Effects Of Environmental Factors On Growth And Development Of Neopyropia Kinositae

Laver is one of the main large-scale economic seaweeds in China,with high nutritional and ecological value.In the context of global climate change and ecological civilization construction,the seaweed industry faces many challenges.For example,global warming has led to frequent disease outbreaks in traditional seaweed production areas,causing the seaweed cultivation area to gradually shift northward.Under the guidance of ecological priority and green development concepts,the trend of seaweed cultivation moving from near-shore to offshore is becoming increasingly apparent.Therefore,developing new seaweed varieties suitable for northern environments and with offshore cultivation potential is of great significance for the sustainable development of the seaweed industry.Neopyropia kinositae,recently discovered in the northern Yellow Sea of China,is an ideal candidate species for the development of northern and offshore seaweed cultivation industries.This paper evaluates the impact of key environmental factors on the growth and development of N.kinositae at different stages of its life history from growth,physiology,and biochemical perspectives,providing scientific basis and technical support for its seedling cultivation and industrial development.The main results are as follows:（1）Study on the effect of environmental factors on the growth and development of N.kinositae’s free-living conchocelis.Within the temperature range of 13-25℃,the relative growth rate（RGR）,maximum photosynthetic efficiency of photosystem II（F_v/F_m）,photosynthetic pigment content,soluble protein content,RuBisCo activity,nitrate reductase（NR）activity,and malate dehydrogenase（MDH）activity all showed a trend of first increasing and then decreasing,reaching their maximum values at 19℃.The content of hydrogen peroxide（H₂O₂）increased with increasing temperature,while the activity of superoxide dismutase（SOD）and the content of reduced glutathione（GSH）were highest at 25℃,and catalase（CAT）activity showed a decreasing trend with increasing temperature.The content of ascorbic acid（AsA）reached its maximum value at 22℃.Under the conditions of 16-22℃,the RGR and adenosine triphosphate（ATP）content of free-living conchocelis showed no significant difference.In the light intensity range of 20-180μmol photons/（m²·s）,the RGR,F_v/F_m,chlorophyll a content,carotenoid content,ATP content,RuBisCo activity,NR activity,phosphofructokinase（PFK）activity,and MDH activity generally decreased with increasing light intensity,remaining at relatively high levels when the light intensity was between 20-60μmol photons/（m²·s）.With increasing light intensity,the contents of H2O2,SOD activity,CAT activity,glutathione reductase（GR）activity,AsA content,and GSH content generally increased.The RGR,F_v/F_m,phycobiliprotein content,soluble protein content,ATP content,RuBisCo activity,NR activity,and MDH activity of free-living conchocelis reached their maximum values under nitrogen concentrations of 3 mg/L and phosphorus concentrations of 0.3 mg/L.In summary,the growth rate,photosynthetic efficiency,photosynthetic pigment content,and key metabolic enzyme activities of N.kinositae’s free-living conchocelis.（2）The study on the effect of environmental factors on the growth and development of N.kinositae conchocelis.Within the temperature range of 15-22.5℃,the germination rate of N.kinositae conchocelis showed a trend of increasing first and then decreasing with the increase of temperature,reaching its maximum at 17.5℃;RGR gradually increased with the rise of temperature,reaching its maximum at 22.5℃.Within the light intensity range of 10-100μmol photons/（m²·s）,the germination rate and RGR both increased with the increase of light intensity,reaching their maximum at 100μmol photons/（m²·s）.Based on these findings,the suitable conditions for Neopyropia kinositae conchocelis inoculation are 17.5℃and 100μmol photons/（m²·s）;the suitable growth conditions for N.kinositae conchocelis are 22.5℃and 100μmol photons/（m²·s）.In the study of the effects of temperature（17-26℃）,light intensity（10-100μmol photons/（m²·s））,photoperiod（8L:16D-12L:12D）,nitrogen and phosphorus concentrations（N:0.1-10mg/L,P:0.01-1mg/L）,and iron concentration（0.001mg/L-0.8mg/L）on the development of N.kinositae conchocelis,the sporangial branch formation rate formed under various conditions was found to change as follows:it increased first and then decreased