Forest Seeds and Nursery Technology 2024 PDF

WOLLEGA UNIVESITY GIMBI CAMPUS Faculty of Natural and Environmental Science Department of Forestry. Course Title/Code: Forest Seeds and Nursery Technology (For3091) Course credit: 3 Cr Hrs. and 5 ECT....

WOLLEGA UNIVESITY GIMBI CAMPUS Faculty of Natural and Environmental Science Department of Forestry. Course Title/Code: Forest Seeds and Nursery Technology (For3091) Course credit: 3 Cr Hrs. and 5 ECT. Instructor: Yadesa A. 2024 A.Y. [email protected] 11/18/2024 1 Contents. 4. Handling of Fruit and Seed between Collection and Processing. 5. Seed Processing. 6. Seed Testing. [email protected] 11/18/2024 2  4. Handling of Fruit and Seed between Collection and Processing  Seed handling refers to the processes involved in collecting, sorting, cleaning, storing, and preparing seeds for planting or processing, ensuring seed viability and quality.  Effective seed handling enhances crop yield by ensuring high-quality seeds are planted, thus playing a vital role in agricultural productivity.  Proper seed handling techniques support ecosystem restoration efforts by promoting the growth of native plant species necessary for habitat and biodiversity recovery [email protected] 11/18/2024 3 4.1. Reduction of bulk and Maintaining Viability Almost invariably: it is fruits, not seeds, which are picked from trees. Sun drying of fruits and extraction of seeds is carried out in the field in some countries where the climate is suitable. In others it is considered preferable to transport the fruits as quickly as possible to the seed processing depot, where the conditions of extraction can be controlled much more closely than in the field. [email protected] 11/18/2024 4 Cont.… If seeds are not extracted in the field, great care must be taken of the fruits both in the forest and during transport. Bulk quantities of fruits in high temperature and humidity are very susceptible to deterioration through the action of: moulds /other fungi and through overheating due to a high rate of respiration.  The importance of good ventilation in reducing these dangers cannot be overemphasized.  If fruits are stored temporarily in separate containers, they should not be filled to the top. [email protected] 11/18/2024 5 Cont.…  In particular, sacks containing fresh cones should be only half-filled; in this way space is left for expansion of scales as cones dry.  Otherwise, scales may acquire a set which severely impairs subsequent seed extraction.  To facilitate air circulation within sacks, as well as for easy handling during transport,  it is advisable to put only 10–20kg of fruits in each.  Loose-weave hessian sacks or nylon-mesh laundry bags allow good air circulation through the side of the container. [email protected] 11/18/2024 6 Cont.…  In the case of fruits with very small seeds, close-weave cotton bags should be used if there is any chance of the fruits opening during transit.  Large open-mesh baskets are ideal for promoting free air circulation in cones and other large fruits and may be constructed from locally available materials, whether metal, willow, bamboo or rattan.  Aeration in loose-piled fruits can be improved by inserting loosely- constructed “chimneys” of wooden slats in the middle of the piles.  Daily turning of loose-piled fruits or/ of sacks can do much to improve access of air to the less exposed fruits. [email protected] 11/18/2024 7 Cont.…  If fruits cannot be transported at once to the seed processing depot, temporary field storage must be arranged, under some kind of shelter.  For most orthodox seeds some degree of advance drying of the fruits in the field is a good thing.  Drying of orthodox seeds to under 12 % before shipment by air has been recommended. Drying can be facilitated by the use of open-weave sacks.  Polyethylene bags are not suitable for temporary storage of fruits of these species, [email protected] 11/18/2024 8 Cont.… Since they prevent drying and may encourage fungal moulds and overheating. However, fruits of recalcitrant species must be kept cool and moist to maintain viability of their seeds. Polyethylene bags, which prevent drying, are suitable as containers for species of this type. [email protected] 11/18/2024 9 Cont.… 4.2. Maintaining Identity To ensure maintenance of seed lot identity, each container of fruit must be labelled correctly when it is filled. As an additional insurance against accidental loss of the exterior label, identical labels should be placed both inside and outside the container. Weatherproof labels should be used and the minimum information recorded on the lables should include: species, seed lot number, geographic location or name of seed source weight of seed contained, date of collection and collector's name. [email protected] 11/18/2024 10 Cont.…  A copy of the seed collection data sheet or certificate of origin with reference to seed lot number must be attached to the documents accompanying the seed - or preferably be mailed before the seed is dispatched. In large-scale operations, information may be coded. In the case of small collections for research purposes, e.g. provenance collections or single-tree collections for progeny trials, additional information is recorded on a separate certificate of seed origin or collection data sheet and reference to seed lot number is important. [email protected] 11/18/2024 11 4.3. Hygiene and contamination  Special measures may be needed to prevent damage from pests and diseases.  