Pollen cone

Cycads pollination by insects may be one of the earliest forms of insect-pollination. Like conifers, cycads bear their reproductive cells in cones rather than flowers. Individual cycad plants are either male or female, male plants having pollen cones and female plants, seed cones. Fertilization requires transfer of pollen grains from pollen cones to seed cones. The role of insects in this process has received attention in a cycad commonly known as the cardboard palm (Zamia furfuracea). This is a handsome horticultural plant with... 

The weevils do not linger to feed and breed in seed cones as they do in pollen cones, even though starch is plentiful here as well. This behavioral difference is not yet completely understood, but it seems that the cones of female plants contain an active poison called beta-(methylamino)alanine (BMAA). This substance is a recognized neurotoxin for mammals and is believed to affect insects as well. The male plants pollen cones also contain BMAA, but in a bound form that renders it harmless, allowing the weevils to nest and feed with impunity. In contrast, seed cones contain free toxic BMAA that presumably repels weevils and causes them to depart after quick examination and inadvertent pollination. 

Caron, G. E. and Powell, G. R. (1991). Proliferated seed cones and pollen cones in young black spruce. Trees, 5, 65-74. 

Douglas-fir is monoecious. Trees commonly reach reproductive maturity at 12 to 15 years of age. Primordia of undifferentiated buds are already present when vegetative buds flush in the spring of the year preceding the cone crop (Hermann and Lavender 1990). By mid-June, vegetative bud primordia, pollen cone primordia (usually clustered near the base of the extending shoot), and seed cone primordia (borne singly near the tip of the shoot) (Allen and Owens 1972) can be separated based on histochemical differences. 

Lodgepole pine is monoecious, with male and female strobih ( flowers ) usually home separately on the same tree. Female strobih are usuaUy at the apical end of main branches in the upper crown, while pollen strobih originate in the lower crown. Female strobih are reddish-purple and develop in whorls of two to five. Pollen cones are pale yellow to yehowish- orange and occur in crowded clusters at the base of new shoots (Lotan and Critchfield, 1990). 

Caron and Powell, 1992). Initial pollen cone production may lag behind that of seed cones by several years (Simpson and Powell, 1981 Caron and Powell, 1989). 

Caron, G.E., and G.R. Powell. 1989. Patterns of seed-cone and pollen-cone production in young Picea mariana trees. Can. J. For. Res. 19 359-364. 

Feeding and breeding in the cone leaves the weevils covered with ripened pollen. As they move in the search for a new male cone to assault, they also come upon female plants bearing seed cones ready for pollination. Although they produce little heat to... 

Sperms so far as known ciliated and motile ovules with a pollen-chamber with or without strobili, the sporophylls either being in cones or in rosettes or indeterminate axes secondary growth rare (as compared to Strobilophyta mostly relatively small plants, with pith and cortex large, and wood scanty little branched ) leaves usually compound or else angiospermous and with several carpels borne on each sporophyll.Phylum Cycadophyta (Page 17)... 

Phenology Pollen released in March-April. Cones ripen in September-October of the following year. 

Ho, R.H. 1991. A guide to pollen- and seed-cone morphology of black spruce, white spruce, jack pine and eastern white pine for controlled pollination. Ontario Ministry of Natural Resources, Ontario Forest Research Institute. 31 pp. 

Stem injection of gibberellin A4/7 in May or June increases both pollen and seed cone production (Ross, 1991 Eysteinsson and Greenwood, 1995 Shearer et al, 1999). Protocols for in vitro germination of western larch pollen have been developed (Dumont-BeBoux et al, 2000). The detailed documentation of the reproductive cycle of western larch by Owens and Molder (1979a, b) - illustrated in Figure 4 - is thought to hold for other species of Larix as well, albeit with some differences in timing (Owens, 1995). 

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