- plant seed, the reproductive organ of the angiosperms
- Uses of Seeds to Man
- Main Functions of Plant Seeds
- Exception to the Natural Process of Seed Formation
- More Variations in Plant Seeds
- You might like these. . .
- Angiosperm seeds
- ALL ABOUT SEEDS
- How Do Seeds Find a Good Place to Grow?
- 1. Wind Dispersal
- 2. Animal Dispersal
- 3. Water Dispersal
- SLEEPY SEEDS
- 4. Self Dispersal
- Why Does the Seed Move Away?
- ANCIENT DATES
- How Does a New Plant Grow?
- CLEVER SEEDS!
- Plant Parts
- What Is A Seed – A Guide To The Seed Life Cycle And Its Purpose
- What is a Seed?
- Where Do Seeds Come From?
- Types of Seeds
- How does a tiny seed grow into a tree?
- Structure of a seed
- Germination and its requirements
- Seed dormancy
- Why do some seeds take longer than others to germinate?
- Structure of a Seed
- Functions of Seeds
- Dispersion of Seeds
- Solved Example for You
- What’s Inside a Seed? All This
- The Parts of a Seed
- Hot (or Temperate) Enough For Ya?
- More Than “Just Add Water”
- Three Fascinating Steps to Your New Plant
plant seed, the reproductive organ of the angiosperms
The plant seed is an organ found in plant shoot, attached to the stem, and originating from a flower. It is a structure that is formed by the maturation of the ovule within the ovary of the angiosperms. It is often described as a “mature ovule”.
In angiospermous plants, the natural process of seed development occurs through double fertilization. This proceeds after pollination, the transfer of pollen grains from an anther to the stigma of a flower.
In double fertilization, one of the two sperm nuclei (1N) in the germinating pollen (pollen tube) unites with the egg nucleus (1N) in the female gametophyte or embryo sac within the ovule to form the diploid (2N) embryo of the seed. The other sperm nucleus (1N) in the pollen tube unites with the polar nuclei (2N) in the embryo sac to form the triploid (3N) endosperm. Meanwhile, the sorrounding integuments of the ovule form the seed coat (2N).
To complete the process, the ovary which encloses the ovule develops into a fruit. As a result, the plant seed consists of a diploid embryo, a triploid endosperm, and a diploid seed covering. The seed or seeds which develop from the same flower are enveloped by a fruit.
Various seeds of plants on display, including corn caryopsis
Uses of Seeds to Man
Seeds have multiple uses to man. Examples are as source of food (e.g. cereals, grain legumes, seed vegetables), beverages (e.g. coffee, cacao, coconut water), and spices (e.g. anise, nutmeg, mustard, sesame). Many seeds also provide raw materials for the industrial processing of various products such as vegetable oil, starch, biofuel, lubricants, and fiber.
Cereal seeds are rich in carbohydrate; legume seeds contain more protein than the seeds of other plant types. There are seeds also that are rich in oil such as castor bean, jatropha and sunflower. The seeds of the desert shrub jojoba (Simmondsia chinensis) contain a wax that is used as a substitute for sperm whale oil in the production of lotions, shampoos and other cosmetic products, and even machine oil (Postlethwait and Hopson 1989).
Main Functions of Plant Seeds
The primary function of seeds is reproduction in which plants perpetuate themselves, mainly sexually. This has been exploited in the deliberate production of seedlings known as plant propagation.
Further, seeds help in the development of fruits. For example, the parts of the fruits of jackfruit, soursop and durian with less number of fully developed seeds tend to be depressed.
In addition, this organ also serves as a diaspore or dispersal unit of many plants. Many seeds are equipped with adaptations which ensure or enhance dispersal such as dust-like and balloon seeds, wing-like appendages, hairs, parachutes, feathers and hooks, and water repellant surfaces.
Exception to the Natural Process of Seed Formation
The development of the plant seed follows pollination, the transfer of pollen from the anther to the stigma, and double fertilization. Double fertilization is a unique process in which two fertilizations occur, one leading to the formation of a diploid embryo and another which is responsible for the triploid endosperm.
But in apomixis, the seed is developed without fertilization and the resulting embryo is of maternal origin. Consequently, the plant that is propagated from apomictic seed possesses the gene constitution that dictates the characters of the parent plant from which the seed is sourced just like in asexual or vegetative propagation.
This is the reason why Gregor Mendel failed to duplicate his results on garden pea. He wanted to show that his observations also apply to other plants but, unfortunately, he chose hawkweed (Hieracium sp.) which is an apomict, or apomictic species.
Apomixis occurs mostly in three plant families: Poaceae or Gramineae (grass family), Rosaceae (rose family), and Asteraceae (sunflower family). Apomictic crops include the Citrus species, mangosteen (Garcinia mangostana), lanzones (Lansium domesticum), and blackberries (Rubus fruticosus).
