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Topic: Recalcitrant seeds

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	GLOBAL VOICES OF SCIENCE: Protector of the Seeds: Seminal Reflections from Southern Africa -- Berjak 307 (5706): 47 -- ... (Site not responding. Last check: 2007-10-27)
		Maize (corn), which produces orthodox seeds, is the staple crop of much of Africa, yet it is ill-suited to the drought-prone conditions that prevail in many regions, where it is cultivated in preference to the native cereal, sorghum.
		The term "recalcitrant," defined as "obstinately disobedient," was first applied by seed scientists to describe the responses of seeds that could not be stored under the conventional low-temperature and low-relative humidity conditions used for orthodox seeds.
		Recalcitrant seeds--whether coconuts or the "pips" of a litchi, mango, or avocado pear--are generally large.
	www.sciencemag.org /cgi/content/full/307/5706/47 (2575 words)

	Content of adenylate nucleotides and energy charge in the early stage of germination of orthodox and recalcitrant seeds
		Recalcitrant seeds are desiccation sensitive and have a high moisture content, which is necessary to maintain seed viability for a certain period of time.
		The increase in ATP levels in orthodox seeds during the early stages of germination is considered to be due to the onset of respiration and concomitant oxidative phosphorylation in the mitochondria as soon as seeds are hydrated (Hourmant and Pradet, 1981; Attucci et al., 1991).
		Recalcitrant seeds have not been examined in terms of energy metabolism in the early stage of seed germination.
	ejournal.sinica.edu.tw /bbas/content/1996/4/bot374-01.html (4658 words)

	University of Witwatersrand, APES
		Recalcitrant seeds, unlike their orthodox counterparts, do not undergo a period of maturation drying during their development, and as a consequence, they are shed from the parent plant at high water content.
		Furthermore, the natural loss of viability of recalcitrant seeds, which is accompanied by leakage of biomolecules due to loss of membrane integrity, in conjunction with the relatively warm, humid storage conditions provides an excellent environment for fungal proliferation and this exacerbates deterioration.
		Because their seeds are short lived, and in order to maintain desirable cultivars crop species that produce recalcitrant seeds are vegetatively propagated.
	www.wits.ac.za /apes/plasmres.html (1840 words)

	Seed Germination Tips
		Many other seeds go into a period of dormancy that must be broken for them to germinate.
		Considering that "tropical seeds" encompass plants growing in such varying, and often subtlely different climates, there are a number of different strategies for germinating tropical seeds in your garden.
		Also note that many tropical seeds may be planted in sub-optimal conditions, only to germinate months (sometimes even a year or more) later when the soil warms up, or conditions are more favorable.
	www.tradewindsfruit.com /seed_germination_tips.htm (491 words)

	SignOnSanDiego.com > News > Weblogs > The Big Bang Blog
		Recalcitrant seeds cannot be stored using traditional methods because they are very wet, and drying injures these seeds.
		Short- and medium-term storage—Corn and bean seeds would be stored in environments as dry and as cool as possible.
		The smallest unit for recalcitrant seeds is the embryonic axis—the potential new plant.
	www.signonsandiego.com /news/weblogs/thebigbang/archives/001185.html (465 words)

	News (Site not responding. Last check: 2007-10-27)
		Many economically important plant species produce recalcitrant seeds, and species producing seeds of this type also form a significant proportion of the flora of the moist tropics, areas that are currently threatened with substantial species loss and diversity reduction.
		Recalcitrant seeds are essentially un-storable by conventional techniques, inhibiting normal commerce and season-to-season storage, and the conservation of endangered germplasm in gene banks.
		Recalcitrant seeds are desiccation sensitive and so cannot be dried for storage; they are also hydrated and so cannot be frozen without lethal freezing damage.
	www.sles.und.ac.za /news.asp?RecordVAR=31 (393 words)

	Seed Germination Tips (Site not responding. Last check: 2007-10-27)
		Many other seeds go into a period of dormancy that must be broken for them to germinate.
		Considering that "tropical seeds" encompass plants growing in such varying, and often subtlely different climates, there are a number of different strategies for germinating tropical seeds in your garden.
		Also note that many tropical seeds may be planted in sub-optimal conditions, only to germinate months (sometimes even a year or more) later when the soil warms up, or conditions are more favorable.
	www.bonus.com /contour/tropicalfr_db/http@@/www.tradewindsfruit.com/seed_germination_tips.htm (491 words)

