Study On Absorption、Utilization And Transformation Of N Of Grateloupia Turuturu Yamada

Based on the large algae Grateloupia turuturu as the research object, this paperstudied the effects of the forms of nitrogen, nitrogen concentration, nitrogen limitationand different combined nitrogen ratio on the absorption of nitrogen, composition ofnitrogen pools and transforming rules of G. turuturu. The main aim of this paper wasto further explain the physiological processes of nitrogen metabolism in macroalgae,and provide theoretical basis for repairing marine environment and ecologicaldistribution of biology.1Effects of different nitrogen sources on nitrogen absorption of G. turuturu.The experiment studied the effects of different NH₄⁺-N and NO₃^--Nconcentration ratio on nitrogen absorption of G. turuturu. The results were as follows:NH₄⁺-N uptake rate of G. turuturu was independent of NO₃^--N concentrationsubstantially, the greatest value appeared at1h, which existed the same trend. Uptakerate of NH₄⁺-N increased with increasing NH₄⁺-N concentration. When NH₄⁺-Nconcentration reached300μmol·L^-1, the greatest value was3.1750-3.7007μmol·g^-1·h^-1. The uptake rate of NO₃^--N in G. turuturu was lower than that of NH₄⁺-N.The concentration of NH₄⁺-N affected the uptake of NO₃^--N in G. turuturusignificantly. When NH₄⁺-N：NO₃^--N equal200：200μmol·L^-1，maximum uptake rateof NO₃^--N appeared at3h. Negative value appeared when NH₄⁺-N：NO₃⁺-N equal200：200μmol·L^-1and300:300μmol·L^-1.2Effects of different nitrogen sources on growth and nitrogen pools of G.turuturu.The experiment studied the effects of different nitrogen forms （NH₄⁺-N andNO₃⁺-N） and different nitrogen proportion （with NH₄⁺-N: NO₃⁺-N at1/8、1/4、1/2、 1/1、2/1、4/1） on growth and nitrogen pools of G. turuturu. The results showed that:Different nitrogen forms:（1） growth:Compared with the NH₄⁺-N, NO₃⁺-N was more beneficial to the growth.Different nitrogen sources had greater effect on weight than length. Different NO₃⁺-Nconcentration had a significant impact on the specific growth rate of G. turuturu.（2） The percentage of nitrogen pools:The content of nitrogen pools of protein and amino acid were maximum amongnitrogen pools, which had basically reached99%. Proportion of nitrogen pools ofprotein decreased gradually while proportion of nitrogen pools of amino acidincreased with increasing nitrogen concentration. Phycoerythrobilin was more thanchlorophyll a, and nitrate content was much higher than ammonium content.（3） The nitrogen pools:The total nitrogen content of G. turuturu was affected by nitrogen concentration,but not by nitrogen form. NH₄⁺-N was more beneficial to synthesize protein thanNO₃⁺-N. Amino acid content increased with increasing nitrogen concentration.Compared with NH₄⁺-N, NO₃⁺-N was more beneficial to synthesize phycoerythrobilin.Two forms of nitrogen sources had no difference in the synthesis of chlorophyll a.The effect of different nitrogen concentration on chlorophyll a had the same trendwith that of phycoerythrobilin, but the former content was lower. There was nodifference between the effects of two forms nitrogen on ammonium pool basically,while the effect on ammonium pool was less than that of nitrate pool.Different nitrogen ratio:（1）Growth:There was no significant influence on specific growth rate of G. turuturu whenthe proportion of the two forms of nitrogen were changed under the condition that thetotal nitrogen concentration kept basically constant.（2） The percentage of nitrogen pools:The content of nitrogen pools of protein and amino acid were maximum, whichhad basically reached99%. Proportion of nitrogen pools of protein decreased gradually while proportion of nitrogen pools of amino acid increased with increasingNH₄⁺-N proportion. Nitrate pool content was the maximum among the rest nitrogenpools, which was higher than that of pigment pools and ammonium pool.Phycoerythrobilin was slightly higher than that of chlorophyll a.