Seed Assign.

FACTORS AFFECTING VEGETABLES SEED STORAGE LIFE

Submitted to Jimma University, Collage of Agriculture and Veterinary Medicine for the Course Vegetable Seed Science and Technology

By: - Sintayehu Musie ID. No. 06181/01

April, 2009 Jimma, Ethiopia

Tables of Content Page 1. Introduction................................................................................................................1 2. Vegetable Seed Storage ...............................................................................................2 2.1. Long-term storage:................................................................................................2 2.2. Short-term storage: ...............................................................................................2 3. Reasons for Vegetable seed Storage.............................................................................3 4. Factors Influencing the Life Span of vegetable Seeds ..................................................4 4.1. Internal Factors.....................................................................................................4 4.2. Hard Seed .............................................................................................................5 4.3. Pre-harvest Field and Mechanical Factors .............................................................5 4.4. Seed Maturity .......................................................................................................5 4.5. Relative Humidity and temperature.......................................................................6 4.6. Seed Moisture.......................................................................................................6 4.7. Temperature .........................................................................................................7 4.9. Illumination ..........................................................................................................8 4.8. Genetic Factors.....................................................................................................8 4.10. Presence of Micro flora.......................................................................................9 5. Controlling the Storage Environment.........................................................................10 5.1. Construction of Seed Store..................................................................................10 5.2. Temperature Control........................................................................................... 10 5.3. Control of Seed Moisture ....................................................................................10 6. Types of seed storage ................................................................................................ 11 6.1. Open seed Storage (with out Humidity or temperature Control) .......................... 11 6.2. Cryogenic Storage .............................................................................................. 11 6.3. Hermetic Storage ................................................................................................ 12 6.4. Conditioned Storage ........................................................................................... 12 7. Summary and Conclusions ........................................................................................ 13 Appendix 1....................................................................................................................15 References..................................................................................................................... 16

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List of Table

Page

Table 1. Approximate Years of Storage Life of Seeds under Cool, Dry Conditions……3

List of Appendix

page

Appendix 1. Relative life Expectancy of Vegetable seeds stored under favorable conditions…..15

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Seed Storage or Handling

1. Introduction Seeds are usually stored for varying lengths of time after harvest. Viability at the end of storage depends on (a) the initial viability at harvest, as determined by factors of production and methods of handling; and (b) the rate at which deterioration takes place. This rate of physiological change, or aging, varies with the kind of seed and the environmental conditions of storage, primarily temperature and humidity (Hartmann and Kester, 2002). When seed extraction and drying have been completed it is necessary to keep the seed under the best possible conditions to ensure that the maximum potential germination and other seed quality factors are maintained. Stored seeds are the primary input of a country’s vegetable cropping programme and are vital links between successive crop generations. In commerce seed in store represents a significant proportion of the seed company’s material assets (George, 1989). Seeds are uniquely equipped to survive as viable regenerative organisms until the time and place are right for the beginning of a new generations; however, like any other form of life, they cannot retain their viability indefinitely and eventually deteriorate and die. Fortunately, neither nature nor agricultural practice ordinarily requires seeds to survive much longer under the proper conditions (Copeland and McDonald, 1995).

Maintenance of high seed germination and vigor from harvest until planting is of the utmost importance in a seed programme. Seeds are practically worthless if, upon planting, they fail to give adequate plant stands in addition to healthy and vigorous plant. Good seed storage is , therefore, a basic requirement in seed production (Agrawal, 1989).

Therefore, the aim of this term paper is to discuss the factors affecting Vegetable seed longevity in the Storage and prolonging the storage life by providing optimum conditions.

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Seed Storage or Handling

2. Vegetable Seed Storage The storage period may be relatively short, perhaps even only weeks, but it is also possible that seed-lots have to be stored for several years. The storage period of seed should be defined as the total time from seed maturity through to sowing (George, 1985). The longevity of seed is primarily dependent on its inherent keeping quality which varies with species. Some species, e.g. onion, Allium cepa, and leek, Allium porrum, are relatively short-lived. Sweet corn, zea mays, and the larger seeded Phaseolus spp. Are intermediate, while seed of many genera of the Cucurbitaceae, e.g. Cucurbita spp., are relatively long lived in storage (George, 1985). 2.1. Long-term storage It is very important that seed be thoroughly dry. Freshly harvested seed should be cured for a minimum of three to four weeks before placing in long-term storage. At least one week before the seeds are placed in airtight containers, they should be transferred to an air-conditioned or heated room or other low humidity environment before being placed in a jar with a rubber-gasketed lid.

