3.1 Photosynthesis parameters
Under the treatments of Mt200 and Mt500,
there was no significant change of Fv/Fm compared with the control group
(Fig.1A). However, the value decreased significantly
under Pal addition. When the alga
was incubated with Pal200 and Pal500 for
72 h, the Fv/Fm data decreased from 0.6 to 0.5 (Fig. 1A).
The rETRmax did
not vary significantly upon Mt addition (Fig. 1B), although it increased
at 24h and decreased afterwards. After 24h, the rETRmaxunder Mt500 reached were 128.5 μmol electrons
m-2s-1 and remained higher than the
control group. In contrast, Pal addition dramatically reduced the
rETRmax values from about 105 to 62.9
μmol electrons
m-2s-1 at Pal200 and
56.7 μmol electrons m-2s-1 at
Pal500.
3.2 P uptake, cell number andCO2emission rate
When P supply was 3.15 mg/L, the P uptake declined from 3.0 to 2.8 mg/L
at Pal500 (Fig. 2A). When the P concentration in the
medium was 31.5 mg/L, the P uptake increased significantly under Pal
addition. However, the increase of P uptake was much lower under Mt
addition (Fig. 2A).
As
for the growth of C. reinhardtii , Mt and Pal had contrasting
effects. Mt200 and Mt500 respectively
increased the cell number from 27.4 to 28.6 and
29.9*107 ml-1 (Fig. 2B). However,
the number of cells significantly
decreased to 26.1 and 21.0*107 ml-1treated by Pal200 and Pal500,
respectively
At Mt200, the respiration showed no evident fluctuation.
When Mt was elevated to 500 mg/L, the CO2 emission rate
slightly decreased from 35.0 to 32.3 mg C 10-10 cells
h-1 (Fig. 2C). Nevertheless, the CO2emission rate showed a persistent increasing trend from
Pal0 to Pal500, reaching 46.0 mg C
10-10 cells h-1.