Recalcitrant seed

"Recalcitrant seeds" (sometimes known as unorthodox seeds) are seeds that do not survive drying and freezing during ex-situ conservation. [cite web| last = | first = | coauthors = | title = Frequently Asked Questions| work = | pages = | language = | publisher = National Center for Genetic Resources Preservation, USDA| date = | url = http://www.ars-grin.gov/ncgrp/center_faq.htm#Q20
accessdate = 2008-01-09] Moreover, these seeds cannot resist the effects of drying or temperatures less than 10° C thus they cannot be stored for long periods like "Orthodox seeds" because they can lose their viability. Plants that produce recalcitrant seeds include avocado, mango, lychee, some horticultural trees, and several plants used in traditional medicine.

=Mechanisms of da

The two main mechanisms of action of damage to recalcitrant seeds are desiccation effect on the intracellular structures and the effect of metabolic damage from the formation of toxic chemicals such as free radicals. [cite web| last = Berjak| first = Patricia| authorlink = | coauthors = N.W. Pammenter; J. A. Vozzo Editor| title = Ch 4. Orthodox and Recalcitrant Seeds| work = Tropical Tree Seed Manual| publisher = USDA Forest Service| date = | url = http://www.rngr.net/Publications/ttsm/ch4/file| format = PDF| doi =| accessdate = 2008-01-15] An example of the first type of damage would be found in some recalcitrant nontropical hardwood seeds, specifically the acorns of recalcitrant oaks, which can be stored in a nonfrozen state for up to two years provided that precautions be taken against drying. These seeds showed deterioration of cell membrane lipids and proteins after as few as 3-4 days of drying. [cite journal| last = Connor| first = Kristina F| authorlink = | coauthors = | title = Update on oak seed quality research: Hardwood recalcitrant seeds| journal = Proc. RMRS| volume = P| issue = 33| pages = 111–116| publisher = USDA, Rocky Mountain Research Station| location = | date = 2004| url = http://www.treesearch.fs.fed.us/pubs/9489| doi = | id = | accessdate = 2008-01-09] Other seeds such as those of "Castanea sativa" - sweet chestnut show oxidative damage resulting from uncontrolled metabolism occurring during the drying process. [cite journal| last = Leprince| first = Olivier| authorlink = | coauthors = J Buitink and F Hoekstra | title = Axes and cotyledons of recalcitrant seeds of Castanea sativa Mill. exhibit contrasting responses of respiration to drying in relation to desiccation sensitivity| journal = J. Exp. Bot.| volume = 50| number = 338| pages = 1515–1524| publisher = Oxford University Press| location = | date = 1999| doi = | id = | accessdate = 2008-01-09 ]

ee also

*Micropropagation
*Plant propagation
*Seedbank

Notes