Is there any convincing report that in diclinous plants the male flowers are not only larger, but open flowers also earlier on a daily basis as compared to the female flowers to guide the visitors from pollen donors to pollen acceptors?
Dear Klaus:
This is a very interesting question and I don't know whether it has been tested. It should be easy to test based on order of flowering and simple measurements. I would suggest you put the words Begonia, pollination into a Search Engine and see what happens. Everyone insists that, in Begonia, the less common, female flowers mimic the more common male flowers on the same stem.
Bisexual flowers that lack nectar and offer pollen as their only reward are often protogynous but the early female phase in the bisexual flower (when anthers remain shut) may last only a fraction of the full length of the flower's life-cycle. Therefore, the ratio of flowers in the female phase is far lower than in surrounding flowers on the same plant in the male phase. I found this to be the case in Echeandia macrocarpa and in many Australian Acacia species. I believe that Dr Dafni referred to this as "automimicry."
Well, referring first to Peter Bernhardt, I checked for the phenological overlap in Grassy Bells, Edraianthus (protandorus flowers with secondary pollen presentation) and observed that at the beginning of the flowering stage, both within the inflorescence and the whole plant, as well as during the whole flowering period between June-October with an absolute peak in midd June, the female phase lasts for shorter periods which significantly extends at the end of the flowering phase where it seems that the plant in a female phase takes a "sit-and-wait" strategy (as put by Schoener TW (1971) Theory of feeding strategies. Annual Review of Ecology and Systematics 2:369-404). To that end, corollas of late flowering plants with distinctively elongated female phase are significantly shorter than corollas of early and/or peak flowering plants, when duration of a male phase clearly exceeds female phase.
Dear Dr Lanau,
I studied a monoecious species in which male flowers display white petals whereas female flowers have no petals (American Journal of Botany 97(4): 672–679, 2010).
Dear all, particularly Peter,
my favourite candidate is a cucurbit, e.g. Bryonia, which has all preconditions. The flowers are unisexual and in some cases male flowers are bigger than female flowers; moreover some species are diclinous and both sexes offer reward. I would like to hypothesize that for optimal pollinator guidance each day the male flowers would open before the female flowers do and thus pollinators are directed towards the male flowers where they are loaded with pollen grains and only afterwards towards the female flowers where they can pollinate. The Kiwifruit genus Actinidia might also represent a good candidate. And as both candidates are relevant crop species, there might be literature about the daily opening of male as compared to female flowers.
Klaus
Dear Klaus, I see the avocado bloom as a good example for your hypothesis (and see my paper: Ish-Am G., 2009. Daily patterns of avocado bloom and honeybee activity. Cal. Avocado Soc. Yearbook 2008-09, 91:105-127). The bisexual avocado flower opens twice, in two successive days, each time for half a day, with intermediate closing. On the first day it opens as a female and on the second one as a male. All the tree flowers bloom simultaneously: they open and close together. The avocado cultivars divided into two types. Type A avocados open female flowers on the morning and close them at noon, and then open male flowers for the other half day. Type B avocados open the female flowers at noon, close them on the evening, and then open them as male flowers on the next morning for half a day. Both female and male flower stages secrete nectar, and are visited by bees. This unique flowering behavior provokes cross pollination: in the morning from B type trees to A types, and vice versa during the afternoon. Moreover, in the morning the B type trees male flowers open earlier then the A type female ones, and similarly in the afternoon the male bloom of the A type trees opens before the female bloom of the B types. Honeybee activity follows the blooming pattern: both in the morning and at the afternoon they visit first the male blooming trees, and afer an hour or two they move to the female ones. See in the bellow Fig. the daily pattern bloom and bee activity on A type avocado 'Reed' cultivar and on B type 'Nabal' avocado.
Dear Gad, perfect! I would appreciate very much to receive a copy of your paper.
Klaus
Dear Klaus, I'm glad to give you a copy of my paper.
You may find it here in ResearchGate:
https://www.researchgate.net/search.Search.html?type=publication&query=+Daily+patterns+of+avocado+bloom+and+honeybee+activity
- Badges
- Science topic
- Similar topics
- Social Psychology
- Attitude