Information

Can I imbibe seeds before sterilization?


For an experiment I want to germinate lettuce seeds. For logistical reasons it would be convenient to imbibe the seeds by placing them in the cold for 2 days, afterwards I would sterilize the seeds using dilluted bleach. I mostly see people apply stratification or imbibition after sterilization, does the order matter? Would there be a difference for cold treatment (stratification) or wet treatment (imbibition)?


Personal anecdote: Once I planned to sterilize seeds of Silene latifolia for tissue culture but after the first step (washing the seeds in water for an hour) I had to do other things and the seeds did spend the night wet in room temperature. The next day some of the seeds were showing first signs of germination - a little crack in seed coat. I decided to sterilize them anyway, since there was nothing to lose. The result: Some seeds did germinate after sterilization and were fine. Some seeds died. Interestingly, in some seeds the bleach destroyed only the exposed root meristem resulting in rootless seedlings.

I have never worked with lettuce seeds but I would consider questions:

  1. How fast the seeds germinate and what conditions they need for germinating? You cannot sterilize seed that have already germinated.
  2. Could the inbibition change the properties of the seed coat and make it easier for the bleach to pass through and kill the embryo? I suspect not, but cannot be sure.
  3. Wet environment is good for bacteria and fungi growth. "Dirtier" seeds are sometimes harder to sterilize - they need longer exposure to bleach or stronger bleach concentration to completely remove contamination. Stronger bleach or longer treatment can sometimes kill some (especially small) seeds. It is hard to say weather two days of wetness can make any difference. The cold should slow down the bacterial and fungal growth.

At the end of the day I reccomend you to try with few seeds and see the result. Maybe include negative control with usual order of steps. If the survival is the same for both groops you are good to go.


Temperature to Kill Seeds

Compost, potting soil and other garden amendments can harbor seeds from unwanted grasses and broadleaf weeds. You can prevent unwanted seeds from competing with your lawn and garden plants by using a heat treatment of the right duration and intensity. The exact temperature needed to kill a seed depends on the species of plant it came from, but in most cases heating seeds to 140 degrees Fahrenheit is sufficient to sterilize them.


Mutations are permanent changes in the DNA sequence of an organism, and can be inherited. If the organism is a single cell (like a bacterium), the "daughter cells" that formed when it divided, might each have the mutation, assuming that the mutation is not lethal. If the organism is multicellular, such as a human being, the mutation can be inherited only if it occurs in the cells that form the eggs and sperm. A mutation that occurs in one of the cells on your arm, for example, cannot be passed on to the next generation.

Mutations can be caused by a number of things. Chemicals found in tobacco smoke, for example, cause mutations. Mutations can also be caused by forms of electromagnetic radiation, including ultraviolet (UV) light, X-rays and gamma rays.

UV light from the Sun causes DNA damage to exposed skin. But UV light does not penetrate your skin very far. It stops after it travels a few cell-thicknesses into the skin. X-rays also cause DNA damage. X-rays are more energetic and more penetrating than ultraviolet rays. That is why they are so useful for getting a picture of your bones or teeth&mdashthey pass through the soft tissues and are absorbed by the hard tissue. On an X-ray film, the light regions form where lots of X-rays have struck the film (soft tissue). The dark regions form where fewer X-ray photons have passed through (bones). The X-ray you get at the dentist or when you have a chest X-ray is safe because the dose is so low.

In this plant biology science fair project, you will investigate how radish seeds are affected by gamma irradiation. Gamma rays are even more powerful than X-rays. For the purpose of irradiating food, the gamma rays are produced by a highly radioactive version of the element cobalt, called cobalt 60 (see the Bibliography for more about cobalt 60). It is important to understand that the seeds in this science fair project have been "irradiated," which means they were treated with gamma rays. The seeds are not radioactive.

Because they are so energetic, gamma rays can penetrate deeply into tissue. Gamma rays are a form of ionizing radiation, which means that they can form ions, or charged particles, in irradiated tissue. When gamma rays cause DNA damage, most of the damage is due to the reaction of these ions with the DNA molecule. DNA damage caused by gamma rays can result in breakage of both strands of the DNA molecule. The higher the dose of gamma rays, the more damage there is to the DNA.

