Cue Column | Note-Taking Area
| Cue | Notes |
|---|---|
| Total cells? | 7 cells |
| Total nuclei? | 8 nuclei (central cell has 2 polar nuclei) |
| Egg apparatus location? | Micropylar end |
| Egg apparatus composition? | 1 egg cell (n) + 2 synergids (n each) |
| Synergid function? | Filiform apparatus guides pollen tube chemotropically |
| Central cell? | 1 large cell; 2 polar nuclei (each n); fuse with sperm → PEN (3n) |
| Antipodals? | 3 cells at chalazal end; nutritive; degenerate after fertilization |
| Largest cell in embryo sac? | Central cell |
| Development? | Functional megaspore → 3 mitotic (free nuclear) divisions → 8 nuclei → cellularize → 7 cells |
| Why "8-nucleate"? | Central cell = 1 cell but 2 polar nuclei |
| Fate of each cell post-fertilization? | Egg → zygote (2n); Central cell → endosperm (3n); Synergids/antipodals → degenerate |
Summary
The embryo sac is "7-celled, 8-nucleate" — the most tested phrase. The discrepancy between cell and nucleus count comes from the central cell (1 cell, 2 polar nuclei). The egg apparatus at the micropylar end is the fertilization site; synergids guide the pollen tube via the filiform apparatus; antipodals at the chalazal end degenerate after fertilization.
Diagram
