Forest tree seeds at the end of 20th century : major accomplishments and needs

Edwards D.G.W., . (2000) Forest tree seeds at the end of 20th century : major accomplishments and needs. [Proceedings Paper]

Based on the State of Knowledge Report for Research Group 2.09.00 Seed Physiology and Technology this paper reviews developments and accomplishments indicates what remains unknown and suggests directions for research during the early years of the new millennium. The main focus is on tree seed production storage and longevity and seed quality testing and nursery performance. It is pointed out that although conservation efforts are underway a 1998 estimate declared 10 of the worlds tree species as threatened with extinction. Seed orchards and other tree seed production areas have been developed for numerous economically-important forest species but the bulk of tree seed crops continue to be derived from wild plants in natural stands. Forest tree seed biology remains poorly researched for many species but advance-forecasting of good crops is possible in some. However erratic crop production uncontrolled insects and diseases and the need to make collections at the right time to ensure the maximum germination and vigour plus correct post-harvest handling remain priorities for most species. In general seed processing methodologies can now eliminate all or almost all unfilled seeds but only one method a Swedish development applied to some conifers separates live-filled seeds from filled-dead ones. Despite these difficulties large increases in tree seed production particularly in species and provenances selected for desirable attributes are going to be needed to meet the challenge of successful forest regeneration worldwide. Collaborative efforts to determine more-appropriate species and to improve production of genetically and physiologically-improved seeds are underway in some regions but these probably need to be broadened. Seed storage to combat sporadic crops and stabilize supplies to nurseries remains a major research issue. Three broad classes of seeds based principally on their desiccation tolerance and sensitivity to low temperature are now recognized. So-called orthodox and recalcitrant seeds are opposite extremes of a continuum between which lies a broad spectrum of seeds with intermediate storage-behaviour characteristics. The report outlines a number a major findings concerning the causes and reasons for desiccation tolerance. A complex suite of mechanisms is involved and further research is required to resolve all the components into an integrated system. One notable factor is that unlike orthodox seeds cell organelles in recalcitrant seeds remain differentiated and actively metabolic and vulnerable to any amount of dehydration. Seed dormancy common in orthodox seeds and some temperate non-orthodox seeds but rare in tropical species increases the complexity. Predictions of tree seed longevity are still largely empirical but data is slowly accumulating. For operational forestry and germplasm conservation especially for hard-to-store materials major research efforts continue to be needed. Even the better moist-chiling treatments to overcome seed dormancy require weeks or months to apply often only work on some seedlots or some seeds within a lot. Seed moisture control during chilling produces more rapid synchronous germination permits seeds to be cold-stored in a non-dormant state for 1 to several years is used operationally for several conifers and when combined with growth regulators for some broadleaves also. Yet faster more versatile dormancy-breaking treatments are needed for nursery production and laboratory testing. Difficult-to-standardize subjective tests such as tetrazolium staning are still used for tree seeds but they often underestimate/overestimate seed quality. Laboratory tests that correlate with nursery production on a local level have been developed but more work is needed to make these applicable regionally. Vigour testing adapted from agriculture/horticulture is not widely successful in tree seeds mainly because of the inherent heterogeneity in crops from natural stands and even those from seed orchards. Some indicators such as respiratory activity of embryonic axes in beech or of entire subalpine fir seeds as well as protein levels in fir have been suggested as possible vigour indices but much more work is required. A brief review of the organization of the Research Group is appended and several suggestions for the future are made. Contribution to the SKR are acknowledged.

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Abstract

Based on the State of Knowledge Report for Research Group 2.09.00 Seed Physiology and Technology this paper reviews developments and accomplishments indicates what remains unknown and suggests directions for research during the early years of the new millennium. The main focus is on tree seed production storage and longevity and seed quality testing and nursery performance. It is pointed out that although conservation efforts are underway a 1998 estimate declared 10 of the worlds tree species as threatened with extinction. Seed orchards and other tree seed production areas have been developed for numerous economically-important forest species but the bulk of tree seed crops continue to be derived from wild plants in natural stands. Forest tree seed biology remains poorly researched for many species but advance-forecasting of good crops is possible in some. However erratic crop production uncontrolled insects and diseases and the need to make collections at the right time to ensure the maximum germination and vigour plus correct post-harvest handling remain priorities for most species. In general seed processing methodologies can now eliminate all or almost all unfilled seeds but only one method a Swedish development applied to some conifers separates live-filled seeds from filled-dead ones. Despite these difficulties large increases in tree seed production particularly in species and provenances selected for desirable attributes are going to be needed to meet the challenge of successful forest regeneration worldwide. Collaborative efforts to determine more-appropriate species and to improve production of genetically and physiologically-improved seeds are underway in some regions but these probably need to be broadened. Seed storage to combat sporadic crops and stabilize supplies to nurseries remains a major research issue. Three broad classes of seeds based principally on their desiccation tolerance and sensitivity to low temperature are now recognized. So-called orthodox and recalcitrant seeds are opposite extremes of a continuum between which lies a broad spectrum of seeds with intermediate storage-behaviour characteristics. The report outlines a number a major findings concerning the causes and reasons for desiccation tolerance. A complex suite of mechanisms is involved and further research is required to resolve all the components into an integrated system. One notable factor is that unlike orthodox seeds cell organelles in recalcitrant seeds remain differentiated and actively metabolic and vulnerable to any amount of dehydration. Seed dormancy common in orthodox seeds and some temperate non-orthodox seeds but rare in tropical species increases the complexity. Predictions of tree seed longevity are still largely empirical but data is slowly accumulating. For operational forestry and germplasm conservation especially for hard-to-store materials major research efforts continue to be needed. Even the better moist-chiling treatments to overcome seed dormancy require weeks or months to apply often only work on some seedlots or some seeds within a lot. Seed moisture control during chilling produces more rapid synchronous germination permits seeds to be cold-stored in a non-dormant state for 1 to several years is used operationally for several conifers and when combined with growth regulators for some broadleaves also. Yet faster more versatile dormancy-breaking treatments are needed for nursery production and laboratory testing. Difficult-to-standardize subjective tests such as tetrazolium staning are still used for tree seeds but they often underestimate/overestimate seed quality. Laboratory tests that correlate with nursery production on a local level have been developed but more work is needed to make these applicable regionally. Vigour testing adapted from agriculture/horticulture is not widely successful in tree seeds mainly because of the inherent heterogeneity in crops from natural stands and even those from seed orchards. Some indicators such as respiratory activity of embryonic axes in beech or of entire subalpine fir seeds as well as protein levels in fir have been suggested as possible vigour indices but much more work is required. A brief review of the organization of the Research Group is appended and several suggestions for the future are made. Contribution to the SKR are acknowledged.

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Item Type:	Proceedings Paper
Additional Information:	Summary only En
AGROVOC Term:	SEED PRODUCTION
AGROVOC Term:	SEED TREES
AGROVOC Term:	SEED STANDS
AGROVOC Term:	SEED STORAGE
AGROVOC Term:	QUALITY
AGROVOC Term:	SEED
AGROVOC Term:	PLANT PRODUCTION
AGROVOC Term:	SEED TESTING
AGROVOC Term:	SEED INDUSTRY
Geographical Term:	MALAYSIA
Depositing User:	Ms. Norfaezah Khomsan
Last Modified:	24 Apr 2025 05:27
URI:	http://webagris.upm.edu.my/id/eprint/16520

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