title: Influence of summer sowing dates, N fertilization and irrigation on autumn VSP accumulation and dynamics of spring regrowth in alfalfa (Medicago sativa L.).
abstract: Herbage yield of alfalfa (Medicago sativa L.) depends on forage management or environmental conditions that change C and N resource acquisition, and endogenous plants factors such as root organic reserves and number of active meristems. The aim of this work is to study the influence of two sowing dates in summer (12 July or 9 August), N fertilization (0 or 100 kg ha(-1)) and/or irrigation applied during the first year of alfalfa establishment on (i) the accumulation of N organic reserves (soluble proteins and more specifically vegetative storage protein) in taproots during autumn, (ii) the number of crown axillary meristems present at the end of winter and (iii) the dynamics of spring shoot growth. Delaying the sowing date for one month reduced root growth and root N storage, especially vegetative storage proteins (VSP) during autumn. Irrespective of sowing dates, N fertilization did not affect root biomass, number of crown buds, total root N, root soluble protein or VSP concentrations. By contrast, water deficiency during alfalfa establishment in the early summer reduced both root growth and N reserve accumulation. When spring growth resumed, there is a significant linear relationship between leaf area development and soluble protein and VSP concentrations in taproots, and also the number of crown buds. The results showed that an early sowing date and adequate water status during the summer allowed alfalfa plants to accumulate N reserves by increasing taproot mass and soluble protein concentrations, especially VSPs. This resulted in rapid shoot regrowth rates the following spring.
authors.affiliation: INRA, Unité d' Agronomie de Châlons-Reims, BP 224, 51686 Reims cedex 2, France.
authors.forename: Eric
authors.initials: E
authors.lastname: Justes
authors.forename: Pascal
authors.initials: P
authors.lastname: Thiébeau
authors.forename: Jean-Christophe
authors.initials: JC
authors.lastname: Avice
authors.forename: Gilles
authors.initials: G
authors.lastname: Lemaire
authors.forename: Jeffrey J
authors.initials: JJ
authors.lastname: Volenec
authors.forename: Alain
authors.initials: A
authors.lastname: Ourry
mesh_terms: D002244:Carbon / Q000378:metabolism; D005308:Fertilizers; D000455:Medicago sativa / Q000187:drug effects / Q000254:growth & development* / Q000378:metabolism; D018519:Meristem / Q000187:drug effects / Q000254:growth & development / Q000378:metabolism; D008954:Models, Biological; D009584:Nitrogen / Q000008:administration & dosage* / Q000378:metabolism; D010940:Plant Proteins / Q000187:drug effects / Q000378:metabolism*; D018517:Plant Roots / Q000187:drug effects / Q000254:growth & development / Q000378:metabolism; D018520:Plant Shoots / Q000187:drug effects / Q000254:growth & development / Q000378:metabolism; D012621:Seasons; D012639:Seeds / Q000187:drug effects / Q000254:growth & development / Q000378:metabolism; D013997:Time Factors; D014867:Water / Q000378:metabolism*
chemical_list: D005308:Fertilizers; D010940:Plant Proteins; D014867:Water; D002244:Carbon; D009584:Nitrogen