Bisexuality in Salix chi friesiana on the Sefton Coast (v.c.59: South Lancashire)

摘要

Willows and poplars (Salicaceae) are characteristically dioecious, with male and female flowers (catkins) on separate plants. I was therefore surprised on 16th April 2009, when visiting a population of the rare hybrid Salix xfriesiana (S. repens x S.viminalis (Creeping Willow X Osier)) at Cabin Hill National Nature Reserve near Formby, to find a bush with bisexual catkins (at O.S. grid ref: SD28412.05082). This individual was essentially female, but, in a sample of 103 catkins, 35 (34%) showed bisexual characters, the top of the catkin being female and the base male with a fairly sharp horizontal division between the two sexes. Styles, stigmas, filaments and anthers appeared normal, but the proportion of male and female sections varied, some catkins having more of one sex than the other (see plates). This bush was one of several hybrid willows retained when a lha dune-slack was cleared of dense scrub, mainly S. cinerea (Grey Willow), in November/December 2005 (Smith & Kimpton 2008). Only one of 29 bushes known to be of this taxon in the vicinity had bisexual catkins, and I have not previously noticed this feature in about 200 bushes of S. x friesiana studied in recent years on the Sefton Coast (see Colour Section, Plate 2).