with the increase of temperature,reaching its highest at 20℃;it increased first and then decreased with the increase of light intensity,reaching its highest at 30μmol photons/（m²·s）;it increased with the decrease of light duration,reaching its highest at 8L:16D;it increased with the increase of nitrogen and phosphorus concentrations,reaching its highest at nitrogen concentration of 10mg/L and phosphorus concentration of 1mg/L;it gradually increased with the increase of iron concentration,reaching its highest at 0.8mg/L.By comprehensively cultivating N.kinositae conchocelis under the above suitable development conditions,the proportion of sporangial branches formed in vegetative filaments can reach about 50%within one month.In the temperature range of 6-20℃,the discharge amount of N.kinositae conchospores showed a trend of increasing first and then decreasing with the increase of temperature,with the suitable temperature range for discharge being 7-12℃and the peak discharge amount of shell spores reaching 100,000-400,000 spores/shell/day.Under the conditions of temperature（9-21℃）,light intensity（10-130μmol photons/（m²·s））,nitrogen and phosphorus concentrations（N:0.1-10mg/L,P:0.01-1mg/L）,and salinity（20-35）,the changes in the germination rate and RGR of N.kinositae conchospores were as follows:with the increase of temperature,the germination rate and RGR showed a trend of increasing first and then decreasing,reaching their highest at 17℃;with the increase of light intensity,the germination rate and RGR showed a trend of increasing first and then decreasing,reaching the highest germination rate at 70μmol photons/（m²·s）and the highest RGR at100μmol photons/（m²·s）;with the increase of nitrogen and phosphorus concentrations,the germination rate and RGR both showed a trend of increasing first and then decreasing,reaching the highest germination rate at nitrogen and phosphorus concentrations of 3mg/L and 0.3 mg/L,respectively,while the highest RGR was observed at nitrogen and phosphorus concentrations of 0.5 mg/L and 0.05 mg/L,respectively;salinity levels of 25-30 were favorable for the germination and growth of N.kinositae conchospores.（3）The influence of environmental factors on the growth of N.kinositae thallus was studied.The effects of temperature（7-16℃）,light intensity（30-200μmol photons/（m²·s））,and nitrogen and phosphorus concentrations（N:0.1-10 mg/L,P:0.01-1mg/L）on the growth of N.kinositae thallus were investigated.As the temperature increased,the RGR,F_v/F_m,apparent photosynthetic rate,initial slope,light compensation point,light saturation point,dark respiration rate,maximum net photosynthetic rate,and ATP content of N.kinositae thallus generally showed an increasing trend,reaching the highest value at 13℃.As the temperature increased,the H₂O₂ content of N.kinositae thallus gradually increased,and the activities of SOD and CAT were positively correlated with H₂O₂ content.With increasing light intensity,the F_v/F_m and initial slope of N.kinositae thallus showed a decreasing trend,while the half-saturation light intensity gradually increased.The activities of CAT and the content of AsA generally showed a decreasing trend,then an increasing trend.The soluble protein content,RuBisCo activity,and MDH activity all showed an increasing trend with increasing light intensity,reaching the highest value at 70μmol photons/（m²·s）.When the light intensity was higher than 70μmol photons/（m²·s）,the H₂O₂ content gradually increased.As nitrogen and phosphorus concentrations increased,the initial slope of N.kinositae thallus gradually increased,and the half-saturation light intensity gradually decreased.The content of photosynthetic pigments,RuBisCo activity,NR activity,and MDH activity all showed an increasing trend with increasing nitrogen and phosphorus concentrations,reaching the highest value when nitrogen and phosphorus concentrations were 3 mg/L and 0.3 mg/L,respectively.The soluble protein content,ATP content,and PFK activity increased with increasing nitrogen and phosphorus concentrations.As nitrogen and phosphorus concentrations increased,SOD activity,H₂O₂ content were significantly higher in the N:0.1 mg/L P:0.01 mg/L treatment group,and CAT activity and AsA content showed a similar trend.In summary,the suitable growth conditions for the thallus of N.kinositae are as follows:temperature of 10-13℃（optimal at 13℃）,light intensity of 70μmol photons/（m²·s）,nitrogen concentration of 3 mg/L,and phosphorus concentration of 0.3 mg/L.