发菜的光合作用、呼吸作用和形态学的研究

STUDIES ON PHOTOSYNTHESIS,RESPIRATION AND MORPHOLOGY OF NOSTOC FLAGELLIFORME

用氧电极法测定光强、温度、pH、盐度、藻丝体长度和重新吸水对发菜(Nostoc flagclliforme Born.et Flah.)光合作用和呼吸作用的影响。结果表明,它的光补偿点为40—90umol 光子,m^2,s^1,光饱和点为1200umol 光子,m^2,s^1,。光合作用的最适温度为25℃。最适 pH 为7.5。呼吸速率的最高值在35—40℃,最适 pH 值为7.5—8.0。发菜在盐度为0.15mol/L 的 BG-11培养液中净光合速率最高。呼吸速率则随盐度增高而降低。藻丝体长度为0.5cm 时光合和呼吸活性提高,以后随长度增加而有所下降。重新吸水后光合和呼吸活性恢复时间随其贮存时间加长而延长。扫描电镜观察到,发菜细胞包埋在胶质中,往往两两成对连结较紧密,两对之间较疏;有时藻丝有分枝。原植体顶端的皱褶明显,说明其表面积大,有利于吸水和细胞生长。

Nostoc flagelliforme Born. et Flah. is one of the terrestrial cyanobacteria naturally distri- buted in arid and semi-arid areas in the Northern and the North-western parts of China. The cyanobacterium is an edible delicacy with special medical value. However, commercial N. flagel- liforme has nov been collected from the field only. For cultivation of this valuable cyanobac- terium, it is necessary to understand how it grows and how it adapts to the environment. The experimental material was collected in Siziwangqi of Nei Monggol. The effects of li- ght intensity, temperature, pH, salinity, length of thallus and rewetting on photosynthesis and re- spiration of N. flagelliforme were measured using an oxygen electrode. The results were as fol- lows: The photosynthetic light compensation point was around 40—90μmol photons. m^-2.s^-1, the light saturation point was 1200umol photons'm^2 .s^-1, and no photoinhibition appeared when the light in.tensity was increased to 1800μmol photons-m^-2's^-1. N. flagelliforrne exhibited its photo- synthetic and respiratory activities in the temperature range of 5—45℃. The optimum temperature for its photosynthesis was 25℃ and that for respiration was 35--40℃. Between pH range of 4.5—9.5 N. flagelliforrne had photosynthetic activity and respiratory activity at pH range of 4— 10, with optimum pH for photosynthesis at 7.5 and for respiration at 7.5—8.0. N. flagelliforme exhibited maximum net photosynthesis in 0.15mol/L of NaC1 in BG-11 medium. When the salinity was increased to 0.9 mol/L the net photosynthesis dropped down to zero. Respiration decreased concordantly with the increasing salinity as well. Maxima photosynthesis and respiration was also detected when the thallus of N. flagelliforme reached a length of 0.5cm and aftewords the more the length the less the activities. The recovery time attaining to the maximum photosynthesis and respiration activities after rewetting was dependent on storage time in dryness. The cyanobac- terial mats after being reserved for 3 months, attained its maximum photosynthesis by 0.5h after rewetting, and that being reserved for 18 months needed 3.5h after rewetting. For respiration, the mats reserved for 3 months and 18 months required 5 minutes and lh after rewetting, res- pectively to attain its maximum. Under scanning electron microscope, cells of N. flagelliforme were wrapped up within a gluey sheath, and usually attached closely to each other in pairs and the filaments were uni-trichome with branches in some cases. The surface of thallus tip was rou- gher than other parts which meant that the tip portion had greater surface area beneficial to water absorption and cell growth.