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need pollen germ. and growth method

Jose' A. Feijo' jose.feijo at bio.fc.ul.pt
Mon Sep 30 05:18:21 EST 1996

>> Now, Do pollen tubes show directional growth with respect to the presence
>> of stigmatic tissue? Does the pollen of self sterile flowers germinate in
>> the presence of 'self' stigmas? There is a suggestion that Ca+ ions are
>> involved - is this verifiable?  Is there a diurnal rhythm in pollen growth?
>> etc etc
>We have a film (VCR) demonstrating that one of the lily pollens (Crinum, I
>think) grows toward the stigma when placed close to it on agar.  We have
>used this in our organismal biology course and it works pretty reliably if
>the pollen is close to a piece of the stigma.  I wonder if the calcium is
>universally involved or only in some species.

The chemotropic hypothesis of pollen guidance goes back to the 60's
(especially the work of Rosen and colleagues) and calcium was believed in
those days to be in fact THE major chemoatractor. However experiments by
Joseph Mascarenhas in the mid-70's have shown that calcium couldn't be the
only chemoatractor (if at all). I can remember a dozen of different
hypothesis of chemoatraction, involving sucrose, invertase, calcium,
potassium, lipid (specially triglucerides with linoleic acid) and more
recently (Alice Cheung et al, published on Cell last year) arabinogalactans,
were suggested. Plus some physical factors like low DC electric fields (very
effective) and strong electromagnetic fields. In vitro they all seem to have
some effect, but, to the best of my knowledge, nobody seems to have ever
proved such uniqueness in vivo. I guess the same is true concerning the
experiments involving tissues or parts of tissues atracting pollen tubes
The rise and fall of the calcium story in well reviewed by Mascarenhas
(1974) in the Botanical Review ("The biochemistry of angiosperm pollen" I
Hope it helps

Jose' A. Feijo'

Dep. Biologia Vegetal, Fac.Ciencias Univ. Lisboa
Campo Grande, Ed.C2, P-1700 LISBOA, PORTUGAL

tel. +351.1.7500069, fax +351.1.7500048
e.mail: jose.feijo at bio.fc.ul.pt
URL: http://www.fc.ul.pt/departs/biologia_vegetal/ejf.html

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