STUDIES ON DESICCATION-SENSITIVITY AND PEROXIDATION OF MEMBRANE LIPIDS IN LYCHEE(Litchi chinensis Sonn. ) SEEDS

Roberts has divided seeds into orthodox seeds and recalcitrant seeds according to their storage behaviours. The former can tolerate desiccation and freezing temperatures, whereas the latter are susceptible to the two factors. When their water contents are lower than cer-

Conservation and fruit biology of Sichou oak {Quercus sichourensis,Fagaceae)- A critically endangered species in China

Several conservation programs have been started for the critically endangered Sichou oak(Quercus sichourensis) since 2007.These programs include detailed field investigations,seedling cultivation and research on the fruit biology of the species.In this study,we first report on the five mature individual trees found in our 9-year field investigation.Thus far,a total of 10 mature individuals have been recorded.All Q.sichourensis trees are healthy and most produce healthy acorns.Acorns of Q.sichourensis are large with dry masses of 8.0-14.0 g.These acorns had high moisture contents at collection and died shortly after(7-28 d) when dried with silica gel.Characteristics of Q,sichourensis acorns varied between populations.Compared with the acorns from Funing,the acorns collected from Ceheng were bigger,more viable(germination percentage was up to 96%),less sensitive to desiccation,and germinated faster.Q.sichourensis occurs in regions with a distinct 5-6 month dry season.Habitat degradation is largely responsible for the rareness of Quercus sichorensis,but desiccation sensitivity of the acorns may also limit the regeneration of the species and potentially lead to its continued rareness.As a species with extremely small populations(PSESP),Q.sichourensis is facing high risk of extinction and should be defined as a Critically Endangered species in the global IUCN Red List.

Response of Chinese Wampee Axes and Maize Embryos to Dehydration at Different Rates

Survival of wampee （Clausena lansium Skeels） axes and maize （Zea mays L.） embryos decreased with rapid and slow dehydration. Damage of wampee axes by rapid dehydration was much less than by slow dehydration, and that was contrary to maize embryos. The malondialdehyde contents of wampee axes and maize embryos rapidly increased with dehydration, those of wampee axes were lower during rapid dehydration than during slow dehydration, and those of maize embryos were higher during rapid dehydration than during slow dehydration. Activities of superoxide dismutase （SOD）, ascorbate peroxidase （APX） and catalase （CAT） of wampee axes markedly increased during the early phase of dehydration, and then rapidly decreased, and those of rapidly dehydrated axes were higher than those of slow dehydrated axes when they were dehydrated to low water contents. Activities of SOD and APX of maize embryos notable decreased with dehydration. There were higher SOD activities and lower APX activities of slowly dehydrated maize embryos compared with rapidly dehydrated maize embryos. CAT activities of maize embryos markedly increased during the early phase of dehydration, and then decreased, and those of slowly dehydrated embryos were higher than those of rapidly dehydrated embryos during the late phase of dehydration.