The use of insecticidal or fungicidal dusts may be advisable in some circumstances,  if there is a high risk of severe damage, but great care is needed in treating fresh and relatively moist seed, to avoid damage from the chemicals themselves.  Maintaining fruit hygiene, particularly through good ventilation, is usually preferable to reliance on chemicals. [email protected] 11/18/2024 12 Cont.…  Storage of sacks off the ground will itself give some protection against rodents.  The incidence of pests and diseases is often worst on the forest floor and  prompt collection of fallen fruits can do much to minimize subsequent losses. [email protected] 11/18/2024 13 Cont.… 4.4. Temporary storage at seed processing depot.  If fruits cannot be transported at once to the seed processing depot,  temporary field storage must be arranged, in sheds or under some kind of shelter.  Shelter is needed against rain and, for some species, against too high insolation.  Sheds should be open-sided or otherwise well ventilated and sacks well spaced on racks or hung from hooks to allow free air circulation.  Hanging from hooks has the added advantage of giving protection against rodents. [email protected] 11/18/2024 14  Cont.…  If storage is in the open, overhead shelter may be provided by canvas tarpaulins or polyethylene sheeting.  If the collecting season coincides with a period of reliably dry but not too hot weather, no overhead shelter is necessary.  Sacks should never be piled on top of each other in large heaps.  For most orthodox seeds some degree of advance drying in the field is a good thing.  Drying of orthodox seeds to under 12 % before shipment by air has been recommended. [email protected] 11/18/2024 15 4.5. Condition during transport It is important to ensure that the minimum possible time should elapse between the dispatch of fruits or: extracted seed from the collecting site local seed collecting depot and its arrival at the central seed processing depot. Part of the planning operation must be to provide transport which is adequate in quantity and quality to avoid delays in dispatch and breakdowns enrooted. Even short stop-overs add to the heat build-up in fruit and cone sacks during transit. [email protected] 11/18/2024 16 Cont.…  Vehicle drivers should be informed of the nature of their loads and the need for proper care and prompt delivery.  Road transport is commonly used for at least the first part of the journey.  Railway transport may be more economical over long distances and air transport quicker,  but both involve some loss of control over storage conditions in transit and any transshipment means extra handling and delay.  Road transport is likely to be the preferred method in most conditions. [email protected] 11/18/2024 17  Cont.…  If transport distances are short and large quantities of a single species and provenance are to be transported, fruits may be loaded into vehicles without containers.  The vehicle must be cleaned of all seed carried on previous trips before a new lot is loaded.  For most species open trucks and trailers should be used in preference to closed vans in order to promote air circulation.  But for species which need to maintain a high moisture content if they are to retain viability,  care must be taken to prevent excessive drying; use of polythene bags and provision of shade against insolation are necessary. [email protected] 11/18/2024 18  Cont.…  Rapid transport direct to the final destination and immediately after collection may be essential for some species which either germinate naturally or lose their viability soon after seed fall at normal temperatures.  Provision of special insulated containers, to control temperature and humidity in transit, may also be needed. [email protected] 11/18/2024 19 [email protected] 11/18/2024 20 5. Seed Processing  Almost invariably it is the fruits, not the seeds, of forest trees which are harvested.  In some species it is also the fruits which we sown in the nursery and they are then often referred to loosely as “seeds”,  In the majority of species, fruits are collected but seeds are sown,  therefore at some stage the seeds must be extracted from their covering of fruits. [email protected] 11/18/2024 21 Cont.…_________________________________________________________________  Extraction is sometimes done close to the site of collection, but it is frequently carried out at a central processing and storage depot.  The purpose of extraction and associated processes is the maximum production of clean seed having high viability.  Seed processing includes: —sorting, —extraction, —cleaning, and —drying. [email protected] 11/18/2024 22 _______________________________________________________________________ 5.1. Forest seed sorting  Seed sorting is a process in which the goal is to achieve a high level of purity and quality in the final product.  Prediction and control of such processes are generally considered very difficult. 5.1.1. Importance of forest seed sorting i. Enhancing germination rates: seed sorting plays a crucial role in removing underdeveloped or damaged seeds, which can hinder optimal germination  By ensuring that only the highest quality seeds are planted, and germination rates can improved significantly. [email protected] 11/18/2024 23 Cont.