Biology » Seed Plants » Angiosperms

Summarizing Angiosperms

Summary

Angiosperms are the dominant form of plant life in most terrestrial ecosystems, comprising about 90 percent of all plant species. Most crops and ornamental plants are angiosperms. Their success comes from two innovative structures that protect reproduction from variability in the environment: the flower and the fruit. Flowers were derived from modified leaves. The main parts of a flower are the sepals and petals, which protect the reproductive parts: the stamens and the carpels. The stamens produce the male gametes in pollen grains. The carpels contain the female gametes (the eggs inside the ovules), which are within the ovary of a carpel. The walls of the ovary thicken after fertilization, ripening into fruit that ensures dispersal by wind, water, or animals.

The angiosperm life cycle is dominated by the sporophyte stage. Double fertilization is an event unique to angiosperms. One sperm in the pollen fertilizes the egg, forming a diploid zygote, while the other combines with the two polar nuclei, forming a triploid cell that develops into a food storage tissue called the endosperm. Flowering plants are divided into two main groups, the monocots and eudicots, according to the number of cotyledons in the seedlings. Basal angiosperms belong to an older lineage than monocots and eudicots.

Glossary

anther

sac-like structure at the tip of the stamen in which pollen grains are produced

Anthophyta

phylum to which angiosperms belong

basal angiosperms

a group of plants that probably branched off before the separation of monocots and eudicots

calyx

whorl of sepals

carpel

single unit of the pistil

corolla

collection of petals

cotyledon

primitive leaf that develop in the zygote; monocots have one cotyledon, and dicots have two cotyledons

dicot

(also, eudicot) related group of angiosperms whose embryos possess two cotyledons

filament

thin stalk that links the anther to the base of the flower

gynoecium

(also, carpel) structure that constitute the female reproductive organ

herbaceous

grass-like plant noticeable by the absence of woody tissue

monocot

related group of angiosperms that produce embryos with one cotyledon and pollen with a single ridge

ovary

chamber that contains and protects the ovule or female megasporangium

perianth

part of the plant consisting of the calyx (sepals) and corolla (petals)

petal

modified leaf interior to the sepals; colorful petals attract animal pollinators

pistil

fused group of carpels

sepal

modified leaf that encloses the bud; outermost structure of a flower

stamen

structure that contains the male reproductive organs

stigma

uppermost structure of the carpel where pollen is deposited

style

long, thin structure that links the stigma to the ovary

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