2010年冬季寒冷天气对闽江口3种红树植物幼苗的影响

2010年10月8日-2011年2月26日,跟踪监测了闽江河口互花米草治理试验区人工种植的秋茄(Kandelia candel)、无瓣海桑(Sonneratia apetala)和拉关木(Leguncalaria racemosa)1年生幼苗叶片相溶性物质含量以及活性氧代谢等生理生化指标.结果表明:可溶性糖和脯氨酸含量均随气温的逐步降低而增加,秋茄可溶性糖含量最高,拉关木脯氨酸含量最高；整个监测期无瓣海桑和拉关木幼苗叶片超氧阴离子(O2)产生速率显著高于秋茄(P＜0.01),而超氧化物歧化酶(SOD)和过氧化物酶(POD)活性显著低于秋茄(P＜0.01)；3种植物叶片丙二醛(MDA)含量及电解质渗透率均随着气温的降低而增加,其中无瓣海桑和拉关木MDA含量及电解质渗透率与日最低气温为显著和极显著的负相关关系.2010年冬季持续寒冷天气对闽江河口湿地1年生土著种秋茄幼苗无破坏,对引进种无瓣海桑和拉关木造成了严重的低温胁迫并使幼苗基本全部死亡.

Effects of cold weather on seedlings of three mangrove species planted in the Min River estuary during the 2010 winter

As part of a restoration project to establish new communities on estuarine wetland dominated by the invasive species Spartina alterniflora, we investigated the potential to establish mangrove species after S. alterniflora removal. In order to achieve good establishment it is essential that the newly planted seedlings can survive their first winter where they may be susceptible to cold temperatures. To investigate this we carried out a comparative study of the cold tolerance response of one-year old seedlings of three mangrove species planed in salt marsh cleared of S. alterniflora in the Min River estuary, Southeast China. The species planted included a native species (Kandelia candel) and two alien ones, Leguncalaria racemosa from Mexico and Sonneratia apetala from Bangla Desh. We measured a range of physiological attributes in the leaves of seedlings of the three species over winter (early-October 2010 to late-February 2011), the measurements included: soluble sugar and free proline concentrations, SOD,POD and CAT activities, O₂^- generation rate, MDA and relative electrical conductivity.Over the entire monitoring period, the leaf soluble sugar concentrations of all three mangrove species seedlings increased, then decreased; K.candel had the greatest concentrations and L. racemosa the least. The rate of O₂^- generation from the leaves of K. candel showed a similar response to the sugar concentrations; S. apetala and L. racemosa on the other hand exhibited the same initial increase but the high rates were maintained at significantly greater rates than K. candel (P<0.01). However, SOD, POD and CAT activities showed the opposite response (P<0.01), with POD and CAT activities in the leaves of L. racemosa and S. apetala seedlings declining significantly in late winter. Free proline concentrations of L. racemosa were higher than that of K. candel and S. apetala; all increased as air temperature reduced. The contents of MDA and relative electrical conductivity of all three plant species increased as minimum daily air temperature decreased. L. racemosa and S. apetala seedlings had significant higher level of MDA than K. candel seedlings (P<0.01), but there was no obvious difference between L. racemosa and S. apetala seedlings(P>0.05). The relative electrical conductivity of K. candel seedlings was significantly lower than that of L. racemosa and S. apetala seedlings(P<0.01). K. candel seedlings did not show symptoms characteristic of freezing injury during the winter of 2010/11 with damage/death caused mainly by biotic factors (ducks and other water fowl). However, serious damage was detected in seedlings of both alien species (L. racemosa and S. apetala seedlings), indeed all seedlings of these species died in late February 2011. In short, under current climatic conditions the native species K. candel has a competitive advantage in that its seedlings can persist over winter in the Min River estuary and may be suitable for restoration of salt marsh after Spartina alterniflora removal. The two alien species, L. racemosa and S. apetala, cannot colonize at the moment because they cannot survive over winter but may be able to suitable in the Min River estuary if older seedlings were transplanted which had been acclimatized to the colder condition.