Pistil Starch Reserves at Anthesis Correlate with Final Flower Fate in Avocado (Persea americana)

Abstract

A common observation in different plant species is a massive abscission of flowers and fruitlets even after adequate pollination, but little is known as to the reason for this drop. Previous research has shown the importance of nutritive reserves accumulated in the flower on fertilization success and initial fruit development but direct evidence has been elusive. Avocado (Persea americana) is an extreme case of a species with a very low fruit to flower ratio. In this work, the implications of starch content in the avocado flower on the subsequent fruit set are explored. Firstly, starch content in individual ovaries was analysed from two populations of flowers with a different fruit set capacity showing that the flowers from the population that resulted in a higher percentage of fruit set contained significantly more starch. Secondly, in a different set of flowers, the style of each flower was excised one day after pollination, once the pollen tubes had reached the base of the style, and individually fixed for starch content analysis under the microscope once the fate of its corresponding ovary (that remained in the tree) was known. A high variability in starch content in the style was found among flowers, with some flowers having starch content up to 1,000 times higher than others, and the flowers that successfully developed into fruits presented significantly higher starch content in the style at anthesis than those that abscised. The relationship between starch content in the ovary and the capacity of set of the flower together with the correlation found between the starch content in the style and the fate of the ovary support the hypothesis that the carbohydrate reserves accumulated in the flower at anthesis are related to subsequent abscission or retention of the developing fruit.

Optimization of controlled pollination in avocado (Persea americana Mill., Lauraceae)

“…This fifteen fold increase suggests that natural pollination is still a limiting factor in avocado production but also that, in spite of pollinating all the flowers of the inflorescence, still a low percentage of them are able to develop into fruits probably due to differences in flower quality at the time of anthesis (Alcaraz et al, 2010(Alcaraz et al, , 2013.…”

“…For this reason, performing crosses that involve genotypes of the same floral group is difficult. Moreover, avocado is an extreme case of a species with a very low fruit to flower ratio, with less than 1% of the flowers produced able to set fruits due to a massive drop of flowers and developing fruitlets (reviewed in Alcaraz et al, 2013) making the development of progenies with high number of individuals difficult.…”

Phosphorous Nutritional Level, Carbohydrate Reserves and Flower Quality in Olives

“…Such effect may be most pronounced during the period of flowering and fruit set when carbohydrate demand is highest. Starch reserves were previously demonstrated be correlated to flower viability of several fruit trees including apricot [21], avocado [23, 24], and citrus [60]. In olives, Reale et al [27] showed that ovary and ovule starch levels were closely related to perfect flower development.…”

“…In general, flower carbohydrate reserves support pollen tube growth and early development of embryos [21] and therefore are thought to be significant enhancers of productivity [22–24]. In olive, flowering induction does not seem to rely on carbohydrate reserves as shown by Stutte and Martin [25], using manipulation of light and CO 2 , and by Cherbiy-Hoffmann et al (2015), using manipulations of light intensity.…”

Taxonomic value of histochemical features of the style in early lineages of Asteraceae

“…Studies performed in ovaries and styles of avocado and other crop species (Alcaraz et al 2013) yielded that at anthesis the cells of the style were rich in starch, and starch content decreased in the days following anthesis suggesting a role in nutritive reserves in flower fertilization. Also, the starch content in the pistil at anthesis could be a good indicator of flower quality because it was present in all flowers that developed into fruits.…”