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Plant Life Cycles and Plant Parts
Plant life is determined by the specific life cycle of each plant. There are three basic plant life cycles, and all plants fall into one of these three categories:
- annuals: They complete a life cycle in one year.
- biennials: They require up to two years to complete their life cycle.
- perennials: They can live two or more years.
All About Annuals
Plants with an annual life cycle go from seed to seed in a single growing season, or one year. This annual process occurs in four distinct parts:
- seed
- vegetative growth
- flowering
- death.
Some of the most notable annuals are marigolds, tomatoes and petunias. Many weeds are annual plants. Understanding a weed's life cycle can be critical to controlling its growth.
Understanding Biennials
These plants complete their life cycle in a period no longer than two years. Some notable biennials are daisies and roses. Biennials follow this two-year life cycle sequence:
- first year: The plant produces leaves and food storage organs. Then it spends a dormant winter.
- second year: The plant produces flowers, fruits and seeds, and then it dies.
Some biennials can go from seed germination to production in the first year. This process is called bolting and it occurs when the plant is subjected to extreme conditions, such as drought or unusual temperature variations.
Perennial Plantings
Perennials live for two years or more. During the first year, their non-woody stems die back to the ground in the winter. But new stems grow from the plant's crown each spring. Woody perennials, such as trees and shrubs, can comfortably withstand harsh winter temperatures. Notable perennials include parsley, carrots and foxglove.
Plant Parts
All plants feature the same basic external parts, including leaves, stems, roots, flowers, fruits and seeds. An organ is a group of tissues that work together and perform a specific function. Plant organs fall into two specific categories:
- sexual/reproductive organs: The buds, flowers and fruits produce the seeds that will ensure a new generation of plants.
- vegetative organs: The roots, stems, shoot buds and leaves are used in asexual forms of reproduction: for cutting, budding and grafting.
The Parts of a Flower
The flower is the showiest part of a plant. Its sole function is sexual reproduction. A flower's beauty, color and fragrance attract pollinators such as insects and birds to help in its reproductive process.
The flower's parts are intricate, and each one performs a vital function to ensure the plant's health, safety, growth and reproductive success. These parts include:
stamen: This is the male flower part. It's a pollen sac or anther with a supporting filament. The pollen is dispersed by the wind and it attracts birds and insects.
- pistil: This is the female flower part. It contains the flower's eggs that, when fertilized, become seeds.
- sepals: These are green leaf-like structures at the flower base. They protect the flower bud.
- petals: The petals are highly colored and sometimes perfumed.
- roots: Roots anchor the plant in soil, absorbing nutrients and moisture in the process.
- stems: They support the buds and leaves, and serve as vascular conduits for water and food.
- buds: Buds are undeveloped shoots from which leaves or flowers grow.
- leaves: They absorb sunlight and help the plant to manufacture sugars through a process called photosynthesis.
- fruit: The fruits of the plant are fertilized, mature ovules. They may be fleshy (like an apple) or dry and hard (like corn).
- seeds: Seeds contain the plant's genetic information. Each seed contains an embryo, a food supply called the endosperm and a seed coat for protection. Sometimes, the seeds are enclosed (as in apples, peaches, or oranges) or they're on the outside (as in corn and strawberries).
