title: Mycorrhizal colonisation and P-supplement effects on N uptake and N assimilation in perennial ryegrass under well-watered and drought-stressed conditions.
abstract: To compare the effect of arbuscular mycorrhiza (AM) and P-supplement on N uptake and N assimilation under well-watered or drought-stressed conditions, Glomus intraradices-colonised, P-supplemented non-mycorrhizal (P) and non-mycorrhizal (control) plants of Lolium perenne were exposed to 12 days of water treatment. Leaf water potential (Ψ (w)), photosynthetic ability, and N and P nutritional status were measured at the beginning (day 0) and end (day 12) of water treatment. N absorption, amino acid and protein synthesis were quantified using the isotopic tracer (15)N at day 12. Under well-watered conditions, growth response and physiological parameters were similar in AM and P plants, as compared to controls. Drought (10% water) significantly decreased these parameters in all three treatments. As compared to control plants, the negative impact of water deficit on the Ψ (w), photosynthesis, biomass, and N and P content was highly alleviated in AM plants, while only slightly improved or remained the same level in P plants. The effect of AM symbiosis on N absorption and N assimilation was greater than that of the P supplement under well-watered and drought-stressed conditions, and this effect was highly enhanced under drought-stressed conditions. At terminal drought stress on day 12, the effect of AM colonisation on de novo synthesis of amino acids and proteins was 4.4- and 4.8-fold higher than that of the P supplement. These results indicate that the AM symbiosis plays an integrative role in N nutrition by alleviating the negative impacts of drought on N or P uptake and N assimilation, whereas the efficiency of a direct P supplement is very limited under drought-stressed conditions.
authors.affiliation: Environment-Friendly Agriculture Research Center (EFARC), Department of Animal Science, Institute of Agricultural Science and Technology, College of Agriculture & Life Science, Chonnam National University, Buk-Gwangju, P.O. Box 205, Gwangju 500-600, South Korea.
authors.forename: Bok-Rye
authors.initials: BR
authors.lastname: Lee
authors.forename: Sowbiya
authors.initials: S
authors.lastname: Muneer
authors.forename: Jean-Christophe
authors.initials: JC
authors.lastname: Avice
authors.forename: Woo-Jin
authors.initials: WJ
authors.lastname: Jung
authors.forename: Tae-Hwan
authors.initials: TH
authors.lastname: Kim
mesh_terms: D001692:Biological Transport; D003681:Dehydration / Q000378:metabolism; D055864:Droughts; D007553:Isotope Labeling / Q000379:methods; D008129:Lolium / Q000378:metabolism / Q000382:microbiology* / Q000502:physiology; D038821:Mycorrhizae / Q000254:growth & development* / Q000378:metabolism; D009566:Nitrates / Q000378:metabolism; D009584:Nitrogen / Q000378:metabolism*; D009587:Nitrogen Isotopes / Q000378:metabolism; D010758:Phosphorus / Q000378:metabolism*; D010788:Photosynthesis; D018515:Plant Leaves / Q000378:metabolism / Q000502:physiology; D018517:Plant Roots / Q000378:metabolism / Q000382:microbiology; D018520:Plant Shoots / Q000378:metabolism; D013559:Symbiosis; D014867:Water / Q000378:metabolism*
chemical_list: D009566:Nitrates; D009587:Nitrogen Isotopes; D014867:Water; D010758:Phosphorus; D009584:Nitrogen