…_________________________________________________________________ ii. Improving plant quality: enhances the over all quality of the plants produced, as it increases the likelihood of selecting genetically superior seeds.  This leads to plants that are more resilient to diseases, pests, and environmental stresses, ultimately ensuring better survival and growth rates. iii. Economic benefits: effective seed sorting translates into economic gains for farmers and products.  Higher germination rates and improved plant quality can reduce costs associated with re-seeding and crop failures, enabling producers to achieve better returns on their investments. [email protected] 11/18/2024 24 Cont.…_________________________________________________________________ 5.2. Pre-cleaning Cones and fruits need to be cleaned of twigs, bark, foliage and other impurities before they go for extraction, cleaning, storage or sowing. In large extraction plants cleaning is accomplished with oscillating screens or vibrators. Preclearing by flotation is also an other alternative method. In small operations the major debris may be removed by hand. For some species, pre-cleaning, together with drying in some cases, is the only operation needed before storage or sowing. [email protected] 11/18/2024 25 Cont.…_________________________________________________________________  It can be done by the following methods: ꟷ screen cleaning by using sieves of different pore sizes, ꟷ air separation/winnowing or by aspirators, ꟷ de-winging reduces storage volume, make upgrading possible, sowing easier and removes pathogen, ꟷ empty seeds can be removed by liquid floatation, and ꟷ seed drier, seed grader, seed separator, seed blower, seed scarifier, sieves, etc. are some of the useful equipment of seed processing [email protected] 11/18/2024 26 5.3. Pre-Curing Pre-curing is the deliberate storage and slow air drying of fruits and contained seeds in order to render them more suitable for subsequent operations of: kiln drying, extraction and long-term seed storage. The processes assisted by pre-curing are seed maturation and fruit drying. Fruits do not all ripen at the same time, even for the same species and in the same forest. [email protected] 11/18/2024 27 Cont.…_________________________________________________________________  Thus, even when a collection is perfectly timed at the peak maturity of the crop, there will always be a proportion of sound seeds which are not fully mature. The minimum period for maturation in certain species is two weeks, but many demand more than 6–8 weeks. For most species of the humid tropics immature fruits can be encouraged to ripen by storage at room temperature in a sheltered, well-ventilated place. Temperatures below 20°C and above 35°C are likely to be detrimental. [email protected] 11/18/2024 28 Cont.…_________________________________________________________________ Ventilation can be provided by keeping the fruits loosely packed in open bags or boxes so that normal respiration can take place. Rapid or excessive drying should be avoided. The aim should be to keep the fruits alive and healthy as long as possible so as to gain time for their seeds to mature. [email protected] 11/18/2024 29  5.4. Seed extraction  Extraction is the process of removing seed from fruits.  Appropriate extraction methods vary by species and fruit type.  dried fruit of some species open readily to release their seed: ꟷ to facilitate seed gathering for processing, the fruit of these species should be dried on big plastic sheets or tarps under direct sunlight. ꟷ normally, 2-3 days of drying is enough. ꟷ rubbing and crushing the fruits will expedite seed extraction. dried fruit of other species open slowly over an extended period of time. [email protected] 11/18/2024 30 Cont.…_________________________________________________________________ ꟷ to hasten seed extraction, fruits of this type should be placed in sacks and lightly beaten with a stick or firmly crushed. The fruit of some species need to be scraped with an abrasive material such as sand or ash to remove the fleshy outer layer. Some fruits need to be scrubbed and washed with water to separate fleshy material from the seed. ꟷ Before washing, the fruit can be soaked in water overnight and, if necessary, crushed or lightly beaten to soften the flesh. ꟷ It is important to scrub and wash away all the fleshy material and juice, otherwise insects and fungi may infest the seed. [email protected] 11/18/2024 31 Cont.…_________________________________________________________________ The fruits of some species are simply broken, open and the seeds removed. The seed of some species do not require extraction. ꟷ Rather the fruit are firmly rubbed together to remove the outer skin and other debris. ꟷ While not truly extraction, this process serves the same purpose, preparing fruit for cleaning and grading. All extraction methods should be conducted carefully to avoid damaging seed. ꟷ Some common tools used during extraction include sacks, tarps, trays, buckets, tanks and sandpaper or other abrasive material. [email protected] 11/18/2024 32 5.5.1. Methods of Seed Extraction methods of extracting seeds from fruits are determined mainly by the characteristics of the fruits. Fleshy fruits are treated by a depurating process which usually involves