You will use gamma-irradiated WARD's Rapid Radish TM seeds in the experimental procedure. The seeds have already been irradiated with several doses of gamma rays. The doses were not so high that the seeds were all killed, as in food sterilization, but the doses were high enough that the growth of some of the seeds could be affected. The unit used to measure the level of gamma irradiation is the mrad. An mrad is a measure of how much energy has been deposited in a material by the irradiation. A rad is equal to 1,000 mrads. The rad is the original unit developed for expressing absorbed dose, which is the amount of energy from any type of ionizing radiation deposited in any medium (e.g., water, tissue, air). A dose of one rad is equivalent to the absorption of 100 ergs (a small but measurable amount of energy) per gram of absorbing tissue. The rad has been replaced by the gray in the SI system of units (1 gray = 100 rad).

If the gamma rays have caused mutations in the DNA sequence of the plants that grow up from the seeds, then the plants have an altered genotype. The genotype of the plant consists of its DNA sequence. If the DNA damage causes a change in the observable appearance or behavior of the plant, then the plant is said to have an altered phenotype. The phenotype you will observe is seed germination, so you will observe the part of the plant that emerges from the seed first, the embryonic root, termed a radicle, or primary root. Let's get started!


Treatments for Managing Bacterial Pathogens in Vegetable Seed

Infested seed can be the source of the pathogen for important bacterial diseases occurring in the northeastern United States. These diseases include black rot affecting crucifer crops, bacterial spot affecting tomato and pepper, and bacterial speck and bacterial canker affecting tomato. They can cause substantial damage if not controlled.

The first strategy to use for controlling any disease is to eliminate or reduce the amount of the pathogen available to initiate disease. Therefore, the use of disease-free seed and transplants are some of the most important management practices for bacterial diseases. Some seed companies have the resources to produce seed in areas where these diseases do not occur and to test seed for the pathogens. First look at the seed package to determine if your seed has been tested for these pathogens and/or has been treated. Check with the seed company if the package does not contain this information. Hot water, hydrochloric acid, calcium hypochlorite, sodium hypochlorite, and peroxyacetic acid are treatments that seed companies use for bacterial pathogens. Infested crop debris, infested planting supplies (especially wooden stakes for trellising tomatoes) and infected weeds are additional sources of bacterial pathogens and must also be managed in an effective control program.

Seed can be treated by growers with hot water or Clorox® bleach (labeled formulations only) to kill the pathogen. Hot-water treatment is more thorough than Clorox because it affects bacteria inside the seed however, high temperatures can adversely affect germination if proper precautions are not taken and bacteria deep inside seed may survive treatment. It is best to have seed custom treated, which some seed companies will do. Realize before you start that when you treat the seed, the seed company’s liability and guarantees are null and void. Seed that is coated or fungicide-treated should not be treated with hot water or Clorox. Also do not treat old seed. Make sure seed has not already been hot-water treated as a second treatment can kill the seed.

Precise control of conditions is essential for successfully hot-water treating seed yourself. Realize that there is a small margin between the temperature and length of exposure needed to kill pathogens and the treatment conditions that will kill seeds, and that the highest temperature seed can tolerate varies among crops. Use the following temperatures and times. (See Managing Pathogens Inside Seed with Hot Water for a more complete list.)

  • Tomato seed treat at 50 o C (122 o F) for 25 minutes or 51.5 o C (125 o F) for 20 minutes.
  • Pepper, cabbage and Brussels sprout seed treat at 50 o C for 25 minutes.
  • Cauliflower and broccoli seed treat at 50 o C for 20 minutes.
  • Carrot seed treat at 50 o C for 20 minutes.
  • Celery seed treat at 50 o C for 30 minutes.
  • Lettuce seed treat at 47.8 o C (118 o F) for 30 minutes. Some feel lettuce is too sensitive to treat.

Hot water treatment can be damaging or impractical for seed of other crops including pea, bean, cucumber, sweet corn, and squash. Water temperature needs to be carefully controlled during treatment. The best way to control temperature while treating seed is to use precision water baths (See Managing Pathogens Inside Seed with Hot Water). Next best is a stirring hot plate and a precision laboratory thermometer. Hot plates and thermometers can be purchased from a laboratory supply company such as Fischer Scientific or VWR International. A recommended thermometer is Fischer catalogue # 15-114 (0 – 80 C range), which sells for $35.43 (2005 price). Fischer carries a 10′ x 10′ stirring hot plate that sells for $525 (Cat. No. 11-600-100SH) and a 7′ x 7′ stirring plate for $418 (Cat. No 11-600-49SH). A magnetic stir bar is also needed. A 3-in long bar sells for $13.20 (Cat. No 14-513-68). A large glass container will be needed because metal can crack the hot plate surface. The larger the container used, the easier it is to maintain water temperature and the less the impact on temperature of adding room-temperature seed. Hot-water treatment can be done successfully using a large pot on a stove top and a precision laboratory thermometer.

