Post-pollination prefertilization drops affect germination rates of heterospecific pollen in larch and Douglas-fir.
Pollen of larch (Larix × marschlinsii) and Douglas-fir (Pseudotsuga menziesii) was used in homospecific and heterospecific crosses. Germination of heterospecific pollen in ovulo was reduced in post-pollination prefertilization drops. This provides evidence of selection against foreign pollen by open-pollinated exposed ovules in these two sister taxa, which share the same type of pollination mechanism. Of the other prezygotic stages in pollen-ovule interactions, uptake of pollen by stigmatic hairs did not show any selection. Pollen tube penetration of the nucellus was similar for hetero- and homospecific pollen tubes, but heterospecific tubes only delivered gametes in one cross. To test for differences in the post-pollination prefertilization drops of each species, drops were gathered and analysed. Glucose and fructose were present in similar amounts in Douglas-fir and larch, while sucrose was found in larch only. Other carbohydrates such as xylose and melezitose were species-specific. In P. menziesii, sucrose is absent due to its conversion to glucose and fructose by apoplastic invertases. In contrast, Larix × marschlinsii drops have sucrose because they lack apoplastic invertases. The presence of invertase activity shows that the composition of gymnosperm post-pollination prefertilization drops is not static but dynamic. Drops of these two species also differed in their calcium concentrations.
Department of Biology, Centre for Forest Biology, University of Victoria, Victoria, BC V8W 3N2, Canada. pvonader@uvic.ca
Patrick
P
von Aderkas
Massimo
M
Nepi
Marlies
M
Rise
Federico
F
Buffi
Massimo
M
Guarnieri
Andrea
A
Coulter
Karen
K
Gill
Patricia
P
Lan
Sarah
S
Rzemieniak
Ettore
E
Pacini
D002118:Calcium / Q000032:analysis / Q000378:metabolism; D002241:Carbohydrates / Q000032:analysis; D003433:Crosses, Genetic; D018525:Germination / Q000502:physiology*; D006824:Hybridization, Genetic; D028221:Larix / Q000201:enzymology / Q000502:physiology* / Q000648:ultrastructure; D056771:Ovule / Q000201:enzymology / Q000502:physiology / Q000648:ultrastructure; D011058:Pollen / Q000201:enzymology / Q000502:physiology* / Q000648:ultrastructure; D053205:Pollen Tube / Q000201:enzymology / Q000502:physiology / Q000648:ultrastructure; D054817:Pollination / Q000502:physiology*; D028224:Pseudotsuga / Q000201:enzymology / Q000502:physiology* / Q000648:ultrastructure; D043324:beta-Fructofuranosidase / Q000378:metabolism
D002241:Carbohydrates; D043324:beta-Fructofuranosidase; D002118:Calcium