> 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.