Final answer:
White pines reproduce sexually, involving the production of both male and female spores in cones through meiosis and subsequent fertilization of the egg by sperm. The resulting seed contains an embryo and the female gametophyte, which develops into a new pine tree.
Step-by-step explanation:
Sexual Reproduction of White Pines
White pines are species of conifers that reproduce via sexual reproduction. This process involves the alternation of generations, where the tree, which is the sporophyte, produces both male and female spores (gametes) within their respective cones. The male cones, or staminate cones, produce pollen through meiosis, and the pollen grains are carried by the wind to the female cones. Once the pollen reaches a female cone, a pollen tube grows, allowing sperm to unite with an egg for fertilization. The result is a seed that contains an embryo and the female gametophyte, packaged within a seed coat that is dispersed by wind or sometimes by birds.
Through this process, cell division occurs in several stages. Firstly, meiosis happens in the cones to produce haploid male and female spores. Following pollination, mitosis occurs for the development of the pollen tube and the division of the generative cell within the pollen grain. Finally, fertilization incorporates the fusion of haploid nuclei to form a diploid zygote that develops into the embryo within the seed. Conifers like white pines represent a complex lifecycle that predominantly takes place as a diploid sporophyte with a brief phase as a haploid gametophyte.