Plants, like all living things, go through a cycle of birth, growth and reproduction.
Most plants start out life as seeds that sprout to become mature plants with flowers and fruit; later, these mature plants produce new seeds via fertilization or pollination, and eventually reproduce further seeds themselves.
Seeds
Plants are living organisms that rely on food, water, air and sunlight to flourish. Their roots, leaves and flowers all play a part in this growth. Seeds are the first sign of life a plant produces – they contain an embryo which begins growing immediately upon being placed into soil and an outer hard coating known as seed coat which softens when exposed to moisture and eventually starts germinating as the embryo germinates within it.
Seeds with an excellent start can become plants that produce food and pollinate each other to produce even more seeds, which then get dispersed to new places where their cycle can resume. Some plants even use fibre-coated seeds that allow them to glide in the air when falling from their respective plants, covering greater distances when dispersed into the environment.
Figure below depicts two generations in a plant’s life cycle – the sporophyte and gametophyte generations (for nonvascular plants such as ferns and mosses, respectively). Sporophytes tend to dominate, with larger and longer-living individuals than gametophytes (in nonvascular species such as ferns).
At this early stage of development, seedling roots take in moisture and nutrients from their environment while leaves use energy from light sources to produce food for their plants – this process is known as photosynthesis.
Once a seedling reaches an age that allows it to thrive on its own, it begins flowering. Flowers produce seeds in the form of fruit that can then be planted and used to establish another plant that continues the cycle.
Life cycles of plants vary by species and are highly affected by environmental factors. Germination season and flowering time have huge influences on how many seeds are produced per year; furthermore, how quickly a seedling transitions to maturity affects how many generations a given plant completes in any one year.
Environmental conditions play a complex role in germination and dormancy, yet some key cues have an effect. Thickness and color of seed coat, for instance, can affect its permeability to oxygen; light wavelengths reaching seeds can alter imbibition dynamics as well as oxidative processes.
Seedlings
Plants follow a lifecycle that begins from seed, developing into a seedling and eventually maturing to full maturity with leaves, stems, roots and flowers. Germination and photosynthesis are two key processes involved in turning seedlings into fully grown plants.
Germination occurs when an embryo inside of a seed takes in nutrients and water to begin growing its seedling. At this point, its cotyledons – leaf-like structures inside its surface – open, allowing sunlight into its interior so photosynthesis can take place and produce food through photosynthesis.
Seedlings grow and expand as they absorb water, minerals and other nutrients from the soil. When they reach a certain size, they create their first root which serves both as an anchor point in the ground while simultaneously taking in moisture from its environment.
Next, a green shoot begins to grow upward towards the sun. As it nears light sources, its color changes from green to yellow as chlorophyll absorbs into its cells allowing photosynthesis to occur and produce food through photosynthesis.
Once a seedling has enough energy and resources to begin its journey towards becoming an adult plant, it will begin putting out true leaves – miniature versions of adult leaves that store energy until photosynthesis can take place on its own.
Wild plants typically die if their roots cannot absorb enough moisture from the soil, often due to drought conditions but other factors may also play a part.
Temperature can also play an influential role on seedling growth; warmer environments have been found to encourage seedling germination.
But, according to meta-analysis, this effect was insignificant; likely due to warmer temperatures not remaining constant and having different impacts depending on species’ individual needs for water or temperatures.
Overall, climate did not significantly impact seedling emergence as measured by climate data or treatments simulating reductions in snow cover. Treatments simulating early snowmelt followed by rising temperatures had an indirect positive impact on germinated seed proportion.
Flowers
Seeds are the start of every new life for plants. Containing all the necessary instructions, these seeds also contain concentrated energy sources to fuel their development as they begin to sprout into new life.
At an ideal temperature and with enough sunlight, air, and water available for growth, seeds germinate and begin their journey toward becoming plants. They produce more leaves, longer stalks or stalks, root hairs that help absorb nutrients from the soil and further blossom as plants.
At this stage of their growth, plants make their own food by converting energy from sunlight and water into sugars that they store in their leaves and roots – the latter are vital in anchoring them down while their stem stretches towards the sun.
Flowers are the reproductive parts of plants, producing pollen grains to pollinate other flowers in order to produce seeds and set off reproduction cycle.
Some flowers use vibrant hues and scents to attract birds and insects that carry pollen from flower to flower, while others – which use wind pollination instead – do not require pollinators at all – their anthers are placed outside so the wind can carry pollen grains towards their stigmas and stamens.
Pollen from flowers can be spread between different flowers by insects and birds that visit for nectar feeding or collecting nectar, wind, rain or birds. When animals pass by a flower on their fur, they too can pick up pollen that sticks onto it and is then transferred between other blooms.
Pollen grains traveling along pollen-bearing hairs reach the pistil, or female part, of a flower and can then be fertilised to form seeds. A pistil comprises four components – style, stigma, ovary and ovules – that work together in the formation of seeds.
Fertilized ovules quickly transform into seeds that contain an embryo with shoots and roots, while their protective wall grows into pods or fruits to shield the seed from predators and promote its spread to other areas by wind or animals. Once spread, seeds may begin a new cycle.
Fruits
Fruits play an integral part in the lifecycle of plants. They provide food necessary for plant growth and reproduction as well as carrying seeds that will start new plant life.
Seeds are small objects containing an embryo (an unformed plant). A seed contains all of the vital nutrient elements required for its healthy development; when placed in an appropriate environment it will germinate and begin its journey as a full grown plant.
Most seeds require moisture, oxygen and warmth in order to germinate; additional light exposure will boost their chances.
Germination is the initial step of plant lifecycle. Once a seed germinates, its roots and shoots begin to take hold, absorbing water and nutrients from its environment.
At this stage, the plant begins producing flowers. Each bloom consists of male anthers which produce pollen which is then spread throughout its female pistil by insect pollinators and distributed onto it via stigma, style and ovary – where sperm cells enter to fertilize its ovules inside.
Once fertilized, an egg becomes fertilized and produces fruit – this fruit may contain either one seed or multiple smaller ones. Once it ripens off its tree or plant it will either be eaten by animals or left for humans to pick.
Apples and pears rely on flowers to reproduce while bananas have the ability to clone themselves and form multiple trees or plants.
Some plants’ flowering cycles span multiple years. Annuals such as violets complete their cycle in one year while biennial and perennial species produce flowers and seeds every other year.
Dispersal of fruit seeds is another essential part of its lifecycle, helping new plants take root and blossom. Animals such as deer, squirrels and birds help spread them by eating its flesh to soften and disperse its seeds over the land.
Some fruits, such as acorns and oranges, rely on their seeds to travel to new environments where they can flourish. These seeds might travel via burrs or white fluff of dandelion leaves or animal droppings; whatever their form, their journey can often include many miles.