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FLOWERING PLANT LIFECYCLE (BRIEF)
Plant Terminology | Life Cycle | Types of Photosynthesis
 

This page introduces you to the basic steps in the lifecycle of flowering plants.

Germination: sprouting of the seed. Timing is critical. Germinating too early, too late, or in the wrong place spells death. Plants use various germination cues. These include the ratio of daylight to darkness, temperature, moisture (timing and quantity), fire, abrasion, and even animal digestive enzymes. For example, passing through the digestive system of an animal usually indicates that the seed has been dispersed (moved away) from its parent (so won't compete), that the seed might be deposited under a nurse tree if the animal is a bird that defecated while perched, and that there is some fertilizer.

Growth: development from seedling to mature plant.

Reproduction: production of offspring.

  • Egg/Sperm Production:
    • eggs are produced in the ovary, along with two polar nuclei per egg
    • sperm is produced and packaged in the anther (2 sperm cells per pollen grain)honey bee pollination
  • Pollination: transfer of pollen from anther to stigma (by wind, water or animal).
  • Double Fertilization: when pollen is accepted by the stigma, a pollen tube grows down the style and into the ovary. Both sperm cells from the pollen grain travel down the pollen tube to the ovary. One sperm cell fertilizes the egg to form the zygote which develops into the embryo and eventually the new plant. The other sperm cell fuses with the two polar nuclei to form the endosperm which provides food for the embryo. (Next time you eat a peanut, look for the small embryo, which has the leaves; the rest is endosperm (see picture).peanut
  • Seed Production: the embryo and endosperm are surrounded by a seed coat to form the seed.
  • Seed Dispersal: movement of seeds away from parent. Seed dispersal is critical to avoid competition with the parent plant and to occupy new, maybe better, sites. Plants use various, ingenious methods to disperse their seeds (e.g., hooked seeds to stick on a passing animal, edible ovary to be eaten and dispersed by an animal, etc.).

Death: if plants die after less than a year, then they are called annuals (or ephemerals). If plants die after two years, then they are called biennials, and if they live for more than two years, then they are called perennials.