Recalcitrant seed
Encyclopedia
Recalcitrant seeds are seed
s that do not survive drying and freezing during ex-situ conservation
. 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
, cocoa, rubber
, some horticultural trees, and several plants used in traditional medicine.
effect on the intracellular structures
and the effect of metabolic damage from the formation of toxic chemicals such as free radicals. 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. Other seeds such as those of the sweet chestnut (Castanea sativa) show oxidative damage resulting from uncontrolled metabolism occurring during the drying process.
Seed
A seed is a small embryonic plant enclosed in a covering called the seed coat, usually with some stored food. It is the product of the ripened ovule of gymnosperm and angiosperm plants which occurs after fertilization and some growth within the mother plant...
s that do not survive drying and freezing during ex-situ conservation
Ex-situ conservation
Ex-situ conservation means literally, "off-site conservation". It is the process of protecting an endangered species of plant or animal outside of its natural habitat; for example, by removing part of the population from a threatened habitat and placing it in a new location, which may be a wild...
. 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
Avocado
The avocado is a tree native to Central Mexico, classified in the flowering plant family Lauraceae along with cinnamon, camphor and bay laurel...
, mango
Mango
The mango is a fleshy stone fruit belonging to the genus Mangifera, consisting of numerous tropical fruiting trees in the flowering plant family Anacardiaceae. The mango is native to India from where it spread all over the world. It is also the most cultivated fruit of the tropical world. While...
, lychee
Lychee
The lychee is the sole member of the genus Litchi in the soapberry family, Sapindaceae. It is a tropical and subtropical fruit tree native to Southern China and Southeast Asia, and now cultivated in many parts of the world...
, cocoa, rubber
Rubber
Natural rubber, also called India rubber or caoutchouc, is an elastomer that was originally derived from latex, a milky colloid produced by some plants. The plants would be ‘tapped’, that is, an incision made into the bark of the tree and the sticky, milk colored latex sap collected and refined...
, some horticultural trees, and several plants used in traditional medicine.
Mechanisms of damage
The two main mechanisms of action of damage to recalcitrant seeds are desiccationDesiccation
Desiccation is the state of extreme dryness, or the process of extreme drying. A desiccant is a hygroscopic substance that induces or sustains such a state in its local vicinity in a moderately sealed container.-Science:...
effect on the intracellular structures
Organelle
In cell biology, an organelle is a specialized subunit within a cell that has a specific function, and is usually separately enclosed within its own lipid bilayer....
and the effect of metabolic damage from the formation of toxic chemicals such as free radicals. An example of the first type of damage would be found in some recalcitrant nontropical hardwood seeds, specifically the acorns of recalcitrant oaks
Oaks
-Horse races:"Oaks" is generally used to describe a Thoroughbred horse race restricted to 3-year-old fillies. Among the best-known races using the term are:*Epsom Oaks, The Oaks Stakes, at Epsom Downs Racecourse, Surrey, England; the original "Oaks" race...
, 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. Other seeds such as those of the sweet chestnut (Castanea sativa) show oxidative damage resulting from uncontrolled metabolism occurring during the drying process.