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Seed Technology

  1. 1. Nature and Importance of Seed Technology
  2. 2. Seeds have been and still are the most important staple food of the world. Rice, for instance is the main carbohydrate source of two-thirds of the world’s population. Likewise, legumes (e.g. mungbean, peanut and soybean) are rich sources of proteins essential to a balanced human diet. Importance of Seeds
  3. 3. What is a seed? A seed is a minute plant with nourishing and protecting tissues (Edmond et al., 1978). -is a mature ovule consisting of an embryonic plant together with stored food, all surrounded by a protective coat (Copeland, 1976).
  4. 4. A seed is an embryonic plant in a resting stage usually – though not always – supplied with food reserves in cotyledons (seed leaves), endosperm (tissue normally derived from the triple fusion of two polar nuclei of the ovule with the second sperm nucleus of the pollen tube), or perisperm (tissue derived from nucellus); all this usually contained within protective structures consisting of the testa derived from the integuments of the mother plant and possibly other structures formed in a variety of ways (Roberts, 1972).
  5. 5. What is Seed Technology? A body of knowledge which deals on the production, handling and storage of seeds.
  6. 6. Seeds are the easiest and fastest means of plant multiplication. Therefore, knowledge in producing, handling and storing high quality seeds is necessary for successful crop production. What is the importance of Seed Technology to crop production?
  7. 7. Seeds remain to be the most important form of germplasm. As such maintaining the viability of seeds under storage ensures the availability of genetic material which could be used for crop improvement.
  8. 8. What is the importance of Seed Technology to crop science? By studying the seed or germinating seedling, man has gained knowledge about growth regulators, respiration, cell division, morphogenesis, photosynthesis and other metabolic processes. This is possible since inside each seed is a living plant capable of exhibiting almost all the processes found in the mature plant.
  9. 9. What are the uses of seeds to man? a. Food and animal feed such as cereals, legumes and vegetables seeds (squash, watermelon etc.). b. Spices and condiments such as blackpepper, achuete, anise, etc. c. Beverage such as coffee, cocoa and chocolate. d. Edible oil from coconut, soybean, peanut and sunflower. e. Fiber such as cotton. f. Commercial materials such as button, soap, paints.
  10. 10. Grains Grains, the seeds produced from a number of cereal grasses, are among the most important food crops in the world. Cooked or ground and processed into flours, oils, and other substances, they are an excellent source of energy for both humans and livestock. Beer and other alcoholic beverages are made from fermented grains.
  11. 11. Wheat Grains Wheat grains must be ground into flour before they can be made into easily digestible foods such as pasta and bread. Flour has played an important role in the diet of Western civilization since ancient times.
  12. 12. Coffee Beans Mature coffee beans are actually fruit that when fully ripe take on a deep crimson color. After drying and roasting, the beans change to a brown or black color and are ready for grinding.
  13. 13. Cacao The cacao tree produces a fruit from which cocoa is derived. Following harvest the fruit is fermented to give the cocoa seed, or bean, its distinctive flavor. Cocoa, containing approximately 20 percent protein, 40 percent carbohydrate, and 40 percent fat, is high in nutritive value. Côte d’Ivoire, Ghana, Nigeria, and Brazil are leaders in cocoa production.
  14. 14. Soybeans Soybeans, cultivated for many centuries throughout Asia, are a leading crop in the United States. Soybeans are used primarily to produce protein meal and oil.
  15. 15. Cotton Cotton is natural vegetable fiber of great economic importance as a raw material for cloth. Cotton's strength, absorbency, and capacity to be washed and dyed also make it adaptable to a considerable variety of textile products.
  16. 16. Coconut The coconut palm, cultivated throughout the tropics worldwide, grows to a height of nearly 30 m (100 ft). All parts of the coconut palm can be used. Besides the fruit itself, the terminal bud, called the palm cabbage, and young stems are edible and in some areas are considered a delicacy. The sap can be made into beverages, while dried coconut husk fibers and leaves can be transformed into a variety of household items.
  17. 17. Sunflower Sunflower plants are cultivated for their seeds. Refined sunflower- seed oil is edible and considered by many equal in quality to olive oil. Cruder sunflower oil is used for making soap and candles. The oil cakes (solid residues after oil is expressed) are used as cattle feed. The raw seeds are used in poultry mixes and are consumed by humans as well.
  18. 18. Black Pepper Native to India and long considered the world’s most important spice, the black pepper has been used to flavor foods for over 3000 years. The black pepper plant produces a single-seeded fruit called a peppercorn, which if dried while immature and green, produces the spice, black pepper.
  19. 19. Cashew Although cultivated in parts of Asia and Africa, the cashew is native to the western hemisphere. Related to the mango, pistachio, poison ivy, and poison oak, the cashew has a wide variety of nonfood applications, including the use of cashew oil in the manufacture of varnishes and plastics.
  20. 20. Pili Nut Pili nuts have a rich, buttery flavor, often said to be superior to that of almonds. They are slender, with a length of appproximately 2-1/2 inches and a diameter of around 3/4”. Pili nuts have a hard shell which protects a single, sweet kernel.
  21. 21. What is RA 7308? An act to promote and develop the seed industry in the Philippines and create the National Seed Industry council and for other purposes.
  22. 22. a) conserve, preserve and develop the plant genetic resources of the nation; b) encourage and hasten the organization of all sectors engaged in the industry, integrate all their activities and provide assistance to them; c) consider the seed industry as a preferred area of investment; What are the responsibilities of the government under RA 7083?
  23. 23. d) encourage the private sector to engage in seed research and development and in mass production and distribution of good quality seeds; and e) provide the local industry protection against unfair competition from imported seeds.
  24. 24. Republic Act 7308, otherwise known as the Seed Industry Development Act was enforced in 1992. The Bureau of Plant Industry then had been in the forefront before a bill relevant to Seed industry was enacted and became a law.
