Study On Physioecological Characteristics And Tissue Culture Of The Brown Alga Sargassum Muticum

Seasonal investigation on morphological characteristics, nutrient uptake, growthand reproduction, and resource storage of the perennial brown alga Sargassummuticum, which collected from the tidal pool along the coast of Taipingjiao, Qingdao,was conducted from June2011to April2012. Simultaneously, the probability of usingthe adventitious buds induced from the explants of S. muticum by tissue culture asartificial seedlings was confirmed, which will provided a basis for the establishmentof rapid propagation technique for artificial seedings of S. muticum.1. Seasonal morphological characteristics of S. muticumMean fresh weight of alga individual increased slightly from June to August2011followed by a sharp decrease to the minimum value of8.78g in October, andthen increased gradually to the maximum value of113.06g in April2012. The meannumber of primary laterals decreased from7.5in June to3.5in December2011, andthen increased to6.9in February2012followed by a slight decrease to5.7in April.The mean number of secondary laterals increased slightly from June to August2011followed by a sudden decrease to0.8in October, and then increased gradually to themaximum value of94.4in April2012.The mean length of primary laterals increased from10.28cm in June to16.99cm in August followed by a sudden decrease to the minimum value of6.00cm inOctober, and then remained about13cm from December2011to February2012followed by an increase to the maximum value of19.54cm in April. The mean lengthof stems decreased gradually from0.93cm in June to0.56cm from in December, andthen increased to1.03cm in April2012. The individuals with pneumathodes werehigher than90％in every month except for October, in which the percentage was10％. The individuals with receptacles was20％and100%in June and August2011, respectively, and absent in any other month. The life cycle of S. muticum in theintertidal zone along the coast of Taipingjiao, Qingdao could be divided into fourstages according to the seasonal morphological characteristics mentioned above. Theyare slow growth stage (October-Februare), rapid growth stage (Februare-June),maturation stage (June-August), and shedding and withering stage (August-October).2. Seasonal nutrient uptake of S. muticumSeasonal uptake rates of NO3—N, NH4+-N and PO43--P of S.muticum in responseto temperature and nutrients were examined. The uptake rate of NO3--N remainedless than30μg g-1h-1from June to August2011, and ranged from30μg g-1h-1to120μg g-1h-1from December2011to April2012. The uptake rate of NH4+-N wasalways lower than40μg g-1h-1throughout the year. The uptake rate of PO43--Premained less than2μg g-1h-1in June, remained negative from August to December,and varied between2to4μg g-1h-1from February to April. The suitabletemperature for the uptake of NO3--N ranged from10to24℃in June and August,and5to24℃in December,5to30℃from February to April, respectively. Thesuitable temperature for the uptake of NH4+-N ranged from5to30℃. The suitabletemperature for the uptake of PO43--P ranged from15to30℃in June, and5to30℃from February to April. The uptake rate of NO3--N was obviously higher than that ofNH4+-N from December to April, but was as same as that of NH4+-N from June toAugust.The uptake rate of NO3--N saturated from June to August when the nitrogenconcentration was up to2000μg l-1, and the maximum value was lower than50μg g-1h-1. However, the uptake rate of NO3--N did not saturate from December toApril when the nitrogen concentration ranged from1800to8000μg l-1, and themaximum value ranged from60to170μg g-1h-1. The uptake rate of NH4+-Nsaturated in June, August, and February when the nitrogen concentration was up to2000μg l-1, but did not saturate in December and April when the nitrogenconcentration was up to2500μg l-1, and the maximum value was lower than50μg g-1h-1. The uptake rate of PO43--P did not saturate throughout the year when the phosphorus concentration was up to120μg l-1, and the value was2-4μg g-1h-1fromJune to August, lower than2μg g-1h-1in December, and4-8μg g-1h-1from Februaryto April.Young sporophyte of S.muticum could absorb NO3—N, NH4+-N and PO43--P at15-30℃, and the uptake rate of NO3--N was higher than that of NH4+-N. The uptakerates of NO3--N and NH4+-N did not saturate when the nitrogen concentration was upto3000μg l-1, and the maximum value was lower than30μg g-1h-1. The uptake rateof PO43--P saturated when the phosphorus concentration was16μg l-1, and themaximum value was lower than4μg g-1h-1.3. Seasonal growth and resource storage of S. muticumSeasonal changes in the specific growth rates, the content of chlorophyll a and c,and the contents of carbon and nitrogen in response to temperature and nutrients wereexamined. The SGRs of algal fresh weight and length remained a positive value, at10-24℃in June and December2011, and at5-24℃in February and April2012, nomatter the nutrients were present or absent. The SGRs of fresh weight and lengthremained at4-15%d-1and4-13%d-1, respectively, in June, February, and April, butremained at1-12%d-1and3-9%d-1, respectively, in December. The SGR of freshweight was generally higher in NP-enriched treatment than in NP-removed treatment,especially in June, February, and April.The contents of chlorophyll a and c in the wild S.muticum reached the lowest inAugust (0.51mg g-1and0.10mg g-1, respectively), and the highest in February (1.33mg g-1and0.26mg g-1, respectively). The content of chlorophyll a in the alga afterculture was generally lower than that before culture at10-30℃in June and5-24℃inFebruary and April, and the decline was more obvious in NP-removed treatment thanin NP-enriched treatment. However, in December, the content of chlorophyll a in thealga after culture was higher than that before culture for NP-enriched treatment, butlower than that before culture for NP-removed treatment. The content of chlorophyll awas generally higher for NP-enriched treatment than for NP-removed treatment, especially in June, December, and April. The content of chlorophyll c in the alga afterculture was close to that before culture, and the content was higher for NP-enrichedtreatment than for NP-removed treatment in December and April.The contents of carbon and nitrogen in the wild S.muticum reached the lowest inAugust (290.33mg g-1and35.45mg g-1, respectively), and the highest in April(376.03mg g-1and51.03mg g-1, respectively). The carbon content in the alga afterculture had little difference with that before culture in June, December and February,but generally lower than that before culture in April. The supply of nitrogen andphosphorus had little effect on carbon content. The nitrogen content in the alga afterculture was commonly lower than that before culture, and the decline was moreobvious for NP-removed treatment than for NP-enriched treatment.Young sporophytes of S.muticum had a positive growth at10-30℃, and the SGRfor NP-enriched treatment was significantly higher than that for NP-removedtreatment at15-25℃. The content of chlorophyll a in the alga after culture was at thesame level as before culture for NP-enriched treatment, but was lower than that beforeculture for NP-removed treatment. The content of chlorophyll c in the alga afterculture was generally higher than that before culture, and was higher for NP-enrichedtreatment than for NP-removed treatment. The carbon content in young sporophyteafter culture was slightly higher than that before culture, and no significant differencein carbon content was found between NP-enriched treatment and NP-removedtreatment. The nitrogen content in the alga after culture was higher than that beforeculture for NP-enriched treatment, but lower than that before culture for NP-removedtreatment.4. Tissue culture of S.muticumThe induction rate of adventitious buds, the number and length of theadventitious buds were compared among two algal explants (holdfast and stem), threetemperature treatments, and four colleting seasons. It showed that the parameters wereoptimal, at20and24℃for holdfast explants in September and October, but at15to 20℃for stem explants in February and March. Artificial seedlings of S.muticumwere acquired by reproduction of matured alga originated from tissue culture.