	Cryopreservation and seed storage
		The impact of Berjak's work on storage problems of seeds that behave in a predictable manner, or 'orthodox' seeds, was manifested when she was invited as one of a select group of scientists to consider the conservation of seeds considered unstorable, the 'recalcitrant' seeds, the behaviour of which is unpredictable.
		That meeting, in the UK in 1980, was to prove to be a pivotal point, heralding the phase that was to establish her group as among the foremost researchers on seed recalcitrance in the world.
		At that congress a doyen of seed research, JD Bewley, commented that "this was the first time anyone had provided a meaningful explanation of the basis of recalcitrant seed behaviour".
	www.scienceinafrica.co.za /seed.htm (1557 words)

	Making Winter for Seeds - A Cold Stratification Guide from Alchemy Works
		Mix the seeds with the sterile soil--it's good not to use too much, because unless the seeds are large, you will be sowing the soil together with the seeds once they start germinating.
		Seeds are planted either directly in the ground in a cold frame or in pots left in a protected area.
		Seeds that use cold to germinate are closer to the wild and so have a good reason to stagger their germination - more are likely to survive that way, and you will get more genetic variation.
	www.alchemy-works.com /fall_planting.html (3153 words)

	FAQs
		You can plant seeds from that apple and get a tree in about 5-10 years, but the fruit from the new tree will not be the same as the apple that you enjoyed.
		A recalcitrant seed, in contrast to most crop seeds, is a seed that cannot survive drying and so cannot survive in the freezer.
		Recalcitrant seeds are frequently produced by temperate-zone forest trees, riparian species, and plants from the tropics.
	www.ars-grin.gov /ncgrp/center_faq.htm (1201 words)

	University of Witwatersrand, APES (Site not responding. Last check: 2007-10-27)
		Recalcitrant seeds, unlike their orthodox counterparts, do not undergo a period of maturation drying during their development, and as a consequence, they are shed from the parent plant at high water content.
		Furthermore, the natural loss of viability of recalcitrant seeds, which is accompanied by leakage of biomolecules due to loss of membrane integrity, in conjunction with the relatively warm, humid storage conditions provides an excellent environment for fungal proliferation and this exacerbates deterioration.
		Because their seeds are short lived, and in order to maintain desirable cultivars crop species that produce recalcitrant seeds are vegetatively propagated.
	sunsite.wits.ac.za /apes/plasmres.html (1840 words)

	BGCI - Plant conservation - Seed conservation research: IPGRI's strategies and activities
		Seeds of this type are termed "recalcitrant" and even when stored under optimal conditions, their lifespan is limited to a few weeks, occasionally months.
		In comparison with truly recalcitrant seeds, the storage life of these intermediate seeds can be prolonged by some drying, but it remains impossible to achieve the long-term conservation which can be realized for orthodox seeds.
		In the case of recalcitrant and intermediate seed types, research should be aimed at developing ways for manipulating or treating seeds or embryos in order to induce desiccation and chilling tolerance.
	www.bgci.org.uk /conservation/Seed_conservation_research:IPGRI.html (2288 words)

	Royal Botanic Gardens, Kew: Millennium Seed Bank Project: Temperate Seed Dormancy (Site not responding. Last check: 2007-10-27)
		The phenotypic or genotypic nature of the response is not clear as the provenance of the seeds used to establish the trees in the UK from which the seeds were harvested for experimentation is not known.
		Recalcitrant seeds of horse chestnut are dormant, only being capable of variable levels of germination within a narrow high temperature range.
		The chilling response of the seeds is similar to that observed in the seeds of many summer annuals.
	www.rbgkew.org.uk /msbp/research/res_dormancy.html (352 words)

	Steve's place - Seeds
		Seeds are resistant to environmental extremes because they are metabolically inactive: they are either quiescent (in seeds that are too dry to germinate) or dormant (in seeds wet enough to germinate, that don't).
		Seeds contain hygroscopic proteins: at 60% RH, seeds will have about 12% MC at equilibrium, but the water is tightly bound to the matrix, so the water potential is very low, and solutes cannot diffuse.
		Cryopreservation of seeds, embryos dissected from seeds, pollen, or tissue cultures in liquid nitrogen with cryopreservants has many advantages: small recalcitrant seeds can be impregnated with cryopreservant and become orthodox, and the system is simpler than growing cultures to maintain.
	www.steve.gb.com /science/seeds.html (2668 words)

