Study On Gametophyte Culture And CAMP System Of Undaria Pinnatifida

Undaria pinnatifida is one of the three main seaweed species under commercialcultivation in china because of its high nutritional value, good economic and socialefficiency. With the breeding scale expanding,it is necessary to improve its' quantityand quality of artificial breeding. In this paper the effects of daylength, irradiance onthe vegetative growth, maturation and a proper concentration of nitrogen for rapidvegetative propagation of U.pinnatifida gametophytes were studied using a factorialexperimental design in culture. In addition, in order to regulate and make full use ofsexual reproduction of algae, improve the technique of algae breeding, cultivatewell-bred algae. The cAMP messenger system in the development and fertilization ofU.pinnatifida gametophytes was studied. The regulation of sexual reproduction wasresearched as well.Firstly, the development and the maturation of U.pinnatifida gametophytes werestudied. The growth of Undaria gametophytes increased with increasing daylength (8,12and16h), but the maximum fertility occurred at a daylength of12h. Gametophytesgrew better at the16h daylength under the same mean daily irradiance (MDI) of20μmolm-2s^-1. However, the fertility was higher at the short daylength (8h). Vegetativegrowth and sporophyte production of gametophytes were better at60μmolm-2s^-1thanat30μ molm-2s^-1under a8:16h LD (Light:Dark) cycle, and their growth andmaturation were density-dependant in16and12h daylength, respectively. Thesporophyte recruits per unit has been enhanced with increasing spore settlementdensity at8and12h daylength which indicated that high settlement density gave abenefit for maintaining population, but the sporophyte production of each female plantis inhibited. In conclusion, the vegetative growth, reproduction and sporophyteproduction of U. pinnatifida gametophytes are retarded at a low irradiance abovegrowth saturation and a high settlement density, and are determined by daylength.Secondly, the nitrogen for rapid vegetative propagation of U.pinnatifidagametophytes was studied. U. pinnatifida gametophytes utilized NH₄⁺and NO₃^-simultaneously, no suppression of NH4+by NO₃^-uptake, or of NO₃^-by NH₄⁺uptake was observed, but nitrate was taken up faster than ammonium. under theconcentration of30μM, the gametophytes increased their weight by25%per day.Ammonium and nitrate uptakes were measured for U.pinnatifida gametophytes. Thehighest uptake rates24.3μmolg^-1h^-1of NH4+and20.73μmolg^-1h^-1of NO₃^-wereobserved at the highest substrate concentrations. NO₃^-uptake increased linearly withNO₃^-concentration. Similarly, NH4+also increased the uptake by the increasing ofNH₄⁺concentration.Finally, the adenosine3',5'-cyclic monophosphate(cAMP) was detected in thematuration and fertilization of U. pinnatifida gametophytes. U. pinnatifidagametophytes elicit a rise in intracellular cAMP levels during its' maturation andfertilization. We treat the U. pinnatifida gametophytes with light off-on stimulationand high concentration of K+, the results show that the light and high concentration ofK+has less effect in changing the cAMP level in the U. pinnatifida gametophytes.When the U. pinnatifida gametophytes treated with blue, white, red and green light,we found that the blue light play the most important role in the growth andreproduction of gametophytes, the different quality of light trigger the changing ofcAMP. Addition of cAMP modulation increase the cAMP levels did not promote thematuration of U. pinnatifida gametophytes, but increase the eggs ovulated by femalegametophytes which do good for the formation of the sporophyte. However, lower thecAMP level delayed the development of the gametophytes.