a combination of soaking in water with pressure or gentle abrasion. Cones and other woody or leathery fruits are first dried until cone scales open or seeds become detached from the placenta of the fruit, and then treated manually or mechanically by tumbling or threshing in order to separate the dry seeds from the dry fruits. [email protected] 11/18/2024 33 5.6. Operations between extraction and storage. After extraction, the seed lot may contain debris including empty seed and fragments of stems, leaves, fruit, wing, flesh, etc. To maintain high seed quality and viability during storage all debris must be discarded. When seeds have been extracted from their fruits, several operations are needed before they are fit to go into storage. Sound seeds must be separated from empty and nonviable seeds and from inert fragments of fruits; winged seeds of some but not all species need to be de-winged; [email protected] 11/18/2024 34 Cont.…_________________________________________________________________ If seeds are to be stored, their moisture content must be tested and, if necessary, raised or lowered to the percentage most suitable for storage. If uniformity in growth of nursery stock is considered desirable, seeds may also be graded by size.  Inert material takes up space both in storage and transport and may cause uneven stocking in the nursery seed beds.  It also carries a greater risk of introducing pests or diseases than do the seeds themselves; e.g. spores of needle cast are carried on needle fragments rather than seeds. [email protected] 11/18/2024 35 Cont.…_________________________________________________________________  Cleaning to a high standard of purity is easy in some species, but more difficult in others. Cleaning of seeds to a purity higher than a given percentage is undesirable in some species; beyond that, an increasing amount of good seed is separated out with the impurities. [email protected] 11/18/2024 36 5.7. Seed Storage. Seed should be stored after processing until dispatching for various purposes. It is the preservation of viable seed until their sowing/ requirement and essential to offset the uncertainty of seed production/ availability during bad seed years. It delays deterioration, maintains viability and protects seed from rodent and insect damage. The longevity of seeds is a species-specific characteristic. The seed of most of the species can be stored at low temperature and low moisture content in sealed containers. It is important to dry the seed uniformly to prevent fluctuation in moisture content during storage. [email protected] 11/18/2024 37 Cont.…_________________________________________________________________ The moisture content of most of the seeds for storage ranges between 10 to 12 percent. The respiration continues at low temperature, which is necessary to keep the embryo alive. Polythene bags make good containers because they are impermeable to water but less so to oxygen and carbon dioxide. However, many species of moist tropical forests are so thoroughly adapted for germination that their seeds are almost impossible to store or even to transport. Seed storage is necessary for several reasons. [email protected] 11/18/2024 38 Cont.…_________________________________________________________________  Because: ꟷ Seed ripening and collection often does not correspond with the appropriate time for seedling production and tree planting. ꟷ The location of the seed sources may be far from intended planting sites.  Government agencies, forest industry companies and commercial seed dealers need to store seed before and while it is being shipped to field staff or consumers.  The length of time seed will remain viable varies greatly by species and storage conditions. [email protected] 11/18/2024 39 Cont.…_________________________________________________________________ Under fair to good conditions at the farmer- and NGO-level, orthodox seed of most species will remain viable when stored for 1 to 2 years. General guidelines for seed storage are consistent for all orthodox seed. Key factors to consider when storing seed are: Seed will remain viable for a long time when stored at a consistent cool temperature. The cooler the temperature the better! Temperature However, a fluctuating temperature will cause a loss of seed viability. [email protected] 11/18/2024 40 Cont.…_________________________________________________________________ Seed stores best under low air humidity. The lower the air humidity the better. High humidity conditions will cause seed to Humidity: absorb moisture and lose viability. As with temperature fluctuating, levels of humidity accelerate a loss of seed viability. [email protected] 11/18/2024 41 Cont.…_________________________________________________________________ Seed stores best at consistent low moisture contents. Moisture contents of 8-12% can be achieved by sun Moisture drying or air-drying. content Maintaining consistent low moisture content in seed is directly dependent on maintaining low levels of air humidity (as discussed above). [email protected] 11/18/2024 42 Cont.…_________________________________________________________________ Exposure to direct sunlight deteriorates seeds’ protective outer coat. Deterioration of the seed coat facilitates moisture absorption and a loss of viability. Light Under high moisture conditions, exposure to light encourages germination. To avoid these problems seed should be stored in the dark or in covered nontransparent containers. [email protected] 11/18/2024 43 Cont.