Influence of nitrogen and phosphorus ratios on P-32 uptake and growth in
diatom; Chaetoceros gracilis and Skeletonema costatum
ผลกระทบจากการผันแปรอัตราส่วนไนโตรเจนและฟอสฟอรัสต่อการดูดซึมฟอสฟอรัส-32 และต่อการเจริญเติบโตของไดอะตอม : Chaetoceros gracilis และ Skeletonema costatum
Pikul Wanichapichart, Asst. Prof., D. of Physics, F. of Sci., PSU.
Anun Santa-amorntad, D. of Physics, F. of Sci., PSU.
Tida Pechmanee, National Institute of Coastal Aquaculture, Songkhla
Corresponding e-mail : vpikul@ratree.psu.ac.th
Grant : Government Budget 1995-1996
Published : Songklanakarin J Sci Technol 2000, 22(3) : 321-327
Key words : phosphate uptake, radioisotope counts, N : P ratio, growth, diatom
An artificial sea water (ASW) was prepared with 3 levels of ammonium for nitrogen (N) source,
1 mM, 20 mM and 40 mM, and 5 levels of phosphate for phosphorus (P) source, 1 mM, 2 mM, 5 mM, 10 mM and 20 mM. Phosphate uptake into Chaetoceros gracilis and Skeletonema costatum was studied
by means of P-32 radioisotope counts. There was an interaction between ammonium and phosphate (P<0.05) for both diatoms. Under N limitation, an increase in external phosphate inhibited phosphate uptake for C. gracilis, but showed no effect for S. costatum. On the contrary, under P-limitation an increase in ammonium level enhanced phosphate uptake (P<0.01) in both diatoms. This enhancing effect was more pronounced when the ammonium level in ASW was 40 mM. Cells cultured in 2 P
levels; 1 mM and 10 mM and the same N levels as above, showed consistency in P-32 studies; that is, a greater ammonium level in the ASW enhanced cell growth. It was concluded that the N : P ratio of 40 : 1 is suitable for culturing C. gracilis. Possible N : P ratios for culturing S. costatum were 40 : 1
and 20 : 1, but the latter provided a higher survival rate.
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