| â… Effects of diel fluctuating temperature on germination, growth, biochemical composition, nutrient uptake and photosynthesis of several macroalgae1 Effects of circadian rhythms of fluctuating temperature on growth and biochemical composition of Ulva pertusaThe marcoalga Ulva pertusa was cultured under (20±2)℃, (20±4)℃, (20±6)℃, (20±8)℃and (20±10)℃circadian rhythms of fluctuating temperature conditions, and constant temperature of 20℃was used as the control. The growth rate of macroalga at (20±2)℃, (20±4)℃and (20±6)℃were significantly higher than that at constant temperature of 20℃, while growth rate at (20±8)℃and (20±10)℃were significantly lower than that at constant temperature of 20℃. The growth rate of macroalga was a quadratic function of the thermal amplitude. Such a growth model can be described by G=β0+β1(TA)+β2(TA)2 where G represents the relative growth rate, TA is thermal amplitude in degree Celsius,β0 is the intercept on the G axis, andβ1 andβ2 are the regression coefficients. The optimal thermal amplitude for the growth of thallus at mean temperature of 20℃was estimated to be±3.69℃. Analysis of biochemical composition at the final stages of thaulls growth revealed that diel fluctuating temperature caused various influences (P<0.05).The content of chlorophyll, protein and total solute carbohydrate at (20±2)℃ and (20±4)℃were slightly higher than those at constant temperature of 20℃, however no statistically significant differences were found among them (P>0.05). While osmolytes (total solute carbohydrate and free proline) at (20±10)℃were significantly higher than that at 20℃(P<0.05). Therefore, more chlorophyll and carbohydrate production might account for the enhancement in the growth of macroalga at the diel fluctuating temperatures in the present study.2 Effects of diel fluctuating temperature on germination and early growth of Grateloupia turuturuThe marcoalga Grateloupia turuturu was cultured under (15±3)℃, (20±3)℃and (25±3)℃diel fluctuating temperature conditions, and constant temperatures of 15℃, 20℃and 25℃were used as the controls, respectively. The spores germination, early growth were observed in this experiment. The type of G. turutur germination belongs to Nemalion type. There was no significant difference in the spores'size between 2 cells stage and 8 cells stage after spores attached(P>0.05). The germination rate of macroalga at (15±3)℃, (20±3)℃were significantly higher than that at constant temperature of 15℃and 20℃respectively(P<0.05).3 Effects of diel fluctuating temperature on growth and nutrient uptake of Gracilaria vermiculophyllaThe marcoalga Gracilaria vermiculophylla was cultured under (15±3)℃, (20±3)℃and (25±3)℃diel fluctuating temperature conditions, and constant temperatures of 15℃, 20℃and 25℃were used as the controls, respectively. The specific growth rate, nutrient uptake and NO3--N removal were determined in this experiment. The result showed that diel fluctuating temperature can enhance the growth rate, nutrient uptake and NO3--N removal of Gracilaria vermiculophylla than that under the constant temperature(P<0.05).4 Effects of high day temperature and low night temperature on nutrient uptake and photosynthesis of Gracilaria vermiculophyllaThe marcoalga Gracilaria vermiculophylla was cultured under (15±3)℃, (20±3)℃and (25±3)℃diel fluctuating temperature conditions, and constant temperatures of 15℃, 20℃and 25℃were used as the controls, respectively. The specific growth rate, nutrient uptake and photosynthetic rate and respiratory rate were determined in this experiment. The results showed that high day temperature and low night temperature play the different role during the temperature fluctuation. High day temperature not only can accelerate the NO3--N removal of Gracilaria vermiculophylla but also can enhance the net photosynthetic rate(P<0.05), and low night temperature can inhibit the respiration compare with the macroalga under the constant temperature(P<0.05).â…¡Effects of periodical emersion on growth and biochemical composition of Ulva pertusaThe influence of emersion on the growth and biochemical composition were investigated with Ulva pertusa thalli grown under laboratory conditions with periodical emersion and submersion treatments. The accumulated biomass and daily increments of thalli with 0.5h, 1.0h and 2.0h periodical emersion every 12h were faster than those without emersion, while growth rate with 5h periodical emersion every 12h was significantly lower than that without emersion. Analysis of biochemical composition at the final stages of thalli growth revealed that periodical emersion caused various influences (P<0.05). The final content of total solute carbohydrate with 0.5h, 1.0h and 2.0h periodical emersion every 12h was significantly higher than that without emersion, while osmolyte with 5h periodical emersion every 12h was significantly higher than that without emersion (P<0.05). Therefore, mild periodical emersion could enhance the growth of Ulva pertusa, while severe periodical emersion could inhibit the growth of Ulva pertusa.