  25. 25. Reproductive Structures of Flowering Plants
  26. 26. Reproductive Structures of Flowering Plants  Flowers are the reproductive shoots of angiosperm sporophytes  Spores that form by meiosis inside flowers develop into haploid gametophytes
  27. 27. Stamens  Stamens consist of a filament with an anther at the tip  Anthers contain pollen sacs, in which diploid cells produce haploid spores by meiosis  Spores differentiate into pollen grains (immature male gametophytes)
  28. 28. Carpels  Flowers have one or several carpels, each with a sticky stigma to capture pollen grains  The ovary contains ovules which undergo meiosis to form a haploid female gametophyte
  29. 29. Fig. 30-2a (2), p. 508 stamen carpel (male reproductive part) (female reproductive part) filament anther stigma style ovary petal (all petals combined are the flower’s corolla) ovule (forms within ovary) sepal (all sepals combined are flower’s calyx) receptacle
  30. 30. Pollination  Pollination: The transfer of pollen from the male anther to the female stigma
  31. 31. Why is Pollination Important?  Sexual reproduction is important for evolution:  Sexual reproduction produces variable offspring, creating diversity and variation among populations (shuffling of genes)  You need variation for Natural Selection to occur  Sexual reproduction is advantageous to an organism only if it happens with someone other than itself!
  32. 32. Pollen Distribution  Wind- not efficient and not spp. specific  Animals Insects Birds Mammals Reptiles amphibians
  33. 33. Seed Formation  After fertilization, mitotic cell divisions transform the zygote into an embryo sporophyte  Endosperm becomes enriched with nutrients  Ovule’s integuments develop into a seed coat  Seed (mature ovule)  An embryo sporophyte and nutritious endosperm encased in a seed coat
  34. 34. Seeds as Food  As an embryo is developing, the parent plant transfers nutrients to the ovule  Humans also get nutrition from seeds (grains)  Embryo (germ) contains protein and vitamins  Endosperm contains mostly starch
  35. 35. Seed Dispersal  Fruits function to protect and disperse seeds  Fruits are adapted to certain dispersal vectors:  Mobile organisms such as birds or insects  Environmental factors such as wind or water
  36. 36. Stages of Embryo Development in Monocot  Zygotic stage. This single- celled stage follows fusion of the haploid egg and sperm.
  37. 37. Stages of Embryo Development in Monocot  Globular stage. This stage occurs 2–4 DAP (days after pollination). Following an initial horizontal division to create the apical and basal cells, a series of variable cell divisions create a multilayered, globular embryo.
  38. 38. Stages of Embryo Development in Monocot  Coleoptile stage. At 5 DAP, the coleoptile (specialized tubular first leaf), shoot apical meristem , root apical meristem, and radicle (embryonic root) form.
  39. 39. Stages of Embryo Development in Monocot  . Juvenile vegetative stage. At 6–10 DAP, the shoot apical meristem initiates several vegetative leaves
  40. 40. Stages of Embryo Development in Monocot  Maturation stage. During 11–20 DAP, the expression of maturation- related genes precedes the onset of dormancy
  41. 41. Seed Chemistry
  42. 42. Carbohydrate Stored in Seeds  Carbohydrate is the major storage substance in seeds of most cultivated plants.  Cereals are especially rich in carbohydrates and low in fats and proteins.  Starch and hemicellulose are the major forms of carbohydrate storage in seeds.
  43. 43. What are Carbohydrates?  class of organic macromolecules made up of carbon, hydrogen and oxygen and are often called "sugars and starches"  There are three classes of carbohydrates, based on the number of sugar units:  1) Monosaccharides  2)Disaccharides  3) Polysaccharides
  44. 44.  There are three types of starch:  (1) Amylose: a non-branching straight chain of glucose - used to store glucose in plants.  (2) Amylopectin: a branched chain, also used to store glucose in plants.  (3) Glycogen: another branched chain molecule used to store glucose in animals.
  45. 45. Forms of Starch
  46. 46. Hemicellulose  other major form of carbohydrate storage in seed.  hemicellulose is usually found in the cell walls of plants, they are also found as reserve food material.  includes xylans, mannans and galactans.  found in the thickened tertiary layers of cell wall of the endosperm in cotyledons
  47. 47. Mucilages  complex carbohydrates consisting of polyuronides and galacturonides which chemically resemble the pectic compounds and hemicellulose.  become very sticky when wet and in some cases it tends to cling on the material that it touches. It is a seed dispersal mechanism. 
  48. 48. Pectic Compounds  occur in seeds and in other plant parts, mainly as components of the cell wall and the middle lamella where they serve to bind the cell walls together  propectins differ from pectins since they have larger molecule chain  when propectins are converted into pectins, they are instrumental in softening of ripening fruits.
  49. 49. Lipids  substances that are insoluble in water but soluble in ether, chloroform, benzene or other fat solvents  either esters of fatty acid and glycerol or their various hydrolytic products  known as glycerides or more especially as triglyceride, because each glycerol molecule is combined with three fatty acid molecules
  50. 50.  Fatty acids are so named because they are constituents of natural fats and in the free state, they resemble fats in physical properties.  Free fatty acids are seldom found in plant parts other than in germinating or deteriorating seeds as a result of fat hydrolysis.
  51. 51.  Glycerol and other alcohols are combined with fatty acids to form different kinds of lipids. Of these, trihydroxy alcohol and glycerol or glycerine are mostly often involved and form esters (glycerides) with many different fatty acids. 
  52. 52. Proteins  Proteins are nitrogen-containing molecules of huge size and exceedingly complex structure; the greater part of which yield amino acids upon hydrolysis.  Proteins comprise a valuable food storage component in seeds of most plant species.  Soybeans are one of the few species known in which protein comprises more of the reserve food supply than do fats or carbohydrates.  Most of the plants known to have high protein seed are legumes having nitrogen-fixing capacity.
  53. 53. Essential Amino Acids
  54. 54. Nonessential Amino Acids
  55. 55. Storage Proteins  Storage stored in specialized structures called protein bodies which are located in cotyledons and endosperm of the seed  Enzymes (proteinases) are required to catabolize storage proteins into amino acids which in turn can be used by the developing embryo for new protein synthesis  These enzymes can be present in stored forms in the dry seed, but the majority of proteinases are synthesized as new enzymes following imbibition.