With any of these methods, expect to spend some time adjusting settings to achieve the desired temperature and have it maintain, especially with the stovetop. A very low hot plate or stove setting will probably provide the correct temperature. Wait to begin treatment until the water temperature in the pot is maintained. Have containers of hot and cold water nearby in case the water temperature does not stay at the desired temperature. Place seed in a tea infusion ball or in a piece of cotton cloth. Add a metal weight to keep the seed container submerged, but make sure it is not on the pot bottom. Agitate the water continuously. A wooden spoon works well when using a stovetop. Check the temperature constantly. Keep the thermometer off the hot bottom of the pot this can be accomplished by taping it to the inside of the wooden spoon used for stirring. Upon removing, cool the seed under tap water. Spread the seed out on paper towels to air dry at 70-75°F. It is recommended to conduct a preliminary germination test with a small quantity of treated and untreated seed from each variety and lot number before treating all the seed. Some seed lots produced from stressed plants may not stand up to hot water treatment and germination may be adversely affected (though this is rare with pepper seeds).

Clorox Commercial Solutions® Clorox® Germicidal Bleach (EPA Reg. No 5813-100) and Clorox Commercial Solutions® Ultra Clorox® Germicidal Bleach (EPA Reg. No 67619-8) are labeled for pepper (bacterial spot pathogen) and tomato (bacterial canker pathogen) treatment. There is less chance of seed being damaged with bleach than hot water however, chemical controls such as Clorox are effective for pathogens on the seed surface only hot-water treatment can kill bacteria inside as well as on the outside of seed. These have 7.85% and 5.84% available chlorine, respectively. To Clorox treat seed, prepare a solution with 10,000 ppm available chlorine. Mix 16.7 or 22.2 fl oz of these products, respectively, with 1 gallon of water to obtain treatment solution. Use 1 gallon of this solution per pound of seed. Put up to 1 pound of seed in a cheesecloth bag, submerge in this solution and provide continuous agitation for 40 minutes, rinse seed under running tap water for 5 minutes, then dry seed thoroughly on paper towel. Put the seed in a new package, not back in the original one. Prepare a fresh batch of the dilute Clorox solution for each 1-pound batch of seed. The soak can stimulate germination, so if the seed is dried and held too long, germination will be reduced. To legally make this treatment, only these formulations can be used and the full label with this use must first be obtained from the Clorox company (800-446-4686) or by going to the New York DEC website. Enter ‘Clorox Germicidal Bleach’ in the ‘Product Name’ box on the form. Click on ‘Search’ below the search section. When the results are displayed, click on the ‘More’ button in the lower right corner of the box for either product. Note that the search results will include other products that do not have use directions for seed treatment.

Either seed treatment should be done within a few weeks of planting. Best is doing right before planting as treatment can prime seed for germination. Afterwards a fungicide can be applied to prevent damping-off and other pathogens from infecting seeds. There are several formulations of Thiram registered for application as a dust or slurry.

Please Note: The specific directions on fungicide labels must be adhered to — they supersede these recommendations, if there is a conflict. Any reference to commercial products, trade or brand names is for information only no endorsement is intended.


3. Pennyroyal

Pennyroyal is a plant in the mint genus that has been used as birth control by the ancient Greeks and Romans. This herb works as an emmenagogue to promote menstrual flow and as an abortifacient to initiate self-abortion.

Pennyroyal can be taken in combination with other herbs to stop pregnancy.

Both fresh and dried leaves of this herb can be used for birth control. Pennyroyal tea can help induce menstruation and abortion.

  1. Boil eight ounces of spring or distilled water.
  2. Remove from heat and add one teaspoon of dried pennyroyal to the boiling water and allow it to stand for 10 to 15 minutes.
  3. Strain and add a little honey if desired.
  4. Drink the tea immediately following unprotected sex and before implantation of a fertilized egg can occur for maximum effectiveness.

Note: Pennyroyal as natural birth control should be taken cautiously as it can cause liver and kidney damage, nervous system damage and a host of other problems. Do not drink more than three cups of pennyroyal tea within a six-day period. Do not drink this tea if your menstrual period is more than 10 days late.


