title: Carbon utilization by fruit limits shoot growth in alternate-bearing citrus trees.
abstract: Fruit load in alternate-bearing citrus trees is reported to alter shoot number and growth during spring, summer, and autumn flushes, and the source-sink balance, which affects the storage and mobilization of reserve nutrients. The aim of this work was to assess the extent of shoot growth inhibition resulting from the presence of fruits in 'Moncada' mandarin trees loaded with fruit (ON) or with very light fruit load (OFF), and to identify the role of carbohydrates and nitrogenous compounds in the competition between fruits and shoots. Growth of reproductive and vegetative organs was measured on a monthly basis. (13)C- and (15)N-labeled compounds were supplied to trace the allocation of reserve nutrients and subsequent translocation from source to sink. At the end of the year, OFF trees produced more abundant flushes (2.4- and 4.9-fold higher in number and biomass, respectively) than ON trees. Fruits from ON trees accumulated higher C amounts at the expense of developing flushes, whereas OFF trees exhibited the opposite pattern. An inverse relationship was identified between the amount of C utilized by fruits and vegetative flush growth. (13)C-labeling revealed an important role for mature leaves of fruit-bearing branches in supporting shoot/fruit growth, and the elevated sink strength of growing fruits on shoots. N availability for vegetative shoots was not affected by the presence or absence of fruits, which accumulated important amounts of (15)N. In conclusion, our results show that shoot growth is resource-limited as a consequence of fruit development, and vegetative-growth inhibition is caused by photoassimilate limitation. The competence for N is not a decisive factor in limiting vegetative growth under the experimental conditions of this study.
authors.affiliation: Centro de Citricultura y Producción Vegetal, Instituto Valenciano de Investigaciones Agrarias, E-46113 Moncada, Valencia, Spain. Electronic address: martinez_belalc@gva.es.
authors.forename: Belén
authors.initials: B
authors.lastname: Martínez-Alcántara
authors.affiliation: Centro de Citricultura y Producción Vegetal, Instituto Valenciano de Investigaciones Agrarias, E-46113 Moncada, Valencia, Spain. Electronic address: iglesias_dom@gva.es.
authors.forename: Domingo J
authors.initials: DJ
authors.lastname: Iglesias
authors.affiliation: Instituto Agroforestal Mediterráneo, Universidad Politécnica de Valencia, E-46022 Valencia, Spain.
authors.forename: Carmina
authors.initials: C
authors.lastname: Reig
authors.affiliation: Instituto Agroforestal Mediterráneo, Universidad Politécnica de Valencia, E-46022 Valencia, Spain.
authors.forename: Carlos
authors.initials: C
authors.lastname: Mesejo
authors.affiliation: Instituto Agroforestal Mediterráneo, Universidad Politécnica de Valencia, E-46022 Valencia, Spain.
authors.forename: Manuel
authors.initials: M
authors.lastname: Agustí
authors.affiliation: Centro de Citricultura y Producción Vegetal, Instituto Valenciano de Investigaciones Agrarias, E-46113 Moncada, Valencia, Spain.
authors.forename: Eduardo
authors.initials: E
authors.lastname: Primo-Millo
mesh_terms: D018533:Biomass; D002244:Carbon / Q000378:metabolism*; D002247:Carbon Isotopes; D002957:Citrus / Q000378:metabolism*; D035264:Flowers / Q000378:metabolism; D005638:Fruit / Q000378:metabolism*; D009584:Nitrogen / Q000378:metabolism; D009587:Nitrogen Isotopes; D024301:Plant Bark / Q000378:metabolism; D018515:Plant Leaves / Q000378:metabolism; D018520:Plant Shoots / Q000254:growth & development* / Q000378:metabolism; D012098:Reproduction; D012621:Seasons; D013213:Starch / Q000378:metabolism; D014197:Trees / Q000378:metabolism*
chemical_list: D002247:Carbon Isotopes; D009587:Nitrogen Isotopes; D002244:Carbon; D013213:Starch; D009584:Nitrogen
keywords: Alternate bearing; Carbohydrates; Citrus; Nitrogen; Shoot growth