More Variations in Plant Seeds
Angiosperms or flowering plants have seeds enclosed within fruits, as contrasted to the gymnosperms in which seeds lie exposed on the cone or similar structures. The term angiosperm in fact means “covered seeds” or “enclosed seeds.”
Seeds vary in size, form, shape, texture, color, and chemical composition. Size varies from the extremely small, dust-like seeds of orchids to the giant seeds of the palm Seychelles nut or coco de mer or double coconut (Lodoicea maldivica).
The smallest seeds that are found in orchids can be 0.11 mm long, each weighing less than 0.5 μm. In contrast, the largest seed, which belongs to the Seychelles nut (actually a one-seeded fruit), can be 50 cm long and weigh up to 20 kg, but takes 7-10 years to mature (Kesseler and Stuppy 2009).
Plant seeds can also be classified as to longevity and germination based on their tolerance to drying or dessication and low-temperature storage. Orthodox seeds are tolerant to both drying and low temperature while recalcitrant seeds are sensitive. Those which can be dried to minimal levels of moisture content without significant adverse effect on germination but are sensitive to low temperature storage are called intermediate seeds.
(Ben G. Bareja, edited Apr. 23, 2019)
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In the typical flowering plant, or angiosperm, seeds are formed from bodies called ovules contained in the ovary, or basal part of the female plant structure, the pistil. The mature ovule contains in its central part a region called the nucellus that in turn contains an embryo sac with eight nuclei, each with one set of chromosomes (i.e., they are haploid nuclei). The two nuclei near the centre are referred to as polar nuclei; the egg cell, or oosphere, is situated near the micropylar (“open”) end of the ovule.
With very few exceptions (e.g., the dandelion), development of the ovule into a seed is dependent upon fertilization, which in turn follows pollination. Pollen grains that land on the receptive upper surface (stigma) of the pistil will germinate, if they are of the same species, and produce pollen tubes, each of which grows down within the style (the upper part of the pistil) toward an ovule. The pollen tube has three haploid nuclei, one of them, the so-called vegetative, or tube, nucleus seems to direct the operations of the growing structure. The other two, the generative nuclei, can be thought of as nonmotile sperm cells. After reaching an ovule and breaking out of the pollen tube tip, one generative nucleus unites with the egg cell to form a diploid zygote (i.e., a fertilized egg with two complete sets of chromosomes, one from each parent). The zygote undergoes a limited number of divisions and gives rise to an embryo. The other generative nucleus fuses with the two polar nuclei to produce a triploid (three sets of chromosomes) nucleus, which divides repeatedly before cell-wall formation occurs. This process gives rise to the triploid endosperm, a nutrient tissue that contains a variety of storage materials—such as starch, sugars, fats, proteins, hemicelluloses, and phytate (a phosphate reserve).
The events just described constitute what is called the double-fertilization process, one of the characteristic features of all flowering plants. In the orchids and in some other plants with minute seeds that contain no reserve materials, endosperm formation is completely suppressed. In other cases it is greatly reduced, but the reserve materials are present elsewhere—e.g., in the cotyledons, or seed leaves, of the embryo, as in beans, lettuce, and peanuts, or in a tissue derived from the nucellus, the perisperm, as in coffee. Other seeds, such as those of beets, contain both perisperm and endosperm. The seed coat, or testa, is derived from the one or two protective integuments of the ovule. The ovary, in the simplest case, develops into a fruit. In many plants, such as grasses and lettuce, the outer integument and ovary wall are completely fused, so seed and fruit form one entity; such seeds and fruits can logically be described together as “dispersal units,” or diaspores. More often, however, the seeds are discrete units attached to the placenta on the inside of the fruit wall through a stalk, or funiculus.
The hilum of a liberated seed is a small scar marking its former place of attachment. The short ridge (raphe) that sometimes leads away from the hilum is formed by the fusion of seed stalk and testa. In many seeds, the micropyle of the ovule also persists as a small opening in the seed coat. The embryo, variously located in the seed, may be very small (as in buttercups) or may fill the seed almost completely (as in roses and plants of the mustard family). It consists of a root part, or radicle, a prospective shoot (plumule or epicotyl), one or more cotyledons (one or two in flowering plants, several in Pinus and other gymnosperms), and a hypocotyl, which is a region that connects radicle and plumule. A classification of seeds can be based on size and position of the embryo and on the proportion of embryo to storage tissue; the possession of either one or two cotyledons is considered crucial in recognizing two main groups of flowering plants, the monocotyledons and the eudicotyledons.