…_________________________________________________________________ Exposure to pests and diseases during storage decreases seed viability and even kills seed. To avoid such problems seed should be thoroughly cleaned and stored in sealed containers. Insects When available, chemical or organic pesticides can be and applied to stored seed: diseases Some organic pesticides include: neem oil or leaves, gliricidia leaves, and soap. Local methods used to protect agricultural seeds may be appropriate for tree seed and should be tested. [email protected] 11/18/2024 44 Cont.…_________________________________________________________________ Of those mentioned above, the two most important storage factors are temperature and humidity. It can not be over-emphasized that maintaining seed viability during storage is directly dependent on maintaining consistent low temperatures and low air humidity as mentioned above! The best way to achieve optimal storage conditions is to store seed in containers in a room specifically dedicated for seed storage. [email protected] 11/18/2024 45 Cont.…_________________________________________________________________ The seed storage room should be: cool, dry, dark, well ventilated and protected from insects and diseases. When dispatching seed, give users full documentation, plus information on any seed treatments required for a high and uniform level of germination. [email protected] 11/18/2024 46 Cont.…_________________________________________________________________  Formal seed dealers are certified to supply quality seed, they carry out seed quality tests before dispatching and  they ensure that supplied seeds are accompanied by the necessary information on seed source and seed quality.  suppliers usually distribute seeds with formal test conducted and with any descriptive information. [email protected] 11/18/2024 47 [email protected] 11/18/2024 48 Quiz 1: (10%) Full Name: _____ _____ Id. No. _______ Signature: ______ 1. Describe seed extraction and its uses.(3pts) ____________________________________________________ ____________________________________________________ _________________________ 2. List the tree seed pre-cleaning methods.(3pts) ____________________________________________________ ____________________________________________________ _________________________ 3. Write the key factors to consider when storing tree seeds.(4pts) ____________________________________________________ ____________________________________________________ _________________________ [email protected] 11/18/2024 49 6. Seed Testing  Forest seed testing measures the physiological quality of seeds, or how many healthy plants can be expected to grow from a given amount of seed.  The tests can include: purity, authenticity, seed weight, germination, viability, moisture content, and seed health and damage.  The International Seed Testing Association (ISTA) develops and publishes standard procedures for testing seed quality, and most countries use these procedures for seed quality assurance. [email protected] 11/18/2024 50 6.1. Seed Quality and Sampling 6.1. 1. Seed Quality Seed quality refers to the purity, viability, vigor and health of a particular seed lot. Seed quality is measured by seed testing, which should be conducted shortly after seed is collected or bought. Testing should be repeated after a long period of storage, which may negatively impacted seed quality. to estimate the amount of seed required to produce the number of seedlings needed for field planting. [email protected] 11/18/2024 51 Cont.…_________________________________________________________________ 6.1.2. Seed Sampling It should be noted that most seed tests are destructive, and should not be conducted needlessly. should be conducted on a representative of seed lot sample. Samples are drawn from the seed lot just prior to seed testing. The followings are simple sampling criteria for seed testing that can be used: ꟷ samples should be representative of the entire seed lot. ꟷ should contain enough seeds to conduct all the tests required, simple planning and calculating. [email protected] 11/18/2024 52 Cont.…_________________________________________________________________ ꟷ If the seed lot is large, sub-samples should be drawn from each container or from several parts of large containers to form a composite sample. ꟷ If more than one seed lot is to be tested, sample and test them separately. ꟷ However, if a few small-sized seed lots are to be used for seedling production, they can be mixed together, then sampled and tested as a single seed lot. Once samples are drawn, seed testing should proceed immediately. Key seed tests are: purity, moisture content, seed weight, and germination/viability. Of these tests, the germination/viability test is the most important. [email protected] 11/18/2024 53 ___________________________________________________________________________ 6.2. Genuiness (True-to-type) test  True-to-type refers to seeds that reliably produce offspring with consistent and predictable characteristics mirroring the parent tree.  This predictability is crucial for ensuring the success of reforestation projects, maintaining the genetic diversity of tree populations, and optimizing the quality and yield of timber and fruit production.  