  56. 56. Proteins  Proteins are nitrogen-containing molecules of huge size and exceedingly complex structure; the greater part of which yield amino acids upon hydrolysis.  Proteins comprise a valuable food storage component in seeds of most plant species.  Soybeans are one of the few species known in which protein comprises more of the reserve food supply than do fats or carbohydrates.  Most of the plants known to have high protein seed are legumes having nitrogen-fixing capacity.
  57. 57. Functions of Protein  Physiological functions of protein include:  act as enzymes that catalyze biochemical reactions  structural or mechanical functions  involved in cell signaling and transport through membranes
  58. 58. Seed Proteins  In seeds, the greatest quantity of proteins is found in storage proteins.  Many of the enzymes present in seeds are essential for storage reserve utilization by the embryo during the germination process.  There still remain many diverse proteins that have structural (e.g., components of cell membranes and walls) or metabolic functions (e.g., enzymes and transporters)  Some proteins found in seeds also provide protection against pests and pathogens.
  59. 59. Storage Proteins  Storage proteins are stored in specialized structures called protein bodies which are located in cotyledons and endosperm of the seed  Enzymes (proteinases) are required to catabolize storage proteins into amino acids which in turn can be used by the developing embryo for new protein synthesis  These enzymes can be present in stored forms in the dry seed, but the majority of proteinases are synthesized as new enzymes following imbibition.
  60. 60. Four Classes of Seed Proteins  1) Albumins, soluble in water at neutral or slightly acid pH. This fraction is primarily enzymes.  2) Globulins, soluble in saline solution, but insoluble in water  3) Glutelins, soluble in acid or alkali solutions  4) Prolamins, soluble in 70-90% ethanol
  61. 61. Corn Protien  In maize seeds, zein (a prolamin) is the most abundant storage protein.  Zein is relatively rich in alanine and leucine, with low levels of lysine and almost no tryptophan.  Thus, maize protein is of poor quality if used as the only protein source in monogastric animal nutrition.  Zein is primarily stored in protein bodies in the maize seed endosperm.
  62. 62. Legume Protein  The percentage of protein concentration in dicotyledonous seeds is high, with soybean and other legume seeds ranging from 25 to 50% compared to only 10 to 15% in cereal seeds.
  63. 63. Other chemical compounds found in seeds Alkaloids  Alkaloids are chemically heterogeneous organic compounds containing nitrogen.  Alkaloids may also serve as protective mechanisms of seeds against pests and pathogens because of their bitter flavor.  Alkaloids can be classified according to their molecular structure.
  64. 64. Other chemical compounds found in seeds  Tannins are groups of complex astringent polyphenolic compounds occurring widely in plants.  Tannins are especially common found in tree bark, unripe fruits, and leaves.  They also occur in seeds, particularly in the seed coat. Examples of seeds containing tannins are cocoa, many legumes (especially red and black beans), pecans, cashews and walnut.
  65. 65. SEED GERMINATION
  66. 66. Seed Germination © 2008 Paul Billiet ODWS
  67. 67. Seed maturation  Takes place in the fruit on the parent plant  Endospermous seeds: Retain the endosperm tissue, which eventually dies but it is surrounded by a layer of living cells, the aleurone layer.  Non-endospermous seeds: The endosperm tissue is absorbed by the cotyledons. These then become the food reserve for the seed. © 2008 Paul Billiet ODWS
  68. 68. Endospermous Seeds  The single massive cotyledon is termed the scutellum, while the plumule and radicle are enclosed by protective structures termed the coleoptile and the coleorhiza.
  69. 69. Endospermous Seeds  Endospermic seeds are seeds whereby the endosperm is present in the mature seed and serves as food storage organ.  In an endospermic seed, the embryo is small compared to the volume of the seed, with the rest of the space being occupied by the endosperm.  A good example is the wheat seed where the bulk of the seed is endosperm (the starch we use as food) and the embryo is a small shield-shaped thing at one side, the so-called "wheat germ".
  70. 70. Non Endospermous Seeds  The cotyledons serve as sole food storage organs.  During embryo development the cotyledons absorb the food reserves from the endosperm.  The endosperm is almost degraded in the mature seed and the embryo is enclosed by the testa.
  71. 71. Non Endospermous Seeds  Examples: rape (Brassica napus), and the legume family including pea (Pisum sativum), garden or French bean (Phaseolus vulgaris), soybean (Glycine max)
  72. 72. Seed viability  Viability: When a seed is capable of germinating after all the necessary environmental conditions are met.  Average life span of a seed 10 to 15 years.  Some are very short-lived e.g. willow (< 1 week)  Some are very long-lived e.g. mimosa 221 years  Conditions are very important for longevity  Cold, dry, anaerobic conditions  These are the conditions which are maintained in seed banks © 2008 Paul Billiet ODWS
  73. 73. Germination: The breaking of dormancy The growth of the embryo and its penetration of the seed coat Break down of barriers Abrasion of seed coat (soil particles) Decomposition of seed coat (soil microbes, gut enzymes) Cracking of seed coat (fire) Change in physical state - rehydration Destruction and dilution of inhibitors Light, temperature, water Production of growth promoters© 2008 Paul Billiet ODWS
  74. 74. Germination STAGE EVENTS PREGERMINATION (a) Rehydration – imbibition of water. (b) RNA & protein synthesis stimulated. (c) Increased metabolism – increased respiration. (d) Hydrolysis (digestion) of food reserves by enzymes. (e) Changes in cell ultrastructure. (f) Induction of cell division & cell growth. GERMINATION (a) Rupture of seed coat. (b) Emergence of seedling, usually radicle first. POST GERMINATION (a) Controlled growth of root and shoot axis. (b) Controlled transport of materials from food stores to growing axis. (c) Senescence (aging) of food storage tissues.© 2008 Paul Billiet ODWS
  75. 75. Environmental factors affecting seed germination Water Temperature Light Gases
  76. 76. Water Requirement  A seed must have an ample supply of moisture for germination to occur.  Moisture content needed for germination to occur ranges from 25% to 75%.  Once the germination process begins, a dry period or lack of water will cause the death of the developing embryo.