- epigeal germinationTime-lapse video of the epigeal (cotyledons emerge aboveground) germination of a dwarf French bean (Phaseolus vulgaris ‘Borlotto Firetongue’), filmed over two weeks.Video by Neil Bromhall; music, Telemann Trio/Musopen.org (A Britannica Publishing Partner)See all videos for this article
- hypogeal germinationTime-lapse video of the hypogeal (cotyledons remain belowground) germination of runner beans (Phaseolus coccineus ‘Enorma’), filmed over a three-week period.Video by Neil Bromhall; music, Paul Pitman/Musopen.org (A Britannica Publishing Partner)See all videos for this article
Seedlings, arising from embryos in the process of germination, are classified as epigeal (cotyledons aboveground, usually green and capable of photosynthesis) and hypogeal (cotyledons belowground). Particularly in the monocots, special absorbing organs may develop that mobilize the reserve materials and withdraw them from the endosperm; e.g., in grasses, the cotyledon has been modified into an enzyme-secreting scutellum (“shield”) between embryo and endosperm.
ALL ABOUT SEEDS
After the seeds have formed, the petals drop off. The flower dies. The ovary becomes a fruit. The seeds are inside the fruit. Some fruits can be soft and juicy. Others are hard and tough. The flesh of an apple is the ovary. Nuts have hard, tough ovaries. Sometimes, seeds do not form inside fruits. Strawberries have seeds covering the outside.
The pollen fertilizes the egg (left). The ovary forms a fruit (right).
How Do Seeds Find a Good Place to Grow?
Plants spread their seeds. This is called seed dispersal. There are four main ways that plants do this.
1. Wind Dispersal
You may have seen sycamore seeds spinning in the air. Or maybe you have seen dandelion seeds blowing in the breeze. These seeds are moving away from their parent plants. Sycamore seeds have a “wing.” When they fall from a tree, they spin in circles. This helps them stay in the air longer than if they fell straight down.
A breeze or wind can blow the seeds. They will land far from the parent tree. Dandelion seeds are very light. They easily carry a long way on a breeze.
Each dandelion seed has a fluffy parachute. The parachute carries the seed in the air far from the parent plant.
2. Animal Dispersal
Many people enjoy seeds and nuts. Animals and birds enjoy seeds and nuts, too. Seeds have a tough outer coat. When an animal eats a seed, the tough coat protects the seed. The seed does not break down in the animal’s stomach. Instead, it passes out in the animal’s waste. This helps it travel a long way from the parent plant.
Other seeds are sticky. Some have hooks on their surfaces. When an animal brushes past the plant, the seeds cling to the animal’s fur. Eventually, the animal cleans its fur. The seed falls off.
This seed is hooked onto a mammal’s fur. Eventually it will drop off and it may grow into a new plant.
This coconut seed is sprouting into a new tree. It will grow roots and a long trunk. One day it may produce its own seeds.
3. Water Dispersal
Coconuts are huge seeds. They are seeds that float on water. If coconuts fall on a beach, the sea may carry them away. They can survive in the water for many weeks. Eventually, they might wash up on another beach. There they can grow into a new coconut tree.
Seeds must have the right conditions to grow into a new plant. Until they do, they can lie inactive, or dormant, for many years. Being dormant is like being in a long sleep.
This Himalayan balsam plant forms pods. When the pod dries, the seeds get flung out far and wide.
4. Self Dispersal
Some plants have clever ways to disperse their seeds. They do not need animals, water, or the wind. Peas form inside a pea pod. When the pod dries up, the peas are flung out. This is like a tiny explosion.
Why Does the Seed Move Away?
If a seed grows next to its parent plant, it may not grow very well. Both plants need energy from the Sun. If they are too close together, they could shade each other from the Sun. They both also need minerals from the soil. They could end up fighting each other for food and light.
Seeds can survive a long time. The oldest seed ever to grow into a plant was two thousand years old. It was a date palm. The date palm seed survived buried in the ground near the Dead Sea in Israel. Scientists thought that this type of date palm was extinct. Luckily, they were wrong!
How Does a New Plant Grow?
If a seed is lucky, it will land on good soil. When the conditions are right, it may grow into a new plant. This is called germination. Seeds contain their own energy store. They do not need light at first. But they do need water, warm temperatures, and oxygen.
Seeds know which way is up. If you plant a seed upside down, the root will always grow down. The shoot will always grow up.
If a seed has the right conditions, it grows a root. The root pushes down into the soil. Then it grows a shoot. The shoot pushes up through the soil. When it reaches the air, its new leaves uncurl. At this point, the seed can use its leaves to trap energy from the Sun. It does not need its own energy store any more. Now, it carries out photosynthesis. This will help it grow into a strong, full-grown plant.
The growth stages of a seed—from young roots and shoot to a long stem and leaves.
This crop of rice is sprouting. As soon as the green leaves develop, photosynthesis starts to take place.
Plants with stems that are usually soft and bendable. Herbaceous stems die back to the ground every year.
Plants with stems, such as tree trunks, that are hard and do not bend easily. Woody stems usually don’t die back to the ground each year.
A process by which a plant produces its food using energy from sunlight, carbon dioxide from the air, and water and nutrients from the soil.
