Title: Factors influencing pollen germination in three Explorer ™ roses
Authors: Richer, C., Poulin, M. and Rioux, J.A.
Authors affiliation: Agr and AGri Food Canada, Hort Res and Dev Ctr, St Jean PQ J3B 3E6 Canada.
Published in: CANADIAN JOURNAL OF PLANT SCIENCE 87 (1), pages 115-119, JAN 2007.
Abstract: “Pollen germination is useful for the estimation of pollen viability. For three cultivars from the Explorer ™ series, Champlain, Nicolas and Frontenac, a liquid medium with a pH of 5.6 and a saccharose concentration of 15% provides optimal germination conditions. Four flower stages were determined and evaluated according to the following scale: flower bud at stage 0 (closed bud), stage 1 (closed petals but open sepals), stage 2 (bud with petals three-quarters open) and stage 3 (fully open flower). Pollen germination was higher when the pollen was collected at stages 0 and 1 for Champlain, at stages 1 and 2 for Frontenac and at stage 2 for Nicolas. Based on the results of the evaluation of pollen drying techniques, it is recommended that pollen be dried for 24 h in darkness before use in crossing.”
Hi Henry,
Wow, what a great article topic! At first I wondered if maybe the different stages of opening and what was best for each cultivar had to do with how double each flower is and that the actual best stage of opening just corresponded to the same stage in terms of time of anther development. Perhaps that is not the case because it seems like Nicolas is much less double than Frontenac and benefits from a later stage of development for anther collection.
Thanks for keeping an eye out for new research Henry.
Sincerely,
David
This is a tad confusing…what is meant by pollen germination? Is it the same as viability?
Is it considered germination when pollen releases from the anthers or when pollen penetrates the stigmas?
And what exactly is “a liquid medium with a pH of 5.6 and a saccharose concentration of 15%” ??
Is this a special liquid present on the anthers and/or pollen at the time of release?
Where and when is this liquid present, and what is saccharose?
Dee,
Each pollen grain has two nucleii: one is for growing a pollen tube down the style, the second moves down the style to meet the ovule and make a new plant.
I’ll guess that a lot of folks are familiar with Ruth Cole’s 1917 paper in the Botanical Gazette “Imperfection of Pollen and Mutablility in the Genus Rosa” (vol 63(2): 110-123. (It’s available through the JStor search engine.)
Cole looked at pollen before it was shed.
The first sentences in her conclusion:
“The species of Rosa are characterized by a large amount of abortive pollen and also by great variability. Both pollen sterility and variability have long been recognized as two main characteristics of hybrids.”
(Other conclusions dealt with hypothesizing which species were hybrids, etc. and how this fit with Darwinian theory.)
What surprised me was the amount of pollen that wasn’t ‘right’ from the getgo.
Thanks Ann. I understand that in terms of pollen germination, but I’m still waiting for Henry to tell me what saccharose is.
Hi,
From last Tuesday to this Tuesday we are hosts to our daughter’s family (i.e. 4 grandchildren to entertain) so I can only get to the computer during nap time or before they get up.
See:
Link: dictionary.reference.com/browse/saccharose
It’s O.K Henry, I thought this sugary medium might be similar to the sticky substance produced by the stigmas, but at this point I’m less sure than before.
15 % sugar is about the standard amount used in laboratory rose pollen germination medium.
http://www.springerlink.com/content/k74671kn00308387/
Yeah, it seems like 15% sucrose is the common concentration for pollen germination assays. That is 150 grams of sucrose in a liter of water. That takes awhile to dissolve all that! I compared that with 15 grams per liter for my hanging drop pollen germination studies and found for at least Rosa macounii the 15 grams (1.5%) produced longer pollen tubes after 2 hours and decided to just go with that. I really like pollen germination studies to assess pollen viability. Seeing long pollen tubes growing from pollen grains shows for sure that the pollen is alive and viable because it is producing growth. Another common assessment is just to look at pollen under the microscope and those that are obviously empty and shriveled we know are not viable, but sometimes the dark, plump ones can be misleading. We can assume they are viable, but they may not be. Seeing if they actually germinate and produce a pollen tube is convincing that they really were viable and had a chance to participate in fertilization of an egg to produce a seed. It’s amazing how fast pollen tubes grow. I have an article a few years back in the newsletter with a step by step process of the hanging drop pollen germination assay I use with pictures.
I’ve mainly used pollen germination assays to compare different pollen storage temperatures and treatments and how fast and to what degree viability has been lost.
Sincerely,
David
You can buy refined liquid sucrose at Haggens for like 2 bucks a bottle, lol. I use it for cooking 
Thank you for all this fascinating stuff…
…and for the links, Henry.