Effects Of Temperature And Solar Radiation On The Growth And Nitrate Reductase Activity Of Ulva Prolifera

This paper studies the growth of Ulva prolifera, which is the chief criminals of green tide in the Yellow Sea in recent years, its’ nitrate reductase activity (NRA) and the relation between the growth of Ulva prolifera and NRA with enough nutrients under different temperatures and light intensities. And combining intracellular nitrate, intracellular nitrite, POC/PON ratio and silver nitrate concentration, we preliminarily analyzed the process of nitrate absorption and assimilation in order to discuss the internal mechanism of Ulva prolifera under different temperatures and light intensities. And the conclusions are summarized as follows:(1)This article determined the experimental conditions of the vitro method in NRA of Ulva prolifera cell, from the aspects of the optimum homogenized time, the constant velocity time, Km-NO3、Km-NADH and PMS, and the methods of intracellular nitrate through salicylic colorimetric. The results showed that the optimum homogenized time is 6min, the constant velocity time is 30min, the concentrations of KNO3 and NADH is 10mmol/L and 0.36mmol/L and the volume of PMS is 50μL. According to salicylic colorimetric method in measuring nitrate concentrations of Ulva prolifera, the optimum amount of salicylic acid-sulfuric acid solution (reagent) is 0.4mL.(2)Ulva prolifera can grow under five given temperatures, and quickly enter the growth stage, indicating that Ulva prolifera can quickly adapt to changes in ambient temperature. The growth conditions of Ulva prolifera characterized by wet weight and the average daily relative growth rate show that the optimum temperature for Ulva prolifera is 15℃. During culture period, NRA of Ulva prolifera at 10～20℃shows a trend of increasing firstly and then decreasing, but at higher temperatures(25℃and 30℃), NRA of Ulva prolifera shows a trend of decreasing in the early culture period. Under different temperature, the changs of Ulva prolifera NRA with time resulting in the changs of Ulva prolifera POC/PON:they show a trend of increasing firstly and then decreasing at lower temperatures, however, they show a trend of increasing firstly, decreasing and then increasing at higher temperatures. Intracellular contents of nitrite and nitrate are positively correlated with the NRA under different temperature. The order of NRAmax under five temperature is 15℃> 10℃>20℃>25℃≥30℃, the average of NRAmax under five temperature is 10℃≈15℃>20℃>25℃≥30℃, this is consistent with the growth of Ulva prolifera under different temperature. And the average of NRAmax are positively correlated with the daily relative growth rate, indicating that the growth conditions of Ulva prolifera can be regulated by temperature through regulating NRA.(3)When light intensity is 75～150 W·m-2, Ulva prolifera can grow normally, and when light intensity is 0‖22.5 W·m-2, Ulva prolifera grows little. In addition to O W·m-2, NRA of the rest groups shows a trend of increasing to a maximum firstly and then decreasing. For higher light intensity groups (150 W·m-2 and 112.5 W·m-2), Ulva prolifera NRA is lower overall. And with higher photosynthetic rates, the POC/PON is higher. However, for groups of lower light intensity (75、22.5 and 0 W·m-2), Ulva prolifera NRA is higher, but the light is limited, so POC/PON shows a little change. When light intensities is 22.5-150 W·m-2, intracellular contents of nitrite and nitrate are positively correlated with the NRA. The order of NRAmax under five light intensities is 75 W·m-2>22.5 W·m-2>150 W·m-2>112.5 W·m-2>0 W·m-2, the average of NRAmax is OW W·m-2≈22.5 W·m-2>75 W·m-2>150W W·m-2>112.5 W·m-2,this is not consistent with the growth of Ulva prolifera under different intensities, indicating that though light intensities can influence NRA, it can’t completely reflect the impact of light on internal mechanism of the Ulva prolifera growth.