| 摘要: |
| 将细基江蓠繁枝变型在铁限制条件下连续培养60天，分析海藻体内铁、色素、各种元素(N、P、C等)及总氨基酸水平的变化特征、铁限制对细基江蓠繁枝变型光反应系统的影响以及铁限制的细基江蓠繁枝变型对N、P和Fe3+的吸收动力学特征。结果表明，在铁限制培养60天过程中(海水中铁的总浓度为451nmol/L)，细基江蓠组织中铁的含量和色素水平均随着铁限制时间的延长极显著地呈现指数下降。组织铁含量仅为对照组的5.26%，叶绿素和藻红素含量分别为对照组的7.9%和33.8%。在铁限制培养过程中，组织中的N:P比由起始的29.53降低到23.68，而C:N比值几乎保持恒定。比生长率与组织中铁含量呈显著的正相关，铁限制使完整组织低温下的荧光发射强度受到不同程度的影响，荧光发射峰位蓝移，光系统I与光系统II的荧光发射强度之比PSI:PSII降低。在适度铁限制条件下(铁限制培养30天)，细基江蓠对Fe3+的还原和吸收能力都明显增强，铁限制海藻铁吸收速率的大小与铁限制的培养过程中以及铁吸收实验过程中介质的氮源种类有关，即在以NO3--N为惟一氮源进行铁限制培养后，在以NH4+-N为氮源的介质中铁的吸收速率远大于在以NO3--N为氮源的介质中铁的吸收速率。铁限制在不同程度上影响了细基江蓠对氯、磷的吸收能力，尤其对NO3--N的吸收影响较大，其最大吸收速率(Vmax)降低为对照组的33.4% 。 |
| 关键词: 细基江蓠繁枝变型，铁限制，生理生态学反应 |
| DOI： |
| 分类号: |
| 基金项目:国家重点基础研究发展规划项目，G1999012011号；国家杰出青年科学基金资助项目，397250239号；福建省青年科技人才创新项目，2001J049号。 |
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| PHYSIOLOGICAL AND ECOLOGICAL RESPONSE OF GRACILARIA TENUISTIPITATA VAR.LIUI TO IRON STRESS |
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LIU Jing-Wen1,2, DONG Shuang-Lin3, FENG Li-Ji4
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1.Aquaculture Laboratory, Ocean University of China;2.College of Bio-engineering, Jimei University;3.Aquaculture Research Laboratory, Ocean University of China;4.Laboratory of Photosynthesis and Environmental Molecular Physiology, Institute of Botany, Chinese Academy of Sciences
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| Abstract: |
| The total nitrogen(TN)，total carbon(TC)，total phosphorus(TP)(% DW)，pigment，total amino acid and Fe in tissues of Gracilaria tenuistipitata var.liui were measured during a 60-day period in Fe-stressed condition．Iron content decreased exponentially during Fe-stress to only 5.26% of its original level．TN，TC，TP also decreased，especially the content of TC．The C:N ratio remained constant while N:Fe and C:Fe ratios increased．Total amino acid content decreased after 60 days to 83.7% of its original level．Chl and phycoerythrin(PE)content both declined with decreasing tissue iron content．The absorption spectrum of Chl and PE both reduced，while Fe-stressed cultures induced a blue shift at the fluorescence emission peak(at 436nm and 560nm)and also caused a decreased fluorescence intensity ratio of PSI：PSII．These results suggested that during the early period of Fe-stressed cultures，PSI may be more sensitive to iron stress than PSII．All the biological uptake kinetics parameters(Vmax，Ks and a)of NO3-，NH4+and PO43-by G.tenuistipitata var.liui decreased under Fe-stressed condition(especially NO3-，P<0.01)．The effects of Fe-stress on nutrient uptake rates were in the order of NO3- > NH4+ > PO43-．The Fe3+ reduction was conducted using BPDS method and the 55Fe uptake rate for cultures grown on NO3- were measured after re-suspension in either N source NH4+ or NO3- (-Fe，+Fe/ NH4+； -Fe，+Fe/NO3-)．Compared with the control，Fe3+’s reduction after Fe-stressed culture for 30 days was faster and，after 60 days of Fe-stress，only a small reduction of Fe3+ was detectable．Enhanced 55Fe uptake developed under Fe-stress．During Fe-stress，the highest Vmax appeared in –Fe/ NH4+ 45.7pmol/(mg?h)and the lowest in +Fe/ NO3- 12.3pmol/(mg?h)．The requirement for N accelerates further Fe uptake．The growth rate of the algae continued to decline．After 40 days of iron deficiency no further growth was detectable．Chlorosis resulted at the end of the iron stress period．The lower growth rates，chlorosis and even death of the marcoalgae under iron stress were caused by reduced nitrogen utilization，pigment content and photosynthetic capacity． |
| Key words: Gracilaria tenuistipitata var.liui,Iron stress,Physiological and ecological response |
