loci were detected for seminal root length at low phosphorus (two pairs) seminal root number at low phosphorus (eight pairs), seminal root length at high phosphorus (four pairs), and seminal root number at high phosphorus (two pairs), which accounted for 23.2, 50.6, 32.2, and 20.3% of the total variations, respectively. Seminal root traits observed here were positively yet weakly correlated with shoot biomass in the field under low phosphorus, although no coincident QTL were detected. These results suggest that epistatic interactions are important in controlling genotypic variation associated with seedling seminal root traits.
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Affiliation(s)
- Jinming Zhu
- Department of Horticulture, Pennsylvania State University, University Park, PA 16802, USA
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160
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Watt M, Silk WK, Passioura JB. Rates of root and organism growth, soil conditions, and temporal and spatial development of the rhizosphere. ANNALS OF BOTANY 2006; 97:839-55. [PMID: 16551700 PMCID: PMC2803425 DOI: 10.1093/aob/mcl028] [Citation(s) in RCA: 47] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/06/2005] [Revised: 10/05/2005] [Accepted: 01/05/2005] [Indexed: 05/07/2023]
Abstract
BACKGROUND Roots growing in soil encounter physical, chemical and biological environments that influence their rhizospheres and affect plant growth. Exudates from roots can stimulate or inhibit soil organisms that may release nutrients, infect the root, or modify plant growth via signals. These rhizosphere processes are poorly understood in field conditions. SCOPE AND AIMS We characterize roots and their rhizospheres and rates of growth in units of distance and time so that interactions with soil organisms can be better understood in field conditions. We review: (1) distances between components of the soil, including dead roots remnant from previous plants, and the distances between new roots, their rhizospheres and soil components; (2) characteristic times (distance(2)/diffusivity) for solutes to travel distances between roots and responsive soil organisms; (3) rates of movement and growth of soil organisms; (4) rates of extension of roots, and how these relate to the rates of anatomical and biochemical ageing of root tissues and the development of the rhizosphere within the soil profile; and (5) numbers of micro-organisms in the rhizosphere and the dependence on the site of attachment to the growing tip. We consider temporal and spatial variation within the rhizosphere to understand the distribution of bacteria and fungi on roots in hard, unploughed soil, and the activities of organisms in the overlapping rhizospheres of living and dead roots clustered in gaps in most field soils. CONCLUSIONS Rhizosphere distances, characteristic times for solute diffusion, and rates of root and organism growth must be considered to understand rhizosphere development. Many values used in our analysis were estimates. The paucity of reliable data underlines the rudimentary state of our knowledge of root-organism interactions in the field.
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Affiliation(s)
- Michelle Watt
- CSIRO Plant Industry, GPO Box 1600, Canberra, ACT 2601, Australia.
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161
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Zhu J, Kaeppler SM, Lynch JP. Topsoil foraging and phosphorus acquisition efficiency in maize (Zea mays). FUNCTIONAL PLANT BIOLOGY : FPB 2005; 32:749-762. [PMID: 32689172 DOI: 10.1071/fp05005] [Citation(s) in RCA: 83] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/30/2004] [Accepted: 05/05/2005] [Indexed: 05/24/2023]
Abstract
In soybean and common bean, enhanced topsoil foraging permitted by shallow root architectures is advantageous for phosphorus acquisition from stratified soils. The importance of this phenomenon in graminaceous crops, which have different root architecture and morphology from legumes, is unclear. In this study we evaluated the importance of shallow roots for phosphorus acquisition in maize (Zea mays L.). In a field study, maize genotypes with shallower roots had greater growth in low phosphorus soil than deep-rooted genotypes. For physiological analysis, four maize genotypes differing in root shallowness in the field were grown in solid media with stratified phosphorus availability in a controlled environment. Of the four genotypes, one shallow and one deep genotype were also inoculated with arbuscular mycorrhiza (AM). Shallower genotypes had significantly greater growth and phosphorus accumulation compared with deeper genotypes at low phosphorus availability. Mycorrhizal colonisation altered root shallowness under low phosphorus conditions, increasing shallowness substantially in a deep-rooted genotype but slightly decreasing shallowness in a shallow-rooted genotype. Mycorrhizal colonisation increased phosphorus acquisition under low phosphorus availability. Respiration costs of roots and shoots of phosphorus-efficient genotypes were significantly lower under low phosphorus conditions compared with inefficient genotypes. The physiological efficiency of phosphorus acquisition, expressed as root respiration per unit of phosphorus acquisition, was greater in shallow rooted genotypes. Our results demonstrate that genetic variation for root shallowness exists in maize, that phosphorus and AM can modulate root shallowness independently, and that a shallower root system is beneficial for plant performance in maize at low phosphorus availability. We propose that root architectural traits that enhance topsoil foraging are important traits for improved phosphorus acquisition efficiency of annual grain crops such as maize in addition to legumes.
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Affiliation(s)
- Jinming Zhu
- Department of Horticulture, Pennsylvania State University, University Park, PA 16802, USA
| | - Shawn M Kaeppler
- Department of Agronomy, University of Wisconsin, Madison, WI 53706, USA
| | - Jonathan P Lynch
- Department of Horticulture, Pennsylvania State University, University Park, PA 16802, USA
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