A Preliminary Study On Compensatory Growth Of Prorocentrum Donghaiense Lu Under The Stress Of Nitrogen And Phosphorus Deficiency

The variation in tolerance ofProrocentrumdonghaienseLuto N deficiency or Pdeficiency, and its compensatory growth under normal nutrients condition (f/2culturemedia) were studied. Two different groups of experiments, including nutrientsdeficiency period and without nutrients stress period, were conducted in the study.Firstly, P. donghaiensewas cultures for10days under the conditions of nutrient stress,including poor nutrients, N deficiency, P deficiency, and N plus P deficiency, whilenormal nutrients condition (f/2culture media) was served as control. Secondly, thenutrients stress was removed, and the treated group and the control were simultaneouslycultured for another ten days under conditions of same inoculation density andsufficient nutrients supply. Cell density, growth rate, relative growth rate, generationtime and Chlorophyll-a were determined during the two periods. The result indicatedthat the nutrient stresses have an inhibitory effect on the growth cell. The cell under Pdeficiency had the least inhibitory effect, but the cell under N plus P deficiency had acomparatively large inhibitory effect. The growth differencebetween the treated groupsand the control was significant (P<0.05). Maximum cell density of Control，Poornutrients，N deficiency，P deficiency and N plus P deficiency were83×104cells.ml-1,32×104cells.ml-1,43×104cells.ml-1,78×104cells.ml-1and29×104cells.ml-1, respectively.Maximumgrowth rate were0.64d-1,0.53d-1,0.61d-1,0.54d-1and0.51d-1；maximumaverage relative growth rate were0.61d-1,0.39d-1,0.44d-1,0.44d-1and0.35d-1;minimum generation time were1.13d,1.76d,1.58d,1.58d and2.00d and maximum content of chlorophyll-a were723.7μg.μL-1,286.4μg.μL-1,427.1μg.μL-1、694.2μg.μL-1and292.9μg.μL-1, respectively.During the nutrients stress-removedperiods, It was found that after subjectingto the nutrients stress, P.donghaiensehadabilityof compensatory growth, particularly the P deficiencytreatment. Thegrowth differencebetween the treated group and the controlwassignificant(P<0.05).Themain character ofthe compensatory growth of P.donghaiensewas that the treated group had higheraverage relative growth rate, more number of cells and higher chlorophyll-a contentthan those of the control group in the initial culture time. In addition, the maximal rateof net cells increase was0.30%～80.95%，generationtimeof cell was shorten. But, as theculture time proceeded, the difference between the treated groupand the controldecreased gradually. Eventually, all parameters of the treated group and thecontroltrended to be equivalent.Those results showed that P.donghaiensehave anover-compensatory growth under the conditions of nutrient stress, particularly duringthe P deficiency. This might be an internal cause of harmful algae blooming in theChina Seas, where characterized by the P deficiency all year round.In this study, ProrocentrumdonghaienseLu was used as experimental material forstudying the effect of compensation and its regularities on physiology. The significanceof this study was that the results from this study could be used as some sciences data foestudying the compensation in algae. Meanwhile, the regularity of compensation couldbe used to as guidance for controlling the bloom of harmful algae and carrying outaquiculture of useful algae.