Startup Spotlight: How Zayndu is cleaning up seeds with non-toxic plasma tech

There’s a lot that goes into the planting process and most of it happens before the seed even hits the soil. For food safety purposes as well as yield-boosting measures, seeds are frequently disinfected prior to planting.

Various strains of bacteria and fungi can reduce seed germination rate, while d iseases carried on the outside of seeds can contaminate the soil they’re planted in. That can lead to a chronic infection in the soil that affects future crops, Ralph Weir, CEO of seed sterilization startup Zayndu, tells AFN.

The UK-based company’s devices use a non-toxic plasma disinfectant to kill pathogens while boosting germination rates at the same time. Launched in January 2019 and built around several decades of research carried out at Loughborough University, Zayndu has so far been funded through limited debt finance, investment from the founders, and loans and grants from the UK government’s Innovate UK .

“We are now in the grey zone of pre- or post-revenue,” Weir says. “We have early orders for evaluation systems, but in terms of funding, we would still class ourselves as seed. And yes, there are many, many jokes about a seed company needing seed funding and having field trials in a real field!”

Read on to hear more from Weir about Zayndu’s startup journey.

AFN: How does your technology work?

Ralph Weir: The cleaning technology we refer to as ‘activated air’ functions by running a very small amount of electricity through a closed chamber of air. We place the seeds in a sealed rotating drum, and the seeds tumble around. We then run the current through the air to create plasma in the drum, which creates what we call ‘activated air’.

[This] cold plasma, which splits oxygen and nitrogen molecules into individual atoms, [is] technically a blend of RONS [reactive oxygen and nitrogen species] which is a powerful disinfectant.

The RONS are desperate for something to latch on to and tear apart bacteria, fungi, or viruses present in the chamber. The seeds are not affected as they are protected by their comparatively thick seed walls. [At the end of the] process, the ‘activated air’ just converts itself back to air – so coming out of the drum is just seeds and fresh air.

What makes this unique is that it’s a process designed for scale. Our plasma does not require any fancy atmosphere, vacuum, or elevated temperatures.

Why is this solution needed when there are already many alternatives out there?

Our method of seed decontamination exists for two reasons.

The first is the elimination of chemical seed treatments – because chemical usage is becoming heavily restricted and costs of use are rising – and also because of documented cases of environmental harm due to chemical seed treatments.

The second is to treat seeds that are otherwise untreatable. There are some seed diseases for which no effective chemical treatment has been developed – for example, mucilaginous seeds like basil, where any moisture-based treatment causes seeds to clump into goopy bricks which are useless for planting or further processing. There are some seeds for which chemical treatment is not viable. For example, fast-growing salads – where you can’t put chemicals on them because there’s no time for the chemical to dissipate. If it goes from germination to plate in a couple of weeks, the chemical is still there, and it’s on somebody’s plate. So this is something that we can disinfect that nobody else can.

Who is your target customer?

Targets are the big seed producers, so very much B2B. The goal is to establish the cold plasma technique as the de facto approach to disinfecting seeds. For completeness, we’re based in the UK, which has a decent local market for us. But the Netherlands is the epicenter of vegetable seed production, and in normal times, we can drive to key hotspots [there] in a few hours.

Do you have a lot of competitors? What does the landscape look like?

We’re not aware of any other viable plasma technology that can process seeds at a factory scale. There are research groups working on a teaspoonful in a vacuum or in a noble gas, but that doesn’t work if you need to process a ton or more of seeds – which is where we are heading! The real competitors are the technologies we are displacing like chemicals and ‘physical’ processes, like dipping seeds in hot water.

Our edge here at Zayndu is that the chemicals are becoming persona non grata by either being banned or just being seen as unwelcome and untrusted by consumers, while hot water can devastate germination rates, and simply cannot be used on some seeds.

If you could change one ag policy, law, or regulation, what would it be – and why?

At the moment, it’s regulatory. There are treatments that are approved for disinfecting seeds for intercontinental shipments, and they are mainly chemical. Plasma is not one of them, despite being more effective than many treatments that are approved. Domestically, that’s not an issue. Shipments within the US or within the EU are unaffected, but shipments to say Australia from the EU are. So, a focus for the Zayndu team in the coming year is to engage with the regulators and prove that plasma is safer, cleaner, and more effective than the approved options so that we can get it approved.

What is the biggest challenge you’re facing right now?

