Wen Bin, Song Songquan
Xishuangbanna Tropical Botanical Garden, Chinese Academy of Sciences, Mengla, Yunnan, China.
Cryo Letters. 2007 Mar-Apr;28(2):109-18.
A desiccation-based cryopreservation protocol was employed to study the development of cryotolerance and desiccation tolerance in maize embryos from 23 to 50 days after pollination (DAP). Tolerances were acquired gradually and concomitantly. Maize embryos had low desiccation tolerance at 23 DAP when assessed by survival (embryo elongation) and emergence (root and shoot growth) after dehydration. Desiccation tolerance increased progressively, reached its maximum at 38 DAP, and remained constant afterwards. Cryotolerance, assessed by survival and emergence of post-thaw embryos, however, was nil until 26 DAP. Embryos at 29 DAP withstood cryoexposure within a very narrow moisture range only. Throughout development cryotolerance increased gradually, reached a maximum at 44 DAP and then remained at this level. The correlation between moisture content and cryopreservation success was notably influenced by the maize embryo's development stage. As seeds developed, the moisture content allowing 90% dehydrated embryos to survive and to emerge decreased, while the upper moisture content allowing 50% post-thaw embryos to survive and to emerge increased. Moisture contents of c. 14% allowed no less than 50% post-thaw embryos to emerge at the later development stages (e.g. c. 44 DAP); but no embryos within the same moisture range survived cryoexposure at 29 DAP, although they could withstand desiccation to this moisture level without impairment of survival and emergence. The relationship between cryotolerance and desiccation tolerance during maize seed development is discussed.
采用基于干燥的冷冻保存方案，研究授粉后23至50天玉米胚胎的耐冻性和耐干燥性的发育情况。耐受性是逐渐并同时获得的。通过脱水后的存活率（胚胎伸长）和出苗率（根和芽生长）评估，授粉后23天的玉米胚胎耐干燥性较低。耐干燥性逐渐增加，在授粉后38天达到最大值，之后保持稳定。然而，通过解冻后胚胎的存活率和出苗率评估的耐冻性，在授粉后26天之前为零。授粉后29天的胚胎仅在非常窄的水分范围内能耐受冷冻处理。在整个发育过程中，耐冻性逐渐增加，在授粉后44天达到最大值，然后保持在这一水平。水分含量与冷冻保存成功率之间的相关性受玉米胚胎发育阶段的显著影响。随着种子发育，使90%脱水胚胎存活并出苗的水分含量降低，而使50%解冻后胚胎存活并出苗的上限水分含量增加。在发育后期阶段（如授粉后约44天），约14%的水分含量能使不少于50%的解冻后胚胎出苗；但在授粉后29天，处于相同水分范围内的胚胎没有一个在冷冻处理后存活，尽管它们能耐受干燥至该水分水平而不影响存活和出苗。本文讨论了玉米种子发育过程中耐冻性与耐干燥性之间的关系。