The movement of pollen from one plant to another. Pollination is necessary for seeds to form in flowering plants.
What’s the difference between a fruit and a vegetable?
A fruit is what a flower becomes after it is pollinated. The seeds for the plant are inside the fruit.
Vegetables are other plant parts. Carrots are roots. Asparagus stalks are stems. Lettuce is leaves.
Foods we often call vegetables when cooking are really fruits because they contain seeds inside.
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What Do Different Plant Parts Do?
Plant parts do different things for the plant.
Roots act like straws absorbing water and minerals from the soil. Tiny root hairs stick out of the root, helping in the absorption. Roots help to anchor the plant in the soil so it does not fall over. Roots also store extra food for future use.
Stems do many things. They support the plant. They act like the plant’s plumbing system, conducting water and nutrients from the roots and food in the form of glucose from the leaves to other plant parts. Stems can be herbaceous like the bendable stem of a daisy or woody like the trunk of an oak tree.
|A celery stalk, the part of celery that we eat, is a special part of the leaf structure called a petiole. A petiole is a small stalk attaching the leaf blade of a plant to the stem.||In celery, the petiole serves many of the same functions as a stem. It’s easy to see the “pipes” that conduct water and nutrients in a stalk of celery.||Here the “pipes” are dyed red so you can easily see them.|
Most plants’ food is made in their leaves. Leaves are designed to capture sunlight which the plant uses to make food through a process called photosynthesis.
Flowers are the reproductive part of most plants. Flowers contain pollen and tiny eggs called ovules. After pollination of the flower and fertilization of the ovule, the ovule develops into a fruit.
Fruit provides a covering for seeds. Fruit can be fleshy like an apple or hard like a nut.
Seeds contain new plants. Seeds form in fruit.
|Disclaimer/Credits||Copyright © 2009 Missouri Botanical Garden|
What Is A Seed – A Guide To The Seed Life Cycle And Its Purpose
Most organic plant life starts out as a seed. What is a seed? It is technically described as a ripened ovule, but it is so much more than that. Seeds house an embryo, the new plant, nourish and protect it. All types of seeds fulfill this purpose, but what do seeds do for us outside of growing new plants? Seeds may be used as food for humans or animals, spices, beverages and are even used as industrial products. Not all seeds fill all of these needs and, in fact, some are poisonous.
What is a Seed?
Plant life starts with seeds unless the plant reproduces by spores or vegetatively. Where do seeds come from? They are the byproduct of a flower or flower-like structure. Sometimes seeds are encased in fruits, but not always. Seeds are the primary method of propagation in most plant families. The seed life cycle starts with the flower and ends with a seedling, but many steps in between vary from plant to plant.
Seeds vary in their size, dispersal method, germination, photo response, need for certain stimuli, and many other complicating factors. For instance, look at the seed of the coconut palm and compare it to the minute seeds of an orchid and you will get some idea of the vast variety in sizes. Each of these also has a different method of dispersal and has certain germination requirements that
are only found in their natural environments.
The seed life cycle can also vary from just a few days of viability to up to 2,000 years. No matter the size or life span, a seed contains all the information necessary to produce a new plant. It is about as perfect a situation as nature has devised.
Where Do Seeds Come From?
The simple answer to this questions is from a flower or fruit, but it is more complex than that. The seeds of conifers, such as pine trees, are contained in scales inside the cone. The seeds of a maple tree are inside the little helicopters or samaras. The seed of a sunflower is contained in its large flower, familiar to most of us because they are also a popular snack food. The large pit of a peach contains a seed inside the hull or endocarp.
In angiosperms, seeds are covered while in gymnosperms, seeds are naked. Most types of seeds have a similar structure. They have an embryo, cotyledons, a hypocotyl, and a radicle. There is also an endosperm, which is the food that sustains the embryo as it begins to sprout and a seed coat of some sort.
Types of Seeds
The appearance of seeds of different varieties varies greatly. Some of the grain seeds we commonly grow are corn, wheat and rice. Each has a different appearance and the seed is the primary part of the plant we eat.
Peas, beans and other legumes grow from seeds found in their pods. Peanut seeds are another example of a seed that we eat. The huge coconut contains a seed inside the hull, much like a peach.
Some seeds are grown just for their edible seeds, like sesame seeds. Others are made into beverages as in the case of coffee. Coriander and clove are seeds used as spices. Many seeds have a powerful commercial oil value too, such as canola.
The uses of seeds are as diverse as the seeds themselves. In cultivation, there are open pollinated, hybrid, GMO and heirloom seeds just to add to the confusion. Modern cultivation has manipulated many seeds, but the basic make up is still the same – the seed houses the embryo, its initial food source and some sort of protective cover.
How does a tiny seed grow into a tree?
Imagine This is a podcast with big ideas for little ones. Listen to the episode here. It is based on the following article first published by The Conversation.
