Progress 01/01/00 to 12/31/04
Outputs
The overall goal of this project was to discover and understand traits that contribute to efficient nutrient use in crop plants. The project was successful in contributing to this goal by discovering several new traits and providing better genetic, physiological, and agroecological understanding of traits previously discovered by our group and others. Specifically, we found that: 1) Superior adventitious rooting is an important adaptation to low soil P availability by enhancing topsoil foraging and because adventitious roots are metabolically more efficient than other root classes. Genetic variation exists for adventitious rooting in common bean under P stress, which is controlled by several major and minor QTL. 2) Cortical aerenchyma formation is an important adaptation to low soil P availability by reducing the respiratory and metabolic cost of soil exploration. Genetic variation exists for this trait in maize and bean. 3) Root hairs are important for P acquisition
from low P soils. Substantial genetic variation exists in maize and bean for root hair length and density, controlled by several major and minor QTL, some of which cosegregate for acid exudation into the rhizosphere, which is also important for P uptake. In bean, genetic variation in root hair length is directly associated with field performance in low P tropical soils, and contributes to P uptake in both mycorrhizal and nonmycorrhizal plants. Root hair length and density are regulated by P availability in a coordinated manner to achieve morphological synergy for P uptake. Plants with more root hairs are more competitive in low P soils. 4) Root architectural traits that enhance topsoil foraging such as shallow basal roots and adventitious rooting may incur tradeoffs in terms of water acquisition, as shown in simulation modeling as well as empirical studies of contrasting genotypes in field and greenhouse environments. 5) Fractal geometry may be a useful way to characterize root
architecture in the field, especially in several fractal metrics (fractal number, fractal dimension, and lacunarity) are included in the same analysis. Fractal geometry of root systems in the field is associated with P uptake from low P soil. 6) A novel technique was developed to spatially map phosphorus net influx capacity in intact bean root systems. The method is based on digital autoradiography and permits the quantification of phosphorus influx at high spatial resolution (2 mm). 7) Root gravitropism determines the relative distribution of plant roots in different soil layers, and may therefore influence the acquisition of shallow soil resources such as phosphorus. We identified 16 QTL controlling basal root gravitropism and demonstrated cosegregation of some of these with P uptake in the field. 8) We identified promising sources of salinity tolerance in wild Phaseolus species from saline and semi arid regions of Mexico, and characterized their physiological responses to salinity
stress. 9) We showed that salinity stress leads to rapid increases in cytosolic Na and changes cytosolic Ca dynamics but does not disturb cytosolic pH.
Impacts
Our discoveries have had tangible impact in the breeding and selection of crop genotypes with greater productivity in low fertility soils, such as those that predominate throughout the tropics and the developing nations of the world. Specifically, common bean genotypes with enhanced root traits and enhanced P efficiency are being used and developed in breeding programs in Africa and Latin America as a result of this work. Collaboration with colleagues in China has resulted in the development and release of new soybean cultivars with enhanced P efficiency. Our research has also had impact within the research community, by identifying and elucidating specific root architectural traits, and their genetic and agroecological aspects. The conceptual and methodological tools developed in this research have been very useful to other plant biologists concerned with root architecture.
Publications
- Tomscha, J.L., Trull, M.C., Deikman, J., Lynch, J.P. and Guiltinan, M.J. 2004. Phosphatase under-producing mutants have altered phosphorus relations. Plant Physiology 135, 334-345.
- Liao, H., Yan, X., Rubio, G., Beebe, S.E., Blair, M.W. and Lynch, J.P. 2004. Genetic mapping of basal root gravitropism and phosphorus acquisition efficiency in common bean. Functional Plant Biology 31, 959-970.
- Walk, T.C., Erp, E. and Lynch, J.P. 2004. Modelling applicability of fractal analysis to efficiency of soil exploration by roots. Annals of Botany 94:119-128.
- Rubio, G., Sorgona, A. and Lynch, J.P. 2004. Spatial mapping of phosphorus influx in bean root systems using digital autoradiography. Journal of Experimental Botany 55:2269-2280.