  77. 77. Problems associated with water uptake (imbibition)  Imbibition injury - due to too rapid water uptake resulting in solute leakage  The initial phase of water uptake is very rapid.  Because the process of drying causes membranes to become ‘leaky’ there is a risk that sugars and electrolytes can leach out the seeds during this period of rapid uptake before the membranes have restored their normal function.
  78. 78. The effect of temperature on germination  Speed of germination.  Range of temperatures over which germination  can occur.  Seasonal physiological changes as seeds become more or less dormant.
  79. 79. The effect of light on germination  Most cases seeds are indifferent  Many require light e.g. small-seeded annuals  Few are inhibited  Seeds sensitive to duration, intensity and especially quality  All light responses controlled by phytochrome
  80. 80.  Many growers believe that most seeds require darkness for germination - this is wrong.  In fact most seeds germinates equally well in light or dark.  Many seeds only germinate in the light and only a a few will only germinate in the dark.  Even in a single batch of seeds, the response may vary depending on other environmental factors. e.g. temperature.
  81. 81. The effect of gases on germination Reduced O2 or elevated CO2 usually reduces germination.  Except some submersed aquatics where germination is stimulated by anaerobic conditions.  Nitrogen dioxide gas may have potential for dormancy breaking.
  82. 82. Seed Dormancy
  83. 83.  Seed dormancy is a condition where seeds will not germinate even when the environmental conditions (water, temperature and aeration) are permissive for germination (Copeland and McDonald, 2001).  Dormancy does not only prevent immediate germination but also regulates the time, conditions and place for germination to occur.
  84. 84. Importance  Seed dormancy provides a mechanism for plants to delay germination until conditions are optimal for survival of the next generation (Finkelstein et al. 2008).
  85. 85.  Creation of a “seed bank”.  In nature, a seed banks ensures that not all the sees for a species germinate in a single year.  This is an insurance against years where flowering or fruiting may not occur for some catastrophic environmental reason.  Some seeds remain dormant in a seed bank for decades.
  86. 86. Ideally plants should be preserved in the wild in the habitat where they naturally grow. However human-induced habitat loss is already great and likely to continue. Seed banks are a very efficient way of ensuring their survival.
  87. 87. Classification of Seed Dormancy  Primary dormancy is the inability of seeds to germinate even in the presence of environmental conditions favoring it.  Secondary dormancy is a type of dormancy imposed by certain adverse environmental conditions in previously nondormant seeds, or seeds in which primary dormancy has been broken.
  88. 88. Classification of Primary Dormancy  Endogenous • embryo characteristic prevents germination  There are two types of endogenous dormancy – morphological and physiological.
  89. 89. Morphological Dormancy  Morphological dormancy is where the embryo has not completed development at the time the seed is shed from the plant.  The embryo must complete development prior to germination.  Seeds with morphological dormancy can have either rudimentary or undeveloped embryos (Atwater, 1980).
  90. 90. Morphological Dormancy  Species with rudimentary embryos have little more than a proembryo embedded in a massive endosperm.  These are found in Ranunculaceae (Anemone, Ranunculus), Papaveraceae,(Papaver, Romneya), and Araliaceae (Aralia, Fatsia).  Seeds with undeveloped embryos have embryos that are torpedo shaped and up to one-half the size of the seed cavity.  Important families and genera in this category include Umbellifereae, (Daucus), Primulaceae (Cyclamen, Primula), and Gentianaceae (Gentiana).
  91. 91. Overcoming Morphological Dormancy  Warm temperatures (> 20oC) favor germination, as does gibberellic acid treatment.  Orchids have rudimentary embryos, but they are not considered dormant in the same sense as others in this category and special aseptic methods are used for germination.
  92. 92. Physiological Dormancy  This involves physiological changes within the embryo that results in a change in its growth potential (Baskin and Baskin 1971) that allows the radicle to escape the restraint of the seed coverings.  Physiological dormancy includes non-deep, intermediate and deep categories. By far, endogenous, non-deep physiological dormancy is the most common form of dormancy found in seeds (Baskin and Baskin 1998).
  93. 93. What is after ripening?  It is the period of usually several months of dry storage at room temperature of freshly harvested, mature seeds and is a common method used to release dormancy and to promote germination (Bewley, 1997).  In a broad sense, after-ripening describes the loss of the dormant state in a seed over some period of time. In the strictest sense, after-ripening refers to the loss of dormancy mechanisms imposed by the Mother Plant (http://www.seedimages.com/dormancy/dormancy-mechanisms.html).
  94. 94.  “After-ripening” is the time required for seeds in dry storage to lose dormancy. It is the general type of primary dormancy found in many freshly harvested seeds of herbaceous plants (Atwater 1980; AOSA 1993, Baskin and Baskin 1998).  This type of dormancy is often transitory and disappears during dry storage, so it generally not a problem by the time the grower sows the seeds.
  95. 95. Photodormant seeds  Seeds that either require light or dark conditions for germination are termed photodormant.  The basic mechanism of light sensitivity in seeds involves phytochrome (Bewley and Black 1994, Taylorson and Hendricks 1977).  Exposure of the imbibed seed to red light (660 to 760 nm) usually stimulates germination, while far-red light (760 to 800 nm) or darkness causes a physiological change that inhibits germination (Van derWoude 1989).
  96. 96. Another Type of Primary Dormancy  Exogenous dormancy is considered to be on the outside of the seed; associated with the seed's external covering structures such as the seed coat or pericarp.  Classification of exogenous dormancy  Physical - tissues impermeable to water (preventing seed imbibition).  Chemical -tissues contain chemical germination inhibitors.  Mechanical- tissues restricting embryo expansion and development.