Thereafter the seed may be transferred to the refrigerator or other cool environment. Before opening the jar, always allow the jar to warm up to room temperature. Try to do this on a dry day so that humid air is not introduced to the jar. Note: never store seed in a closed container unless the seed has been dried thoroughly first. 2.2. Short-term storage For short-term seed storage, it is not necessary to store seed in airtight jars. Seed can be stored in large envelopes, paper bags, cloth bags, or other non-airtight containers. Porous containers are not recommended for storing seed for long term unless the surrounding air remains cool and dry. Zip lock bags and most plastics allow water vapor to pass through and therefore these materials are for short-term seed storage only. When seed extraction and drying have been completed it is necessary to keep the seed under the best possible conditions to ensure that the maximum potential germination and other seed quality factors are maintained. Stored seeds are the primary input of a country’s vegetable cropping programme and are vital links between successive crop generations. In commerce seed in the store represents a significant proportion of the seed company’s material assets (George, 1985).

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Seed Storage or Handling Table 1. Approximate Years of Storage Life of Seeds under Cool, Dry Conditions Asparagus -- 3

Muskmelon -- 5

Beans -- 3

Mustard -- 4

Beets -- 4

Okra -- 2

Broccoli -- 5

Pea, English -- 3

Brussels sprouts -- 5

Peppers -- 4kins -- 4

Cabbage -- 5

Pump

Carrots -- 3

Radishes -- 5

Chard, Swiss -- 4

Rutabagas -- 5

Collards -- 5

Southern peas -- 3

Corn -- 1-2

Spinach -- 5

Cucumbers -- 5

Squash -- 5

Eggplant -- 5

Tomatoes --4

Kale -- 5

Turnips -- 5

Kohlrabi -- 5

Watermelons -- 5

Lettuce -- 5

3. Reasons for Vegetable seed Storage The period of storage may be relatively short, perhaps even only weeks but sometimes it is necessary to store seed for several years. There are many reasons for storing seed of specific crops beyond the next possible sowing season. In some cases it may be uneconomic to multiply each seed stock annually. In addition the recurrent annual cost of multiplying each cultivar offered by a seed house or seed marketing organization has to be considered. Seed yield is influenced by many factors including provenance and seasonal variations during development and pre-harvest ripening, and it is not always possible to make accurate forecasts of yields; thus satisfactory storage is a useful way of ensuring that surplus seed is kept for future use. (George, 1985). An increasing number of Agricultural and horticultural crop programmes in developing countries are adopting the United Nations Food and Agriculture Organization’s recommendation to maintain stored seed stocks for contingencies. This is especially important in countries with relatively harsh climates where unpredictable drought, flooding or other disasters can resulting sudden seed shortages.

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Seed Storage or Handling

4. Factors Influencing the Life Span of vegetable Seeds According to Ells, et al., (2008), Conditions essential to good seed storage are just the opposite of those required for good germination. Good germination occurs when water and oxygen are present at a favorable temperature. Good seed storage results when seeds are kept dry (below 8 percent moisture) and the temperature is kept low (below 40 degrees). When seed moisture and storage temperature are low, the presence of oxygen has not been shown to be a factor in seed longevity. Germination is unaffected by storage in atmospheres of nitrogen, carbon dioxide, partial vacuum or air. Relative humidity (RH) influences the moisture content of seed if it is not stored in moisture-proof containers. For example, at 15 percent RH, seed will dry down to 6 percent moisture and will store safely in this condition for several years. However, at 90 percent RH, seed will dry down to only 19 percent moisture and germination will be poor after one year. 4.1. Internal Factors The physical condition and physiological state of seeds greatly influence their life span. Seeds that have been broken, cracked, or even bruised deteriorate more rapidly than undamaged seeds (McDonald 1985; priestly 1986). Even in the absence of physical symptoms, seeds may be physiologically impaired and become susceptible to rapid deterioration. Several kinds of environmental stresses during seed development, and prior to physiological maturity, can reduce the longevity of seeds for example, deficiency of minerals (N, K, and Ca), water, and temperature extremes. Immature and small seeds within a seed lot do not store as well as mature and large seeds within a seed lot. Hard-seeded ness also extends seed longevity (Copeland and McDonald, 1995).