- Zhu, J., Kaeppler, S. and Lynch, J.P. 2004. Mapping of QTL controlling root hair length in maize (Zea mays L.) under phosphorus deficiency. Plant and Soil, Accepted for Publication.
- He, Z.X., Ma, Z., Brown, K.M. and Lynch, J.P. 2004. A novel application of the Gini coefficient in the assessment of inequality of root hair density in Arabidopsis thaliana: a close look at the effect of phosphorus and its interaction with ethylene. Annals of Botany, Accepted for Publication.
- Zhu, J. and Lynch, J.P. 2004. The contribution of lateral rooting to phosphorus acquisition efficiency in maize (Zea mays L.) seedlings. Functional Plant Biology 31:949-958.
- Lynch, J.P. and St. Clair, S. 2004. Mineral stress: the missing link in understanding how global climate change will affect plants in real world soils. Field Crops Research 90: 101-115.
- Ho, M.D., McCannon, B.C. and Lynch, J.P. 2004. Optimization modeling of plant root architecture for water and phosphorus acquisition. Journal of Theoretical Biology 226(3):331-340.
- Yan, X., Liao, H., Beebe, S.E., Blair, M.W. and Lynch, J.P. 2004. QTL mapping of root hair and acid exudation traits and their relationship to phosphorus uptake in common bean. Plant and Soil, Accepted for Publication.
- Lynch, J.P. 2004. Root architecture and nutrient acquisition. Invited chapter in a book entitled `Plant nutrient acquisition an ecological perspective, Accepted for Publication.
- Lynch, J.P. and Ho, M. 2004. Rhizoeconomics: carbon costs of phosphorus acquisition. Plant and Soil, Accepted for Publication.
|
Progress 01/01/03 to 12/31/03
Outputs
We examined the effects of salinity on four wild (Phaseolus angustissimus, P. filiformis, P. microcarpus, and P. vulgaris) and two cultivated (P. acutifolius and P. vulgaris L.) Phaseolus species. Relative growth rate (RGR, g/g/day), unit leaf rate (ULR, g/square m/ day), leaf area ratio (LAR, square m/g), specific leaf area (SLA, square m/g), leaf weight ratio (LWR, g leaf/g), and rate of ion uptake were calculated between 10 and 20 days after planting. Salinity significantly reduced RGR, ULR, LAR, and SLA, but LWR showed no definite trend. In all species except in P. filiformis, ULR was significantly correlated with RGR, indicating that ULR was an important factor underlying the salinity-induced differences in RGR among species. In P. filiformis, high salinity reduced SLA, and consequently LAR. The significant correlation of SLA and LAR with RGR suggested that growth components affecting leaf area expansion were the primary factors explaining the inhibition of
growth in this species. The rate of carbon assimilation decreased gradually with salinity, showing significant reductions only at the highest salt level (80 mM NaCl). Approximately two-thirds of the reduction in carbon assimilation rate at high salinity was attributable to reduced stomatal conductance. In P. filiformis, neither stomatal conductance nor carbon assimilation were affected by salt stress. Leaf water and osmotic potentials declined significantly as stress intensified. However, osmotic adjustment permitted the maintenance of positive turgor. Salinity had a significant effect on tissue concentrations and uptake rates of sodium, potassium, calcium, and chloride. Thus, in addition to the toxic effects of high concentrations of sodium and chloride in plant tissue, saline-induced changes in mineral nutrient uptake likely contributed to the reduction of plant growth. It appears that salt tolerance in P. filiformis is associated with sodium exclusion and organ sodium
compartmentation in roots and stems as well as sustained potassium concentration in leaves and better stomatal control through osmotic adjustment. All other Phaseolus species are sodium excluders, and maintained turgor-driven extension growth by accumulating chloride (osmotic adjustment), but subsequent weight gain reductions suggest that this led to ion toxicity. In another project, we showed that using a buffered form of phosphorus (Al-P) for production of marigold plants improved their tolerance to drought compared with plants fertilized conventionally using soluble fertilizer with high phosphorus. Al-P fertilization produced plants with equal total dry weight, more flowers and reduced leaf area compared to control plants. Whole-shoot photosynthetic carbon assimilation expressed on a leaf area basis was nearly twice as high in Al-P plants as in controls. In Al-P plants, smaller leaf area resulted in reduced whole-plant transpiration. Moreover, the relative water content of the
growing medium was significantly lower at wilting. The improved water acquisition in plants fertilized with Al-P could be explained by increased root proliferation via longer main roots and less densely distributed lateral roots.