	Seed Banks
		Recalcitrant seeds are all seeds that cannot tolerate the low humidity and low temperature storage conditions required for seedbank storage.
		The development of alternative methods of seed preservation for this type of seed is needed to ensure that recalcitrant species are not excluded from long-term conservation efforts.
		The high number of recalcitrant species in the wild cannot be preserved in seedbanks by current methods, leaving conservation of these species a difficult task.
	www.rbg.ca /cbcn/en/information/seedbanks/index.html (997 words)

	Bioline International Official Site (site up-dated regularly) (Site not responding. Last check: 2007-10-27)
		Desiccation of seeds was associated with decreased antioxidative enzymic capacity (of peroxidase and polyphenoloxidase), and thus increased likelihood of free radical attack and decreased viability (germinability).
		Seed soluble sugar and lipid content increased with developmental maturity and during desiccation (Figures 3 and 4, respectively).
		Seeds dried at the lower temperature maintained viability (as assessed by % germination) for longer periods during the desiccation treatments, probably due to a slower rate of moisture loss.
	www.bioline.org.br /request?jb03006 (3299 words)

	[No title]
		Ephemeral seeds are of species with only brief viability in forest soils which germinate quickly when water for imbibition is available, otherwise they die (~‘recalcitrant’ seeds in the terminology of seed technologists, meaning seeds which lose viability quickly when stored and typically have high water content and are killed by desiccation).
		Persistent seeds are of species which have extended viability in soil (often several to many years, but data on residence times are inadequate to be precise).
		These are the ‘Orthodox’ seeds of seed technologists which can be stored for long periods and which have low moisture content and are tolerant of desiccation.
	www.nbu.ac.uk /tropical/SSBprotocol_Swaine.doc (895 words)

	FOREST GENETIC RESOURCES INFORMATION No 21
		where n = number of seeds to be sampled; t = the value of the normal deviate corresponding to the desired confidence level; s = the standard deviation of the factor to be tested; d = the level of precision or the margin of error.
		Seed moisture is one of the most important factors affecting viability and storability of seeds.
		Bonner (1982), in working with recalcitrant seeds of temperate species, suggested that a precision to tolerance of variability of up to 2.5% is acceptable for large seeds with moisture content of more than 12%.
	www.fao.org /DOCREP/006/V3030E/V3030E08.htm (1929 words)

	NRF - Publications - news@nrf (Site not responding. Last check: 2007-10-27)
		Her research group is considered as one of the foremost working on seed desiccation sensitivity in the world, and is considered internationally as a major centre of expertise on seed recalcitrance.
		She was elected a Fellow of the University of Natal in 1994, a Fellow of the Royal Society of South Africa in 1996, and was awarded the Silver Medal of the South African Association of Botanists for research excellence in 2001.
		He became involved in her work on recalcitrant seeds, with the result that they are involved in considerable teamwork, sharing this common interest and contributing their different areas of expertise to the common problem.
	www.nrf.ac.za /publications/news@nrf/may2002/berjak.stm (579 words)

	Seed Savers Network: Notes on keeping seed cool, clean, dry, and pest-free (Site not responding. Last check: 2007-10-27)
		Vegetable seeds are at their peak for storage when they reach maximum dry weight on the mother plant.
		Heating is caused by the respiration of seeds, of fungi and bacteria in and on the seed, and of insect populations, which may build up rapidly in a moist environment.
		Seed storage life is doubled for each 5¡ C reduction in storage temperature.
	www.genevar.com.au /seedsavers/resources/9.html (815 words)

	NISC South Africa
		The phenomenon of non-orthodox seed behaviour is presented in the framework of the probability of being much more common than might be expected, considering that scientific knowledge about seeds is largely drawn from what has been established for a mere handful of cultivated crop species.
		Recalcitrance is considered not as deviant, but rather as one extreme of a continuum of seed behaviour based on the response to dehydration, the other extreme being manifested by those orthodox seeds that are able to tolerate almost total desiccation.
		Finally, the limited potential for storage of recalcitrant seeds is discussed, and the alternative biotechnological approach of germplasm conservation by means of cryostorage of embryonic axes, is presented.
	www.nisc.co.za /oneAbstract?absId=63 (343 words)

