FAO FORESTRY PAPER 20/2
A guide to forest seed handling
with special reference to the tropics
First printing 1985
The designations employed and the presentation of material in this publication do not imply the expression of any opinion whatsoever on the part of the Food and Agriculture Organization of the United Nations concerning the legal status of any country, territory, city or area or of its authorities, or concerning the delimitation of its frontiers or boundaries.
All rights reserved. No part of this publication may be reproduced, stored in a retrieval system, or transmitted in any form or by any means, electronic, mechanical, photocopying or otherwise, without the prior permission of the copyright owner. Applications for such permission, with a statement of the purpose and extent of the reproduction, should be addressed to the Director, Publications Division, Food and Agriculture Organization of the United Nations, Via delle Terme di Caracalla, 00100 Rome, Italy.
F O R E W O R D
FAO and the DANIDA Forest Seed Centre have cooperated closely over the past two decades in the field of tree improvement and seed procurement. A representative of the Seed Centre has been a member of the FAO Panel of Experts on Forest Gene Resources since it was established in the sixties, while a representative of FAO's Forestry Department is a member of the Project Committee of the Seed Centre. This has ensured a high level of integration between the programmes of the two organizations. A particularly fruitful example of cooperation has been the series of training courses on tree improvement, seed handling and afforestation, jointly sponsored by FAO and DANIDA, and held successively in Denmark, Kenya, Thailand, Nigeria and Venezuela. Currently the Seed Centre is providing storage facilities for seed collected through FAO's project on Genetic Resources of Arid and Semi-arid Zone Arboreal Species for the Improvement of Rural Living.
The present publication is a further example of this cooperation. It gathers together information from a number of sources, including the FAO/DANIDA training courses mentioned above, Working Papers from FAO field projects, as well as technical leaflets and notes compiled by the Seed Centre. A draft edition of the Guide was published in 1983 in a limited number of copies, which were distributed for comments. The present edition has been revised in the light of comments from readers and illustrations have been added.
The increased rates of tree planting, which is apparent in so many countries today, emphasizes more than ever before the need for good seed. Seed quality has a critical effect on the quality of the trees established and on the economics of planting them. This is equally true whether planting is in large-scale commercial plantations or in small-scale diffuse farm woodlots or as scattered single trees. Seed quality comprises both the physiological viability and vigour of the seeds and their genetic quality - their ability to produce healthy offspring which are well suited both to the sites where they are planted and for the products or services which they are intended to provide. This Guide is concerned with the physiological quality of seeds and it is hoped that it will be useful especially to developing countries in the tropics, where publications on forest seed handling are few in comparison with those for the temperate zones.
The guide was compiled by R.L. Willan, consultant. The following specialists kindly submitted valuable, written comments on earlier drafts: H. Barner, F.T. Bonner, A.G. Gordon, S.K. Kamra, F. Ng, P.G. Pattanath, M. Robbins, M. Simak, B. Suszka, J.W. Turnbull and B. Wang.
Illustrations have been provided from a wide variety of sources; many have appeared in earlier publications. FAO and DANIDA are grateful to all who generously gave illustrative material and permission to reproduce it. The source of each illustration is shown in the individual credit lines. The line drawing on the cover is by M. Robbins.
Facilities and help given by all staff at the DANIDA Forest Seed Centre and by library staff at the Commonwealth Forestry Institute in Oxford are acknowledged with thanks.
FOOD AND AGRICULTURE ORGANIZATION OF THE UNITED NATIONS
Rome, 1985 © FAO
Hyperlinks to non-FAO Internet sites do not imply any official endorsement of or responsibility for the opinions, ideas, data or products presented at these locations, or guarantee the validity of the information provided. The sole purpose of links to non-FAO sites is to indicate further information available on related topics.
This electronic document has been scanned using optical character recognition (OCR) software. FAO declines all responsibility for any discrepancies that may exist between the present document and its original printed version.