We are about to start fundraising, so that feels like it will be my biggest challenge for the next few months!

The other challenge is keeping all the potential users happy. Our launch machine is great for high-value crops, but we’re being asked for a smaller machine targeting the extremely high-value crops like tomato seed, and larger machines that can handle throughputs of tons-per-day.

The important thing is to take small steps, but quickly. So, we have a machine that is an order of magnitude larger than the launch machine running, and another order of magnitude in design. But we’re learning lessons from each, and using that to manage the risks of each machine development.

How has Covid-19 impacted your operations and growth plans?

Zayndu has been fortunate in that we have three main workspaces: a biology lab, which already adhered to high standards of sanitization to eliminate contamination of seeds by operators. The team was already wearing face masks to protect the seeds. Then there’s the workshop, which is a relatively large space where machines are developed and tested and which has significant social distancing, just because of scale. Office work can largely be performed from home.

What has been more challenging is working with customers. Many of our customers are in the EU, particularly in the Netherlands. Travel from the UK to the Netherlands has been seriously restricted. We have had to train customers to install their own machines and to provide remote training on operation, which was not our intention but has actually been relatively easy, and is probably a permanent benefit. We have also upgraded the remote monitoring capability of the systems, which helps diagnose any issues before they arise. Again, that is a permanent benefit. We miss the face-to-face contact and unquestionably we would have been bringing more partners into our early adopter program but generally, we’ve suffered less than many businesses.

Any advice for other agrifoodtech startups out there?

I’ve been involved in several successful startups, and the best advice is to talk to potential customers early, pin back your ears, and listen! Even when you do talk to potential users, it’s very easy to hear what you want to hear. I see founders who tell industry experts they are wrong or stupid, rather than understanding their problems. You have to walk a mile in their shoes, really understand what they are trying to do, and be part of the solution – not just an irritation. That way you’ll get engagement.

The current Zayndu architecture is nothing like the first proposals we showed potential users. It was refined with their input and is now something that is incredibly well-received. Had we pushed on with our first concepts we would have failed to generate any traction even with the same core technology.


Absorbent (Moch) as a Contraceptive

Rabbinic commentators are divided as to the exact meaning of the talmudic passage &ldquoThe Beraita of the Three Women.&rdquo Does Rabbi Meir mean that the three women may use a moch [absorbent], and the sages that they must not use one? Or does Rabbi Meir mean that they must use a moch, and the sages only disagree with him in that the three women are not obliged to use a moch but may do so if they wish? The medieval commentator Rashi states that Rabbi Meir means &ldquomay use&rdquo and the sages mean &ldquomay not,&rdquo whereas his grandson Rabbenu Tam reports that Rabbi Meir means &ldquomust&rdquo and the sages mean &ldquomust not but may.&rdquo

Moreover, what precisely is meant by the word moch? Is it a device used to absorb semen during intercourse or only after unimpeded intercourse has taken place? Adopting the strictest interpretation, some rabbinic authorities in the early part of the century refused to permit the use of artificial means of contraception in any circumstances. But the majority of authorities interpret the passage as permitting the use of a contraceptive when the doctors are of the opinion that a pregnancy will do serious harm to the wife.


Non-Fiber Diet for Colonoscopy

High-fiber foods should normally be a part of your diet because they help improve colon health. But fiber can leave residue in your colon that can obscure your doctor's view of polyps and other issues. Polyps are small clumps of cells that may grow on the lining of your colon.

While most polyps are harmless, some can become cancerous. Your doctor will need to be able to see these, if they're present, to determine if they need to be examined further. That's why it's important to avoid fiber before your appointment.


What is germination?

It all starts with a seed .

Seeds come in all shapes and sizes. Some tropical rainforest orchids have seeds that are smaller than a pinhead—so small,in fact, that they are like dust. At the other end of the scale is the enormous Coco de Mer seed which can be up to 40 centimetres long and weigh as much as 18 kilograms, about the same weight as a medium-sized dog!

