Fruit as a midday resevoir: solving a controversial problem

doi:10.3969/j.issn.1009-9980.2008.04.001

Abstract：The so-called "fruit as a midday reservoir" theory was queried and challenged in the 1970's and 1980's by the reason that the experimental methods the previous researchers used instead of intact plants were excised shoots, which might induce the development of unnatural water potential gradients. The present authors conducted experiments with potted and field-grown citrus plants with both tritium tracing and water potential measurements to verify the assumption that transpiring leaves are capable of drawing water directly from fruit. Translocation of tritiated water was detected from fruit to leaf, and the presence of fruit on a shoot might moderate, whereas the absence of fruit might accentuate the leaf water deficits during the day-time. It is pointed out that fruit may not necessarily be inferior to the leaves, as fruit may compete successfully with leaves for water during the night-time when their water potentials become lower than that of the leaves. It is considered that the figurative use of the word "reservoir" as a scientific jargon does not appropriately denote the actual behaviours of a living fruit.