Is the pollination efficiency of long-lived orchid flowers affected by age?

Rúbia Santos Fonseca,Milene Faria Vieira,Flávia Aparecida Dos Santos

doi:10.1590/0034-737x201562040003

Rúbia Santos Fonseca, Milene Faria Vieira + Show 1 more

Open Access

https://doi.org/10.1590/0034-737x201562040003

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Abstract

The long-lived flowers of orchids increase the chances of pollination and thus the reproductive success of the species. However, a question arises: does the efficiency of pollination, expressed by fruit set, vary with the flower age? The objective of this study was to verify whether the flower age of Corymborkis flava(Sw.) Kuntze affects pollination efficiency. The following hypotheses were tested: 1) the fruit set of older flowers is lower than that of younger ones; 2) morphological observations (perianth and stigmatic area), stigma receptivity test by using a solution of hydrogen peroxide and hand-pollination tests are equally effective in defining the period of stigmatic receptivity. Flowers were found to be receptive from the first to the fourth day of anthesis. Fruit set of older flowers (third and fourth day) was lower than that of younger flowers. Morphological observations, the stigma receptivity test and hand-pollinations were equally effective in defining the period of stigmatic receptivity. However, to evaluate the maximum degree of stigma receptivity of orchid species with long-lived flowers, we recommend hand-pollinations, beyond the period of receptivity.

Highlights

Pollination is essential for the conservation and evolution of species and communities of plants (Kearns & Inouye, 1997), ensuring the maintenance of the genetic variability in natural populations
The adherence of the pollinia in the stigmatic area can be regarded as an indicator of stigma receptivity in C. flava
Morphological observations and the stigma receptivity test were effective in defining the period of stigmatic receptivity as well as handpollination

Summary

Introduction

Pollination is essential for the conservation and evolution of species and communities of plants (Kearns & Inouye, 1997), ensuring the maintenance of the genetic variability in natural populations. The success of pollination is mainly influenced by three factors: the period of stigmatic receptivity, which is defined by the capacity of the stigma to ensure pollen germination; the ability of the pollen tube to grow within the style; and the viability of ovules (Sanzol & Herrero, 2001; Dafni et al, 2005) These factors are associated with floral anthesis (Schoen & Ashman, 1995), which is the period between flower opening and senescence, when pollinator visits occur (Primack, 1985). This author found that the receptivity lasted, on average, 15 days and 89.68% of the handpollinated flowers set fruit (83.33–100%) between the 2nd and 19th day of anthesis In this case, it was found that pollination efficiency was not affected by the flower age. The following hypotheses were tested: 1) the fruit set of older flowers is lower than that of younger ones, 2) the observation of morphological changes (stigmatic area color, presence of exudates and aspect of the perianth), stigma receptivity test by using a solution of hydrogen peroxide (for detecting the presence of stigmatic peroxidases) and hand-pollination tests are effective in defining the period of stigmatic receptivity

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