Chapter 1 INTRODUCTION
Purpose and Content of this Guide
The Importance of Seed in Present-Day Forestry
Chapter 2 SEED AND FRUIT DEVELOPMENT, GERMINATION, DORMANCY
Pollination and Fertilization
Angiosperm Seed Development
Angiosperm Fruit Development
Seed Dispersal in Angiosperms
Gymnosperm Seed Development
Gymnosperm Fruit Development
Seed Dispersal in Gymnosperms
Hazards of Seed Production
Chapter 3 PLANNING SEED COLLECTION
Determining Species, Provenances and Stands
Determining Seed Quantities
Determining the Year for Collection
Effect of periodicity
Counting the fruit crop
Fruit crop rating methods
Estimating full seed content by cutting test.
Determining the Best Dates for Collection
Collection of Immature Seeds
Determining Which Trees to Collect From
Small-scale research collections
Single tree collections
Single clone collections
Collections for conservation
Assembling Resources for Seed Collection
Special Considerations for International Expeditions
Chapter 4 SEED COLLECTION
Collection of Fallen Fruits or Seeds from the Forest Floor
Collection of seed after dispersal
Collection from the Crowns of Felled Trees
Collection from Standing Trees with Access from the Ground
Cutting, breaking and sawing
Use of rifle
Collection from Standing Trees with Access by Climbing
Climbing into the crown by way of the bole
Climbing into the crown directly
Climbing and picking fruits within the crown
Collection from Standing Trees with Other Means of Access
Productivity in Fruit Collection
Training and Safety
Chapter 5 FRUIT AND SEED HANDLING BETWEEN COLLECTION AND PROCESSING
Seed Extraction Close to the Collection Site
Special Precautions for Recalcitrant Seeds in the Humid Tropics
Chapter 6 SEED PROCESSING
Operations Prior to Extraction
Temporary storage at the processing depot
Methods of Extraction
Drying of Fruits without Artificial Heat
Drying under cover
Drying of Fruits with Artificial Heat
Types of Drying Kiln
Stationary tray kilns
Vertical progressive kilns
Horizontal progressive kilns
Rotating drum kilns
Other Methods of Extraction
Operations after Extraction
Seed Cleaning Methods
Screening or sieving
Sorting according to length
Specific gravity separation
Other cleaning methods
Control of Moisture Content
Relationship of Seed Moisture Content to Atmospheric Humidity
Drying of Orthodox Seeds
Mixing before Storage
Chapter 7 SEED STORAGE
Natural Longevity of Tree Seeds
Hard-coated orthodox seeds
Orthodox seeds without hard seedcoats
Factors Affecting Longevity in Storage
Storage conditions and ageing of seeds
Seed moisture content
Choice of Storage Method
Storage at ambient temperature and humidity
Dry storage with control of MC but not of temperature
Dry storage with control of both MC and temperature
Dry storage for long-term gene conservation
Moist storage without control of MC or temperature
Moist cold storage with control of temperature
Materials freely permeable to moisture and gases
Materials completely impermeable, when sealed, to moisture and gases
Materials resistant, but not completely impermeable, to moisture
Use of desiccants in containers
Choice and use of container
Design and Engineering of Seed Storage Facilities
Design and equipment
Chapter 8 SEED PRETREATMENT
Classification of Types of Dormancy
Treatments Designed to Break Seed-Coat Dormancy
Soaking in water
Dry heat and fire
Special treatments for mechanical dormancy
Treatments Designed to Break Endogenous or Embryo Dormancy
Overcoming physiological dormancy -cold stratification
Other moist prechilling methods
Chemical treatment of physiological dormancy
Other treatments for endogenous dormancy
Treatments Designed to Overcome Double Dormancy
Seed Dressing and Pelleting
Materials and methods
Other Types of Pretreatment
Chapter 9 SEED TESTING
Use of seed triers
Reducing the size of composite samples
Non-mechanical methods of dividing
Mechanical methods of dividing
Weight of sample