When applied "true-to-type" to tree seeds signifies a high degree of genetic fidelity to the parent tree.  The use of true-to-type tree seeds is paramount in forestry × Using seeds that are not true-to-type – those exhibiting genetic inconsistencies or originating from uncontrolled crosses – carries significant risks. [email protected] 11/18/2024 54 Cont.…_________________________________________________________________  The true identity of seed can be tested in three basic ways: i. Identification of parent tree and certification of seed lot. ii. Using analytical key and comparison with other. iii. Identification of seeding  In addition: External and Internal appearances can also used. [email protected] 11/18/2024 55 6.3. Purity Test In addition to seed of the specified species, seed lots contain debris including seeds of other species; pieces of fruits, twigs, leaves, and dirt. Pure seed refers to exclusively to the seed of the specified species – both viable and non-viable. The purity test calculates the percent of a seed lot composed of pure seed. Seed purity is determined by separating a sample into two components: pure seed, and all other matter. [email protected] 11/18/2024 56 Cont.…_________________________________________________________________  The sample size should be approximately one handful.  Purity is calculated as follows: 𝑾𝒆𝒊𝒈𝒉𝒕 𝒐𝒇 𝒑𝒖𝒓𝒆 𝒔𝒆𝒆𝒅 𝑷𝒖𝒓𝒊𝒕𝒚 % = × 𝟏𝟎𝟎% 𝑻𝒐𝒕𝒂𝒍 𝒘𝒆𝒊𝒈𝒉𝒕 𝒐𝒇 𝒔𝒂𝒎𝒑𝒍𝒆 6.4. Seed Moisture content test  This test determines the percentage of moisture contained in seed.  The test results are primarily used to determine if seed is in the proper condition for storage. [email protected] 11/18/2024 57 Cont.…_________________________________________________________________  Moisture content is calculated by comparing the oven-dried weight of the seed sample with the weight of the sample before drying in the oven (pre-dried weight), as follows: (Predried weight – Oven dried weight) Moisture Conten𝒕% = X 100% Predried weight  The oven-dried weight is determined by drying the seed sample in an oven at 103°C for 17 hours.  orthodox seed stores best at moisture contents of 5-7%.  However, for short-term storage (a few months to 1-2 years) under local conditions moisture contents of 8-12% may be sufficient. [email protected] 11/18/2024 58 Cont.…_________________________________________________________________  If test results indicate moisture contents are too high, seed should be dried further before storage.  Effect of Moisture Content In Orthodox Seeds Seed moisture content % Above 45 – 60 % Germination begins The seed may heat (due to a rapid rate of Above 18 – 20 % respiration and energy release) Above 12 – 14 % Fungus growth can occur Below 8 – 9 % Insect activity much reduced 4–8% Sealed storage is safe. [email protected] 11/18/2024 59 Cont.…_________________________________________________________________ 6.5. Seed Weight determination  This test is calculated by weighing 1000 pure seeds of the specified species.  If seed is in short supply, 100 or 500 pure seed can be used to determine weight.  The resulting value from this tests can be recalculated and expressed in kilograms, pounds, any other unit of weight or as the average weight per seed. [email protected] 11/18/2024 60 6.6. Germination/Viability Test  Conducted to identify the capacity of a given seed lot to produce healthy and vigorous seedlings.  This information is very valuable when estimating the amount of seed required to produce the target number of seedlings for field planting.  There are two approaches, direct testing of germination and indirect testing of viability. 6.6.1. Direct (germination) test  Direct testing is appropriate for seed that is easy to germinate.  For seed that is difficult to germinate or requires long periods to germinate indirect tests are more efficient. [email protected] 11/18/2024 61 Cont.…_________________________________________________________________  Simple procedures for conducting a germination test are as follows: ꟷ Randomly select 100 seed from the sample and apply the pre-sowing treatment appropriate for that species. ꟷ After applying the pre-sowing treatment, sow the seed in a tray containing a good quality germination medium (nursery soil). ꟷ Maintain the medium under moisture conditions to promote germination. ꟷ After 1 week, count the number of germinated seed. ꟷ Note: Some species and seed lot may require 3-4 weeks to achieve complete germination. [email protected] 11/18/2024 62 Cont.…_________________________________________________________________ ꟷ The test should be monitored daily and continue until no additional seeds germination is observed. ꟷ Calculate the percentage of germination using the formula listed below. NG𝑆 PG = × 100%, Where: PG = Percentage of germination NS𝑇 NGS = Number of germinated seeds NST = Number of seeds tested ꟷ Also note the number of seed that are not germinated but viable (see description of ‘viable embryos’ below under cutting test). Include this information on the germination form. [email protected] 11/18/2024 63 6.6.2. Indirect (viability) tests  Indirect tests are appropriate for seed that is difficult to germinate or requires a long time to germinate; or when results are needed quickly.  