Articles
REPRODUCTIVE BIOLOGY OF BANKSIA
Article number
387_22
Pages
187 – 190
Language
Abstract
The genus Banksia is characterised by large inflorescences consisting of many individual flowers.
The flowers are protandrous and the anthers shed their pollen prior to flower opening on a specialised portion of the style called the pollen presenter.
The pollen receptive stigma cells are located within a groove, and do not attain peak receptivity until three days after flower opening, by which time the flower’s own pollen has been removed by foraging fauna.
The time of peak receptivity of the stigma has been determined experimentally by its ability to support pollen germination, and by the production of stigma secretion.
Thus, in the natural situation, protandry is an effective outcrossing mechanism in Banksia. In addition to protandry, most species of Banksia also show a degree of self incompatibility.
Fewer seeds are set following self as compared to cross pollination, and this is due to fewer pollen tubes reaching the base of the style.
Some genotype combinations are more successful than others in terms of fertility, and in some cases are more successful when crossed in one direction than in the other.
Even when all flowers are cross pollinated, however, seed set is still relatively low.
This is partly due to spatial limitations imposed by the size of the infructescence, but is probably also attributable to nutrient allocation within the plant.
This limitation in seed set is a problem in Banksia breeding, particularly in the production of interspecific hybrids.
Nevertheless, some species combinations will produce hybrids, which have potential as new cultivars.
The problems involved in studying reproductive biology of Banksia is discussed in relation to plant improvement.
The flowers are protandrous and the anthers shed their pollen prior to flower opening on a specialised portion of the style called the pollen presenter.
The pollen receptive stigma cells are located within a groove, and do not attain peak receptivity until three days after flower opening, by which time the flower’s own pollen has been removed by foraging fauna.
The time of peak receptivity of the stigma has been determined experimentally by its ability to support pollen germination, and by the production of stigma secretion.
Thus, in the natural situation, protandry is an effective outcrossing mechanism in Banksia. In addition to protandry, most species of Banksia also show a degree of self incompatibility.
Fewer seeds are set following self as compared to cross pollination, and this is due to fewer pollen tubes reaching the base of the style.
Some genotype combinations are more successful than others in terms of fertility, and in some cases are more successful when crossed in one direction than in the other.
Even when all flowers are cross pollinated, however, seed set is still relatively low.
This is partly due to spatial limitations imposed by the size of the infructescence, but is probably also attributable to nutrient allocation within the plant.
This limitation in seed set is a problem in Banksia breeding, particularly in the production of interspecific hybrids.
Nevertheless, some species combinations will produce hybrids, which have potential as new cultivars.
The problems involved in studying reproductive biology of Banksia is discussed in relation to plant improvement.
Publication
Authors
M. Sedgley, A.M. Fuss
Keywords
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