Plant growth, phosphorus nutrition, and root morphological responses to arbuscular mycorrhizas, phosphorus fertilization, and intraspecific density

We examined the effects of arbuscular mycorrhizas (AM), phosphorus fertilization, intraspecific density, and their interaction, on the growth, phosphorus uptake, and root morphology of three facultative mycotrophic crops (Capsicum annuum, Zea mays, and Cucurbita pepo). Plants were grown in pots with or without AM at three densities and four phosphorus availabilities for 10 weeks. AM colonization, plant weight, and shoot phosphorus concentration were measured at harvest. Root morphology was assessed for C. annuum and Z. mays. Phosphorus fertilization reduced but did not eliminate AM colonization of all species. AM, phosphorus, and density interacted significantly to modify growth of C. annuum and C. pepo such that increased density and phosphorus diminished beneficial effects of AM. Increased density reduced positive effects of AM on C. annuum and C. pepo shoot phosphorus concentrations. AM altered both Z. mays and C. annuum root morphology in ways that complemented potential phosphorus uptake by mycorrhizas, but increased density and phosphorus diminished these effects. We infer that increased density predominantly influenced plant responses by affecting whether or not carbon (photosynthate) or phosphorus limited plant growth. By exacerbating carbon limitation, high density reduced the benefit/cost ratio of mycorrhizas and minimized their effects.

[1]  R. Koide,et al.  Effects of mycorrhizal fungi on plant populations , 2002, Plant and Soil.

[2]  Robert B. Jackson,et al.  PLANT COMPETITION UNDERGROUND , 1997 .

[3]  R. Koide.  Density-dependent response to mycorrhizal infection in Abutilon theophrasti Medic , 2004, Oecologia.

[4]  R. Miller,et al.  Chemical and microbiological properties , 1982 .

[5]  P. Tinker,et al.  VII. A detailed study of effects of soil phosphorus on , 1989 .

[6]  B. Hetrick.  Mycorrhizas and root architecture , 1991, Experientia.

[7]  R. Koide,et al.  The effect of mycorrhizal infection of Abutilon theophrasti on competitiveness of offspring. , 1998 .

[8]  M. Mclaughlin,et al.  Interactive effects of arbuscular mycorrhizal symbiosis, intraspecific competition and resource availability on Trifolium subterraneum cv. Mt. Barker , 1999 .

[9]  G. Berta,et al.  VA mycorrhizal infection and the morphology and function of root systems , 1993 .

[10]  R. Koide,et al.  Regulation of reproduction in wild and cultivatedLycopersicon esculentum Mill. by vesicular-arbuscular mycorrhizal infection , 1990, Oecologia.

[11]  P. Tinker,et al.  RELATION OF INTERNAL PHOSPHORUS CONCENTRATION AND PLANT WEIGHT IN PLANTS INFECTED BY VESICULAR‐ARBUSCULAR MYCORRHIZAS , 1980 .

[12]  E. Sieverding,et al.  Practical aspects of mycorrhizal technology in some tropical crops and pastures , 1987, Plant and Soil.

[13]  F. Bazzaz,et al.  The occupation and fragmentation of space : consequences of neighbouring shoots , 1992 .

[14]  H. Marschner,et al.  Extension of the phosphorus depletion zone in VA-mycorrhizal white clover in a calcareous soil , 1991, Plant and Soil.

[15]  Ryan S. Davis,et al.  Influence of Mycorrhizal Fungi on Cytokinin Production in Sour Orange , 1984, Journal of the American Society for Horticultural Science.

[16]  W. Stock,et al.  Density dependent interactions between VA mycorrhizal fungi and even-aged seedlings of two perennial Fabaceae species , 1992, Oecologia.

[17]  B. Hetrick,et al.  Mycorrhizal influence on intra- and interspecific neighbour interactions among co-occurring prairie grasses , 1993 .

[18]  B. Hetrick,et al.  Effects of mycorrhizae, phosphorus availability, and plant density on yield relationships among competing tallgrass prairie grasses , 1994 .

[19]  A. Fitter.  Costs and benefits of mycorrhizas: Implications for functioning under natural conditions , 1991, Experientia.

[20]  R. Leonard,et al.  Membrane-mediated decrease in root exudation responsible for phorphorus inhibition of vesicular-arbuscular mycorrhiza formation. , 1981, Plant physiology.

[21]  M. Allen,et al.  Phytohormone changes in Bouteloua gracilis infected by vesicular–arbuscular mycorrhizae: I. Cytokinin increases in the host plant , 1980 .

[22]  S. Smith,et al.  Mycorrhizal growth responses: interactions between photon irradiance and phosphorus nutrition. , 1988, The New phytologist.

[23]  D. S. Hayman.  The physiology of vesicular-arbuscular endomycorrhizal symbiosis , 1983 .

[24]  D. Janos,et al.  Phosphorus and intraspecific density alter plant responses to arbuscular mycorrhizas , 2004, Plant and Soil.

[25]  C. Vance,et al.  Phosphorus acquisition and use: critical adaptations by plants for securing a nonrenewable resource. , 2003, The New phytologist.

[26]  C. Powell.  Effect of P fertilizer on root morphology and P uptake ofCarex coriacea , 1974, Plant and Soil.

[27]  A. Page.  Methods of soil analysis. Part 2. Chemical and microbiological properties. , 1982 .

[28]  R. Koide,et al.  Mycorrhizal infection of wild oats: maternal effects on offspring growth and reproduction , 1992, Oecologia.

[29]  D. Donnelly,et al.  Pigment Content and Gas Exchange of Red Raspberry In Vitro and Ex Vitro , 1984, Journal of the American Society for Horticultural Science.

[30]  R. Hussey,et al.  Cotton root growth as influenced by phosphorus nutrition and vesicular–arbuscular mycorrhizas , 1989 .

[31]  W. Saunders.  Phosphate retention by New Zealand soils and its relationship to free sesquioxides, organic matter, and other soil properties , 1965 .

[32]  M. Caldwell,et al.  Competing root systems: morphology and models of absorption , 1986 .

[33]  Manuela Giovannetti,et al.  AN EVALUATION OF TECHNIQUES FOR MEASURING VESICULAR ARBUSCULAR MYCORRHIZAL INFECTION IN ROOTS , 1980 .