Carbohydrate supply and demand during fruit development in relation to productivity of grapefruit and 'murcott' mandarin

A. Bustan, E. E. Goldschmidt, Y. Erner

Research output: Contribution to journalArticlepeer-review

9 Scopus citations


A comparison was conducted between grapefruit (Citrus paradisi Macf. cv. Marsh seedless), [large fruit, high, regular yields] and mandarin (Citrus reticulata cv. Murcott) [small fruit, alternate bearing]. To determine fruit demand, maximal fruit absolute growth rate (AGR) and fruit relative growth rate (RGR), trees were trunk girdled and extremely thinned (grapefruit); alternatively, 'Off and regular (control) trees were used (Murcott). Fruit growth was followed weekly and transformed into carbohydrate consumption by CHNOS analysis (McDermitt and Loomis, 1981), and respiration measurements. In grapefruit, fruit thinning resulted in higher AGR and RGR throughout most of fruit development, suggesting long periods of source limitation. Calculation of the daily available carbohydrate also indicated that in grapefruit, fruit demand for carbohydrate exceeded the supply. In 'Murcott', 'Off fruit revealed relatively low AGR values, though higher than 'On' fruit throughout the season. During stage I of fruit development RGR values were unstable and not unequivocally indicative for sink-or source limitations. However, fruit absolute demand was significantly lower than the calculated supply during stage I and the beginning of stage II. Source limitation occurred only when fruit size reached about 20 g (FW), 120 days after anthesis. It is suggested that fruitlet size is a major factor in the source-sink interplay of developing fruits. Murcott fruit development is sink limited for the first three months due to its remarkably small initial size (about 6 mgFW). When source limitation takes over, the self-thinning mechanisms are not fully active any more. Fruit number per tree remains higher than desired, resulting in small fruit size at harvest and overcropping symptoms. In grapefruit, on the other hand, initial fruitlet size is large (72 mgFW) and fruit number per tree is adjusted by the self-thinning mechanism to the available supply during stage I, thus preventing crop overload and resource depletion.

Original languageEnglish
Pages (from-to)81-88
Number of pages8
JournalActa Horticulturae
StatePublished - 1 Jun 1996
Externally publishedYes


  • Citrus
  • Crop modelling
  • Fruit size
  • Relative growth rate
  • Source-sink relations

ASJC Scopus subject areas

  • Horticulture


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