Plants have the capacity to reproduce both sexually and asexually, known as alternation of generations.
Seeds are the building blocks of all plants. Once these seeds find soil rich in oxygen and moisture levels as well as an ideal temperature environment, their outer coating releases and they begin growing, which is known as germination.
Gametophytes are plants’ haploid reproductive stages; by comparison, their diploid offspring (sporophytes) are called sporophytes.
Seeds
Seeds planted into the ground often start their journey as plants. After germinating, they begin growing into seedlings before eventually reaching maturity, whereupon flowers begin producing pollen for reproduction before producing seeds that continue the cycle by continuing the cycle itself.
Seeds contain storage tissue for nourishment during their dormant period and a protective outer coat to shield themselves from the environment. When water enters through absorption into their seeds, they swell up and soften their outer coating as enzymes begin converting their stored food into energy for germination. An embryonic root breaks through and anchors itself in soil while their shoot/plumule emerges to reach sunlight before sprouting and becoming seedlings.
Seedlings rapidly flourish through photosynthesis, steadily growing larger as each time they sprout through photosynthesis. At this stage, leaves and stems develop for support as the seedling expands further each time it does so. Once these stages have taken place, flowering and fruiting take place as fruits or flowers mature and wind, animals, or water scatter or disperse them to new locations where fertilisation may take place and new plants be born; otherwise their seeds won’t germinate at all and thus die away with that plant altogether.
Germination
Seeds lie dormant until conditions in the soil enable them to sprout. Germination requires water, oxygen and temperature for success; when conditions meet these criteria, germination begins in earnest – with roots deep into the ground and shoots reaching upwards towards the sun.
As seeds absorb water they begin to expand through a process known as imbibition; enzymes and food supplies become hydrated or “take up” water through imbibition. Expanding cells also cause turgor pressure to build up, often leading to the outer coating breaking apart and an embryo inside growing inside becoming visible; eventually this becomes what we refer to as a seedling.
Once a seedling has reached maturity, it can be fertilized. Fertilization occurs when pollen from male stamen lands on female pistil and gametes within fuse together to form a diploid zygote which eventually develops reproductive organs – thus repeating itself.
Some plants disperse their seeds by letting them drift away when the time is right; others use pods that explode when their time comes and release seeds into the air. Other seeds are dispersed via wind, animals or mechanical means – once dispersed a seed will germinate at its new location and continue the lifecycle cycle.
Seedlings
Seeds have an outer coating to protect them and contain an embryo (baby plant) with roots, stem and leaf parts ready to sprout under favorable conditions. Seeds require food, water and sunlight in order to grow successfully while producing energy via photosynthesis; this energy comes from converting carbon dioxide, water and minerals into glucose and oxygen through its leaves.
Once germination occurs, seedlings gradually grow into adult plants with leaves, roots and flowers – eventually pollinated and producing seeds to continue the cycle.
Some plants can also reproduce through asexual reproduction. Daffodils and snowdrops use this process, producing bulbs which lie below ground; other plants like yams and potatoes produce tubers beneath the soil that serve as hosts for their reproduction.
Most vascular plants are composed of two generations: the sporophyte generation is known as the “sporophyte”, while its counterpart, known as “gametophyte”, comprises reproductive cells called gametes which mate to produce fertilised eggs and sperm; this process eventually forms a diploid sporangium which undergoes mitosis to create haploid gametes known as spores that are dispersed into nature to begin life cycles again; usually, one dominant sporophyte lives longer than its counterpart!
Mature Plants
Flowers and fruit-bearing plants have reached the mature stage in life. Now is an opportune time for these plants to produce seeds so their lives may continue and new cycles can start.
Pollination occurs when male ‘gametes’ from stamen flowers reach the stigma, where they meet female gametes from pistil flowers to form fertilised eggs, or zygotes. Once fertilised, this fertilised egg or zygote develops into a young sporophyte and becomes food stored as seeds that will allow its continued development at later stages in its life cycle. Meanwhile, its surrounding ovary wall transforms into fruit or pods to protect it.
Natural selection plays an outsized and geographically variable role in regulating the timing and environment for seed to seedling transition in many natural populations. Seasonal conditions affect how quickly this life stage grows over time; earlier transition in autumn would likely result in higher projected population growth rates; conversely if delayed until spring it could result in lower projected population growth rates, showing how important environmental influences on offspring phenotypes is in biological systems.
Pollination
Plants are unique in that they possess two multicellular life stages known as gametophytes and sporophytes. Gametophytes produce single-celled haploid gametes which fuse to form diploid zygotes; sporophytes produce single-celled haploid spores which mature into mature multicellular diploid sporangium (plural: sporangia). This alternation between generations ensures their existence over their lifecycles.
Flowering plants have the ability to reproduce sexually, which allows the transfer of genetic material among members of their species and greater variation among traits. Pollination occurs when pollen grains move from male flowers into the stigmas of female flowers – usually via animals such as birds, bees, butterflies, moths and flies – creating cross pollination – an activity known by experts as cross pollination.
Male gametes can be found within pollen grains that develop on a flower’s antherus. Once transported, these haploid gametes travel to a female flower’s ovary where they fuse with an egg cell that produces sperm; once combined these cells develop into embryonic tissue that then develops within its respective seed created by an ovule.
Wind and animals disperse seeds to start new plants; however, plants are also capable of reproducing asexually without pollinators or flowers – sending out stems called rhizomes which grow into new plants at some distance from their parent or producing bulbs or tubers which grow into new plants when planted in soil.
Fertilization
Plants possess the unique capability of reproducing both sexually and asexually, known as alternation of generations, to adapt to their environment more easily – this ability is particularly essential in vascular plants such as ferns and trees.
Seeds are like the babies of plants; they contain an embryo with essential food sources and an outer coating for protection. Once produced, seeds need a way to disperse themselves so they can find suitable environments in which to germinate and begin their lives; some methods include wind, moving water or animals – some plants such as dandelions have feathery parachutes on their seeds that allow them to fly off when detached from the plant and glide in the air after falling off!
Once a seed meets conditions that support its germination, its embryo begins developing inside. Roots grow deep into the soil while stems reach towards sunlight to take in photosynthesis-inducing sunlight and radiate out as leaves absorb it for photosynthesis.
As plants develop and mature, they produce flowers from modified shoots (determinate apices). Flowers contain male and female parts which are pollinated when pollen from stamen reaches pistil; fertilizing it to produce seeds and fruit. Flowers usually require insects for pollination to occur. Once fertilized, plants begin growing quickly producing seeds which either fall off naturally or are carried off by animals into new lives.