Germination conditions for selected species
Germination testing in the nursery
Testing homogeneity of germination results
Combining Purity and Germination Tests
Indirect Tests of Viability
Topographical tetrazolium test
Excised embryo test
Testing Moisture Content
Calculation of Results
Indirect tests of viability
Interpretation of Results
Special Considerations for Recalcitrant Seeds of Tropical Rainforests
Appendix 1 Seed documentation
1 A An example of an integrated system of seed recording forms as used in Sabah
|Table 1||Seed stands of forest research centre|
|Table 2||Summary of forms and usage|
|Seed form||1||Fruit collection demand note|
|" "||2||Fruit collection advice note|
|" "||3||Sack collection label|
|" "||4||Seed extraction record|
|" "||5||Register of seed stock and disposals|
|" "||6||Seed storage container label|
|" "||7||Purity and germination testing, seed sample transfer envelope|
|" "||8||Moisture content analysis, seed sample transfer form|
|" "||9||Sample test ledger sheet|
|" "||10||Germination and purity test|
|" "||11||Summary of test results|
|" "||12||Seed demand/issue form|
|" "||13||Seed order check list|
|" "||14||Nursery germination record|
|" "||15||Final germination test report|
1 B Selected examples of seed origin data sheets
|1B1||OECD (Certificate of Provenance)|
|1B2||Tanzania Silviculture Research Station|
|1B3||British Columbia Forest Service|
|1B4||British Columbia Forest Service|
|1B5||British Columbia Forest Service|
|1B6||DANIDA Forest Seed Centre|
|1B7||Petawawa Forest Experiment Station|
|1B8||Thai-Danish Pine Project|
|1B9||Commonwealth Forestry Institute|
|1B10||Division of Forest Research, CSIRO, Canberra|
|1B11||Banco de Semillas, ESNACIFOR, Honduras|
1 C Selected examples of other seed forms
|1C1||Cone Collecting Costs, British Columbia|
|1C2||Register of identity numbers:|
|I Index of serial identity numbers|
|1C3||Register of identity numbers:|
|II Index of species|
|1C4||Seed extraction, Thai-Danish Pine Project|
|1C5||Seed germination, Thai-Danish Pine Project|
|1C6||Seed stock, Thai-Danish Pine Project|
|1C7||Combined seed data card, Thai-Danish Pine Project|
|1C8||Combined seed stock & data card, Denmark|
|1C9||International seed lot certificate, ISTA|
|1C10||Germination data sheet for replications of equal weight, Australia|
|1C11||Cone crop survey and evaluation forms, British Columbia|
|1C12||Sample seed testing ledger sheet|
|1C13||Combined seed testing sheet, UK|
|1C14||Standard consignment note and seed certificate, Australia|
Appendix 2 Considerations in the design and equipment of long-term seed-storage facilities for genetic conservation (orthodox species).
Appendix 3 Long-term seed-storage facilities of the regional genetic resources project at Turrialba, Costa Rica. Construction details.
Appendix 4 The use of deep-freeze chests for longterm storage of small seed collections.
Appendix 5 Logistics of collecting 200 kg of Pinus caribaea seed
Appendix 6 Annotated list of equipment which may be needed for collection of seed, site information and herbarium specimens.
Appendix 7 Glossary
Appendix 8 Bibliography
Select Bibliography (some key references)
Appendix 9 Index
LIST OF ILLUSTRATIONS
1.1 Estimated total areas of forest plantations in Tropical Africa, Tropical America and Tropical Asia 1975–1985.
1.2 Estimated annual planting rates. Brazil, India and Tropical Africa.
1.3 Effect of species choice on quantity of seed required per unit area.
2.1 Longitudinal section through a typical pistil just before fertilization.
2.2 Longitudinal sections through ripe seeds of Paulownia tomentosa and Tectona grandis.
2.3 Examples of different types of fruits.
2.4 Longitudinal section through an ovule of Pinus during the period of pollen tube development preceding fertilization.
2.5 Examples of germination in two West African Sterculiaceae. Epigeal in Mansonia altissima and hypogeal in Cola nitida.