Essentially, though, a seed consists of:

  • the dormant GLOSSARYdormant a dormant plant embryo is one in which the young plant’s development is arrested and it is in dehydrated state with low metabolic rate embryo—a young plant that formed from a fertilised egg cell
  • the seed coat—which is a protective layer surrounding the whole package
  • the food store—which contains all the nutrients (carbohydrates and protein) an embryonic plant needs to get going. During its early stages of growth, the seedling relies on this store until it’s large enough for its own leaves to begin making food through photosynthesis. Different seeds store food reserved in different ways—some rely on large reserves of endosperm (nutritive tissue around the embryo), while others store food reserves in embryonic leaves.
  • the cotyledon/s—which may become the embryonic first leaves of a seedling. In angiosperms (flowering plants), species with one cotyledon are called monocots, while plants with two cotyledon are known as dicots

In flowering plants, seeds develop in a fruit. The fruit protects seeds but also helps with their dispersal from one place to another. Sometimes the fruit is nice and soft and delicious, like a berry that attracts animals who then accidently carry the seed to a new home. Other times the fruits are hard and woody, like those of a banksia or eucalypt.

Deep in a mountain on the island of Svalbard off the coast of Norway, tens of thousands of seeds are slumbering. This is the Svalbard Global Seed Vault—a seed bank established by the Norwegian government which holds copies of more than 4,000 plant species from seed banks around the world.

Essentially, these seeds are ‘back-up’ copies should anything (such as war or natural disasters) decimate seeds in local seed banks. The vault holds over 4,000 plant species including essential food crops such as beans, wheat and rice.

The northernmost place in the world with its own airport, Svalbard is the perfect place for the seeds to be delivered from around the world for cold storage. Even if the power fails, the ambient temperature on this chilly island 1,300 kilometres beyond the Arctic Circle will keep the seeds frozen without extra cooling.

What seeds need to germinate

From the outside, seeds may look like they’re pretty inactive—it can be easy to assume there’s nothing much going on in there. In fact, experiments show that some of the tissues inside of seeds remain active, and even carry out some basic metabolic processes, such as cellular respiration GLOSSARY respiration a chemical process whereby energy is released from glucose . In other words, seeds use small amounts of stored energy, staying alive and ‘waiting’ for good conditions to begin to grow.

To germinate, all seeds need:

as well as a suitable place, and a little time.

Water

Most seeds need to take up water to germinate this is known as imbibition GLOSSARY imbibition the taking up of liquid, causing swelling. . Water:

  • hydrates enzymes in the seed, activating them. As a result the seed begins to release energy from its food store for growth.
  • causes pressure to build in the embryo’s cells, causing them to enlarge. This often results in the seed coat breaking open.

Oxygen

Seeds need oxygen so that they can produce energy for germination and growth.

The embryo gets energy by breaking down its food stores. Like all organisms, this is done through a process known as aerobic respiration GLOSSARY aerobic respiration Aerobic means using oxygen—so aerobic respiration is respiration (a chemical process whereby energy is released from glucose) that involves oxygen (in contrast to anaerobic respiration, which doesn’t use oxygen). —a series of reactions where energy is released from glucose, using oxygen. During aerobic respiration:

  • glucose and oxygen are used up
  • carbon dioxide and water are produced as waste, and energy is released.

Temperature

Seeds need the right temperature to germinate, and this varies depending on the species of plant and its environment. Some need fluctuations in temperature. Some need very cold conditions for a few weeks or even months before they will germinate at a higher temperature. This ensures that cold climate seeds, for example, delay germination until after winter.

What about light, you might wonder? Most seeds don’t need light to set off germination—though the seedling will need it later on to carry out photosynthesis for energy, when the seed’s food stores have been used up. Some seeds, however, need certain kinds or amounts of light to break dormancy—a kind of seed sleep, which we’ll look at a bit more later. Such seeds can lie dormant for years, until, say, a tree falls, opening up a gap in the forest canopy and exposing the seed to light.

What happens during germination

Now that we know what a seed needs, let's look at what actually happens during germination.

  1. The seed takes up water, activating enzymes that begin the growth process.
  2. The embryo swells and lengthens.
  3. The embryo breaks through the seed’s covering layers.
  4. The root meristem GLOSSARYmeristem plant tissue responsible for growth is activated and the embryonic root (radicle) pushes through.
  5. Cotyledons (embryonic leaves) break out.
  6. The shoot meristem is activated.
  7. ‘True’ leaves form—the plant is now able to get energy from the sun.

