SEXUAL EXPRESSION IN PINES IN RELATION TO THEIR ONTOGENETIC DEVELOPMENT

In pines male strobiles may form sporadically on young seedlings prior to the onset of the regular pattern of first female and then male flowering.
This may indicate a localized ageing of a tissue while the whole plant is still juvenile.
From observation it is known that male strobiles develop in the central zone of the crown.
Shoots in this zone are shaded, inhibited in growth, poor in rooting ability and have a generally aged appearance.
However, grafts obtained from scions from this part of the crown attain the ability to produce female and then male strobiles later than grafts from the outside zone of the crown.
This would suggest that the outside of the crown, bearing female strobiles, is the most mature zone of the tree and that juvenility is strongest in the poorly-growing, male-flowering shoots inside the crown.
External factors generally favouring ontogenetic progress also favour female, but not male, strobile production.
The above would suggest that the definition of juvenility in monoecious plants should refer to the time prior to development of female organs irrespective of male flowering.

Symposium on Juvenility in Woody Perennials

M. Giertych

https://doi.org/10.17660/ActaHortic.1976.56.8