  97. 97.  (1) inhibiting water uptake;  (2) providing mechanical restraint to embryo expansion and radicle emergence;  (3) modifying gas exchange (i.e. limit oxygen to the embryo);  (4) preventing leaching of inhibitors from the embryo; and  (5) supplying inhibitors to the embryo (Bewley and Black, 1994). The tissues enclosing the embryo can prevent germination by:
  98. 98. Breaking dormancy in hard seeds  This type of dormancy allows dry seed to be successfully stored for many years, even at warm storage temperatures.  Germination in hard seeds can be increased by any method that can soften or “scarify” the covering (Hartmann et al. 1997).  Hardseededness can be variable in a population of seeds.  It is increased by environmental (dry) conditions during seed maturation, and environmental conditions during seed storage (Baskin and Baskin 1998).  Harvesting slightly immature seeds and preventing them from completing desiccation can reduce hardseededness.
  99. 99. Classification of Physiological Dormancy  Nondeep  Intermediate  Deep
  100. 100. Causes of Non Deep Physiological Dormancy  Covering restricts oxygen  Inhibitors in coverings  Embryo cannot break through physical barriers  Endosperm restrict embryo growth
  101. 101.  Seed Scarification  Any process of breaking, scratching, or mechanically altering the seed coat to make it permeable to water and gases is known as scarification.  In nature, this often occurs by fall seeding. Freezing temperatures or microbial activities modify the seed coat during the winter.  Scarification can also occur as seeds pass through the digestive tract of various animals. Techniques to Break Nondeep Physiological Dormancy
  102. 102. Intermediate Physiological Dormancy  Excised embryos will grow  As much as 6 months prechilling needed  Gibberellins, kinetin, thiourea can shorten prechilling requirement  Acer negundo, Acer pseudoplatanus, Acer saccharum, Corylus avellana, Fraxinus americana, Fraxinus pennsylvanica, Fagus sylvatica  Ethylene accelerated and increased germination at 15°C  GA3 increased germination of unchilled seeds at 15°C, 10 weeks prechill negate chemical effect (Seed Sci 2004, p21-33)
  103. 103. Deep Physiological Dormancy  Excised embryos do not grow or produce abnormal seedlings (Prunus will)  Long prechill requirement  Chemicals do not affect germination of intact seeds  Sorbus aucuparis – secondary dormancy induced above 20°C, germinates best at 1-3°C  Acer platanoides, Acer tartaricum, Malus domestica,  Prunus persica – 90 days prechill  Prunus mahaleb – 100 days prechill  3 to 5°C best germination temperature for Prunus mahaleb, Prunus padus
  104. 104. Ways to stratify the seeds  Cold stratification (moist-prechilling) involves mixing seeds with an equal volume of a moist medium (sand or peat, for example) in a closed container and storing them in a refrigerator (approximately 40oF).  Periodically, check to see that the medium is moist but not wet.  The length of time it takes to break dormancy varies with particular species; check reference books to determine the recommended amount of time.
  105. 105. Ways to stratify the seeds  Warm stratification is similar to cold stratification except temperatures are maintained at 68oF to 86oF, depending on the species.  Warm stratification is for all intents and purposes useful for advancing the softening of hard seed coats (warm stratification is equivalent to the seed sitting in warm soil/mud/leaf mold prior to winter's onset;ie: often a whole summer season).
  106. 106. SEED DRYING
  107. 107. What is seed drying? Drying is a normal part of the seed maturation process. Some seeds must dry down to minimum moisture content before they can germinate. Low seed moisture content is a pre-requisite for long-term storage, and is the most important factor affecting longevity. Seeds lose viability and vigor during processing and storage mainly because of high seed moisture content (seed moisture greater than 18%).
  108. 108. Seed is a living hygroscopic material. Relative humidity (RH) and temperature of air influences seed moisture content. If RH is more than the seed, the seed will gain moisture. If moisture within the seed is greater, then vapour will move out of the seed. Seed drying takes place when there is a net movement of water out of the seed into the surrounding air. Principles of Seed Drying
  109. 109. A water potential gradient is established between the surface of the seed and its internal tissues and water begins to diffuse along this gradient. Water evaporates from the surface of the seed at a rate dependent on the water potential difference between the seed and the surrounding air. As the seed approaches equilibrium with the surrounding air the rate of drying slows down exponentially. How seeds dry
  110. 110. Seed size and the resistance of the surrounding 'seed coat' structures have a marked effect on the rate of drying. Large seeds dry relatively slowly compared with small seeds due to the extended internal moisture flow. If large seeds with porous seed coats are dried too quickly, the large moisture differential between the surface and internal layers of the seed may cause structural damage.
  111. 111. In some cases this can lead to a collapse and shrinkage of the seed coat, and the formation of an impermeable barrier. This may prevent further drying and increase the risk of viability loss due to ageing. A thin layer of seeds will dry more rapidly than a deep layer due to more rapid diffusion of water from within each seed to the surface of the seed layer.
  112. 112. The faster the air speed, the faster moist air will be moved away from the surface of the seeds. As an approximation, drying time is halved when the velocity of the surrounding air is doubled.
  113. 113. Effect of temperature • Increased temp. → decreased RH → increased water potential gradient → increased rate of diffusion • Water evaporates more quickly. BUT, heat may reduce viability of long term conservation collections Temperature affects the drying rate in three ways.
  114. 114. Increasing air temperature decreases the RH which will increase the rate of diffusion of water to the surface of the seed layer, and hence the speed of drying. Moisture within the seed diffuses more quickly to the seed surface at higher temperatures.
  115. 115. Raising the temperature will always accelerate drying; a 10°C increase in temperature approximately doubles the rate of drying. High temperatures are usually employed to dry commercial seed lots but will have an adverse effect on seed longevity specially if seeds are wet. In order to avoid unnecessary losses during drying, seeds for long-term conservation should be dried with cool air.
  116. 116. Drying of seed is very important to maintain their vigour and viability for longer periods. It prevent seed deterioration due to increased microorganism activity, heating and mold/fungal growth etc.. Importance of seed drying
  117. 117. In general for long term storage in the gene banks the orthodox seeds should be dried to 3-7% moisture content except soybean. In soybean like crops where low moisture can adversely effect seed viability the seeds are usually dried to 7-8% moisture content.
