In earlier experiments, sucrose at different concentrations (21) and mannitol (22) was
applied in the cryoprotective preculture medium. From these experiments it was concluded
that the cryoprotective effect of sucrose was more than purely osmotic and that adaptive
metabolism was involved. To investigate whether the disaccharide sucrose is replaceable by
other metabolically active sugars, its cryoprotective activity was compared with equimolar
concentrations of the monosaccharides glucose and fructose. Figure 1 shows that other sugars
than sucrose can cryoprotect banana meristems; cryoprotection with 0.5 M glucose or 0.4 and
0.5 M fructose resulted in post-thaw regeneration frequencies that were not significantly
different from 0.4 M sucrose. Surprisingly, the combination of sucrose and glucose with a
total molarity of 0.5 M resulted in significantly lower survival rates. These results deviate
from those obtained with oil palm polyembryonic cultures, where sucrose preculture could not
be replaced by a wide range of other sugars and polyols (9). Other sugars were only effective
when a preculture was followed by dehydration. Here sugar preculture probably improves
resistance towards dehydration rather than to cryopreservation itself. However, when such
dehydration was applied to banana meristematic clumps no increased survival rate after
freezing was noted (21). Also Asparagus shoot-tips and carrot somatic embryos could be
efficiently dehydration-protected with a wide range of sugars and polyols, prior to the
application of the ‘classical’ slow freezing protocol (28, 30). Resistance towards dehydration
with plant vitrification solutions (PVS) prior to cryopreservation could also be induced in
Anigozanthos viridis shoot apices using different sugars and polyalcohols (33). The protective
role of sugars is far from understood. Besides its osmotic and colligative effects, thus
reducing the amount of intracellular freezable water, it is known that sugars are competitive
protein and membrane stabilisers (6). In addition to physical changes, sugar treatments can
also result in different physiological and metabolical changes leading to cryoprotection. These
include alterations in proteins (31, 16), membrane fatty acids (36) and amino acids (7).
In earlier experiments, sucrose at different concentrations (21) and mannitol (22) wasapplied in the cryoprotective preculture medium. From these experiments it was concludedthat the cryoprotective effect of sucrose was more than purely osmotic and that adaptivemetabolism was involved. To investigate whether the disaccharide sucrose is replaceable byother metabolically active sugars, its cryoprotective activity was compared with equimolarconcentrations of the monosaccharides glucose and fructose. Figure 1 shows that other sugarsthan sucrose can cryoprotect banana meristems; cryoprotection with 0.5 M glucose or 0.4 and0.5 M fructose resulted in post-thaw regeneration frequencies that were not significantlydifferent from 0.4 M sucrose. Surprisingly, the combination of sucrose and glucose with atotal molarity of 0.5 M resulted in significantly lower survival rates. These results deviatefrom those obtained with oil palm polyembryonic cultures, where sucrose preculture could notbe replaced by a wide range of other sugars and polyols (9). Other sugars were only effectivewhen a preculture was followed by dehydration. Here sugar preculture probably improvesresistance towards dehydration rather than to cryopreservation itself. However, when suchdehydration was applied to banana meristematic clumps no increased survival rate afterfreezing was noted (21). Also Asparagus shoot-tips and carrot somatic embryos could beมีประสิทธิภาพคายน้ำป้องกันกับน้ำตาลและ polyols ก่อนหน้านี้แอพลิเคชันของการ 'คลาสสิก' ช้าตรึงโพรโทคอล (28, 30) ต้านทานต่อการคายน้ำกับพืช vitrification โซลูชั่น (PVS) ก่อน cryopreservation สามารถยังสามารถเกิดในAnigozanthos viridis ยิง apices ที่ใช้น้ำตาลอื่นและ polyalcohols (33) การป้องกันไกลจากมีเข้าใจบทบาทของน้ำตาล นอกจากผลการออสโมติก และ colligative ดังนั้นลดจำนวนน้ำ intracellular freezable เป็นที่รู้จักกันว่า น้ำตาลแข่งขันโปรตีนและเยื่อ stabilisers (6) นอกจากการเปลี่ยนแปลงทางกายภาพ น้ำตาลสามารถรักษายัง ส่งผลในสรีรวิทยาและ metabolical เปลี่ยนที่แตกต่างนำไป cryoprotection เหล่านี้มีการเปลี่ยนแปลงในโปรตีน (31, 16), กรดไขมันเยื่อ (36) และกรดอะมิโน (7)
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