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4.2. Hard Seed The drier the seeds, the longer they will store. There is a chance of producing what is known as "hard seed" if moisture is reduced below 8 percent. Hard seed resists germination under favorable conditions because it does not absorb enough water. When planted, the seed gradually absorbs water, germinates and produces seedlings over an extended period. A seed lot containing 50 percent hard seed is little better than a lot containing 50 percent dead seed, because neither produces a stand of seedlings when they should. Beans and peas are particularly subject to this condition and therefore should not be dried as completely as other seed. If they have been overdried, they germinate better if exposed to a humid atmosphere for two weeks before planting (Ells, et al., 2008). 4.3. Pre-harvest Field and Mechanical Factors Micro- and macro-nutrient deficiencies during plant growth and development of a potential seed crop can have a major effect on seed storage potential in that initial germination potential is low and, although such extreme conditions do not normally prevail in commercial seed production, the levels of major nutrients have been shown to affect indirectly seed storage life. Mechanical damage to seed during operations such as harvesting, processing or drying can reduce the potential storage life because the damaged seeds lose vigour sooner than undamaged ones. In addition damaged seeds are more vulnerable to storage pests and pathogens. There are various forms of mechanical damaged to seed which can occur before storage, one of which is threshing injury, e.g. cotyledon cracking of Phaseolus vulgaris, and seed coat abrasion of many species especially resulting from incorrect cylinder speed. Damage can also occur during processing if there is excessive moisture in the seed, especially if the seed is immature; the other extreme is over-drying which produces a brittle seed predisposed to breaking (George, 1985).

4.4. Seed Maturity Factors such as temperature, moisture, variety, and nutrient status influence seed maturity, which, in turn, influence seed storability. The greatest storage potential is attained at the time of physiological maturity, or maximum dry weight of the seed.

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Seed Storage or Handling

Although this appears to be a simple principle for individual seeds, many plants (e.g., carrot, grasses) have an indeterminate flowering pattern; that is, the most mature flowers grow at the base of the inflorescence with more immature flowers formed on the newer branches. Harvested seeds from such plants show varying degrees of maturity and different storage potential (Copeland and McDonald, 1995). Although immature seeds have been shown in a number of studies to be inferior to mature seeds in viability and vigor, other factors such as nutrient status can also influence seed longevity. Harrington (1960b) demonstrated that Carrot and pepper plants grow in nutrient

solutions

deficient in nitrogen, potassium, or calcium produced seeds that did not store well over an eight year period (Copeland and McDonald, 1995). 4.5. Relative Humidity and temperature The two most important factors that influences the life span of seeds are relative humidity and temperature. The effects of relative humidity (and its subsequent effect on seed moisture) and temperature of the storage environment are highly interdependent. Most crop seeds lose their viability at relative humidities approximately 80% and temperatures of 25 to 30 0C but can be kept 10 years or longer at relative humidities 50% or less and temperatures of 50C or lower (Toole, 1950). According to Harrington (1973), because of this interdependency, the sum of the percentage of relative humidity plus the temperature in degree Fahrenheit should not exceed 100 for safe storage. 4.6. Seed Moisture The seed most suited for storage has a moisture content not greater than 10 percent of seed weight. A seed’s metabolic rate is extremely low, often undetectable. When in this state it is hydrophilic and is capable of taking in water, even from the water vapour of the atmosphere. Thus, however much care has been taken to lower its moisture content by drying before storage it will quickly take up water again (George, 1985).

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Seed Storage or Handling 4.7. Temperature At temperature of 00C, formation of intracellular ice crystals can disrupt membrane integrity and contribute to seed deterioration. Seeds with moisture levels below 14% do not form ice crystals. It should be noted, however, that at 14% initial moisture, seeds stored in cold rooms below 00C will likely gain moisture. Most cold rooms have a high relative humidity, and seeds achieve equilibrium with that relative humidity after a brief period of storage. Thus, seeds stored at low temperatures must be in conditions in which the relative humidity is controlled or placed in moisture-proof containers to avoid increases in moisture content and increased deterioration (Copeland and McDonald, 1995). 4.8. Relationship between relative humidity and seed moisture content: When storing commercially grown seed, it is impractical and too costly to use desiccant to dry the seed for storage, unless the seed is small and expensive. Commercial seed is usually packaged for short or long term storage under conditions of ambient humidity (unless special equipment is used). Because relative humidity has a significant effect on seed moisture content, it is important to understand the relationship between

humidity

and

seed

moisture.