  118. 118. Moisture increases the respiration rate of seeds, which in turn raises seed temperature. For example, in large-scale commercial seed storage, respiring seeds may generate enough heat to kill the seeds quickly, or to even start a fire if not dried sufficiently. Small-scale growers are not likely to have such an extreme condition, but seed longevity will, nevertheless be affected. Problems associated with high seed moisture
  119. 119. Mold growth will be encouraged by moisture, damaging the seeds either slowly or quickly, depending on the moisture content of the seeds. Some molds that don’t grow well at room temperature may grow well at low temperatures causing damage to refrigerated seeds. In such a case there may be no visual sign of damage.
  120. 120. Important considerations in seed drying Seed with high initial moisture content should not be exposed to extremes of temperatures. Seed drying should not be done at high temperatures Seed should be dried gradually under low temperature and low humidity
  121. 121. Several methods are available for drying the seed. For genebank samples drying should always be done under low humidity conditions. RH 10-15% and temperature of 15 C are recommended by IBPGR Advisory Committee on Seed Storage.
  122. 122. Methods of Seed Drying Sun drying Forced air drying
  123. 123. Sun Drying In the absence of forced air drying facilities, the moisture content of seeds have to be reduced in the field before harvest, and later by sun drying on the threshing floor. The system involves harvesting of crops when they are fully dried in the field, leaving the harvested produce in field for a couple of days to sun dry and later spreading the threshed and winnowed produce in thin layers on threshing floors to sun dry. The main advantage of sun drying is that it requires no additional expenditure, or special requirement. The disadvantages are delayed harvest, risks of weather damage and increased likelihood of mechanical admixtures.
  124. 124. Forced Air Drying In this system air (natural or heated) is forced into seeds. The air passing through damp seeds picks up water. The evaporation cools the air and the seed. The heat necessary for evaporating the water comes from the temperature drop of the air. This is the most fundamental principle of forced air seed drying. .
  125. 125. Simple & economical drying Low temperature drying (40‐45ºC ) Simple to manage Affordable & low level of integration for low capacity drying Fast drying at small capacity (6‐12 hours) Can be dried promptly at farm level Requires labour to stir the grain during drying Able to use for other drying means, like wheat, seeds, beans, nuts, etc. Fixed Flat Bed Batch Dryer
  126. 126. A dry room is the most expensive option, but allows seeds to be left in a dry environment until cleaning is practicable. Moisture is removed from the incoming air, using either sorption or refrigeration. Sorption driers (using silica gel, lithium chloride or molecular sieve types) tend to be more electrically efficient at maintaining low RH conditions than are refrigeration driers Sorption driers generate heat and so need to be used in conjunction with some cooling system.
  127. 127. SEED PROCESSING
  128. 128. Seed processing involves: cleaning the seed samples of extraneous materials, drying them to optimum moisture levels, testing their germination and packaging them in appropriate containers for conservation and distribution. What is Seed Processing?
  129. 129. TYPES OF SEED PROCESSING A.Dry Seed Processing B. Wet Seed Processing
  130. 130. When seeds are ready to be processed, the entire seedpod, capsule, or seed head will become brown and dry. During the maturation process, the ripening pods and capsules change color from green, to yellow green, to yellow, to light brown, to a darker brown, or dark gray. Ripening and maturation may be uneven within the pod or capsule, uneven on the plant, and uneven within the stand of plants. Dry seed processing (pods, capsules, seed heads, etc.
  131. 131. One method of dealing with crops that mature their seed unevenly is to pull the plants and hang them upside down to dry under cover. This allows the seed to continue to mature on the plant while the plant dries.
  132. 132. After harvest, seeds are threshed to remove the seed from the surrounding plant material. A period of air-drying is important before seeds are threshed. Plant material should be spread out in thin layers until all plant material is dry; otherwise, mold, decay, and heat from decay will cause damage to the seeds.
  133. 133. Wet seed processing is used with seed crops that have seeds in fleshy fruits or berries. There are three steps to the process: (1) extraction of the seed from the fruit, (2) washing the seeds, and (3) drying. Wet seed processing (crops with fleshy fruits, fermentation)
  134. 134. The type of extraction process depends on the species. Soft fruits such as tomatoes are cut up, mashed, and then fermented. Cucumbers and melons are cut in half, the seed scraped out along with the fruit pulp surrounding the seed, and then fermented. In watermelons, the entire fleshy fruit is fermented along with the extracted seed. These types of fruits have a gel surrounding the seed that contains germination inhibitors. The presence of the gel also makes handling and drying of the seed difficult.
  135. 135. After fermentation is complete, the seeds are washed to remove pulp, pieces of fruit and debris, and low quality seed. Before washing the seed, it is useful (especially for washing tomato seed) to first scoop out pieces of pulp floating on top of the mash. This is done by straining the mash with your fingers, pulling out the larger chunks. Whether or not there is floating pulp depends on the variety or how thoroughly the fruit was processed. Seed Washing
  136. 136. Seed cleaning involves removal of debris, low quality, infested or infected seeds and seeds of different species (weeds). Seed Cleaning
  137. 137. SEED STORAGE AND HANDLING
  138. 138. Importance of Seed Storage and Handling Good seed is essential for successful crop production, whereas poor seed is a serious farm hazard . It is important to store and handle seeds properly after harvesting to ensure good germination and purity specially, if we want to use them the following season and to store both unsold marketable and consumption seeds .
  139. 139. Improper drying and storage conditions in handling seeds can have an adverse affect on the life of those seeds. Loss in viability, discoloration, toxin production and growth of fungus can take place rapidly if proper preventative measures are not taken.
  140. 140. The safe storage of seeds is also important for these reasons: a. seeds must be preserved for use as human and animal food b. seed viability must also be protected (germplasm protection) for various uses by the plant scientists who maintain a permanent reservoir of seed stock by establishing a seed bank.