Impacts
Identification of sources and mechanisms of salinity tolerance in wild bean germplasm could be used by plant breeders to improve cultivated beans for higher performance on marginal soils, many of which are saline in areas where bean is an important source of protein and calories. Of the species investigated, Phaseolus filiformis was the most promising, based on rapid germination and growth in the presence of salt concentrations damaging to most bean species. Other species could contribute lesser or more transient tolerance to salinity. The response of marigold to buffered phosphorus fertilizer showed that optimizing phosphorus nutrition with solid-phase buffered-phosphorus fertilizer improves drought tolerance by reducing transpiration and increasing water acquisition from the medium. The current commercial practice is to use high concentrations of soluble, unbuffered phosphorus for floriculture crop production. This practice increases the problems of phosphorus
leaching and potential pollution of surface waters, and, as we have shown, reduces the quality and stress tolerance of the crop. Adoption of buffered-phosphorus fertilizer would provide optimum nutrition for the plant while minimizing environmental impact of horticultural fertilization schemes.
Publications
- Bayuelo-Jimenez, J.S., Debouck, D.G. and Lynch, J.P. 2003. Growth, gas exchange, water relations, and ion composition of wild and cultivated Phaseolus species grown under saline conditions. Field Crops Research, 80:207-222.
- Ma, Z., Baskin, T.I., Brown, K.M. and Lynch, J.P. 2003. Regulation of root elongation under phosphorus stress involves changes in ethylene responsiveness. Plant Physiology 131:1381-1390.
- Rubio, G., Liao, H., Yan, X. and Lynch, J.P. 2003. Topsoil foraging and its role in plant competitiveness for phosphorus in common bean. Crop Science 43:598-607. Rubio, G., Zhu, J. and Lynch, J.P. 2003. A critical test of the two prevailing theories of plant response to nutrient availability. American Journal of Botany 90:143-152.
- Fan, M., Zhu, J., Richards, C., Brown, K.M. and Lynch, J.P. 2003. Physiological roles for aerenchyma in phosphorus-stressed roots. Functional Plant Biology 30:493-506.
- Miller, C.R., Ochoa, I., Nielsen, K.L., Beck, D. and Lynch, J.P. 2003. Genetic variation for adventitious rooting in response to low phosphorus availability: potential utility for phosphorus acquisition from stratified soils. Functional Plant Biology 30:973-985.
- Halperin, S. and Lynch, J.P. 2003. Effects of salinity on cytosolic Na+ and K+ in root hairs of Arabidopsis thaliana: in vivo measurements using the fluorescent dyes SBFI and PBFI. Journal of Experimental Botany J. Exp. Bot. 2003 54: 2035-2043.
- Zhu, J. 2003. Composite interval mapping and physiological function of root traits conferring phosphorus efficiency in maize (Zea mays L.). Ph.D. Thesis, The Pennsylvania State University, University Park, PA. 150 pp.
- Borch, K., Miller, C., Brown, K.M. and Lynch, J.P. 2003. Improved drought tolerance in marigold by manipulation of root growth with buffered-phosphorus nutrition. HortScience 38:212-216.
- Halperin, S., Gilroy, S. and Lynch, J.P. 2003. Sodium chloride reduces growth and cytosolic calcium, but does not affect cytosolic pH, in root hairs of Arabidopsis thaliana L. Journal of Experimental Botany 54:1269-1280.
|
Progress 01/01/02 to 12/31/02
Outputs
We have tested alumina-buffered phosphorus fertilizer in field and container systems. In container systems, it reduces phosphorus leaching and increases crop quality. Tests on woody plants showed that drought tolerance was improved. Detailed investigations on container-grown bedding plants and woody plants showed that root development was a major factor likely to be responsible for the improvement in tolerance to drought stress. We have worked with manufacturers to develop industrial-scale production of alumina-buffered phosphorus for use in agriculture. Application of industrially-produced material to fields with phosphorus-deficient soils supplied sufficient phosphorus to support vegetable production in Pennsylvania, with yields similar to fertilized plots. A similar product without added phosphorus was added to very high phosphorus soils. There were no adverse effects on yield, but leaching of phosphorus was reduced.
