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EFFECTS OF BRASSINOLIDE ON GROWTH AND SOME PHYSIOLOGICAL ACTIVITIES OF PLATYMONAS SUBCORDIFORMIS AND ISOCHRYSIS GALBANA

Hou Hesheng; Chen Minzi(Department of Biology, Liaoning Normal University, Dalian 116029)  
This March 1991-July 1992 study using unicellular algae P.subcordiformsand I.galbana suppied by the Second Lingshui Fisheries Culture Fann of Dalian wascanied out to find the optimum Brassinolide (BR) concentrations which stimulate themultiplication and increase the quantity of the algas. It is important to determine theeffects of BR on the growth and physiological activities of the algae because thescientific data thus obtained can be used to increase the production and enhance thequality of the algas treated with BR.The algae were cultured in a sterilized f/ 2 media treated with BR atconcentrations of 0, 5, 10, 50μg/ L for P.subcordiformis, and 0, 1, 5, 10μg/ L for I.Galbana. The cultures were maintained in 12: 12 Ligh-dark cycles at 5 000-10 000 lx,16-23℃ fo P. subcordiformis and at 1 500-3 000 lx, 20-23℃for I.galbana. Thegrowth of the algae during one week of BR treatment were measured withspectrophototometer every morning. Chlorophyll, photosynthesis, nucleic asid,carbohydrate, protein and vitamin C in the algae were measured after 4 days of BRtreatment (10μg/L and 5μg/ L for P. subcordiformis and I. galbana respectively). Theresults show that algas cells multiplications were promoted at low BR concentrations(1, 5μg / L for I.galbana and P. subcordiformis respetively). The growth constantswere 0.23 in the control, 0.27, 0.29, 0.27 in the treated group for P. subcordiformis.Similarly, they were 0.25 in the control, 0.28, 0.30, 0.29 in treared group for I.Galbana. The lag phase of growth were shortened about 0.5 day in every treatedgroup. The optimum concentration of BR used for P. subcordiformis was 10μg/ L, itwas 5μg/ L for I.galbana (Tab. 1). Chlorophyll content and photosynthetic rateincreased by 10.6% and 16.75% respectively for P. subeordiformis and 10.5% and16.48% respectively for I.galbana in treated groups. Dry weight of P. subcordiformistreated with BR was 0.901 g/ L and it was 0.622 g/ L in the control. The increases ofnucleic acids in treated groups were 37.4%, 35.50% (RNA) and 26.3%, 25.0% (DNA)in P.subcordiformis and I.galbana respectively (Tab.2). In addition, carbohydrate,protein, and vitamin C in the algae increased by 4.4%, 14.3%, 22.7% and 5.68%,13.3%, 23.3% respectively after BR treatment (Tab.3).It may be concluded from these results that BR apparently has a growthpromoting effect on the algae and can also improve the nutritive values of the algae-When cultures of the algae are treated with proper amount of BR, the yield will beincrease.
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