How seeds germinate


Effects of Different Treatments on Seed Germination Improvement of Calotropis persica

The purpose of this study was to investigate the effects of different treatments on seed germination in the desert plant species Calotropis persica (Gand.). This species is known to have long time for seed germination considering arid region condition and short time of access moist. An experiment was performed with 13 treatments and 4 replications in a completely randomized design. Treatments included KNO3 with concentrations of 0.1, 0.2, and 0.3 percent, immersion in hot water for five min, acetylsalicylic acid 100, 200, and 300 mg L −1 , ethereal sulfuric acid (60%) for 5 and 10 min, thiourea with concentrations of 0.1% and 0.3%, and prechilling for 10 days. Tap water was used as the control. Our findings indicate that KNO3 0.1% and 100 mg L −1 acetylsalicylic acid were the most effective treatments for improvement of seed germination properties in this species. In a comparison of the two mentioned treatment, KNO3 0.1% treatments is the best.

1. Introduction

Germination is a critical stage in the life cycle of weeds and crop plants and often controls population dynamics, with major practical implications. Seed germination is the critical stage for species survival [1, 2]. In recent 20 years, desertification has been recognized as a major environmental problem and is a major focus of United Nations Environment Programme [3]. Vegetation is a protector of the soil against water and wind erosion as well as a casualty of soil erosion [4, 5]. Each desert-inhabiting plant has its own complex of strategies that enables it to persist in desert habitats [6]. Strategies for improving the growth and development of arid region plant species have been investigated for many years. Treated seeds with chemical compound usually would exhibit rapid germination when absorbing water under field conditions [7].

Calotropis is a genus of flowering plants in the dogbane family, Apocynaceae. They are commonly known as milkweeds because of the latex they produce. Calotropis species are considered common weeds in some parts of the world. The flowers are fragrant and are often used in making floral tassels in some mainland Southeast Asian cultures. Calotropis persica is growing in tropical region only. Iran is a country in the mid-latitude belt of arid and semiarid regions of the Earth. Approximately 60% of Iran is classified as arid and semiarid [8]. Based on results, the seed of full ripening fruits with scarification had the highest germination percent. [9] investigated the effects of salt stress and prime on germination improvement and seedling growth of Calotropis procera L. seeds and the results showed that priming improved the seedling characteristics in all samples, especially in −0.05 MPa, but a decrease with decrease in osmotic potential. The work in [10] studied the effect of temperature, light, pretreatment, and storage on seed germination of Rhodomyrtus tomentosa and their result showed that light significantly improved germination of fresh seeds but storage decreased the light-sensitivity of germination. Soaking for 24 hours in 250–600 mg L −1 gibberellic acid, 5–20% potassium nitrate, or 10% hydrogen peroxide solution increased seed germination. Calotropis sp. is an important economic plant used for drug and other purposes. The purpose of this study was to develop methods to increase germination percentage, shorten germination time, provide more rate germination, and result in more efficient seed propagation techniques for C. persica seeds.

2. Material and Methods

Seeds of C. persica were collected from Jiroft arid regions in southern Iran in 2013. A preliminary germination test was performed and low germination percentage was obtained. To solve this problem, we implemented an experiment with a randomized complete design. Before the start of experiment, seeds were surface sterilized in 1% sodium hypochlorite solution for 5 min, then rinsed with sterilized water, and air-dried for 28 h before putting in petri dishes. Treatments included pretreatment with KNO3 (0.1 and 0.3 percent) for 48 hours, acetylsalicylic acid to the moisture in the petri dish (100, 200 and 100 mg L −1 ), prechilling (4 degrees centigrade for 10 days), hot water (70°C) for 5 min, ethereal sulfuric acid (60%) for 5 and 10 min, thiourea with concentrations of 0.1% and 0.3%, and control treatment (irrigation with distilled water). The seeds were placed on top of Whatman paper number 1 within 10 cm petri dishes containing 10 mL distilled water. Counting number of germinating seeds began from the first day and was done till the end of the experiment (19 days). Germination percentage was recorded daily during the study period. Rate of germination was estimated using modified Timpson’s index of germination velocity [11]. Mean germination time (MGT) was calculated to assess the rate of germination [12]:

where is the number of seeds which in day grow, the total number of seeds grown, and the number of days from the date of germination and the germination rate index was obtained by reversing MGT at the end of this period final germination percentage was recorded. There are no outliers normality of data was checked and nonnormal data transformed by arc sin to verification of this hypothesis arc sin transformation was used for germination percentage before analysis [13]. Experimental data was analyzed by SPSS 17.0 to analyze the data and Duncan’s test at 5% level was used to compare the means.

3. Results

The results of ANOVA (Table 1) showed that there are significant differences (at 1% level) between effective treatments on germination characteristics and the different treatments resulted in significant differences among germination properties (Table 1).

