importance of seed collection
Answers
PROFFESIONAL SEED COLLECTION AND ITS IMPORTANCE:
SELECTION OF MOTHER TREES:
Where possible it is desirable to collect from a large number of individuals that are remote enough from each other to reduce the chance of inbreeding. It has been suggested that l00 m between mother trees is desirable. Other authorities suggest twicethe height of the plant as a suitable distance to avoid inbreeding. Experience both within Australia and overseas has shown
that trees produced from a single specimen, or several closely related trees, show signs of stunting and poor survival afterseveral generations.Collectors need to select healthy, well-grown plants with a suitable form. In the case of seeds required for horticulture, flowercolour and other special ornamental features need to be taken into consideration. Other special features will be important for
re-vegetation projects such as salt and/or lime tolerance, drought resistant, tolerance of wet soils, wind resistance and specialsoil types.Trees for forestry purposes would be selected for disease resistance, growth rate, and quality of timber, soil, rainfall andaltitude.
SEED VIABILITY:
The most important factor in relation to collecting viable seed is ripeness. The period from flowering to ripening of seedsvaries widely from a few weeks to many months. Even in our most import genus Eucalyptus, the time taken for seeds to ripenvaries widely from species to species. Red Gum (E. camaldulensis) flowers between December and February and fruits ripenduring a period between March and August. That is, about 3-6 months.
VIABILITY TESTING:
Seed dormancy can be caused by many factors, many of which are not yet understood. It is for this reasonand also because many batches of seeds collected are very small (less than l kg) that seed testing and certification is unlikelyto become common practice among native seed merchants for some time. The cost of testing would make seed pricesunreasonably high.
COLLECTING SCHEDULE:
Many seed collectors would harvest several hundred batches of seeds each year and may regularly handle up to one thousandspecies or more. In most cases there is an optimum time for collecting but a margin of several weeks or even months will beallowable.
COLLECTING TECHNIQUES:
Tall Trees
Harvesting seeds from tall trees presents the most hazardous and laborious aspect of seed collecting. Falling limbs and evenheavy fruit can cause serious injury and safety glasses and a hard hat should be worn.Collecting of seeds from forest trees is most easily carried out during felling operations but as clearing of natural stands hasbecome less common and even non-existent in South Australia, other methods have to be employed.
Medium Sized Trees
The most effective method of removing fruiting branches from medium size trees about l0m high is the use of long handledsecateurs and a high (45m) three- legged fruit picking ladder. More height can be gained by using telescopic pole pruners,however, there is some risk and much hard work associated with using pole pruners on a ladder. Pole pruners can be used with
more safety from the ground but pole lengths of more than 5m are difficult to handle.
Small Trees and Shrubs
In the case of species like some acacia spp that drop pods with seeds enclosed as soon as they ripen, collecting can be assimple as placing a drop sheet under the tree and beating the branches with a light pole to remove the pods.
Collectors Plant
Useful plant required for collecting would include the following:4 wheel drive vehicleExtension ladder
Fruit pickers ladder (4-5m) Trailer with high wire mesh sides Commando Saw (flexible saw)
Long handled secateurs Fruit pickers bags Secateurs Bow Saw Chain Saw Drop sheets
Telescopic pole pruner Vacuum cleaner & generator (for Chenopods etc) Hard Hats Safety Glasses
Gloves Aluminium pole (fruit knocker) Rifle
Seed Extraction
There are many and varied methods of seed extraction, too many to discuss in any detail here. However, the most common method involves drying fruit followed by tumbling or thrashing, winnowing and screening.
Seed Cleaning
As is the case with seed extraction the methods used to clean seed are many and viable and each collector will develop methods to suit his or her operation.
Screens
Screens, mechanical or hand, are the most important tools used for cleaning seeds. Screen sizes need to vary from as small as 150 micron to 40 mm and a range of aperture shapes from oblong to round and square are useful. To handle a wide range of seed it may be necessary to have 30 or more screens. Two screens are usually used together, one to retain oversize material and the other for the undersize material to pass through.
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Explanation:
Tree improvement programs worldwide have shown that seed collected from trees with particular traits tends to produce trees with similar traits. One can correctly assume that if good parent trees are selected, then most of the resultant offspring will be of desirable quality. Yet despite this concept's proven value and wide understanding, it is seldom applied in the field. To correct this shortcoming, simple parent tree selection guidelines should be developed. These would identify the desired traits and specify the parent trees that reflect those traits. Such traits might include straight trunks, fast growth, and better form. These guidelines are normally met in national or company research programs, but following them will benefit all planters who are careful about the source of their seeds. The traits in turn are chosen to reflect the ultimate desired use of the tree, including building materials, windbreaks, shade, fuelwood, or erosion control. At the same time, these guidelines should not be made cumbersome. For the benefit of those individuals collecting seeds, the guidelines could be a condensed set of simple criteria. Indeed, immediate benefits can be derived from using even the most basic concepts, such as selecting trees of good form and vigor and avoiding trees that are poorly developed, diseased, dying, or are isolated from others of the same species. These simple methods should be applied to large and small programs.