What common structures do the cherry blossoms and tulips that bloom in spring have? We classify the plant world based on flower structures.
Basic Knowledge
Structure of a typical flower (from the outside):
① Sepals (calyx) — At the base of the flower; protect it as a bud
② Petals — Colors that attract insects
③ Stamens — Pollen is contained in the anthers at the tips
④ Pistil — Stigma at the tip, style in the center, and ovary at the base. The ovary contains ovules
When pollination (pollen reaching the stigma of the pistil) occurs, ovules → seeds and ovaries → fruits.
Plants whose ovules are enclosed in an ovary are angiosperms (Angiosperms), while plants without ovaries whose ovules are exposed are gymnosperms (Gymnosperms). Typical gymnosperms include pine, cedar, ginkgo, and cycads.
Pollination (pollination)（Pollen reaching the stigma of the pistil）
Fertilization (fertilization)（The fusion of a sperm cell and an egg cell. It occurs after pollination）
Ovule (ovule)（The part that becomes a seed. It is inside the ovary）
Ovary (ovary)（The part that becomes a fruit. The swelling at the base of the pistil）
Angiosperms (Angiosperms)（Ovules are enclosed in ovaries. Cherry trees and morning glories）
Gymnosperms (Gymnosperms)（They have no ovaries, and their ovules are exposed. Pine trees and ginkgo trees）
Further Study (Background and Significance)
Pine flowers have neither petals nor sepals, and the ovules are exposed on the inner sides of the scales of female cones. The scales of male cones have pollen sacs, and pollen is carried by the wind (wind-pollinated flowers).
Gymnosperms are an ancient type of plant that flourished in the Paleozoic Era, with about 1,000 living species. Angiosperms, on the other hand, appeared during the Cretaceous Period of the Mesozoic Era and rapidly diversified. With more than 250,000 species today, they are the most successful plant group on Earth.
When we eat fruit, seeds appear. This is the result of ovaries becoming fruits and ovules becoming seeds. The edible part of an apple developed from tissue around the sepals, so it differs somewhat from a true “fruit” (false fruit). Many of the “vegetables” we commonly eat, such as tomatoes, eggplants, and cucumbers, are botanically classified as “fruits.”
- Flower structure (outside → inside): sepals, petals, stamens, pistil
- Pistil: stigma, style, ovary, ovules
- Pollination: pollen reaching the stigma
- Ovule → seed, ovary → fruit
- Angiosperms = with ovaries, gymnosperms = without ovaries
- Examples of gymnosperms: pine, cedar, ginkgo, and cycads
- Pine flowers have no petals or sepals and are wind-pollinated flowers
Points to Note (Easily Confused)
① Pollination (pollen reaching the stigma) and fertilization (the fusion of sperm and egg cells) are different. The order is pollination → fertilization. ② Ovules → seeds, and ovaries → fruits. Although the words are similar, be careful about the correspondence. ③ Pine and ginkgo trees are gymnosperms. They produce flowers but have no “petals or sepals.” ④ Cherry trees and tulips are angiosperms, while pine trees are gymnosperms.
Practice
- What is the swollen part at the base of the pistil called?
- What do the ovule and ovary become after pollination?
- Name two examples of gymnosperms.