How can a tiny seed actually grow into a huge tree? – Finney, aged 6, from Bairnsdale in rural Victoria.
Tree seeds fall (like the tiny Eucalypt seeds) or helicopter down (like the winged seeds of the Maple) from their parents with a full set of instructions on how to grow.
A single tree may drop hundreds or even many thousands of seeds. Many of these seeds will become snacks for insects or fall where the ground is too hard, too dry, or just not suitable for trees. Some though will fall where the situation is just right!
Just right might mean bare dirt or some nice decayed mulch with enough sunlight.
The seed contains an embryo – a group of cells ready to form roots, a stem and the first leaves. Once the coat around the seed is moistened, the embryo cells expand and burst out in a process called germination.
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YOUTUBE: Germination video
First, the roots will develop and push out and down into the soil to make sure the new plant can get water. Then the stem cells stretch up to display the first leaves.
The embryo uses food stored in the seed to power its initial growth until the leaves can start producing food. Small seeds don’t have much stored food so they have to fall in just the right spot to be successful. The parent tree has some ways to improve the chances of its seed finding the right spot, like dropping seeds after a bushfire has made the ground bare and free from other plants that would use all the water and nutrients.
For some plants, a bushfire triggers the release of seeds. Image:
For some plants, a bushfire triggers the release of seeds.
Once the roots are in the soil and the first leaves are in the sun, the plant is ready to really start growing.
People stop growing after they’ve become grown-ups but trees just keep getting taller and thicker however long they are alive.
Grass, bamboo and many other plants grow from the bottom up, so if you put a mark on the stem and come back in a little while, that mark will have been pushed further above the ground. But if you put a mark or even nail a board into a tree at one metre above the ground then come back in 10 years, it will still be only one metre above the ground. That’s because trees grow from the outside and the top up.
Some trees can grow to be more than 100 metres tall! Image:
Andrew Malone, Flicker
Some trees can grow to be more than 100 metres tall!
Andrew Malone, Flicker
The newest and outer shell of a tree contains all the living parts of the wood – the parts that move water up from the roots and food down from the leaves. If trees stop growing these outer, living shells of wood, the whole tree dies.
Some trees can grow to be more than 100 metres tall – that’s as tall as a skyscraper! In fact, humans are now building buildings out of wood that are over 50 metres tall and there are plans to go well beyond that.
The tallest tree currently is over 110 metres tall, and scientists think some trees may have been as much as 150 metres tall.
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A problem with getting even taller is that trees use water the same as you use blood – to move the nutrients and oxygen and other vital things around our body. But a tall tree has to move it from the roots to the tip of the leaves. For a 100 metre tall tree, that is like 30 flights of stairs. And a big tree could use more than 200 litres of water every day. Imagine carrying 30 buckets of water up 30 flights of stairs every day!
In our tall buildings, we need huge pumps and generators to move the water to the top, but trees just rely on their amazing structure and a little bit of power from the Sun.
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Seeds grow into larger plants through the process of germination. Germination requires optimum sunlight, temperature, water and air for the seed to turn into a plant.
Isn’t it amazing that a tree as tall as a building can emerge from just a tiny seed? Just as a human embryo contains all the genetic material that determines our development into full-grown adults, the embryo present inside a seed does the same thing!
Mother Nature is brilliant, and knows exactly when the seed is ready to start growing; if the time hasn’t arrived, it withholds its development during seed dormancy. A seed is formed by the flower of the plant during sexual reproduction, but let’s find out what happens after that!
Structure of a seed
The seed is made up of three parts:
- The Embryo – gives rise to the new plant.
- The Endosperm – nourishes and provides food for the seedling.
- The Seed Coat – the hard outer covering that protects the embryo. Some seed coats are hard (peas and corn) while some are comparatively soft (tomatoes and peppers)
Structure of a corn seed (Photo Credit : Fancy Tapis/ )
Germination and its requirements
The process of a seed turning into a plant (seedling) in the presence of optimum sunlight, air and water is known as germination. The seed can grow within its range of minimum and maximum temperatures. Any temperature beyond its given range can either damage the seeds or make them dormant.
The seed coat has tiny holes or pores through which water and air can enter. Just like any living thing, the seed also needs oxygen and gives out carbon dioxide until the leaves grow, at which point it can produce oxygen. The soil needs to be porous, so that water and air can enter and reach the seed.
If the soil is not porous, carbon dioxide won’t leave the seed and it will suffocate. When the optimum conditions are met, the seed absorbs more and more water (imbibition), swells up and bursts open!
Once the seed coat bursts open, a primary root emerges, known as the radical. In almost all plants, the root comes before the shoot. However, there are some exceptions; in coconuts, the plumule or the shoot emerges before the root. Once the root emerges, it starts absorbing water and nutrients from the soil, a function previously performed by the seed coat.
How does the seed get food before the leaves appear?
As we all know, plants are the primary producers in the food chain. The leaves contain chlorophyll, which helps in photosynthesis (making food).
