Like any living thing, plants go through a life cycle. Although each genus may have its own lifespan and duration of each development stage specific to its own species, all plants follow a standard pattern. The basic life cycle begins at the seed stage and ends with the regeneration stage; from there the life cycle starts all over again.
The seed embryo consists of cotyledons, which turn into the first leaves of a seedling. Monocotyledon (monocot) is the term used for species with one cotyledon, while dicotyledon (dicot) is for plants with two. There is no significant growth during this stage. In order for a seed to germinate, the temperature must be right and there must be water to soak the seed. As the seed coat absorbs water, it swells until it opens up. As water absorption increases, it stretches the radicle out into the taproot turning the cotyledons into leaves.
As soon as the leaves start to open, the seedling stage begins. The root emerges first, penetrates the soil rapidly and anchors itself firmly in the soil. Growth stops on the side exposed to light and continues underneath until the seedling is in an upright position. This happens as the hypocotyl (the portion of the embryonic plant axis below the cotyledon) arch emerges from the soil, where the cotyledons rise above the soil surface and expand. This exposes the growing point (epicotyl) of the seedling. The first true leaf emerges from a bud at the first stem node above the cotyledons.
The energy supplied by the sun aids in photosynthesis, where the green pigment in the plant’s leaf (chlorophyll) absorbs energy from the sunlight. The plant uses the energy absorbed, water and carbon dioxide to produce oxygen and simple sugars, which it uses to make more complex sugars and carbohydrates to store energy. It makes cell walls out of cellulose and hemicelluloses and with nitrogen to make proteins. The plant will use its energy depending on the stage of its development and environmental conditions.
When the plant receives five or more hours of light per day, the vegetative growth stage begins. In this stage, the plant rushes to grow leaves and stems that will support the growth of future flowers or fruits. The vegetative stage varies from plant to plant. Vegetative growth continues through cell division (mitosis) and expansion in the epicotyl or growing point of the young plant.
Some plants produce flowers when they turn into adults. Flowers contain male and female parts. In most plants, these appear together in the same flowers while in other plants they are separate flowers on the same plant. Ovaries or carpels make up the female parts of the flower while male parts consist of stamens.
During the flowering period, plants put all their energy towards reproduction. Different plants may differ in the manner they reproduce. Some seeds will only develop once pollinated by a male plant. In other cases, the female plant will continue to produce more flowers in an effort to reproduce until fertilization happens (sexual). In other plants, seeds will develop during the flowering stage without the need for pollination or fertilization (asexual).
Regeneration is the method by which plants reproduce themselves. Seeds produced by plants will go through similar life cycles that parent plants went through. It needs only one seed to survive to replace the parent plant.
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