Regardless of the type of storage conditions, the moisture content of seed eventually comes into equilibrium with the moisture in the surrounding air. The relationship between atmospheric relative humidity and seed moisture content is shown at the above Figure. The curve was derived from measurements of the average seed moisture content of ten vegetable species stored at different relative humidity. Because the curve represents an average of ten different vegetable crop species, the response of individual species may vary. For example, seeds of grains (which contain relatively high percentages of carbohydrate) will have a moisture content of 13 to 15% at 75% relative humidity, whereas seeds rich in oils (such as peanuts) can have a moisture content of 9 to 11% at the same humidity.

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Seed Storage or Handling 4.9. Illumination According to McCormack (2004), the effects of light on stored seed have been studied (including the effects of different wavelengths of light): Some studies showed a benefit and some showed a detriment: the results are inconclusive and controversial. Seeds stored in glass containers should be stored out of direct sunlight because of the localized “greenhouse heating effect” on seeds. This might seem an unnecessary and overly obvious cautionary note, but in my experience, it has happened accidentally more than once. For example, this can happen if jars of stock seed are taken outside for the purpose of removal of some seeds for planting, or for transporting to another location. Though the jar may be temporarily stored in the shade, the angle of sunlight may change quickly and the jar will be in direct sun causing very rapid heating within the jar. Though some commercially produced seed is dried in direct sunlight (in dry climates), drying seeds in the sun is a questionable practice in the Mid-Atlantic and South if the air temperature is above 90oF (32oC).The air temperature at the seed surface is higher because of the conversion of light energy into heat at the seed surface, and the heat is “moist heat” (though this wouldn’t be in an issue in dry climates where evaporative cooling occurs at the surface). I’m not aware of any studies on this issue for our region. Another concern, also not well documented, is that the ultra-violet light from the sun may have a deleterious effect on seed longevity while the seeds are drying (Harrington, 1972). Harrington’s suggestion was based on the known effects of ultra-violet radiation on biological systems (rather than specific data). Whether the ultra-violet exposure is long enough to cause concern, is unknown.

4.8. Genetic Factors Seeds of some species are genetically and chemically equipped for longer storability than others under similar conditions. Most long lived seeds belong to species possessing hard, impermeable seed coats. Seeds of Canna (Sivori et al. 1968), Lotus (Wester 1973), and Lupinus (Porsild and Harrington1967) have been reported to be viable even after 500 years. Other hard seeded genera reported by Harrington (1972) to be germinable after 100 years include Albizia, cassia, Goodia, and Trifolium (Copeland and McDonald, 1995).

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Seed Storage or Handling

Seeds of other species are characteristically short-lived. These include vegetables such as lettuce, onion, and parsnip. Genetic difference in storage potential are not limited to seeds of different species. Differences in seed storability may also occur among cultivars. Thus, inheritance clearly exerts a marked effect on seed longevity and can be focus of breeding programs. It should not be forgotten, however , that the environment strongly alters the genetic potential for seed longevity.

4.10. Presence of Micro flora Two types of fungi invade seeds: field and storage fungi. Field fungi infect seeds that are developing on the mother plant and typically require high relative humidity (90 to 95%) or high seed moisture content (30 to 35%). Since these conditions occur only during seed maturation or imbibitions, field fungi seldom contribute to seed deterioration during storage. In contrast, storage fungi have the capacity to grow without free water. In general, they grow at seed moisture contents in equilibrium with relative humidities from 65 to 90%. The optimum temperature for growth of storage fungi is about 30 to 330C, with a maximum at 550C and a minimum of 00C. Most storage fungi belong to one of two principal genera, Aspergillus and Penicillium (Copeland and McDonald, 1995).

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Seed Storage or Handling

5. Controlling the Storage Environment The Storage environment can be influenced in two main ways, viz. the building (or structure) in which the seed is stored, and its environment (i.e. temperature and relative humidity). It is important that the seed is prepared for storage in a purpose- built structure as quickly as possible after harvesting and a system organized so that the seed remains in the storage environment for as long as is practical prior to distribution for sowing (George, 1985). 5.1. Construction of Seed Store Seed stores should be designed to maximize security, to minimize fire risk, to exclude birds and rodents, and to keep the entry of insects and microorganisms to a minimum. 5.2. Temperature Control According to George (1985), Storage temperature can be reduced by ventilation and refrigeration in addition to insulation and structural features. Complete temperature control is expensive in any part of the world. Total temperature control by refrigeration is, however, used in the long-term storage of germplasm collections and breeders’ material. 5.3. Control of Seed Moisture It is fundamental importance that seed moisture is reduced to a satisfactory and safe level before the seed is sealed in vapor or moisture-proof containers (George, 1985).