These tests do not measure percentage of germination but rather determine the percentage of seed that are alive and should be able to germinate.  Seeds that are alive are called viable, thus these tests are called viability tests.  Indirect tests always give a higher value than the germination test.  There are several methods of indirect testing. [email protected] 11/18/2024 64 Cont.…_________________________________________________________________ Some of these methods require sophisticated laboratory tools and equipment. Other methods are easy to conduct in the field or office with commonly available tools. Three of the easy to conduct methods are: i. ‘cutting test’ is more accurate than the other two methods. ii. ‘soaking test’ and iii.‘shape, size, and color observation test’ are quick and simple tests to determine seed viability. They can be conducted during seed selection before sowing seed without destroying any seed. However, the results are very rough. [email protected] 11/18/2024 65 Cont.…_________________________________________________________________ A. Cutting test ꟷ Randomly select 100 seed from the sample. ꟷ Soak in cool water for 12-24 hours prior to cutting. ꟷ Cut the seed with a sharp tool and observe the embryo. ꟷ Viable embryos will be green or greenish white, moisture and fresh in appearance. ꟷ Non-viable seeds will have deformed or discolored embryos. ꟷ Magnifying glass can be used to enhance observation of the embryos. ꟷ Count the number of seed with viable embryos. [email protected] 11/18/2024 66 Cont.…_________________________________________________________________ ꟷ Seed viability calculated by using the following formula: 𝑵𝑽𝑺 𝑷𝑽 = × 𝟏𝟎𝟎% 𝑵𝑺𝑻 Where: PV = Percentage of viable seeds NVS = Number of viable seeds NTS = Number of seeds tested B. Soaking test ꟷ Randomly select 100 seed from the sample. ꟷ Soak the 100 seed in cool water for 12-24 hours. ꟷ Visually examine the seed. ꟷ Most viable seed will remain immersed in the water, some will have imbibed water and be visibly swollen. ꟷ Non-viable seed may be floating and will not have imbibed water. [email protected] 11/18/2024 67 Cont.…_________________________________________________________________ ꟷ Count the number of viable seeds. ꟷ Calculate seed viability using the formula described under the ‘cutting test’. C. Shape, size, and color observation test ꟷ Randomly select 100 seed from the sample. ꟷ Visually examine the seed. ꟷ Viable seeds usually have a normal shape and size. ꟷ The seed coats of viable seed have a uniform, healthy, and often glossy appearance. ꟷ Non-viable seeds are likely to be smaller, discolored, deformed and often empty (and comparatively light in weight). [email protected] 11/18/2024 68 Cont.…_________________________________________________________________ ꟷ The seed coats of nonviable seeds are often dull, vary in color and contain holes or cracks. ꟷ Count the number of viable seeds. ꟷ Calculate seed viability using the formula described under the ‘cutting test’ again. 6.7. Seed dormancy: Dormancy is defined as the physiological state in which viable seed can not readily germinated, even when subjected to favorable conditions. It is a self-sustaining mechanism that maintains seed viability during adverse environmental conditions, such as annual dry-seasons, wildfires or exposure to insects and disease. [email protected] 11/18/2024 69 Cont.…_________________________________________________________________ These mechanisms hinder germination in the short-term by preventing moisture absorption or other physiological processes. the three most common types of dormancy found in tree seeds are: physical, mechanical and chemical dormancy. Physical dormancy ꟷ Physical dormancy is typified by a hard, thick or waxy impermeable seed coat that prevents water from being absorbed by the seed. ꟷ Without absorbing water seeds can not germinate. [email protected] 11/18/2024 70 Cont.…_________________________________________________________________ ꟷ Eg. Seeds of the following species demonstrate physical dormancy:  Paraserianthes falcataria (falcata), Acacia mangium (mangium), Sesbania grandiflora (turi), Calliandra calothyrsus (red calliandra), and many more. Mechanical dormancy ꟷ Mechanical dormancy is caused by the presence of a hard encasing structure in the fruit that prevents the radical from expanding and exiting. ꟷ Water may enter the fruit but embryo development is physically restricted. [email protected] 11/18/2024 71 Cont.…_________________________________________________________________ ꟷ Eg. Fruits of the following species demonstrate mechanical dormancy:  Tectona grandis (teak), Gmelina arborea (gmelina), Aleurites moluccana (candlenut), and Canarium ovatum (pilinut). Chemical dormancy ꟷ Chemical dormancy is caused by chemical compounds in the fruit, seed or embryo that prevent germination, even in the presence of water. ꟷ This type of dormancy occurs in:  Gmelina arborea (gmelina), Xanthoxyllum rhetsa (nyalin),and Maesopsis eminii (musizi or African wood). [email protected] 11/18/2024 72 Cont.…_________________________________________________________________ Under natural conditions, dormancy may prevent seeds from germinating for days, weeks, months and even years. In order to operate efficient nursery and tree planting programs, methods are required that overcome seed dormancy and accelerate germination. These methods are called seed pre-sowing treatments. 