Impacts
Our solid-phase buffer technology is being used to reduce nutrient pollution and improve plant quality in commercial floriculture production in England and Denmark. Various trials are in progress with commercial growers in the U.S.
Publications
- Bayuelo Jimenez, J. S., Craig, R. and Lynch, J. P. 2002. Salinity tolerance of Phaseolus species during germination and early seedling growth. Crop Science 42:1584-1594.
- Bayuelo Jimenez, J. S., Debouck, D. G. and Lynch, J. P. 2002. Salinity tolerance in Phaseolus species during early vegetative growth. Crop Science 42:2184-2192.
- Boateng, J. 2002. Evaluation of a novel buffered fertilizer for reducing phosphorus runoff and leaching from Pennsylvania Cropland. M.S. Thesis. The Pennsylvania State University, University Park, PA. 153 pp.
- Zhang, Y. J., Kuhns, L., Lynch, J. P. and Brown, K. M. 2002. Buffered phosphorus fertilizer improves growth and drought tolerance of woody landscape plants. J. Environ. Hort. 20:214-219.
- Brown, K. M., Snyder, R., Orzolek, M. D., Otjen, L., Vavrina, C. S. and Lynch, J. P. 2002. Production of high quality tomato transplants with a novel buffered fertilizer. HortTechnology 12:662-669.
- Borch, K., Miller, C., Brown, K. M. and Lynch, J. P. 2002. Improved drought avoidance by manipulation of root growth with buffered-phosphorus nutrition. HortScience. Accepted for Publication.
- Bayuelo Jimenez, J. S., Debouck, D. G., and Lynch, J. P. 2002. Growth, gas exchange, water relations, and ion composition of wild and cultivated Phaseolus species grown under saline conditions. Field Crops Research. Accepted for Publication.
- Rubio, G., Liao, H., Yan, H. and Lynch, J. P. 2002. Topsoil foraging and its role in plant competitiveness for phosphorus in common bean. Crop Science. Accepted for Publication.
- Rubio, G., Zhu, J. and Lynch, J. P. 2002. A critical test of the two prevailing theories of plant response to nutrient availability. American Journal of Botany, Accepted for Publication.
- Bielenberg, D. G., Lynch, J. P. and Pell, E. J. 2002. Nitrogen dynamics during O(3)-induced accelerated senescence in hybrid poplar. Plant Cell & Environment 25:501-512.
- Fisher, M. C. T., Eissenstat, D. M. and Lynch, J. P. 2002. Lack of evidence for programmed root senescence in common bean (Phaseolus vulgaris) grown at different levels of phosphorus supply. New Phytologist 153:63-71.
- Lynch, J. P. 2002. Root architecture and nutrient acquisition. Invited chapter in a book entitled Plant nutrient acquisition an ecological perspective. Academic Press, Accepted for Publication.
|
Progress 01/01/01 to 12/31/01
Outputs
In this project we are analyzing root traits that may confer efficient nutrient acquisition for crop plants, focusing on root architecture. Some of the highlights of our research this last year are that 1) P efficient genotypes of common bean have root systems that have lower respiratory growth requirements than inefficient genotypes, 2) genetic variation in leaf acid phosphatase activity in common bean is unrelated to P efficiency 3) root gravitropism affects interplant competition, 4) P stress does not affect root lifespan in common bean, and 5) morphological responses of roots to P stress are synergistic.
Impacts
Study of the means by which plants adapt to soil stresses will lead to breeding of improved plant cultivars with multiple adaptations for improved stress tolerance. In this work, we have investigated the interaction between phosphorus, an important plant nutrient that is limiting in natural soils throughout much of the world, and root growth and development. These studies will contribute to molecular marker development for traits associated with important changes in root architecture for use by breeders, particularly of common bean, the most important food legume in the world. They will also advance our understanding of how plants respond to stresses in their environment, which has importance for all crops.