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Seed Storage or Handling

6. Types of seed storage 6.1. Open seed Storage (with out Humidity or temperature Control) Many kinds of Orthodox seeds only need to be stored from harvest until the next planting season. Under these conditions, seed longevity depends on the relative humidity and temperature of the storage atmosphere, the kind of seed, and its condition at the beginning of storage. Basic features of the storage structures include (a) protection from water, (b) avoidance of mixture with other seeds or exposure to herbicides, and (c) protection from rodents, insects, fungi, and fire. Retention of viability varies with the climatic factors of the area in which storage occur. Poorest conditions are found in warm, humid climates; best storage conditions occur in dry, cold regions. Fumigation or insecticidal treatments may be necessary to control insect infestation. Open storage can be used for many kinds of commercial seeds for at least (Hartmann and Kester, 2002). 6.2. Cryogenic Storage This storage method places seeds in to liquid nitrogen at a temperature of -1960C at approximately -1500C, to facilitate handling and safety. The differential in seed temperature is not considered significance in influencing seed storage. The advantage of this approach is that seeds are placed at a temperature where little detrimental physiological activity occurs, there by prolonged storage life. From practical perspective. The cost of the liquid nitrogen is minimal compared to maintaining conditioned store rooms. In addition, no working parts are necessary so repair of equipment is not required. Liquid nitrogen is also an inert gas that volatilizes easily. There fore, it remains relatively safe, at though air circulating in the storage room is necessary to guard against the room being filled with nitrogen gas and to prevent asphyxiation (Copeland and McDonald, 1995).

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6.3. Hermetic Storage In recent years, packing seeds in moisture resistance or hermetically sealed containers for storage and marketing has been explored. The purpose of such containers is to maintain seeds at safe storage moisture levels. Ordinary paper and cloth containers were least effective, while various laminate and polyethylene materials were moderately effective. Metal cans were completely effective in maintaining moisture at the initial 5% level. Such completely moisture proof containers hermetically seal the seed and are effective for long term seed storage up to 10 years or more (Harrington1973) cited in Copeland and McDonald (1995). 6.4. Conditioned Storage Seeds of most species may be safely stored for several years by careful control of temperature and relative humidity. Although such conditions are too costly for most agricultural seed lots, they may be extremely valuable for preserving germ plasm and certain high value seed stocks. In some parts of the world, especially in the tropics, conditioned storage is necessary in order to maintain high viability of some seeds from harvest to planting (Copeland and McDonald, 1995).

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7. Summary and Conclusions Moisture and high temperatures cause rapid loss in the ability of vegetable seeds to germinate. Therefore, discard vegetable seeds held in storage buildings, vehicles, and other places with widely fluctuating temperatures and humidities. High temperature and high humidity will degrade your seed quality quickly. Consider them the enemy! Fluctuating temperatures and humidity levels are just as damaging. Help defeat these problems by drying your seed well. Avoid direct sunlight- it can heat the seeds and damage them. Keep drying seeds below a temperature of 96 degrees F. A single layer of seed on a shaded screen with nearby circulating air is the best option. Don’t attempt to dry them on cloth or non-rigid plastic, they can stick and be broken or damaged when removed. Treat them gently (LabLover, 2004). The longer seeds are stored, the more important it is to control moisture and temperature conditions. Low moisture content in the seeds means longer life, especially if seeds must be kept at warm temperatures. Seeds can be stored over, but not touching, calcium chloride, dried silica gel, or freshly opened powdered milk by sealing them in air-tight containers. Bean and okra seeds can be over-dried, resulting in hard seed coats and reduced germination. Seeds can be stored successfully at temperatures above 32 ºF. Between 40 and 50 ºF is satisfactory when moisture content of the seed is not too high. For long-term storage (several months) seeds can be stored in the freezer. Seeds are not harmed if properly dried before storing, but be sure to let them come to room temperature before handling. Do not store chemically treated seeds with vegetables or other food items that are to be eaten. Use airtight containers to store dried seeds. Baby food jars or canning jars with rubber seals work well. You can cut gaskets from rubber inner tubes or similar material to fit larger jars for larger stocks. Vacuum sealers can also be used.