However, a seed that hasn’t grown any leaves yet manages to survive with the food (starch) stored inside the cotyledons of the seed. Once the seed bursts open, the root and the cotyledons are still present, while the seed coat falls in the soil and detaches itself from the plant. The cotyledons continue providing food to the baby plant until the leaves emerge and are capable of making their own food.
A diagrammatic representation of germination (Photo Credit : Designua/ )
After the root, the hypocotyl and the epicotyl begin growing upwards to become the stem of the plant; the epicotyl becomes the first leaves. By the time the epicotyl emerges, the stem has reached above the ground and the leaves start to emerge. The cotyledons fall off, since their job is done and the plant is capable of making its own food. This completes the process of germination. Seeds come in many different shapes and sizes, and also have different requirements for growth. For example, some seeds might need more water or light than others.
Seed dormancy is the sleeping period of the seed, in which it does not germinate, even when the conditions are optimum. The reason for such a staggered germination pattern is to prevent herbivores from eating all the plants at once and to prevent the seeds from catching any virus that may have spread to other plants.
Plants also have hormones, just like us! Our hormones also activate at a certain time (puberty), at which point we emerge into adulthood. In the same way, plants have abscisic acid that inhibits germination, and gibberellin, which ends seed dormancy.
Why do some seeds take longer than others to germinate?
A seed needs optimum conditions for germination (Photo Credit : vovan/ )
All seeds are not created equal; they differ in shape, size, color and requirements for survival. Some seeds have a harder seed coat than others, which takes more time to soften before bursting open. Such seeds must absorb more water to soften the seed coat, which slows germination.
During certain seasons, such as fall and winter, when the soil is too cold, the seed goes into dormancy and only germinates in spring and winter. If the seed is planted too deep, all the energy and food stored in the cotyledon will be used up before the shoot can emerge from the ground. If the soil isn’t watered enough, the seed will dehydrate and die. Finally, if there is too much water, it will suffocate and die due to a lack of oxygen.
Thus, seeds have requirements that must be fulfilled at an optimum level. Any condition outside this optimum range may result in the death of the seed. Every seed has a massive responsibility to turn into a giant tree or life-giving plant, so all the ideal conditions must be fulfilled. Looks like humans aren’t the only species who can be a bit high maintenance!
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The seed in a plant is the part that develops from the ovules after fertilization. They are enclosed in the fruit which develops from the fertilized ovary. The seeds are formed as a result of sexual reproduction and contain the young embryo which can develop into a new plant. Let’s learn more.
Structure of a Seed
Seeds of different plants may vary in many ways, but the basic anatomy remains the same. A typical seed consists of the following parts:
- Tesla: It is the outer coat of the seed that protects the embryonic plant.
- Micropyle: It is a tiny pore in the testa that lies on the opposite of the tip of the radicle. It permits water to enter the embryo before active germination.
- Hilum: Is a scar left by the stalk which attached the ovule to the ovary wall before it became a seed.
- Cotyledon: In some plants, this contains high quantities of starch and will provide a source of food for the developing embryo prior to germination, in other plants this role is performed by an endosperm. In monocotyledons, there is just one cotyledon whereas in dicotyledons there are two. Depending on the type of germination (epigeous or hypogeous) the cotyledons may remain below ground or be pulled above ground.
- Radicle: This is the embryonic root which will develop into the primary root of the plant. It is usually the first part of the embryo to push its way out of the seed during germination.
- Plumule: This is the embryonic shoot. It appears as a bud which will give rise to the shoot and the remaining structures in the plant.
- Endosperm: In many plants, a separate part for storage of starch develops and this is called the endosperm. It is seen in maize and wheat.
Learn more about Stem Structure here in detail.
Functions of Seeds
The seeds perform the following functions:
- They help in germination of the new plant.
- The seeds contain food reservoirs in the form of cotyledons and endosperm.
- The seed coat is protective in nature which protects the embryo inside.
Dispersion of Seeds
Dispersion is defined as the scattering or transport of seeds from one place to another by means of a dispersing agent. It can occur by four modes:
Dispersion by Wind
The seeds that are dispersed by wind are generally light and small such that they can be easily carried away by the wind. Example: cotton seeds
Dispersion by Animals
These seeds have external structures such as spines or hooks such that they can attach themselves to animals and get dispersed to other places. These seeds are generally attractive and so are their fruits. Example: Guava seeds, dates.
Dispersion by Water
These seeds have a structure, generally, hollow such that they can easily float on water. Once they reach a place where the conditions are suitable, they germinate. Example: Mangroves.
Dispersion due to Explosion/Expulsion
Some plants fling or throw their seeds out once the fruit has ripened. This explosion occurs as a result of evaporation of water from the pods. Once the pods dry out, they expel the seeds which are then carried by wind or gravity to other places where they germinate. Example: Viola
Solved Example for You
Q: Which of the following parts does the seed develop from?