3.1 Provenance Regions for Pinus caribaea and P. oocarpa in Honduras.
3.2 Cone crops of Douglas-fir, Vancouver Forest District, 1935–1974.
3.3 Example of a cone-cutter for seed crop estimation on a longitudinal section.
3.4 Seed content is estimated by counting good seeds on one surface of each of several sliced cones.
4.1 The Advanced Line Technique.
4.2 The Schaumann Tree Shaker.
4.3 Funnel for trapping Acacia aneura seed.
4.4 Net retrieval machine.
4.5 Use of vacuum seed harvester for acorns.
4.6 A selection of Acacia seed collecting equipment.
4.7 Saws, pruners, rakes and other hand tools for harvesting tree fruits.
4.8 The High Limb flexible chain saw.
4.9 Tree climbing spurs.
4.10 Two strut sectional ladder.
4.11 Single-strut sectional ladder.
4.12 Tree bicycle, tree gripper or baumvelo.
4.13 Tree bicycle in use.
4.14 Hand picking Larix cones. Tree bicycle.
4.15 Use of hand tools and safety line in picking fruits in the crown.
4.16 Climber controlling own descent by safety line locking method.
4.17 Use of extension platform for cone picking.
5.1 Interim cone storage racks.
5.2 Wire baskets used for temporary storage of cones.
5.3 Temporary cone storage in boxes.
5.4 Temporary frame for field drying eucalypt capsules.
6.1 Precuring sheds with open-air racks.
6.2 Top view of the Dybvig separator.
6.3 Solar drying of pine cones under clear polythene roofing.
6.4 Solar cone drying of Pinus kesiya and Pinus merkusii in rotatable drums.
6.5 Solar drying of pine cones.
6.6 Kiln seasoning. Stacked trays entering a kiln.
6.7 Interior view of a kiln with trays.
6.8 Rotating kiln.
6.9 Portable cone kiln.
6.10 Cone tumbler.
6.11 Double-storied tumbler room.
6.12 The Resilient Tapered Thresher.
6.13 CSIRO 15-cm Flailing Thresher.
6.14 Cement mixer used for dewinging.
6.15 Missoula dewinger for small seedlots.
6.16 Liriodendron tulipifera before and after dewinging.
6.17 Electrically operated laboratory seed blowers.
6.18 Locally made seed cleaner.
6.19 Air/screen seed cleaner.
6.20 Gravity seed separator.
6.21 Equilibrium moisture content of wheat seed, showing separate curves for desorption and absorption.
6.22 Moisture content percentages of fresh seed of Pinus palustris in equilibrium with air at various temperatures and relative humidities.
6.23 Equilibrium moisture contents for 3 orthodox species.
6.24 Equilibrium moisture contents for 4 recalcitrant species.
7.1 Airtight containers used for storing seed.
7.2 Interior view of cold storage room.
7.3 Examples of different types of container used for storage or shipment.
8.1 Effect of several presowing treatments on germination of black locust.
8.2 Benefits of cold stratification for speeding germination of loblolly pine.
8.3 The effect of various pretreatments on germination of Pinus elliottii.
8.4 The effect of pretreatment on germination of Acacia mangium.
8.5 A rinsing trough for washing acid from treated seeds.
8.6 One apparatus for treating large lots of seed with acid.
8.7 Outdoor stratification of Juglans nigra in sand.
8.8 Desired arrangement for stratification in a large barrel.
8.9 Loblolly pine seed prepared for stratification in a plastic bag.
8.10 Effects of several treatments to overcome double dormancy in eastern redbud.
8.11 The US Forest Service recommendation for preparing repellent and applying it to seed of Pinus elliottii.
8.12 Flow-scheme for the removal of mechanically damaged and filled-dead seeds according to PREVAC- and IDS- methods.
8.13 The germinating seeds of IDS/PREVAC-treated Pinus caribaea and P. oocarpa.
9.1 A seed trier.
9.2 Random cup divider.
9.3 Inverted cone dividers.
9.4 Seed dividers (a) Boerner (b) Gamet.
9.5 An opaque glass screen for purity tests and determinations of the number of seeds per kg.
9.6 Two types of weighing scales used in seed laboratories.
9.7 Counting board with seeds of Celtis laevigata.
9.8 Counting head on a vacuum seed counter.
9.9 Open seed germination cabinet and group of cabinets.
9.10 Conviron G 30 germinator.
9.11 Clear and black germination boxes developed for seed testing.
9.12 Copenhagen tank and rolled filter paper for germination tests.
9.13 Acorns of Quercus alba germinating on Kimpak.
9.14 Germination of Douglas-fir and lodgepole pine seeds.
9.15 X-ray radiograph of teak fruits showing the variation in the number of locules.
9.16 X-ray radiographs showing embryo and endosperm classes in coniferous seeds.
9.17 X-ray radiograph of Pinus caribaea seed.
9.18 Quercus seeds cut in halves for oven drying in moisture determination.
9.19 Dole electric seed moisture meter.
9.20 Electric moisture meters.