Editing Conifer (section)

==== Female reproductive cycles ====
Conifer reproduction is synchronous with seasonal changes in temperate zones. Reproductive development slows to a halt during each winter season and then resumes each spring. The male [[strobilus]] development is completed in a single year. Conifers are classified by three reproductive cycles that refer to the completion of female strobilus development from initiation to seed maturation. All three types of reproductive cycle have a long gap between [[pollination]] and [[fertilization]].

'''One year reproductive cycle''': The genera include ''[[Abies]]'', ''[[Picea]]'', ''[[Cedrus]]'', ''[[Pseudotsuga]],'' ''[[Tsuga]]'', ''[[Keteleeria]]'' ''([[Pinaceae]])'' and ''[[Cupressus]], [[Thuja]], [[Cryptomeria]], [[Cunninghamia]]'' and ''[[Sequoia (genus)|Sequoia]] ([[Cupressaceae]])''. Female strobili are initiated in late summer or fall of a year, then they overwinter. Female strobili emerge followed by pollination in the following spring. Fertilization takes place in summer of the following year, only 3–4 months after pollination. Cones mature and seeds are then shed by the end of that same year. Pollination and fertilization occur in a single growing season.<ref name="Singh-1978">{{cite book |last=Singh |first=Hardev |title=Embryology of Gymnosperms |date=1978 |publisher=Gerbrüder Borntraeger |isbn=978-3-443-14011-3 }}{{pn|date=January 2025}}</ref>

'''Two-year reproductive cycle''': The genera includes ''[[Widdringtonia]]'', ''[[Sequoiadendron]]'' (''[[Cupressaceae]]'') and most species of ''Pinus''. Female [[strobilus]] initials are formed in late summer or fall then overwinter. Female strobili emerge and receive pollen in the first year spring and become conelets. The conelet goes through another winter rest and, in the spring of the second year [[archegonia]] form in the conelet. Fertilization of the archegonia occurs by early summer of the second year, so the pollination-fertilization interval exceeds a year. After fertilization, the conelet is considered an immature cone. Maturation occurs by autumn of the second year, at which time seeds are shed. In summary, the one-year and the two-year cycles differ mainly in the duration of the pollination-fertilization interval.<ref name="Singh-1978"/>

'''Three-year reproductive cycle''': Three of the conifer species are [[pine]] species (''[[Pinus pinea]]'', ''[[Pinus leiophylla]]'', ''[[Pinus torreyana]]'') which have pollination and fertilization events separated by a two-year interval. Female strobili initiated during late summer or autumn of a year, then overwinter until the following spring. Female [[strobili]] emerge then pollination occurs in spring of the second year then the pollinated strobili become conelets in the same year (i.e. the second year). The female [[gametophytes]] in the conelet develop so slowly that the [[megaspore]] does not go through free-nuclear divisions until autumn of the third year. The conelet then overwinters again in the free-nuclear female gametophyte stage. Fertilization takes place by early summer of the fourth year and seeds mature in the cones by autumn of the fourth year.<ref name="Singh-1978"/>