  141. 141. Three objectives for storing seeds 1. Very short period between collection and sowing 2. Several years (10 or less) to ensure a reliable supply of seeds in the absence of annual crops 3. Long periods (10 to 50+ years) for germplasm conservation
  142. 142. Factors Affecting Longevity of Seeds Seed Characteristics Two groups based on their storage characteristics: orthodox and recalcitrant (, Dr. E. H. Roberts ,1973 ). Orthodox seeds are those that can be dried to moisture contents of 10% or less; in this condition they can be successfully stored at subfreezing temperatures. Recalcitrant seeds, on the other hand, are those that cannot be dried below relatively high moisture levels (25 to 45%) and therefore cannot be stored below freezing.
  143. 143. Intermediate seeds can be dried to moisture levels almost low enough to meet orthodox conditions (12 to 15%) but are sensitive to the low temperatures typically employed for storage of orthodox seeds. Viability is retained usually only for a few years.
  144. 144. Seed morphology Seed morphology is important to the storage life of seeds in the context of protection for the embryo. The hard seedcoats of species of the Leguminosae help maintain the low level of metabolism in these dry orthodox seeds by excluding moisture and oxygen. Hard, thick seedcoats, such as those of Carya Nutt., Cornus L., and Nyssa L., help protect the embryos from mechanical damage during collection and conditioning. The thinner or softer a seed coat may be, the more likely that the seed has a shorter storage life because of rapid moisture uptake or bruising of internal seed tissues.
  145. 145. Chemical composition General observations of seed behavior in storage has suggested that chemical composition is an important factor in longevity; for example, oily seeds do not store as well as starchy seeds. There is some evidence, however, that suggests that the relative concentrations of particular carbohydrates play key roles in desiccation tolerance, a critical property in determining storage behavior of seeds (Lin and Huang 1994).
  146. 146. Seed maturity Seeds of many orthodox species that are immature when collected (or extracted from fruits) are likely to fare poorly in storage (Stein et al., 1974). The physiological basis for this effect is not known, but it seems logical that immature seeds have not been able to complete the normal accumulation of storage food reserves, develop all needed enzymes and/or growth regulators, or complete their full morphological development and cell organization.
  147. 147. Seed Handling Prior to Storage Poor fruit or seed handling that damages seeds will often lead to reduced viability in storage, especially in orthodox seeds. The most common example of this is impact damage to seeds during extraction and conditioning. Seeds can be bruised during processing, or poor transport systems (Kamra, 1967).
  148. 148. Another factor to consider in damage to seeds during extraction and conditioning is cracks or other breaches of the seed coats that will allow microorganisms to enter. Cracks in seed coats that occur during seed conditioning are usually not visible to the naked eye but can be detected on radiographs . This is one reason why hardseeded legumes are usually not returned to storage after mechanical scarification.
  149. 149. Storage Environment Storage environment is obviously very important in extending the life of seeds. The general objective is to reduce the metabolism of the seeds as much as possible without damaging them and to prevent attack by microorganisms. The ideal metabolic rate in storage will conserve as much of the stored food reserves in the seeds as possible, yet operate at a level that maintains the integrity of the embryos.
  150. 150. Moisture Seed moisture is the most important factor in maintaining viability during storage; it is the primary control of all activities. Metabolic rates can be minimized by keeping seeds in a dry state. For true orthodox and sub-orthodox seeds, optimum moisture contents for storage are 5 to 10%. The normal practice with all orthodox tree seeds is to dry them to these levels and store them in moisture-proof containers that maintain them at these levels.
  151. 151. Temperature Metabolic rates can also be minimized with low temperatures, both for orthodox and for recalcitrant seeds. The storage moisture content determines just how low temperatures can be set for seed storage. From freezing to –15 °C, 20% is the approximate upper moisture limit. Below–15 °C, the limit is about 15%; and in cryogenic storage in liquid nitrogen (–196 °C), 13% is the limit.
  152. 152. Storage Facilities Cold Storage Facilities for seed storage will vary by the amount of seeds to be stored and the projected length of storage. Small seedlots— a liter (quart) or less—can be stored in household refrigerators and freezers. Larger seedlots and quantities will require a walk-in refrigerator or freezer . These units are usually assembled from prefabricated insulated panels and can be made almost any size to fit the owner’s needs. A suggested size for a nursery operation is one large enough to hold a 5-years’ supply of seeds.
  153. 153. Orthodox seeds should be dried to safe moisture contents (5 to 10%) and stored in sealed containers that prohibit absorption of moisture from the atmosphere. The containers used most commonly for tree seeds are fiberboard drums with a thin plastic coating on the inside . These drums are available in different sizes they hold approximately 25 and 50 kg (55 and 110 lb). Any large, rigid container can be used, as long as it can be sealed. The best practice is to insert a polyethylene bag liner for this purpose. It is also a good idea to do this with fiberboard drums, as repeated use of the drums over a number of years will cause breaks in their interior plastic lining. Containers
  154. 154. Moisture Control Refrigerated storage units can be made with controlled humidity so that orthodox seeds can be stored in unsealed containers without danger of moisture absorption. At the low temperatures usually employed for tree seeds, however, this feature would be very expensive. It is much cheaper to dry the seeds and store them in sealed containers.
  155. 155. Storage Recommendations Orthodox Seeds All orthodox seeds should be stored in moisture- proof, sealed containers with seed moisture contents of 5 to 10%. If the period of storage will be 3 years or less for true orthodox species, or 2 years or less for sub- orthodox species, temperatures of 0 to 5 °C are sufficient. For longer periods of storage for both types of orthodox species, freezers (–18 to –20 °C) should be used.
  156. 156. Tropical-Recalcitrant Seeds Storage of tropical recalcitrant seeds is done in the same manner as storage of temperate species, except that temperatures must be kept at a high level. There are differences among species but the lower limits are generally 12 to 20 °C. Successful storage for more than 1 year should not be expected.
  157. 157. SEED TREATMENT
  158. 158. What is seed treatment? Seed treatment refers to the application of fungicide, insecticide, or a combination of both, to seeds so as to disinfect them from seed-borne or soil-borne pathogenic organisms and storage insects. It also refers to the subjecting of seeds to solar energy exposure, immersion in conditioned water, etc.