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Seed Storage or Handling Silica gel, if available, can be added to jar or bag. Store sealed bags in a jar or other rigid container. Jars prevent damage from insects or rodents, which is rather common in less secure storage. Jars and containers should be stored in a cool, dry place where the temperature fluctuates as little as possible. Root cellars are ideal. A basement corner far from open doors or windows is another option (LabLover, 2004). Seeds can also be frozen for longer storage. Seed moisture must be below 8% to avoid the internal moisture from swelling when frozen and damaging the seed. Test to see if moisture levels are low enough. As a general rule of thumb, dried seeds that break when folded, instead of bending, are 8% moisture or lower. Unless you plan to plant the entire contents of your entire storage jar, (never a good idea to plant all your seed at once-if you loose that planting, you loose it all!) when you remove it from the freezer allow the jar to warm to room temperature before opening. This prevents condensation from forming on cold seeds and partially re hydrating them. Partially re hydrated seeds may exceed the 8% moisture level and die when refrozen. Choose the smallest jars possible to avoid frequent openings and temperature fluctuations to keep the remaining seed in best condition (LabLover, 2004). The level of hygiene within the store will have a long-term effect on seed quality and longevity. Only seed which has been through the final stages of processing should be taken in to the store. All other materials should be excluded (George, 1989). A comprehensive programme for rodent prevention should be organized from the outset, rather than waiting for control measures to become necessarily later. The possibility of rodent infestation will depend on the method of containerization within the store as well as on the location and local conditions. Rodent prevention and control programmes include the use of rodenticides (George, 1989).

According to Agrawal (1989), General principle, In view of the various factors affecting seed viability in storage, the following principles emerge as necessary as possible, Seed storage conditions should be dry and cool, Effective storage pest control proper sanitation in the seed stores, Before placing the seeds into storage they should be dried to safe moisture limits, appropriate for the storage system.

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Appendix-1 Appendix 1. Relative life Expectancy of Vegetable seeds stored under favorable conditions Vegetables Asparagus

Years 3

vegetables Kohlrabi

years 3

Bean

3

Leek

2

Beet

4

Lettuce

6

Broccoli

3

Muskmelon

5

Brussels Sprouts

4

Mustard

4

Cabbage

4

Okra

2

Cardoon

5

Onion

1

Carrot

3

Parsley

1

Cauliflower

4

Parsnip

1

Celeriac

3

Pea

3

Celery

3

Pepper

2

Chard, Swiss

4

Pumpkin

4

Chervil

3

Radish

5

Chicory

4

Sea kale 1

Chinese cabbage

3

Southern pea 3

Corn, sweet

2

Spinach 3

Corn, salad

5

Squash 4

Cucumber

5

Tomato

Eggplant

4

Turnip

Kale

4

Water melon

4 4 4

Source: - Lorenz and Maynard (1988).

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References Agrawal, R.L. 1989. Seed technology. Oxford & IBH Publishing CO. PVT. LTD., New Delhi, India. Copeland, L.O. and McDonald, M.B. 1995. Principles of Seed Science and Technology, 3rd ed. Kluwer Academic publishers, London. Ells, J.E., Bass L.N and Whiting, D. 2008. Storing Vegetable and Flower Seeds. Colorado State University Extension. http://www.ext.colostate.edu/Pubs/Garden/07221.html Hartmann, H.T., Kester, D.E., Davies, F.T. and Geneve, R.L. 2002. Plant propagation principles and practices, 7th ed. Prentice Hall, New Jersey. LabLover. 2004. Vegetable Seed Storage and Germination Testing. http://www.alpharubicon.com/primitive/seedgermlablover.htm Lorenz, O.A. and Maynard, D.N. 1988. Knott’s Handbook for Vegetable Growers, 3rd ed. John Wiley & sons, Inc., USA. McCormack, J.H. 2004 Seed Processing and Storage: Principles and practices of seed harvesting, processing, and storage: an organic seed production manual for seed growers in the Mid-Atlantic and Southern U.S. http://209.85.129.132/search?q=cache:LFdHDJ3LW0oJ:www.savingourseed. org/pdf/SeedProcessingandStorageVer_1pt3.pdf+Seed+Processing+and+Stora ge:+Principles+and+practices+of+seed+harvesting,+processing,+and+storage: +an+organic+seed+production+manual+for+seed+growers+in+the+MidAtlantic+and+Southern+U.S.&cd=1&hl=en&ct=clnk&gl=et

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