(a) Ovary (b) Embryo
(c) Embryo sac (d) Ovule
Sol. (d) Ovule
Once fertilization occurs, the ovary starts maturing and eventually develops into the fruit and the ovules contained in them become the seeds.
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Tiny powerhouses. Little superfoods. Small yet mighty. Seeds are crops at their very beginning stage of life. Because they contain all the nutrients essential for growing a healthy and resilient plant, they offer our bodies a wealth of benefits when we eat them.
88 Acres products are built upon a seed blend that features a broad array of nutritional benefits. Pumpkin seeds, sunflower seeds, and flax seeds are true superfoods, packing in high-quality protein, heart-healthy fat and essential vitamins and minerals into a tiny, versatile, and delicious package. Forget multivitamins – seeds offer many of the same nutrients, fiber and plant chemicals that we could never get from a pill.
As plant foods, seeds provide our bodies with nutrient-dense energy while also leaving a low environmental footprint on the Earth. Seeds make healthy food a simple and easy choice for everyone. Seeds provide a similar nutritional profile to nuts and are a great source of plant-based protein. Schools have been sensitive to nut allergies and seed-based products provide an alternative snack option for many classrooms.
But they aren’t just for people with food allergies. Seeds provide an excellent source of protein and healthy fats for omnivores, paleo and low-FODMAP dieters, and vegans alike, serve as a portable and gut-friendly fuel for athletes, and boost optimal immune, hormonal and cardiovascular health in every body. They truly deserve a place in everyone’s pantry and can be incorporated easily into fun and exciting meals and snacks for you and your family.
The shelled kernels inside the seeds of the tall, sun-worshipping sunflower are bursting with Vitamin E. This vitamin serves as an antioxidant in our bodies, and is important for maintaining the strength and integrity of cellular membranes. This is why it is often credited for giving people glowing skin and strong, shiny hair. Just two tablespoons of sunflower seeds provide almost half of the recommended daily value of Vitamin E, which is incredible considering that recent estimates show upwards of 90% of Americans don’t get enough from their diets. Because the body can’t absorb Vitamin E without fat, the oil-brimming sunflower seed provides the perfect package for our bodies to utilize this important antioxidant to its fullest extent.
Sunflower seeds also pack in thiamin and Vitamin B-6, which are both essential for healthy metabolism. This means they help ensure your body gets as much energy from the foods you eat as possible, which is essential for staying on top of a busy, active schedule day in and day out. Sunflower seeds are also a great way to get magnesium, manganese, phosphorus, copper and selenium. Magnesium, when combined with Vitamin B-6 as it is in sunflower seeds, may help to reduce symptoms of PMS. Along with maintaining strong bones, proper muscle contraction and low blood pressure, keeping enough magnesium in our diets may also help keep us calm, cool and collected by staving off symptoms of anxiety.
Green in color, pepitas–the kernels of the seeds inside the orange-fleshed pumpkin–are ripe with vitamin K, iron, magnesium, phosphorus and manganese. Offering many similar benefits as other seeds due to their mineral content, pumpkin seeds stand out for providing a great dose of iron. For vegans and vegetarians who don’t get iron from animal products, pumpkin seeds provide an alternative source. Similar to dark leafy greens, the vitamin K in pumpkin seeds helps promote optimal bone strength and healthy blood clotting. Pepitas are a complete protein, providing all nine essential amino acids along with a rich dose of heart-healthy, inflammation-fighting unsaturated fats.
Flax seeds combine an unrivaled dose of gut-strengthening fiber with a heart-healthy blend of fats as one of the best sources of plant-based omega-3 fatty acids. Locked in flax seeds’ indigestible shell, these nutrients are unable to be absorbed by our bodies unless the seeds are broken down. 88 Acres coarsely grinds the flax seeds used in our craft seed bars to ensure everyone gets the full benefit of this super seed.
The fibers in flax contain a unique type of plant chemical called lignans, which recent research shows may play a role in the prevention of certain types of cancers and are effective at reducing bad, LDL cholesterol in the blood. Lignan fibers are not lost, but are even better absorbed by our bodies when the seeds are ground. Flax seeds also contain a very high amount of omega-3 fatty acids, which help reduce overall inflammation that has been linked to asthma, heart disease, alzheimer’s and many other chronic diseases.
Flax seeds contain omega-3 at a ratio compared to omega-6 that provides maximum benefits to our health.While omega-6 fatty acids are essential, meaning they are needed in human diets in order to survive, they are not very hard to find in the food supply and have been associated with increased inflammation when consumed in high quantities. The type of omega-3 fat in flax seeds is called Alpha Linolenic Acid (ALA). To get the full inflammation-reducing benefit, our bodies must convert omega-3 ALA into the more active forms, DHA and EPA. But ALA still serves as an important source for vegans and vegetarians who are unable to get DHA and EPA in their diets from marine animals like fish and krill.