â…¢Effects of circadian rhythms of fluctuating salinity on growth and biochemical composition of Ulva pertusaThe marcoalga Ulva Pertusa was cultured under 30±3, 30±6, 30±9, 30±12 and 30±15 circadian rhythms of fluctuating salinity conditions, and constant salinity of 30 was used as the control. The growth rate of macroalga at fluctuating salinity conditions were significantly lower than that at constant salinity of 30, while the SGR of U. pertusa at different fluctuating salinity conditions were all kept at least 12%. Analysis of biochemical composition at the final stages of thaulls growth revealed that diel fluctuating salinity caused various influences (P<0.05). The content of chlorophyll a and chlorophyll b at fluctuating salinity conditions were slightly lower than those at constant salinity of 30, however no statistically significant differences were found among them (P>0.05). The content of protein and total solute carbohydrate at fluctuating salinity conditions were significantly higher than those at constant salinity of 30 (P<0.05), and there was a trend that the content of proline increased with the increase of amplitude of fluctuating salinity, while the content of proline at mild change of salinity (30±3) was significantly lower than that at constant salinity (P<0.05).â…£Effects of light on growth and biochemical composition of Ulva pertusa1. Effects of light intensity on growth and chemical constituents of Ulva pertusa The influence of light on the growth and chemical constituents were investigated with Ulva pertusa thalli growth under laboratory conditions with different light intensity. There was a trend that the growth rate of macroalga decreased with the decrease of light intensity under 250μmol/(m2·s), but when light intensity exceed 250μmol/(m2·s), the growth rate of macroalga also decrased with the increase of light intensity(P<0.05). Analysis of chemical constituents at the final stages of thalli growth revealed that different light intensity caused various influences (P<0.05). There was a trend that the content of chlorophyll a and chlorophyll b decreased with the increase of light intensity. The synthesization of protein was accelerated within the lower light intensity. While osmolytes (free proline) at 350μmol/(m2·s) and 400μmol/(m2·s) was significantly higher than other treatments (P<0.05). The content of nitrogen increased with the increase of light intensity from 50 to 300μmol/(m2·s), while the content of nitrogen decreased with the increase of light intensity when light intensity exceed 350μmol/(m2·s), the content of carbon has the same trend with the trend of nitrogen, and the content of hydrogen increased with the increase of light intensity in this study. 2. Effects of circadian rhythms of fluctuating light intensity on growth and biochemical composition of Ulva pertusaThe marcoalga Ulva pertusa was cultured under 200±40μmol/(m2·s), 200±80μmol/(m2·s), 200±120μmol/(m2·s), 200±160μmol/(m2·s) and 200±180μmol/(m2·s) circadian rhythms of fluctuating light intensity conditions, and constant light intensity of 200μmol/(m2·s) was used as the control in experiment 1. The growth rate of macroalga at 200±40μmol/(m2·s), 200±80μmol/(m2·s) and 200±120μmol/(m2·s) were significantly higher than that at constant light intensity of 200μmol/(m2·s) (P<0.05). Analysis of biochemical composition at the final stages of thaulls growth revealed that diel fluctuating light intensity caused various influences (P<0.05).While osmolytes (free proline) at constant light intensity of 200μmol/(m2·s) was significantly higher than those at other treatment (P<0.05).The marcoalga Ulva pertusa was cultured under 250±50μmol/(m2·s), 250±100μmol/(m2·s) and 250±150μmol/(m2·s) circadian rhythms of fluctuating light intensity conditions, and constant light intensity of 250μmol/(m2·s) was used as the control in experiment 2. The growth rate of macroalga at 250±50μmol/(m2·s), 250±100μmol/(m2·s) and 250±150μmol/(m2·s) were significantly higher than that at constant light intensity of 250μmol/(m2·s) (P<0.05). Analysis of biochemical composition at the final stages of thaulls growth revealed that diel fluctuating light intensity caused various influences (P<0.05). .The content of chlorophyll-a at 250±50μmol/(m2·s) and 250±100μmol/(m2·s) was significantly higher than that at constant light intensity of 250μmol/(m2·s) (P<0.05), the content of protein and total solute carbohydrate at 250±50μmol/(m2·s) circadian rhythms of fluctuating light intensity conditions were significantly higher than those at constant temperature of 250μmol/(m2·s), osmolytes (free proline) at constant light intensity of 250μmol/(m2·s) was significantly higher than those at other treatment (P<0.05).3. Effects of light-dark cycles on growth and biochemical composition of Ulva pertusa under different light intensity conditionsThe marcoalga Ulva pertusa was cultured under L:D=24:0,20:4,16:8,14:10,13:11,12:12,11:13,10:14,8:16,4:20 and 0:24 light-dark cycles under 110μmol/(m2·s) and 240μmol/(m2·s) light intensity conditions, respectively. There was a trend that the growth rates of macroalga decreased with the increase of light period. The synthesization of protein and total carbohydrate were accelerated within the shorter light period and longer light period. And free proline was increased with the increase of light period.4. Effects of light spectra and fluctuating of light spectra on growth and biochemical composition of Ulva pertusaThe marcoalga Ulva pertusa was cultured under White, Yellow, Green, Red, Blue, Yellow: Green=6:6h, Yellow: Red=6:6h, Green: Red=6:6h, Green: Blue=6:6h, Red: Blue=6:6h, Blue: Yellow=6:6h light spectra conditions. The growth rate of macroalga at Red light and Green light were significantly lower than that at White light. Emerson enhancement effect occurred at Green: Red=6:6h treatment. The content of chlorophyll, protein and total solute carbohydrate was accelerated by the fluctuating of light spectra. The content of praline was alleviated by the fluctuating of light spectra... |
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