光照强度和氮营养盐浓度对龙须菜生理代谢的影响

The effects of light intensity and nitrogen on the physiology of the red macroalgae Gracilaria lemaneiformis

以龙须菜(Gracilaria lemaneiformis)为材料,以无机氮(NO_3^-︰NH_4^+=2︰1)为氮源配制人工海水,将在低光低氮(L-N-)条件下培养的龙须菜部分给予高光照处理(L+N-),同时另一部分在给予高光照的同时给予更充足的氮源(L+N+),通过测定3种不同处理条件下物质积累、光合色素以及碳氮代谢中的关键酶等多种生理指标,探讨光照强弱与氮源多寡对龙须菜生理代谢的影响。结果表明,在低氮培养时,高光可使藻体可溶性蛋白、含水率、藻红蛋白和叶绿素a的含量下降,而可溶性糖含量上升13.67%;高光培养时,高氮使可溶性蛋白、含水率、藻红蛋白和叶绿素a的含量上升,而可溶性糖含量下降16.3%;相对于低光低氮(L-N-),高光高氮(L+N+)条件培养使藻体中可溶性蛋白和藻红蛋白含量增加,其含水率、叶绿素a和可溶性糖含量并无显著性差异(P>0.05)。从上述结果可以看出,补充氮源能够在一定程度上消除高光照对藻体产生的影响,保证藻体基本生理状态不发生变化的情况下积累蛋白(氮源)。同时补充氮源使得谷氨酰胺合成酶(GS)和天庚酮糖-1,7-二磷酸酶(SBPase)的表达均下调,也反映了光合作用所产生的三碳化合物在氮源充足的条件下主要流向了氮循环。而高光照并未对碳氮代谢关键酶的表达产生影响,可能通过直接破坏叶绿素a而影响藻体的光合作用。

Gracilaria lemaneiformis, which has rich agar, comprises the third-largest seaweed cultivation industry group in China, after Laminaria and Laver. As light intensity gradually strengthens in summer, G lemaneiformis in the surface layer of cultivation areas becomes green, or even white, yet the internal part remains dark red. G. lemaneiformis was cultured in artificial seawater with inorganic nitrogen （NO3- ： NH4＋ =2 ： 1）. Three conditions： low light low nitrogen （L-N-）, high light low nitrogen （L＋N-） and high light high nitrogen （L＋N＋） were settled in this study. The impact of light intensity and nitrogen on physiology and metabolism of G lemaneiformis was studied through measured matter accumulation, photosynthetic pigment, key enzyme during carbon and nitrogen metabolism under three conditions. The results showed that, compared with the L-N- group, the L＋N- group showed decrease of soluble protein, water, phycoerythrin and chlorophyll-a, but the amount of soluble sugar in- creased 13.67%. Compared with the L＋N- group, the L＋N＋ group showed the increase of soluble protein, water, phycoerythrin and chlorophyll-a, but the amount of soluble sugar decreased 16.3%. Compared with the L＋N＋ group, the L-N- group showed the increase of soluble protein, phycoerythrin, but there is no significant difference in its amount of water content, chlorophyll-a and soluble sugar. These results confirm that a sufficient amount of nitrogen can weaken the negative effects of high-intensity light on a red macroalgae.