（3） The nitrogen pools:When NH₄⁺-N: NO₃⁺-N was in proportion of1:1, the content of total nitrogenand protein of G. turuturu reached the greatest value. To increase the proportion ofNH₄⁺-N, amino acid content increased gradually. When the NH₄⁺-N/NO₃⁺-N ratiowas4:1, amino acid content reached the maximum. The phycoerythrobilin andchlorophyll a had the same change trend, both reached the maximum when NH₄⁺-N/NO₃⁺-N ratio was2:1. When the NH₄⁺-N/NO₃⁺-N ratio was1:1, nitrate pool of G.turuturu reached the greatest value. The content of ammonium pool was far less thanthat of nitrate pool. When the NH₄⁺-N/NO₃⁺-N ratio was4:1, the content ofammonium pool reached the maximum.3Effect of recovery after nitrogen limitation on nitrogen absorption，growth andnitrogen pools of G. turuturu.This experiment studied that G. turuturu underwent nitrogen starvation for0d，3d，5d，7d，14d，21d，28d，then nitrogen source was recovered（NO₃^--N concentrationwas200μmol·L-1+NH₄⁺-N concentration was200μmol·L-1）lasting21d. During therecovery of nitrogen source of1h，3h，6h，9h，12h，24h，we studied the change ofNO₃^--N and NH₄⁺-N uptake rate and change regularity of growth and nitrogen poolsduring the whole experiment. The results showed that:（1） Uptake:NH₄⁺-N uptake rate of G. turuturu had the same change trend with time, themaximum value appeared at1h. NH₄⁺-N uptake rate of G. turuturu experiencing3-21days starvation were higher than that of starved0day, especially NH₄⁺-N uptakerate of the G. turuturu experiencing7days starvation reached2.5times that of starved0day. Effects of NO₃^--N uptake rate were different after different starvation days.NO₃^--N uptake rate of G. turuturu experiencing3-7days starvation exceed the G.turuturu of starved0day. G. turuturu had easier NH₄⁺-N uptake activity after starvation.（2）Growth:Specific growth rate of G. turuturu experiencing5days starvation exhibited anincrease. When the G. turuturu suffering from3-14days starvation was recovered bynitrogen sources for5days, the specific growth rate reached maximum. When the G.turuturu suffering28days starvation was recovered by nitrogen sources for3days,the growth rate was still negative.（3）The percentage of nitrogen pools:When nitrogen source was limited, amino acid was consumed firstly, thenphycoerythrobilin and chlorophyll a decreased. Consumption rate of nitrogen pool ofprotein was less than the other nitrogen pools, which was the most stable nitrogenpool. When the G. turuturu suffering7days starvation was recovered by nitrogensources for5days, the percentage of amino acid exceeded normal level.（4） The nitrogen pools:Total nitrogen content of G. turuturu increased with nitrogen recovery firstly.When the G. turuturu suffering7days starvation was recovered by nitrogen sourcesfor5days, total nitrogen content exceeded original level. The change of protein wasstable until G. turuturu was starved from21-28days, which decreased obviously.Nitrogen limitation and recovery affected content of amino acid obviously. When theG. turuturu suffering7days starvation was recovered by nitrogen sources for3-5days,content of amino acid was higher than original content. Phycoerythrobilin wasaffected by nitrogen obviously and remained the same decline rate basically duringnitrogen limitation period. The change of chlorophyll a had the same trend with thatof phycoerythrobilin, but the former content was lower. When the G. turuturusuffering14-21days starvation was recovered by nitrogen sources for5days, nitratecontent of the G. turuturu exceeded normal level. Ammonium pool was the minimumnitrogen pools, when the G. turuturu suffering21days starvation was recovered bynitrogen, ammonium content was higher than original level.