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Joined 2026-09-21 Message
Cross-pollination 2026-10-14
Transfer of pollen between different individuals of the same species; compare self-pollination.[ref]
32.2 Pollination and Fertilization. Biology 2e, §32.2 opening paragraphs: self-pollination and cross-pollination
A flower can contain both reproductive groups and still receive pollen from another individual. Conversely, transfer between two flowers on one plant does not by itself imply cross-pollination. Following the donor and recipient individuals makes pollination useful for studying genetics: organ position alone cannot identify whose alleles meet at fertilization.
Double fertilization 2026-10-14
In the common angiosperm arrangement, one sperm fuses with the ovum to form a diploid zygote; another fuses with the central biological cell's two polar cell nuclei, initiating endosperm with three chromosome sets. The zygote develops into a plant embryo, and the ovule develops into a seed.[ref]
For an original counting example, stipulate a plant with chromosomes and the common two-polar-nucleus arrangement. Each haploid sperm and ovum contributes . The zygote therefore has chromosomes, while the initiating endosperm cell nucleus has . The maternal seed coat remains derived from plant tissue; the whole seed has no single uniform chromosome count. This is bookkeeping for a stipulated example, not identification of a particular species. It follows by counting the chromosome sets entering each fusion, rather than assigning one count to everything enclosed by a seed coat.
Pollen tube 2026-10-14
A growing extension from a pollen grain. In a compatible flower, the pollen tube provides a route for sperm to the angiosperm female gametophyte.[ref]
Pollination Created 2026-10-13 Updated 2026-10-14
In angiosperms, pollination transfers pollen from an anther to a stigma. Fertilization is a later fusion of gametes; seed development follows. Pollination may use animals, wind or water, so an insect visit is neither required for every flower nor sufficient evidence of fertilization.[ref]
32.2 Pollination and Fertilization. Biology 2e, §32.2 opening definition, Pollination by Wind and Pollination by Water
Stigma (botany) Created 2026-10-14 Updated 2026-10-14
The stigma is the carpel's pollen-receiving region. Compatible pollen may form a pollen tube that grows toward an ovule; arrival alone does not establish fertilization.[ref]
32.2 Pollination and Fertilization. Biology 2e, §32.2 Incompatibility Genes in Flowers and Double Fertilization
A useful diagnostic question is what was actually observed: pollen on a stigma, a growing pollen tube, or a new plant embryo? Each observation tests a different stage. A pollen tube germination assay isolates the middle process for direct viewing.