title: Relationship between soil temperature and fruit colour development of 'Clemenpons' Clementine mandarin (Citrus clementina Hort ex. Tan).
abstract: BACKGROUND
  In Citrus, root temperature regulates rind colouration. However, few studies have investigated the range of temperatures and timing which determine rind colour break. The objective of this study was to determine the relationship between range of soil temperature (ST) and rind colour development in the precocious ‘Clemenpons’ Clementine mandarin. Reflective white plastic mulch was used to modify root temperature.
  
  
  RESULTS
  Mulching increased reflected light and reduced daily maximum ST and temperature range, major differences being established 70-30 days before harvest. Rind colour-break correlated positively with 20 °C < ST < 23 °C; thus, 20-23 °C appears to be the ST threshold interval for fruit colouration. The sooner the soil reached it, the sooner the fruit changed rind colour. In our experiments, control trees accumulated 565 h at this ST interval before fruit changed colour, whereas in treated trees it occurred 2 weeks earlier. Hence, in treated trees the colour break was advanced by 2 weeks and this increased the percentage of fruit harvested at the first picking date by up to 2.5-fold.
  
  
  CONCLUSIONS
  Fruit colour-break does not take place at a certain ST, but after several hours at a ST of 20-23 °C. In our experiments, reducing ST during the 2 months before harvest advances the first picking date in the ‘Clemenpons’ Clementine mandarin.
authors.forename: Carlos
authors.initials: C
authors.lastname: Mesejo
authors.forename: Giuliana
authors.initials: G
authors.lastname: Gambetta
authors.forename: Alfredo
authors.initials: A
authors.lastname: Gravina
authors.forename: Amparo
authors.initials: A
authors.lastname: Martinez-Fuentes
authors.forename: Carmina
authors.initials: C
authors.lastname: Reig
authors.forename: Manuel
authors.initials: M
authors.lastname: Agusti
mesh_terms: D000383:Agriculture / Q000379:methods; D002957:Citrus / Q000254:growth & development / Q000378:metabolism*; D003080:Cold Temperature; D018556:Crops, Agricultural / Q000254:growth & development / Q000378:metabolism*; D063427:Food Quality; D005638:Fruit / Q000254:growth & development / Q000378:metabolism*; D010860:Pigments, Biological / Q000096:biosynthesis*; D018517:Plant Roots / Q000254:growth & development / Q000378:metabolism*; D010969:Plastics / Q000737:chemistry / Q000528:radiation effects; D012621:Seasons; D012987:Soil; D013030:Spain; D013472:Sunlight; D013499:Surface Properties; D013997:Time Factors
chemical_list: D010860:Pigments, Biological; D010969:Plastics; D012987:Soil