The seeds you carefully plant in the spring quickly sprout from the ground and by summertime have blossomed into flowers and fruit, sometimes casting their own seeds back to the soil to ensure the next generation. As a gardener, you observe the life cycle of your plants every year, and understanding how plants grow can aid you in making gardening decisions.
Plant life cycles depend on the type of plant you have. Plants are divided into four large groupings--mosses, ferns, non-flowering seed plants and flowering plants--in large part based on differences in life cycle. Mosses and ferns reproduce with spores instead of seeds. The majority of plants produce seeds that develop into their offspring.
Plants originated in the water, and when the first plants moved onto land, they continued to rely on water to transport their sex cells. Mosses and ferns--the most primitive plants still extant on Earth--need rain water to bring sperm and egg cells together. The resulting union produces millions of spores, which carry on the wind and, if successfully established, develop into the next generation of adult plants. Mosses and ferns do not produce seeds and, according to Stephen P. Broker of Yale University, the evolution of the seed was a dramatic advancement for plants.
Seed plants emerge from their seeds when conditions are optimal and begin the process of vegetative growth, which is not involved with reproduction. Soon, circumstances such as optimal light conditions signal the plant to develop reproductive structures. Male structures called microgametophytes produce pollen grains that contain sperm cells, while female structures called megagametophytes produce eggs.
Unlike early plants, the seed plants do not need water to carry the sperm to the egg. In non-flowering seed plants like conifer trees, the wind does the work, bearing pollen onto the exposed seeds found on the tree's cones. Flowering plants often elicit the help of pollinators, who in the process of feeding on the flower's nectar and pollen, cover their bodies with pollen that they carry from flower to flower. When pollen sticks to the seed or the female structures of a flower, it grows into a long tube, penetrating into the plant and fertilizing the egg within. After fertilization, seeds develop that contain the next generation of plants.
Successful gardening requires acknowledging the importance of the plant life cycle to the production of fruit and flowers that most people want from their plants. For example, in plants that require cross-pollination, such as apple trees or pumpkins, pollinating insects are essential. Planting ferns differs from planting seed plants because of differences in life cycle. Better understanding these processes helps you to better care for your plants.