6.8. Seed Pre-Sowing Treatments  Pre-sowing treatments are methods applied to overcome seed dormancy to ensure rapid, uniform and timely seed germination that facilitates seedling production.  these treatments are applied to seeds immediately before sowing. [email protected] 11/18/2024 73 Cont.…_________________________________________________________________ Most methods require only a few minutes to 24 hours. However some pre-sowing methods require a few to several days. Appropriate pre-sowing treatment methods depend on the dormancy characteristics of the seed being treated. The most common pre-sowing treatment methods are discussed below. 6.8.1. Soaking in cool water applied to overcome the physical, mechanical or chemical seed dormancy of some species. Most often seeds are soaked in water for 1 day, the seeds of a few species may require soaking for 2 days. [email protected] 11/18/2024 74 Cont.…_________________________________________________________________ This method is applied to the seed of Sesbania grandiflora (turi), Tamarindus indica (tamarind), Gmelina arborea (gmelina), Gliricidia sepium (gliricidia), and Dalbergia species (rosewoods). 6.8.2. Soaking in hot water applied to overcome the physical dormancy of seeds with hard, thick and waxy seed coats. Water is boiled and removed from the source of heat. Seeds are soaked in hot water while being stirred for 2-5 minutes, and then soaked in cool water for 1 day. Caution: if seed is soaked while the water is being boiled, the seed might be cooked and die. [email protected] 11/18/2024 75 Cont.…_________________________________________________________________ This method is applied to the seed of Paraserianthes falcataria (falcata), Acacia mangium (mangium), Calliandra calothyrsus (red calliandra), and Leucaena species (ipil ipil). 6.8.3. Mechanical (scarification) methods used to overcome the physical and mechanical dormancy of hard and thick seed coats or fruit shells. Small holes are cut or scrapped in the seed coat or fruit shell with a knife, metal file or abrasive material to allow water absorption. Mechanical machines are available for this purpose. After scarification, seeds are usually soaked in cool water for 1 day. [email protected] 11/18/2024 76 Cont.…_________________________________________________________________ These methods are used on the seed of the species mentioned under the hot water pre-treatment, as well as, Eusideroxylon zwageri (ulin or ironwood). The hard shells of some fruits are with a hammer. The fruits are then soaked in water for 1 day. 6.8.4. Fire or heating methods These methods are used to overcome mechanical dormancy of fruits with thick shells. Fruits are spread on the ground and covered with a 2cm layer of dry grass or straw, which is then burned. Alternatively, fruits may be heated in a pan over a fire. [email protected] 11/18/2024 77 6.8.5. Soaking in chemicals  Soaking seeds in sulfuric acid, hydrochloric acid, or hydrogen peroxide for 10-20 minutes to overcomes physical and mechanical dormancy.  Seeds are removed from the chemical soak, rinsed with water for 2-5 minutes and then soaked in cool water for 24 hours.  This method is not recommended because chemicals are dangerous and expensive. 6.9. Trade and distribution of seeds  When seed producers and seed users are geographically or functionally separated, seeds are transferred from producers to users. [email protected] 11/18/2024 78 Cont.…_________________________________________________________________  In market-oriented systems, transfer includes the pricing of seed, which reflects the procurement cost and seed quality.  Physiological quality is documented via the seed testing records.  Genetic quality is documented as documents on origin or seed source.  New types of tree planting by smallholders imply special problems in distribution and supply systems since production systems for tree seeds have large areas while many consumers have small space for planting.  A centralized forest seed supply contains large central units with good facilities for production and procurement but is far from seed users. [email protected] 11/18/2024 79 Cont.…_________________________________________________________________ Alternative decentralized systems with many small producers may have problems meeting high standards of seed quality and dealing with central regulations.  During tree seed Dispatching.  Seed should reach end users with minimum loss of physiological quality (germination capacity).  Shipping implies a risk of physiological deterioration during transit, especially for sensitive seed, long distances, and poor transport conditions.  Seed should be put in transparent sealed bags that allow inspection through the material. [email protected] 11/18/2024 80 Cont.…_________________________________________________________________  End users may cover user groups from plantation owners to small farmers.  Their demand varies in terms of species, quantities, economic resources, and technical background.  They may also cover large geographical areas.  In order to reach each customer group, the dispatch system must be able to address different demands, including giving technical instructions on different levels. ֍ During dispatching Seed Lot Information Outline should be attached. [email protected] 11/18/2024 81