The results of this research showed that germination percentage of C. persica increases due to application of KNO3 in different concentrations and acetylsalicylic acid 100 and 200 mg L −1 and decreased germination percentage due to application of hot water for 5 min, prechilling for 10 days, sulfuric acid 5 and 10 min, and thiourea 0.3%. Acetylsalicylic acid 300 mg L −1 and thiourea 0.1% have the same effect on germination percentage in comparison to control treatment. The increased germination percentage by KNO3 0.1, 0.2, and 0.3% and acetylsalicylic acid 100 mg L −1 was significant (Figure 1).


The seed germination rates of C. persica increased significantly when KNO3 0.1% was used. Acetylsalicylic acid 200 and 300 mg L −1 and thiourea 0.3% increased seed germination rate, but this increase was not significant. However, the germination rate was decreased when hot water for 5 min, prechilling for 10 days, sulfuric acid for 5 and 10 min, KNO3 0.2 and 0.3%, acetylsalicylic acid 100 mg L −1 , and thiourea 0.3% were used (Figure 2).


Mean germination time of C. persica decreased by using KNO3 0.1% but this difference was not significant. In seeds of C. persica, all treatments, except for KNO3 0.1%, caused increase in mean germination time (Figure 3).


4. Discussion and Conclusion

According to the obtained results, KNO3 0.1% and acetylsalicylic acid 100 mg L −1 were the most effective treatments for improvement of seed germination properties in C. persica plant species. In a comparison of the two mentioned treatments, KNO3 0.1% treatment is the best. This technique has become a common seed treatment that can increase rate, percentage, and uniformity of germination or seedling emergence, mainly under unfavorable environmental conditions. Rapid seed germination and stand establishment are critical factors for crop production under stress conditions. Hot water for 5 min and prechilling for 10 days did not show positive effect on germination improvement. The study result of scarification of seeds of Acacia angustissima showed that seeds soaking in hot water cause seed germination induction but increasing duration of seed contact with hot water leads to decline of seed germination percentage [14]. In a research it is shown that prechilling for 10 days had a positive effect on germination rate and mean germination time of both medicinal species of Foeniculum vulgare and Cuscuta epithymum but germination percentage decreased due to application of prechilling [15]. Sulfuric acid for 5 and 10 min did not have positive effect on seed germination of C. persica as a result, seed treatment with sulfuric acid cannot improve seed germination. This result demonstrated that above mentioned treatment had the destructive effect on embryo. It is notified that increasing in doses of sulfuric acid caused germination improvement and suggested chemical scarification in concentrated H2SO4 for 2 hours [16]. In this research thiourea did not have a positive effect on germination improvement of C. persica. Acetylsalicylic acid 100 mg L −1 improved mean germination time and germination percentage in comparison with amount of 200 and 300 mg L −1 .

In this research, KNO3 0.1% is recognized as the best treatment for improvement seed germination properties of C. persica. Similar results were reported in previous studies for the species of Citrullus colocynthis [17], Foeniculum vulgare and Cuscuta epithymum [15], Hypericum aviculariifolium [18], and Avena fatua [19]. According these results, KNO3 0.1% treatment is suggested for improvement of C. persica germination and this treatment is proper for propagation of studied species. Positive effect of KNO3 could be due to its role in balancing hormonal portion within seed which in turn results in germination inhibitors ratio like ABA. (abscisic acid). Virtually all of the cellular and metabolic events that are known to occur before the completion of germination of nondormant seeds also occur in imbibed dormant seeds indeed, the metabolic activities of the latter are frequently only subtly different from those of the former [20]. The seeds of most Mediterranean and desert species have dormancy characteristics or structural properties that prevent immediate germination of at least a proportion of the seeds [21–24]. The results obtained will be useful in carrying out tree improvement and plantings of C. persica trees for fuel wood, local medicine, and industrial production. Rapid seedling growth is also essential for reclamation of desert. This information could ultimately help in the sustainable development of the arid zones.

Conflict of Interests

The authors declare that there is no conflict of interests regarding the publication of this paper.

Acknowledgments

This research was supported by Iranian Revolutionary Guards Navy. The authors would like to thank Hamid Reza Ahmadinia Ph.D. student of Fishery in Gorgan University of Agriculture and Natural Resources for his help with the creation of this work.

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Copyright © 2014 Asghar Farajollahi et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.