Putting it all together, the blend of seeds we choose to use in 88 Acres foods makes it easy to get a wide variety of nutrients from real, whole foods that come along with a myriad of benefits inherent to each plant. Our ingredients are simple, but the range of vitamins, minerals, and nutrients they provide is complex.
Simple ways to incorporate more seeds into your day:
- Break a seed bar into small pieces, or use 88 Acres Seed’nola to sprinkle it over yogurt, oatmeal, or chia pudding
- Blend seeds into a smoothie, like our Green Acres Smoothie
- Whirl Seed Butter into your hot breakfast cereal
- Use seed butter as a dip for fresh fruits and veggies
- Drizzle seed butter on top of a roasted sweet potato or sweet potato toasts for a balance of healthy fats
- Add crunch to your salad or soup by topping with seeds
- Use seeds instead of nuts in trail mix as a snack
- Grind pumpkin seeds in a food processor or coffee grinder and use as 1:1 replacement for almond flour
- Use seeds in place of nuts for a crunch in baked goods or as a crumbly topping for cakes and muffins
- Use ground seeds as a rub on your favorite protein
- Use ground flax seeds to make an egg replacement for baked goods (recipe below)
Flaxseed Egg Replacer
Mix 1 tablespoon ground flaxseed with 3 tablespoons warm water. Stir well and let sit for 15 minutes before incorporating into your recipe in place of eggs.
What’s Inside a Seed? All This
Who remembers this scenario?
It’s kindergarten. Standing in a line next to the window, you and each of your classmates are holding a cup and wet paper towel. Your teacher hands you a little bean and helps you place the bean inside its damp cocoon. And every day you and your friends run to the window to see that exact moment that the bean has sprouted.
Do you remember the parts of the seed? How seeds are made? How to store seeds? How to plant and take care of seeds?
If not, here is a little primer for you. That wonder is still there – plus more than you may have imagined.
The Parts of a Seed
Isn’t it amazing that some of the most dramatic changes to your plants happen before you even see them above the ground? Here’s what’s going on inside that unassuming little seed:
Seed Coat: This is the protective covering around the seed.
Endosperm: Food for the plant embryo to use until it sprouts and can produce its own food.
Plumule: This section will become the plant’s shoot.
Cotyledons: “Seed Leaves” These are the first little leaves that you see when the plant sprouts. They are fully formed, inside the seed.
Hypocotyl: The stem of the plant embryo.
Radicle: The root portion of the embryo. It pushes out and down to become a root, and breaks a hole in the seed coat so the cotyledons can push out and grow upward.
Hot (or Temperate) Enough For Ya?
While you may think growing seeds is a just-add-water sort of experience, in reality, the seed’s first days are by no means guaranteed.
In general, for seeds to remain viable – able to grow under the right conditions – they need to be kept in an environment where the humidity and temperature levels equal less than one hundred degrees Fahrenheit. So for example, if the temperature is 60 degrees, the humidity should be no more than 40%.
Even when they’re not growing yet, seeds are alive – they are just metabolizing incredibly slowly. And plants metabolize faster at higher temperatures. Hence, there’s a need to keep temperatures low when storing your seeds.
Humidity and/or water are also factors in helping the seed germinate.The combination of spring-like temperatures and water cause the shell of the seed to crack so that the seed can finally begin to grow.
More Than “Just Add Water”
Remember that little science lesson about the parts of the seed? Here’s where they finally begin to perform their magic.
The reason most seeds grow in spring, or during warmer times, is that they require both warmth and moisture in order to be activated into the growing process. They’re dormant until then, as you’ve seen from the (possibly many) packets of dried, rather quiet seeds you may have stored in your shed right now.
Interestingly, seeds respirate, just like most living entities. Oxygen must be able to permeate the soil, and the carbon dioxide the seeds give off needs to have room to move away from the emerging plant. That’s why correct aeration is so important and why it can be difficult to grow plants in very clay-like soil.
While seedlings will need sunlight (or proper artificial light), seeds like darkness in order to germinate. In a temperate, rather moist, dark location, the seed will start its fascinating process. Here’s what happens:
Three Fascinating Steps to Your New Plant
1. Imbibition: The seed absorbs moisture and the coat begins to swell and soften.
2. Interim/Lag Phase: The seed is “activated” internally and begins metabolizing faster.
3. Emergence of the Radicle and Root: As the cells inside the seed divide and more room is taken up, the radicle and root emerge out of the seed.
After this point, the root grows downward, creating more roots (generally), and the plant will grow and emerge from the soil. This time period depends upon what it is you’re growing. Some seedlings emerge and are visible within a matter of days.
Now you know the seed’s most fascinating secrets. Treat your seeds and seedlings properly and they’ll have a great foundation upon which to grow and produce at their most beautiful best!
Lead image: sciencing.com
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