  159. 159. General Agronomic Recommendations  Use certified or high quality seed: no old seed prevent introduction of new diseases into your fields prevent making an old problem worse  Select best yielding cultivar for your area adaptation and disease resistance  Seeding date - know your diseases!  Delayed seeding in fall may reduce amount of Fusarium and crown root rot  Delayed seeding in spring may reduce Pythium infection
  160. 160. Benefits of Seed Treatment Prevents spread of plant diseases Protects seed from seed rot and seedling blights Improves germination Provides protection from storage insects Controls soil insects
  161. 161. Types of Seed Treatment 1) Seed disinfection: Seed disinfection refers to the eradication of fungal spores that have become established within the seed coat, or i more deep- seated tissues. For effective control, the fungicidal treatment must actually penetrate the seed in order to kill the fungus that is present.
  162. 162. 2) Seed disinfestation: Seed disinfestation refers to the destruction of surface-borne organisms that have contaminated the seed surface but not infected the seed surface. Chemical dips, soaks, fungicides applied as dust, slurry or liquid have been found successful.
  163. 163. 3) Seed Protection: The purpose of seed protection is to protect the seed and young seedling from organisms in the soil which might otherwise cause decay of the seed before germination.
  164. 164. 1) Injured Seeds: Any break in the seed coat of a seed affords an excellent opportunity for fungi to enter the seed and either kill it, or awaken the seedling that will be produced from it. Seeds suffer mechanical injury during combining and threshing operations, or from being dropped from excessive heights. They may also be injured by weather or improper storage. Conditions under which seed must be treated
  165. 165. 2) Diseased seed: Seed may be infected by disease organisms even at the time of harvest, or may become infected during processing, if processed on contaminated machinery or if stored in contaminated containers or warehouses.
  166. 166. 3) Undesirable soil conditions: Seeds are sometimes planted under unfavourable soil conditions such as cold and damp soils, or extremely dry soils. Such unfavourable soil conditions may be favourable to the growth and development of certain fungi spores enabling them to attack and damage the seeds.
  167. 167. 4) Disease-free seed: Seeds are invariably infected, by disease organisms ranging from no economic consequence to severe economic consequences. Seed treatment provides a good insurance against diseases, soil-borne organisms and thus affords protection to weak seeds enabling them to germinate and produce seedlings.
  168. 168. Seed treatments  Add recommended rate  Overtreatment may lead to decreased emergence  Undertreatment may not provide good control  Undertreatment may lead to fungicide/insecticide resistance  Check labels for compatibility before mixing insecticides and fungicides  Some combinations are toxic to the seed
  169. 169. POLYMER COATING What is polymer coating? It is the process of coating the seeds with polymers of different colours along with nutrients and plant protectants to increase the aesthetic values of the seed with required benefits.
  170. 170. Methodology Coat the seeds with polykote (3 g + 5ml water / kg) after proper dilution Mix fungicide and pesticide with the polykote to increase the resistance to the pest and diseases. Shade the seed before using / storing
  171. 171. RHIZOBIAL COATING What is Rhizobial coating? Rhizobial coating is to enriching the rhizosphere microenvironment with organic nutrients for early establishment.
  172. 172. Methodology Take the seeds in a plastic tray Add proper quantity of adhesive (cool maida 10% gruel) to the seeds or jaggery Shake gently so that the adhesive spreads evenly on all the seeds Sprinkle the required biofertilizer (Rhizobium, Azospirillum, Azotobactor) evenly over the seeds and continue shaking. The wet seed surface will attract the biofertilizer and result in even coating over the seeds Roll the seed for uniformity Shade dry the seed Lentil field in western Manitoba in which plants on right received a commercial rhizobial inoculant while plants on the left were dependent upon endemic naturalized population of rhizobia in the soil for inoculation.
  173. 173. SEED PRIMING What is seed priming? Seed priming is a physiologically based, seed enhancement process for improving the germination characteristics of seeds. Seed priming is accomplished by partially hydrating seeds and maintaining them under defined moisture, temperature and aeration conditions for a prescribed period of time.
  174. 174. Advantages of seed priming Enhances the germination percentage Enhances the speed and uniformity of germination Improves the resistance towards water and temperature stress Increases the shelf life of seed Highly suitable for small seeds Enhances the yield Field sown with primed (right) and non-primed seeds (left))
  175. 175. Seed Quality Control
  176. 176. What is Seed Quality? Seed quality indicates the seed’s ability to germinate and establish “healthy” seedlings under stressful conditions. Germination and vigor are quick and inexpensive lab tests that provide information about seed quality. Germination stated on the seed tag is what you can expect under favorable moisture and temperature conditions.
  177. 177. Why is Seed Quality Important? Seed quality is critical in the establishment of a uniform plant stand, the first step in producing a successful crop, but good planting conditions are also critical since even high quality seed can fail under too much stress.
  178. 178. Healthy, high-quality seed is the first prerequisite for abundant yield. To get a good yield, good quality seed must be sown. The yield can increase with 5-20% when using good quality seed!
  179. 179. The advantages of using good quality seeds
  180. 180. Factors affecting seed quality
  181. 181. Factors affecting seed quality
  182. 182. C. PHYSIOLOGICAL (Viability and Vigor) Seed Viability refers to the capacity of a normal seed to germinate and produce a normal seedling. Seed vigor comprises those seeds properties which determine the potential for rapid, uniform emergence, and development of normal seedlings under a wide range of field conditions (AOSA, 1983).
  183. 183. Seeds have maximum quality at physiological maturity. After that, seed storage success depends on environmental, harvest, postharvest and storage conditions.
  184. 184. D. PHYTOSANITARY ATTRIBUTES (Insect and Seed-borne Diseases) Health of Seed refers primarily to the presence or absence of disease-causing organisms, such as fungi, bacteria, viruses and insects. Insects and fungi generally reduce seed quality.
  185. 185. The End

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