Publications
- Bayuelo-Jimenez, J.S., Craig, R. and Lynch, J.P. 2001. Salinity tolerance of Phaseolus species during germination and early seedling growth. Crop Science, Accepted for Publication.
- Lynch, J.P. and Brown, K.M. 2001. Topsoil foraging- an architectural adaptation to low phosphorus availability, Plant and Soil, Accepted for Publication.
- Ma, Z., Walk, T., Marcus, A. and Lynch. J.P. 2001. Morphological synergism in root hair length, density, initiation and geometry for phosphorus acquisition in Arabidopsis thaliana: a modeling approach. Plant and Soil, Accepted for Publication.
- Fisher, M.C.T., Eissenstat, D.M. and Lynch, J.P. 2001. Lack of evidence for programmed root senescence in common bean (Phaseolus vulgaris L.) grown at different levels of phosphorus supply. The New Phytologist, Accepted for Publication.
- Nielsen, K.L., Eshel, A. and Lynch, J.P. 2001. The effect of P availability on the carbon economy of contrasting common bean (Phaseolus vulgaris L.) genotypes. Journal of Experimental Botany 52:329-339.
- Yan, X., Liao, H., Trull, M.C., Beebe, S.E. and Lynch, J.P. 2001. Induction of a major leaf acid phosphatase does not confer adaptation to low phosphorus availability in common bean. Plant Physiology 125:1901-1911.
- Liao, H., Rubio, G., Yan, X., Cao, A., Brown, K.M. and Lynch, J.P. 2001. Effect of phosphorus availability on basal root shallowness in common bean. Plant and Soil 232:69-79.
- Rubio, G., Walk, T., Ge, Z., Yan, X., Liao, H. and Lynch, J.P. 2001. Root gravitropism and belowground competition among neighboring plants: a modeling approach. Annals Botany 88:929-940.
- Bates, T.R. and Lynch, J.P. 2001. Root hairs confer a competitive advantage under low phosphorus availability, Plant and Soil, Accepted for Publication.
|
Progress 01/01/00 to 12/31/00
Outputs
We are analyzing root traits that may confer efficient nutrient acquisition for crop plants, focusing on root architecture. Some of the highlights of our research this last year are that 1) phosphorus availability increases root hair density in arabidopsis by altering root anatomy so that more trichoblast files are produced, 2) the increased length and density of root hairs under low phosphorus availability increases phosphorus acquisition and the efficiency of phosphorus acquisition in arabidopsis, 3) shallower basal roots, as induced by low phosphorus availability in bean plants, decreases inter-root competition, and 4) phosphorus efficient bean genotypes have less root respiration per unit root growth rate than inefficient genotypes.
Impacts
Study of the means by which plants adapt to soil stresses will lead to breeding of improved plant cultivars with multiple adaptations for improved stress tolerance. In this work, we have investigated the interaction between phosphorus, an important plant nutrient that is limiting in natural soils throughout much of the world, and root growth and development. These studies will contribute to molecular marker development for traits associated with important changes in root architecture for use by breeders, particularly of common bean, the most important food legume in the world. They will also advance our understanding of how plants respond to stresses in their environment, which has importance for all crops.
Publications
- Ge, Z, Rubio, G. and Lynch, J. 2000. The importance of root gravitropism for inter-root competition and phosphorus acquisition efficiency: results from a geometric simulation model. Plant and Soil 218: 159-171.
- Bates, T.R. and Lynch J. 2000. Plant growth and phosphorus accumulation of wildtype and two root hair mutants of Arabidopsis thaliana. American Journal of Botany, 87:958-963. Bates, T.R. and Lynch, J. 2000. The efficiency of Arabidopsis thaliana root hairs in phosphorus acquisition. American Journal of Botany, 87:964-970.
- Ellers-Kirk, C.D., Fleischer, S.J., Snyder, R.H. and Lynch, J. 2000. Entomopathogenic Nematodes' Potential as a Biological Control of Acalymma vittata (Coleoptera: Chrysomelidae) in Cucumbers Grown in Two Soil Management Systems, Journal of Economic Entomology, 93:605-612.
|
|