	Rate of Dehydration and Cumulative Desiccation Stress Interacted to Modulate Desiccation Tolerance of Recalcitrant ...
		Desiccation damage to recalcitrant seed was a functional of two interrelated parameters: the rate and duration of dehydration.
		Farrant JM, Berjak P, Pammenter NW (1993) Studies on the development of the desiccation-sensitive (recalcitrant) seeds of Avicennia marina (Forssk.) Vierh: the acquisition of germinability and response to storage and dehydration.
		Potts SE, Lumpkin TA (1997) Cryopreservation of Wasabia spp.
	www.plantphysiol.org /cgi/content/full/128/4/1323 (4020 words)

	Saving Africa's 'stubborn' seeds - SciDev.Net
		Conventional seed storage relies on drying or freezing to protect seeds from fungal infection and prevent them from germinating.
		One promising approach to the problem of recalcitrant seeds, says Berjak, is to remove the 'embryonic axis' â” the portion of a seed that gives rise to the root and shoot of a new plant â” and preserve it separately it from the rest of the seed.
		This method could, she believes, be used to create artificial seeds, in which the embryonic axis is stored in a gel.
	www.scidev.net /features/index.cfm?fuseaction=printarticle&itemid=358&language=1 (157 words)

	ISTA Online - International Seed Testing Association
		In contrast, when the seeds were stored for some months (which was possible after aril removal and surface-sterilisation, as the season's yield was of very good quality), excised axes had the capacity for shoot development.
		Seeds of eight tropical palms from the genera Phoenix and Syagrus were studied: Phoenix roebelenii, Phoenix rupicola, Phoenix sylvestris, Phoenix theophrasti, Syagrus botryophora, Syagrus flexuosa, Syagrus schizophylla, Syagrus yungasensis.
		Seeds of six species were found to be desiccation tolerant, a trait that matched closely the natural habitat of the species; two species, Phoenix roebelenii and Syagrus schizophylla, are provisionally classified as having desiccation sensitive, Type II or III seeds (formerly described as intermediate or recalcitrant seeds respectively).
	www.seedtest.org /en/content---1--1068.html (2567 words)

	Recalcitrant Seeds in Tropical and Sub-Tropical Africa. Science and Society:
		Important crops producing recalcitrant seeds, in tropical and sub-tropical parts of the world, include mango, litchi, horticultural trees, and plants for traditional medicine.
		Recalcitrant seeds cannot be stored using traditional methods because they are very wet, and drying injures these seeds.
		The smallest unit for recalcitrant seeds is the embryonic axis—the potential new plant.
	www.corante.com /scienceandsociety/archives/2005/03/08/recalcitrant_seeds_in_tropical_and_subtropical_africa.php (589 words)

	World Talk Radio Science & Society: Dr. Patricia Berjak—University of KwaZulu-Natal; Dr. Henry McGill—Southwest ... (Site not responding. Last check: 2007-10-27)
		Subsequently, with her graduate students in Durban, the group focused on the effects of the toxin-producing fungi that remain active in, and cause the degradation of, dry seeds under the relatively poor storage conditions commonly used in rural practice in the sub-tropics and tropics.
		Patricia’s deep commitment to elucidating the basis of the responses of desiccation-sensitive, recalcitrant seeds, was a mid-career shift in her research focus.
		Based on their growing understanding of recalcitrant seed responses, the group has gone on to refine storage practices, define the role of the deteriorative seed-associated fungi, and to focus particularly on the application of the principles of cryobiology to the long-term conservation of the genetic resources and biodiversity of plant species producing recalcitrant seeds.
	www.worldtalkradio.com /archive.asp?aid=3545 (1560 words)

	Papers Presented
		Seeds from Chamwino source were dried from 35 to 5% moisture content in 8 weeks in the shade and in 7 days in an oven at 40°C. In both cases the germination capacity was reduced to almost nil from initially almost 100%.
		Recalcitrant seeds are seeds that are sensitive to desiccation.
		Seeds of tropical recalcitrant species generally have the same moisture and gas-exchange requirements as seeds from recalcitrant species of the temperate regions, but they are subject to chilling damage at the temperatures used to store temperate recalcitrant seeds.
	www.ipgri.cgiar.org /publications/HTMLPublications/67/ch02.htm (12466 words)

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