Comparative Studies On Inorganic Carbon Acquisition By Geneophyte And Juvenile Sporophyte Of L.japonicaXL.longissima

The ways of inorganic carbon acquisition by juvenile sporophyte and gametophyte of L. japonica XL. 1ongissim~? different generation of its life history have been investigated, including the effect of inorganic carbon on their photosynthesis by means of pH梔rift technique and inhibitors as acetazolamide (Az) .~ 4?4?梥othiocyanatosilbene2, 2梔isulfonic acid (DIDSY. 4梐cetamido??梚sothiocyano?, 2?梥tibene梔isulfonate (SITS) 0The results reveal: juvenile sporophyte has rather higher ability of utilizing inorganic carbon than that of gametophyte, but both of them don抰 change alkalinity of seawater in the course of light梔epended carbon acquisition in the closed system, so change of pH can be used revealing variation of inorganic carbon directly if the change of temperature and saltlity is neglectable0 The inhibitor of external carbonic anhydrase (CA)棗Az can strongly inhibit carbon uptake by juvenile sporophyte of L. japonicaXL. ]ongissima. External CA dehydrating HC03 to free CO2 is the main pathway of inorganic carbon utilization by juvenile sporophyte, accounting for 75 percentage of total inorganic carbon acquired in natural seawater (pH 8. 1?. 3) and 100 percentage when the 2 concentration of free CO2 is near to zero (pH 9. 1). Only 25 percentage comes from free CO2 in natural seawater (pH 8. 1?. 3). No direct uptake of HCO3Thas been found. Contrast to juvenile sporophyte, gametophyte can use only free CO2 which doesn?t posses external carbonic anhydrase. The rate of inorganic carbon acquisition by both juvenile sporophyte and gametophyte would increase with the increase of the concentration of inorganic carbon: juvenile sporophyte gains its maximum rate of carbon acquisition at the concentration of 3. 5mmol/L; female and male garnetophyte can increase their rate of carbon acquisition 2. 9 and 2. 5 times under condition of CO2 saturation than that in natural seawater, which indicates the concentration of inorganic carbon in natural seawater can抰 meet the need of optimal growth of L. japonica X L. longissima. When pH changes between 8. 10?. 30, pH doesn?t affect the rate of carbon utilization by gametophyte. But higher than that, the rate of carbon utilization by gametophyte would decrease with the increase of pH. Optimizing culture condition of gametophyte should abide by such principle as maintaining lower pH and higher CO2 concentration.